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AMERICAN ST 085368U INDUSTRIAL HYQIENE ASSOCIATION Volume 17 SEPTEMBER, 1956 Number 3 Symposium on Threshold Limits Present Trends in MAC's.............................................................. Warren A. Cook The Need for Threshold Limits ........................................... Miriam Sacha, MD. Prepared Discussion................................................................ Henry F. Smyth, Jr. Methods of Establishing: Threshold Limits.....................Jamea H. Sterner, M.D. Prepared Discussion................................................... Herbert E. Stokinger, Ph.D. Engineering and Chemical Application of Standards___ Allen D. Brandt, Sc.D. Prepared Discussion ...................................................................... Arthur C. Stem Prepared Discussion ................................................. Theodore C. Waters, LL.B. 273 274 279 280 281 286 292 296 Automatic Instrumentation for Air Pollution Monitorinc--A Progress Report on Automatic Directional Air Sampling................ William A. Munroe A Versatile Portable Air Sampler......................... H. S. Jordan and R. N. Mitchell 298 303 Determination of Internally Deposited Radioactive Isotopes from Excretion Analyses.............................................................. Wright H. Langham 306 Criteria for an Evaluation of Noise Problems......... Charles R. Williams, Ph.D. 319 Flow Calibration of High-Volume Samplers ................................................................... Bernard D. Tebbens, Sc.D., and Donald M. Keagy, M.S. 327 Recent Industrial Hygiene Developments--A Symposium In the Field of Air Pollution.......................................................... Henry N. Doyle In the Field of Chemistry..................................................Ralph G. Smith, Ph.D. In the Field of Engineering...............................................Leslie Silverman, Sc.D. In the Field of Noise........................................................................Vaughn H. Hill In the Field of Radiation.................................................................. Saul J. Harris In the Field of Toxicology ......................................Herbert E. Stokinger, Ph.D. 330 332 333 336 338 340 Hygienic guide series ........................................................................................................................ 345 President's page ........................................................................................................ 362 Selected Titles and Abstracts.......................................................................... 363 Book Review ................................................................................................................. . 354 AIHA Industrial Associates, Officers, Directors, and Committees 366 American Industrial Hyoidnd Association Quarterly. published bjr the American Industrial Hygiene As sociation in March, June, September, and December. Howard N. Schulz, Editor: Hsksist J. Wessr, Advisory Editor: Lloyd E. Coupon. Associate Editor; William S. Johnson, Advertising Editor: Paul D. Halley. Cir culation Editor; A. D. Cloud, Publisher; Dosis Flousnoy, Editorial Assistant. Publication and Editorial Offlees, 605 North Michigan Avenue, Chicago 11, Illinois. Subscription St.00 per year in the United States: S4.50 per year in Canada: S5.00 per year in other countries. Single copies. $1.50--except the June, 1965, issue which is 52.00. Copyright, 1956. the American Industrial Hygiene Association. Entered as second class asstter May 3, 1948, at the post office at Sheboygan, Wisconsin, under the Act of March 3. 1819. The AMERICAN Industrial Hygiene Association Quarterly reserves the right to edit all advertisements and to refuse advertis ing copy when it does not meet the high professional standards adopted by the Association. ST0853685 Symposium on Threshold Limits Present Trends in MAC's Introduction by WARREN A. COOK, Associate Professor Industrial Health and Hygiene, School of Public Health University of Michigan, Ann Arbor he thinking today on the concept of limits and the improper use of them. No Tthreshold limits of injurious materials, where is the present concept of threshold designated by whatever term, has passedlimits more ably and competently expressed through an evolution to a gratifying uia- than in the papers and discussions of this turity. Symposium. Initially the need to know how little of a That the discussants might not have the toxic substance might remain in an indus very last word, it may be permissible for trial atmosphere without injury to those ex this prologue to assume in part the preroga posed was insistently apparent. Such in tive of an epilogue! The following com formation began to be supplied through cor mentaries appear pertinent. relation of concentrations of injurious sub The last publication of the American stances with observed effect on the health Standards Association Z-37 Committee on of the worker for such materials as granite Maximum Acceptable Concentrations of dust1 and lead compounds.2 Results of short- Toxic Dusts and Gases is reported cor time animal experiments had been available rectly as 1949 by Sachs who deplored the even before the present century from such lack of revision of the 1941 Standard for investigators as K. B. Lehmann-'' and later benzene at the obsolete level of 100 parts from Yant and others at the U. S. Bureau per million. It is to be noted that this ASA of Mines,-* with the classic combined long- Committee is now active in the revision and exposure animal experimentation and oc publication of MAC Standards for many cupational study on benzene by Greenburg3 of the materials on which information is in the middle twenties. available. As these threshold limit values became The term "maximum acceptable concen more numerous and were more widely ap trations" was adopted by the ASA Commit plied, it is perhaps not surprising that mis tee for a number of reasons. The word "ac conceptions and aberrant usages occurred. ceptable" does not connote the legal control Some persons erred in considering the levels inherent in the words "allowable" and "lim more precise than the facts justified; others it," but rather a simple acceptability with rejected them because the values could not out further implication. Also, the expres precisely fit all conditions of exposure and sion, MAC, has been widely used over the physiological response. And the detractors years and is now a part of the language. In were for a while more vociferous and seemed fact the Germans adopted a wording which possibly to be more sound than the pro gives the abbreviation, MAK, so that this tagonists. term may be used in international conversa With time, there has been a separation of tion. Their words as used in the title of a the valuable advantages of the threshold paper by Oettel7 are "Maximale Arbeits- Pmntd at the Joint See*ion of the American In dustrial Hycieni Association--American CoNrcuNci <* Governmental Industrial Hygirnirts st the 1956 In dustrial Health Conference, Buffalo, April 26, 1965. platz-Konzentration." It is understood that this same expression is being used in the "MAK" tables of the German Association for Worker Protection. ST0853686 27i September, 1958 However, there can be no really valid ob jection to the term "Threshold Limits'' used by the committee of the American Confer ence of Governmental Industrial Hygienists or to "Hygienic Guides," the term adopted by the American Industrial Hygiene Asso ciation committee. This Symposium would not be complete without reference to the availability of the excellent AIHA Hygienic Guides to which reference is made else where in this Journal. One of the most perplexing problems in arriving at threshold limits is posed by the cancerigens. Stokinger's statement in this Symposium is the first publication on this phase of the subject. However, the use of the procedure suggested by Stokinger as ap plied to nickel carbonyl has already drawn some fire. Quoting in part from a private communication from Oettel whose publica tions'" on "MAK's" include a well-consid ered presentation of the general subject: "We suggest that consideration be given to indicating the suspected cancerigens with an asterisk with reference to a footnote that the hazard exists and consequently especial ly effective control measures be instituted. No man can say today which concentration of the several industrial substances is actu ally required to be cancerigenic . . This statement follows his objection to the pres ent listing by the ACGIH of nickel car bonyl as 0.001 ppm on the basis of its al leged cancerigenicity, which incidentally Oettel's extensive experience with the sub stance causes him to doubt, while failing to include any acknowledgement of the known cancerigenicity of arsenic, chromates and asbestos. Says Oettel "In this I see a great danger. The lists should in any event remain logical." Waters' discussion of Brandt's paper oc cupies the final pages of this publication of the Symposium, but it is believed that Waters would not wish his comments to be considered the last word on the subject of threshold limits--rather that his observa tions are limited essentially to the use of these values in legal codes, rigidly fixed by statute. As the last word in this Symposium, this introductory refers the reader to the concluding paragraphs of the paper by Brandt for his discussion of the philosophy of threshold limits. References 1. Ruatiliu A. E.. Burnt*. R. H.. THOMPSON, L. R.. Bloomfield, 4. 4.; The Health of Workers in Dusty Trades II. Expocure to 8ilieeous Dust (Granite Industry). Public Health Bull. No. 187, 1929. 2. Ruurell, A. E.. Jonu, R. R.. Bloomfield, 4. 4.. Britten. R. H.. Thompson. L. R.; Lead Poisoning In a Storage Battery Plant. Public Health BulL No. 90S. 1988. 1. Lehmann, K. B.: Numerous papers mostly pub* liihed in Archiv fitr Hugiene from the 1880's. 4. Yant. W. P,, and colleagues: Acute Response of Guinea Pin to Vapors of Some New Commercial Or* tranie Compounds. A series of papers published in Public Health Reports during the 1930's. 5. Green suae, L.: Bentoi Poisoning as an Indus* trial Hazard, Public Health fleptt., 41, 1367, 1410, and 1519; 1926. 6. American Standards Association: Standards on Ac ceptable Concentrations of Toxic Dusts and Gases. ASA. 7fl E. 45th Street. New York 17. New York. 7. Oettel, H.: Die maximale Arbeitsplats*Konsentra* tion ( = MAK-Werte) schddlicher Gase. Dimpfc und Staube. Die berufagenoasunachaft, No. 2, February, 1954. K. Oettel. H.: Gewerbliehe Vergfftungen dutch Gase, Dimpfe und Stsubarten. Archiv fur Toxikologie, 15:42. 1964. The Need for Threshold Limits MIRIAM SACHS, M.D. New Jersey State Department of Health, Bureau of Adult and Occupational Health Trenton, New Jersey Probably one of the moat basic needs in purpose as a point of aim for individual human endeavor is for man to have an interpretation. If this seems cryptic, an ex orderliness set to his manner of thinking. ample concerning a common substance may Everyone has a need for discipline, for be cited. boundaries to be drawn, and for limits to be Almost everyone is familiar with the defined. It does not matter that the only use threshold limit values for silica--for dust for some of the limits so defined may be to with a free silicon dioxide content above ignore them; they have still served their 50%, the limit is given as five million parti- Industrial Hygiene Quarterly ST0853587 srs cu per cubic foot of air (MPPCF), for dust ivith a free-silica content below 5%, the lim it is 50 MPPCF, but 20 MPPCF is the value assigned for dusts with 5% to 50% free silica. It is rather difficult to understand how longs could be so selective as to react with fibrosis if air containing more than 5 MPPCF of a 50% silica bearing dust was in haled, but would be expected to remain healthy if a 40% silica content dust at the level of 20 MPPCF was similarly inhaled. It would be of doubtful accuracy for each in dustrial hygienist to interpolate on the enrve of this wide range and apparent dis crepancy. It has always seemed better prac tice to abandon the middle limits and when necessary forward a report (concerning dusts with a free-silica content of about 40%) that "dust with such a dangerously high content of free silica should be main tained in the working environment at less than 5 MPPCF." For agencies who have not conducted any research or original investi gation along these lines, this might have been a precarious position under attack. Fortunately, the trend is toward revision of the limit for silica-bearing dusts.1 An Essential Tool Actually, threshold limits satisfy the need for a tool essential to the protection of the health of the worker. The quantity of tech nical information concerning the biological actions of old and new chemicals is so vast that no single practitioner of industrial hy giene can be expected to be able to as similate more than a very small fraction of this mass of material. A list of guide values prevents the chaos that would result if each investigator conducting plant surveys had to depend on his own comparatively re stricted experiences and background. Two of industrial hygiene's sister specialities are admirable demonstrations of the benefits of having, and the disadvantages of not having, an approximate measurement of hazard. In radiological health and radio logical safety the maximum permissible ex posure value, blessed by national and inter national committees, has made possible much of the rapid adoption of var ious radiological techniques, uses of radio isotopes, and forays into the field of nuclear energy. In air pollution investigation and control, lack of standards for permissible levels of atmospheric contaminants has seriously hampered wise administration of air pollu tion control practices, and has made it al most impossible to weigh the effects of these contaminants on the public health. The need for threshold limit values and the manner of use is quite different for the staffs of governmental or official agencies and for persons employed by private indus try or working with research laboratories, universities or foundations. Official indus trial hygiene agencies must have a screen ing device to apply to literally thousands of industrial processes which are encountered in the day-to-day field work, from one year to the next. A screening device may very well be a single parameter but it should be used only for the purpose of suggesting more intensive and detailed study where the parameter is significantly exceeded. In multiphasic screening for chronic disease, the patient whose survey film is suspect for tuberculosis, cancer of the lung, or ab normal heart outline is referred to his private physician or to an appropriate clinic for more definitive diagnosis. In discussing any screening test proce dure, the question of false negatives versus false positives is certain to be reached. When the risk is permanent disability or death, the governmental industrial hygien ist is so conditioned that he favors the side of the false positive; he tends to be too strict rather than too lenient. For private industrial purposes, the threshold limit values satisfy the need for engineering bench marks. "Almost 100% confidence can be placed in the threshold limits where they are being used for evalu ating and controlling of an industrial en vironment. This is particularly true in the use of these limits as a base line for calcu lating control design specifications in that the usual engineering factors of safety are included in such designs. It should be re membered that under this connotation the base line for comparison need not be ex tremely accurate. Naturally, the more ac curate the figure is, the better economy that can be realized in engineering a control."2 One of the deans of industrial hygiene and toxicology, restated this point of view as, "We need a yardstick even if it's only a rub ber yardstick!" ST 0853688 276 September, 1956 Henry Smyth haa given the most nearly complete description of the toxicological data required to satisfy all needs.* (1) What uniform concentration is tolerable eight hours a day for a working lifetime? (2) What correction in the average must be made for brief peak concentrations? (3) What single brief exposure to a high concen tration is tolerable each day when there is no exposure the rest of the day? (4) What biological test upon the workman can meas ure his actual intake of the chemical at his job? (5) What are the earliest symptoms and objective signs of excessive exposure and how severe can they become before re moval from exposure fails to prevent perma nent injury? (6) What is the best treat ment for the effects of excessive single ex posure or excessive repeated exposure?" For a few industrial materials, all of these ques tions can be answered. The threshold limit values attempt to supply the answer only for question one. The introductory preface to the list advises caution in interpreting even this single answer. The introduction to the 1954 list haa probably been well read. The preface to the 1948 list warrants repe tition: "While it will doubtless be very advantageous to have what might be called permanent or standard maximum allowable concentration values, it must be borne in mind that all our values at the present time are fluid and subject to annual revision. They should not be adopted as fixed or legal values, but merely as guides to assist us in defining more or less safe working condi tions. . . It'must be borne in mind that these values are not indices of toxicity and are not intended to approach that value. Ac cordingly, the comparative toxicity of these compounds cannot be established on the basis of their numerical maximum allow able concentration value. "People vary greatly in their response to drugs and toxic substances. Therefore, it is a figment of the imagination to think that we can set down a precise limit below which there is complete safety and immediately above which there may be a high percentage of cases of poisoning among those exposed. "With these facts in mind the Committee has set values below which it is fair to ex pect reasonable protection and above which it is reasonable to expect that we can have occasional cases of poisoning."4 With so clear a statement of purpose on the books, it has always been somewhat baffling that several persons speak with bit terness and disdain about the threshold lim its list. In all fairness, it must be ad mitted that the acrimony arises because the advice in the foregoing statement has frequently been disregarded and some regu latory agencies have not only allowed but have assisted the entrance of the threshold limits into the sacred and rigid precincts of the law. This is an unfortunate resting place for a scientific instrument that requires con stant adjustment and calibration. A number of excellent papers have been written on maximum allowable concentra tions and threshold limits. In the interests of progress this panel discussion Bhould be more than a review of bibliography. It should be a reflection of the opinions of the ACGIH-AIHA joint membership and some expression of their perspective on the threshold limits, their needs and their sug gestions for changes or additions. Accord ingly, a simple one-page questionnaire on the value of threshold limits was sent to the members of the American Industrial Hy giene Association and the American Con ference of Governmental Industrial Hy gienists (excluding those in foreign coun tries). A copy of the questionnaire appears on the next page. Response to Inquiry Qne thousand and fifty questionnaires were sent out, of which 340 were re turned by the February 10 deadline. Four teen of these were discarded since they were simply courtesy returns with the questions unanswered. Of the 326 completed forms, the expres sions of "confidence" in the Threshold Lim its were divided as: Confidence Number of Replies 100% 80% 50% Less than Qualified 50% 53 173 37 9 54 Total 326 The group of qualified answers were es sentially those who wrote they could not ap ply a numerical rating to their reactions to the threshold limit values or who said they Industrial Hygiene Quarterly ST 0853689 *77 New Jersey State Department op Health Bureau or Adult and Occupational Health 17 West State Street Trenton 8, New Jersey The Need for Threshold Limits (1) How would you rote your confidence in the ACGIH Threshold Limits T (check one) 100%__ 80%__ 60%__ Less than 50%__ (2) Do you think we need a list of Thresh old Limits? Yes__ No__ (3) What standards of performance would you prefer? (4) When you use or instruct as to the use of Threshold Limits, what qualifications or reservations (if any) do you advise? (6) Other Comments (6) May I quote you by name? Yes__ No__ Name Title Affiliation had, for example, 100% confidence in some of the values and little or no confidence in other values, particularly values for some newer substances assigned because of chemical or structural similarity to a ma terial with a well-documented value. At this point it should be emphasized that many, many responses were careful to explain that their confidence rating was for the "value"; that their confidence in the Committee on Threshold Limits was unqualified. The question, "Do you think we need Threshold Limits?" was answered Yes 323 No 3 Total 326 In the qualified answers, in the comments and in the suggestions for other standards of performance, there were many pleas for regrouping of data and for additional in formation. These were expressed in many different ways but lent themselves to a few major headings. There were 103 requests that the list indicate whether the value was sn "injury" value or a "nuisance" or "com fort" value; there were 73 requests for a notation as to whether the value was based on animal experimentation or human experi ence; 75 penons desired a short exposure value, a one-hour tolerance or a value for "pealu"; 32 wanted information on multiple exposures, synergism or additive effects; and 28 thought the references should be printed along with the assigned value. These suggestions may be summarized as follows: Requests for Number Comfort threshold (nuisance level) 611 Chronic toxicity threshold > 103 (injury level) 42 \ Animal experimentation or human data 73 Short exposure threshold, one hour, peaks 75 Synergism, multiple or additive exposures 32 References on list 28 Several of these comments and requests were embodied in enclosed reprints, long letters and telephone calls. With all this ac tive and militant thinking, there should be no great fear that threshold limits will be applied blindly or that a numerical value will ever entirely replace thoughtful, scien tific appraisal of the many factors that must be considered concerning the health of the worker and the status of the workroom en vironment. Especially, the need for medi cal examination and a determination of the general physical condition of the worker seem well understood. What to be Expected of ACGIH List QNE pertinent question remains to be an swered. What can logically be expected of a list, revised annually, compiled by a committee, each member of which is earning his living at a full-time job? One of the major values of the list is that it is revised annually, and new substances added as data are forthcoming. The excellent Z37 series prepared by the American Standards Asso ciation .contains much more information than appears on the Threshold Limits list. However, of the toxic dusts and gases group there have appeared 15 leaflets, the most recent of which was entitled, "The Allow able Concentration of Methyl Chloride" which was published January 5, 1949. "The Allowable Concentration of Benzene" was ST0853690 278 September, 1956 b i i approved and published January 15, 1941 (accuracy . 20%) shows a reading of 260 and states the permissible concentration as milliroentgens for one week, are we to be 100 parts per million parts of air by volume. alarmed? And are we to be complacent with So far as is generally known no revisions of a duplicate reading of 200 milliroentgens this ASA figure have appeared although it taken in the same place for the same week? is commonly agreed that the 1954 ACGIH Actually both readings are the same within 1 value of 35 parts per million is a far safer experimental limits of error and we should working figure and one that is practical. be alarmed in both cases not primarily be rIf it would not unduly burden the Com cause the readings differ but because the ex i, mittee on Threshold Limits it would be ad posure in each situation may be unneces th vantageous to have a regrouping of the sarily high. It is only rarely that working di listed values according to comfort thresholds conditions at a radiation level far below the and chronic toxicity thresholds. And where permissible dosage cannot be obtained with t th they exist and are easily verified, it would but little inconvenience or added expense. co be most helpful to have a special group of "The aim should be to see how low a prac one-hour tolerances or peak short-time per tical operating level can be achieved--not P in missible exposures. The combined mem how high a level without transgressing the en bership of today's audience might give con 300 mr per week medicolegal upper limits th sideration to the publication of a monograph set by radiation safety experts. Even the m< on threshold limits which could very well smallest amount of radiation has some ef th be a compilation of fundamentally sound fect on the living human body. Even if the , material which has already been published. harm is normally undetectable by the in oli The monograph could include the papers al dividual, genetic damage can result from be ready referred to in this article, with per single minute exposures. We must prevent or haps several others that are equally well perceptible harm or damage--we should of known."''17* minimize the likelihood of undetectable be No list of values and no amount of re damage even though we cannot eliminate it do grouping and no increase in the number of entirely." co background references can relieve the indus The fundamental goal should be the im In trial hygienist of the responsibility of ac provement of industrial hygiene practice. ifc quiring sufficient education and training to Threshold Limits, however accurate, and fo do his job properly and to think for himself. however well-documented, serve only as a al It seems desirable to add here another refer guide and a yardstick. No method ever has ar. | ence, "Education in Radiation Protection,"* been, or ever can be, devised that will permit ca the Janeway lecture delivered by Lauriston an exact advance prediction of human haz S. Taylor. The words spoken by Mr. Taylor ard. The closest we can come is human ad * while directed particularly to the field of judgment. \ mi j radiation exposure apply just as well to any industrial chemical exposure. He states: References ve be M3 "The young radiologist should be educated in the background and significance of per 1. Stokingek, H. E.: Standards for Safeguarding the Health of the Industrial Worker. Public Health Reporta. 70:1. 106S. fo he 3 missible dosage or exposures and should at 2. Ckukch. F. W. ( Esso Research and Engineering hi all times retain a sense of proportion and a sense of humor relative thereto. For ex Company. Linden, N.J.I Personal Communication. J. Smyth. H. K.: Toxicological Data---Sources of In formation and Future Needs. AlHA Quarterly, IS: 203. > qu ar ample, the present permissible exposure for the whole body is 300 milliroentgens per week (measured in air;. This figure was de termined from a limited amount of clinical and biological data to which was applied a series of well educated guesses, and yet we may find a person's weekly exposure re corded as, say 163 milliroentgens--a figure that few, if any, practical clinical instru ments can measure with an accuracy of bet ter than : 10%. Again, if a film badge 1954. 4. American Conference of Governmental Industrial Hygienists. 1945. 5. Cook. Warxcn A.: Maximum Allowable Concen trations of Industrial Atmospheric Contaminants. / * duMtrial Medicine, 14:936-946, November. 1946. C. Silson, John E.: The Significance of Maximum Al lowable Concentrations. Monthly Review, 28:6. February, 1949. 7. Stone, RoaaaT S.: The Concept of a Maximum Per missible Exposure. Radiology, 68:639, 1952. 8. Schkenk, H. H.: Interpretation! of Permissible Limits. AlHA Quarterly. 8:66. 1947. 9. Taylor. Lauruton 8.: Education in Radiation Protection. Amer. J. of Roentgenology, 73:193, 1965. j I pa qu ty ar ni so co co of se i u II* - I . M.MU Industrial Hygiene Quarterly ST085369 I 279 Prepared Discussion which is recorded in some of the threshold limit values. Whether we want him to or HENRY F. SMYTH. JR. Mellon Institute not, he ( and that includes every one of us at times) will use threshold limits as estimates of comparative toxicity to meet his urgent Pittsburgh requirement for finding some basis for opin ion. r. sachs has established that the vast To what extent is he wrong? A threshold D majority of our colleagues recognize limit based on comfort, irritation or good their need for a list of threshold limits. Sheengineering practices certainly is not com distinguishes between the need of the official parable to one based on pathological effect. agencies for a screening device to apply to But the former limit is certainly lower than thousands of industrial processes they en one based on injury. The error is on the side counter in field work, and the need of the of safety if it is stated that material A has private industrial hygienist for an engineer a threshold limit based on comfort higher ing bench mark for planning and evaluating than that of material B which is based on environmental control. To satisfy each of injury, therefore material A should be used these needs vapor concentrations must be in the process. measured under operating conditions before No matter which material is chosen it the threshold limits values can be useful. will be employed by persons subjected to the There is a third group which uses thresh same degree of industrial hygiene and medi old limits and needs them because nothing cal scrutiny. By choosing the material with better suited to the need is available. Every the higher threshold limit the probability of one of our profession is a part-time member safe operation has been increased, even if of this group and some are full-time mem the basis on which the choice was made is bers. Reference is made to the arm-chair in not numerically sound. dustrial hygienist. He may never measure a There is one important short-coming in concentration and he may never observe an this argument which points out an im industrial operation. He uses threshold lim portant way in which threshold limits do not its to advise upon the selection of a chemical meet the needs of the arm-chair industrial for a particular application, to select a suit hygienist. If the volatility of a material with able application for a little known chemical a high threshold limit is greater than that and to bolster sales arguments for a chemi of a material with a low limit, then in a cal or mixture of chemicals. particular process the less toxic material When the industrial hygienist is asked to may be more hazardous, because a greater advise whether acetone, propyl acetate, or vapor concentration will be in the atmos methylene chloride would be the safest sol phere. vent in a particular application, it may be I maintain that the list of threshold lim believed that his answer is based on a pro its is our best available source for judg found knowledge of toxicology, but actually ments on comparative toxicity of vapors to he recalls the threshold limits, or refreshes humans. It can be improved for this pur his memory by consulting the list while the pose, but there is nothing better for us to questioner waits on the telephone. Then the use. However, it refers to toxicity, not to answer is given as if the list recorded com hazard. It is the single-phased toxicity of K. parative toxicities, perhaps adding a bit of B. Lehmann. A table of comparative hazards qualitative information on fire hazard and would go back to Lehmann's two-phased type of injury from an excess. toxicity by combining vapor pressure (or What better data are available for the evaporation rate) with toxicity. This table arm-chair industrial hygienist than the an of comparative hazards is what the arm nual list of threshold limits? He must have chair industrial hygienist really needs. It some guidance if he is to do more than toss a would go a long way toward satisfying all coin. If he is given a list based on uniformly of his needs, particularly if it included in conducted animal experiment, he is deprived formation on nature of injury, on the penal of the benefit of the years of carefully ob ty for exceeding the limit and on the degree served and evaluated human experience of hygienic urgency for observing the limit. ST 0853692 280 September, 1956 Methods of Establishing Threshold Limits JAMES H. STERNER, M.D. Medical Director, Eastman Kodak Company Rochester, New York Threshold limits are baaed upon in from industrial or governmental industrial formation derived from many and di hygiene surveys; or it may be incomplete verse sources. For each evaluation, datadata from animal experiments; or reports of developed by many different methods may cases of alleged intoxication from Work need to be considered and weighed; and men's Compensation sources. from this sometimes complicated, often con A still less tangible factor, related to the tradictory, and rarely adequate, complex of experience, training, and critical judgment information, a significant value must be of the individuals performing the evalua developed. tion, is the ability to make a variety of ex It is customary to append, as reference trapolations. In one instance this may in material, the important published studies volve the estimation of the probable effect from which the conclusions were made. In in man from data developed in one or more these studies, particularly if the author felt species of lower animals. The experimental that his contribution permitted such a judg toxicology data may be limited to acute or ment, there is often a proposed threshold subacute experiments; but even if chronic, limit value. Not infrequently, of course, the long-term studies have been done, the trans values suggested by different investigators lation from a few years exposure, even may disagree. The group which is charged though a lifetime for the animal, to the long with the responsibility for establishing span of a working lifetime in man is a diffi threshold limits must consider, in addition cult step. In other cases, the extrapolation to the character of the study, such qualities may be from experimental or clinical data as accuracy, reliability, completeness, and developed with one chemical to the probable purpose--and, a not insignificant factor, effect of an homologous compound or a ma the reputation of the investigator. terial with similar chemical structure. The subject, "Methods of Establishing The behavior of a substance in other fields Threshold Limits," has a connotation be --us a therapeutic agent, an insecticide, or yond that of the procedures and techniques even as a beverage (as in the case of ethyl reported in the industrial hygiene literature. alcohol) may contribute important informa This has to do with the actual mechanism by tion. The background of the individuals which a group or a committee is designated making the judgment, with respect to per to act as a body for establishing threshold sonal experience ranging from animal ex limits, and the principles and practices perimentation through long-term clinical which actually govern the operation of the observation of exposed workmen, with re committee. In the present evolutionary stage spect to a practical and critical appreciation of industrial hygiene, the internal activities of the value and limitations of methods of this committee must weigh heavily in any for making environmental measurements, consideration of "methods." determines the ultimate value with which Threshold Criteria all of these factors, concrete and abstract, are blended to form a valid, practical, and Jt would be worthwhile, if it were possible, acceptable threshold limit. The more sub to record all of the elements of a delibera stantial the documented information, the tion in arriving at a standard. Often, there broader the sources of pertinent data, the is considerable material, undocumented, less the demand for these intangible factors which plays an important role in the evalua to fill the gaps which are inherent in this tion, in addition to the published studies. kind of procedure, This may be limited and fragmentary data The absolute test of a threshold limit has ST0853692 280 September, 1956 Methods of Establishing Threshold Limits JAMES H. STERNER, M.D. Medical Director, Eastman Kodak Company Rochester, New York Threshold limits are based upon in from industrial or governmental industrial formation derived from many and di hygiene surveys; or it may be incomplete verse sources. For each evaluation, datadata from animal experiments; or reportB of developed by many different methods may cases of alleged intoxication from Work need to be considered and weighed; and men's Compensation sources. from this sometimes complicated, often con A still less tangible factor, related to the tradictory, and rarely adequate, complex of experience, training, and critical judgment information, a significant value must be of the individuals performing the evalua developed. tion, is the ability to make a variety of ex It is customary to append, as reference trapolations. In one instance this may in material, the important published studies volve the estimation of the probable effect from which the conclusions were made. In in man from data develpped in one or more these studies, particularly if the author felt species of lower animals. The experimental that his contribution permitted such a judg toxicology data may be limited to acute or ment, there is often a proposed threshold subacute experiments; but even if chronic, limit value. Not infrequently, of course, the long-term studies have been done, the trans values suggested by different investigators lation from a few years exposure, even may disagree. The group which is charged though a lifetime for the animal, to the long with the responsibility for establishing span of a working lifetime in man is a diffi threshold limits must consider, in addition cult step. In other cases, the extrapolation to the character of the study, such qualities may be from experimental or clinical data as accuracy, reliability, completeness, and developed with one chemical to the probable purpose--and, a not insignificant factor, effect of an homologous compound or a ma the reputation of the investigator. terial with similar chemical structure. The subject, "Methods of Establishing The behavior of a substance in other fields Threshold Limits," has a connotation be --as a therapeutic ugent, an insecticide, or yond that of the procedures and techniques even as a beverage (as in the case of ethyl reported in the industrial hygiene literature. alcohol) may contribute important informa This has to do with the actual mechanism by tion. The background of the individuals which a group or a committee is designated making the judgment, with respect to per to act as a body for establishing threshold sonal experience ranging from animal ex limits, and the principles and practices perimentation through long-term clinical which actually govern the operation of the observation of exposed workmen, with re committee. In the present evolutionary stage spect to a practical and critical appreciation of industrial hygiene, the internal activities of the value and limitations of methods of this committee must weigh heavily in any for making environmental measurements, consideration of "methods." determines the ultimate value with which all of these factors, concrete and abstract, Threshold Criteria e are blended to form a valid, practical, and JT would be worthwhile, if it were possible, acceptable threshold limit. The more sub to record all of the elements of a delibera stantial the documented information, the tion in arriving at a standard. Often, there broader the sources of pertinent data, the is considerable material, undocumented, less the demand for these intangible factors which plays an important role in the evalua to fill the gaps which are inherent in this tion, in addition to the published studies. kind of procedure. This may be limited and fragmentary data The absolute test of a threshold limit has Industrial Hygiene Quarterly ST0853693 S81 not boo, and probably will not be achieved if the mnaanra of validity is atrictly conrtneed ia terms of a completely "safe and baaittfoT environment for the occupational lifetiaec of aa individual. Practically, cri teria modi leas complete are accepted, al though the trend ia to the constant improve ment of our -methods for evaluating longtens and mare subtle effects. These more re mote persmrtmi of injury are seen in the extreme in the study of radiation effects, whese consideration is given to such factors as shurtPiring of the total life span, and of Si ialii effects involving future generations. With the gnat majority of physical and chemical agents, we must be content with threshold limits predicated upon lees ex tensive aad leas subtle end-points. If threshold limits, even with their pres ent imperfections, are accepted as useful and deairaUe, they most continue to be fabsfeeated from information which is some times inaccurate, frequently controversial, and alwaya incomplete. Ia this discussion, no attempt wifi be made to define a pattern of amrptihilrtj for the various elements of < i iilmn i which may be considered in estab lishing threshold limits (this might be rsisphrnn1'! as "threshold criteria" for Inrtthiild limits). This will vary with the purpose for which the limits are intended, the character of the group making the judg ment and the need for such standards. At this point, it might be suggested that the various bodies which are responsible for es tablishing standards, attempt to define in genesaJ the purposes, criteria for accepta bility. and limitations of their function-- and perhaps, specifically indicate the basis for their judgment in individual instances when important factors other than the appendnd reports played a significant part. The publication of this information would nt, of course, still all criticism, but it would obviate much of the criticism which is based upon unfamiliarity with the manner ia which a decision is made. It is paradoxi cal, that the greater the need for a thresh old limit (ia terms of the numbers of individaak actually being exposed, and the eveaity of exposure) the greater the justifleatina for accepting a tentative standard oa inadequate aad incomplete information. This practice is defensible, of course, only ** initial guiding limit is continuously and critically tested by a competent clinical study of the exposed people. Sources of Information 'THE two geneeal sources from which sigL nificant information is developed are the experimental laboratory where the exposure is deliberate, and the actual plant operation, where the exposure is incidental (sometimes accidental). The establishing of threshold limits depends increasingly upon a balance of information developed from both these areas. The more complete the laboratory in vestigation, the greater the security of the tentative standard for plant exposures. The inherent uncertainty of extrapolation from the experimental data necessarily places the final judgment upon the clinical evaluation of the exposed workmen. Industrial hygiene laboratory methods run a gamut from the simple, preliminary "screening" procedure using a few small animals to a relatively involved, carefully controlled, clinical experiment in which human subjects are deliberately exposed to a toxic agent. The studies with lower species should define a range from minimal or no effect through severe injury and lethality, and should indicate the various physiologi cal and pathological mechanisms of injury. The exposure levels for the human subjects usually attempt to define levels associated with "discomfort," "minimal," and "earliest reversible" effects. There is no formula at present by which it is possible to estimate the pattern or amount of laboratory experimentation which will be required of this component in estab lishing a threshold limit. In general, the more novel the physico-chemical properties of the agent, the more distantly related to other materials which have had industrial hygiene evaluation, the greater the amount and variety of toxicological procedures which must be employed. The direction and extent of further studies must be deter mined as the pattern of toxicological investi gation unfolds. The importance of the vari ous routes of absorption, the relationship of divided dose administration to the single ef fective do3e, the relative primary irritation and sensitization potencies, the behavior in relation to such factors as species of test animal, age, sex, concurrent disease, are only a few of the important items which ST 0853694 282 September, 1958 must be considered in deciding the im portance of the role which a particular ani mal study may play. Seme of the experimental toxicological findings which suggest caution in evaluat ing a study may be noted. A lethal dose curve whose slope is gradual may overlap the curve of the physiological function upon which the threshold is to be based. A scat tered configuration of delayed deaths sug gests multiple effects or secondary pathology which may be difficult to evaluate. A sub stance which is a sensitizer or allergen, even though indicated solely by skin sensitiza tion tests, may produce systemic or specific internal organ sensitization. Marked vari ance with respect to severe injury or lethali ty among several species of test animals, in creases the difficulty of extrapolation. The failure to reproduce the disease pattern already identified in human subjects defi nitely limits the significance of animal studies. Less clearly identified effects, such as involvement of the central nervous sys tem, or injury which is not easily reversible, such as aplastic anemia, signal caution. Experimental methods with deliberate ex posure of human subjects to low levels of a toxic agent are finding increasing useful ness in establishing threshold limits. Ini tially, many of these tests were concerned with irritation or discomfort levels, and although no injurious effects were noted in animals exposed to higher concentrations, the human experiment values were frequent ly the determining factor in setting a thresh old limit. A possible fallacy in this reason ing lies in the quite common experience of finding conditions in plant operations which are quite irritating or uncomfortable to a person first entering the environment but which are tolerated without complaint--or even, in some cases, with a positive expres sion of benefit--by the acclimated work men. In such an instance it is difficult to de cide which result is significant, the con trolled short-term study using, usually, sub jects whose experience with industrial con ditions may be very limited, or the testi monial evidence of workmen, especially if unsupported by evidence which confirms the absence of injurious effects. Other applications of the controlled hu man-subject experiments may develop more important information. The studies of re tention of a toxin (with the long-term in vestigations of lead and fluorine as classic examples) must play an important role in the establishment of threshold limits for these substances. The obvious advantage in this technique lies in the accuracy with which the relation can be established, as contrasted with the more difficultly con trolled experience in the plant. More of these studies on a long-term basis are needed, but the cost in effort and in dollars imposes dis tinct limitations. This type of experimental approach is of value in determining the earliest (and still reversible) changes in certain physiologic functions, such as vascular instability as measured by blood pressure changes, or metabolite excretion, as in the urine sulfate partition with benzol absorption. The ob jective, of course, is to recognize a reversi ble, functional change which, if unchecked, may lead to permanent injury. A practical difficulty may develop as the acuity of test procedures increases, since the changes fre quently are not specific for the toxin but may occur with many other factors which affect the body--as for example, an excess of alcohol. On the other hand, special applica tion of statistical methods to group ex posures may make these techniques one of the most acute methods of signaling injury. Value of Data on Worker Exposures 'J'HE concept that a careful and compreL hensive study ol' the exposed workmen is the most significant factor in establishing a threshold limit, merits repetition. In prac tice, however, the number of substances for which such complete studies have been re ported are few. A number of factors operate against such long-term, comprehensive in vestigations. The cost of an adequate clini cal program, carried on over many years and with continuing negative results, re quires the support of an unusually intelli gent and understanding management. The development of environmental measure ments so as to be effective for correlation with the clinical findings requires a high degree of cooperation and planning between clinical and industrial hygiene activities. And, finally, the job of organizing the ex tensive data, of deciding that the results are significant, particularly if they are negative in the sense that no injury is found, and Industrial Hygiene Quarterly ST0853695 X8S of preparing for publication (since there is no Journal of Negative Data), demands of an investigator courage to the point of be ing foolhardy. Of the various types of information which can be obtained from actual industrial ex posures, the unsupported testimony of work men and supervisors, even though accom panied by accurate measurements of en vironmental factors, is generally so un reliable as to merit little weight in establish ing a threshold limit. Individuals who are unable to tolerate the work conditions, or those who have actually become ill and left the job, may have been eliminated so gradu ally that recognition of the cause and effect relationship may not have developed in the remaining personnel. Furthermore, human nature is such that under these circum stances the men remaining on the job are apt to dismiss the others who left as being "too weak to take it." As in the case of planning a program of experimental laboratory methods for evalu ating a toxic agent, the in-plant clinical sur vey and environmental analysis must develop in relation to the specific hazard. To the basic elements in the medical examination may be added a variety of special test proce dures selected to detect the earliest changes in physiologic function. If little is known about the kind of toxic reaction which may develop, a "shot-gun" approach may be justified with the hope that one or more of the battery of tests will signal a harmful ef fect. As knowledge of the earliest reactions to specific agents increases, the selection of the most sensitive test procedures becomes more practical, and more reassuring. The recognition of an occupational dis ease is frequently much simpler than the proof that a particular exposure is free from any injurious effect. As exposures to toxic materials are decreased from levels which can injure in a relatively short time, a point is reached where the signs and symp toms may develop only after a very long ex posure time, and the disease so mild as to challenge the best diagnostic program. We can note again the studies with radiation, where minimal shortening of the life span with relatively low exposures can be demon strated in experimental animals but would be impossible to detect, with our present techniques, in the human subject. Clinical Observations 'The broadeb the base of the clinical inA veetigation which is associated with a finding of no injury or no significant injury at a particular exposure level, the greater the reliability of the conclusion. To the critical investigator, however, the job is never complete, never without some area in the study which could not have been strengthened or improved. The period of the study can extend into many years, and yet the end point can remain uncertain. As other techniques are added to the evaluation program--such as studies of morbidity and absenteeism, reasons for dis pensary visits, and analysis of cause of death--the problem of interpretation be comes increasingly complicated. An example may be cited in which two young women em ployees in the same small department developed leukemia within a few months of each other. This occurrence was readily accepted as a chance finding because both girls had clerical positions with no possible exposure to an industrial toxin. Had this oc curred following a common exposure, how ever brief or minor, to a new chemical with a long and unfamiliar name, it is quite like ly that medical testimony would have been developed, in a Workmen's Compensation hearing, attributing the disease to the ex posure. The effect of the incident might well have extended beyond the cost of compensa tion and into the area of threshold limits by the publication of a case report. A fine discretion is required in recognizing the first or isolated instances of injury to a new chemical and yet avoiding the inclusion of cases solely on legal or social motivation. In a study of the long-term effects of a solvent, records were kept of the causes for dispensary visits. A slightly higher in cidence of gastrointestinal complaints was found in the exposed group, and since this had been reported previously by others, it seemed significant. However, the incidence of respiratory complaints was as much lower.for the exposed individuals. In an in terpretation, it would have been equally proper to assume that the solvent vapors "protected" the individuals against respira tory disease, and that this beneficial effect might offset the gastrointestinal difficulties. As might be suspected, when these relations were put to the test of statistical signifi- ST0853696 m September, 1956 cance, both could have been due easily to chance alone. A final word is in order concerning the methods for developing data by which the environment is described--the conditions of exposure. As much variability can be, and is, encountered with this function as with the methods for laboratory experimentation and in-plant clinical examinations. The ac curacy and reliability of the analytical tech niques, the relation of the time and site of sampling to the true exposure, the presence of other agents which might modify the single action of the toxin under study are some of the many factors which must be critically examined in the light of their usefulness for correlation with a given set of experimental or clinical findings. It is obvious that there is no single method or pattern of methods which can satisfy the varied requirements for estab lishing threshold limits. It is equally obvious that even though rigid standards were de scribed which would satisfy a discriminat ing jury of scientists, the available data for establishing threshold limits for all but a very few substances would fail to satisfy such limits. The real use for threshold lim its, as a guide for industry in the control of exposures and as a measure for action by governmental agencies, demands a con tinuing improvement in the quality and quantity of the methods by which truly valid criteria may be achieved. Prepared Discussion their needed contributions (which was far from Dr. Stemer'B intention) or depress the more experienced contributors, it should be immediately pointed out that there are at least two practical and very helpful means of overcoming certain deficiencies inherent in the basic data. One is the safety factor, the other, the periodic re-evaluation of the threshold limit values. The safety factor has been built into most of the values in the threshold limits list.* The factors 2, 5, 10 or even greater have been applied to some values. There are, of course, some notable exceptions, such as the present value for trichloroethylene, for which the threshold limit is the absolute ceiling, but generally such instances are rare. In general, the greater the uncertainty in the data's appli cability to human industrial exposure, the larger the factor applied. This lowering of the limit value by an arbitrary safety factor may at times provoke some controversy, be cause now the value becomes one of opinion, not fact. Be that as it may, the safety factor incorporated in the air standards gives in creased assurance of safety to many doubt ful values. The re-examination of the listed values by the committee provides annually for read justment of all values, whatever their sanc tity, upon submission to the committee of new and experimentally supported findings. Repeated scrutiny and re-appraisal of this sort can lead finally only to assignment of safe values on which complete reliance can be placed. The committee welcomes all such information.** HERBERT E. STOKINGER. Ph.D. Need for more Data Chief, Toxicological Services Public Health Service Cincinnati, Ohio JN THIS CONNECTION another point implied 1 in Dr. Sterner'a discussion should be strengthened--namely, the need for more data substantiating the choice of safe ex posure levels based on industrial experience. DR. sterner has discussed the great diffi Much useful information is undoubtedly in culties attendant on developing ade the files of many plants. Indication of this quate data for threshold limits, the manywas the fine evidence on six industrial sub- imponderables in their interpretation, and . their unsatisfactory and necessarily always 'The incorporated safety factor in the threshold limit values, although added at times because of uncertainty incomplete nature. All these considerations in the value as related to human exposure, often actually should certainly be thoughtfully considered and strongly stressed, because errors in judgment cannot be afforded. But lest these provides an appreciable margin of safety. For this reason the correctness of the term "threshold limit" may be questioned. It might more properly be replaced with "air hygiene standard." many considerations seem so formidable to many potential investigators as to prevent "Allan Colemsn, Chairman Threshold Limits Commit' tee. ACGIH. Connecticut State Department of Health. Hartford 1, Connecticut. Induetrial Hygiene Quarterly ST 0853697 85 stances derived from many years of plant experience that came to light last year at these meetings from the presentation of Herbert J. Weber.*1 Others should have similar material that should be brought to the attention of the Threshold Limits Com mittee. Like Weber's material, all of it need sot be novel or presented to show need for changing existing limits; equally valuable are data confirming existing limits. As never before, interest in the value of the control of industrial environments is being shared by management generally. Greater numbers of industrial hygienists than ever before are being engaged by industry. Is it too much to hope that meetings such as these will orient the thinking of properly placed industrial hygienists to secure much needed plant in formation to aid in the choice of safe lim its of human exposure? The type of information needed may be listed as follows: (1) Air concentrations should be determined for the substances under study through a complete cycle of plant operations and with reasonable regu larity in order to obtain a true picture of the range and fluctuations of exposure. (2) The data should have good accuracy. (3) The observations should be carried out over a reasonable period of time--a minimum of five years. (4) The air concentration data should be correlated with a good medical program. A pattern for such work is that of Dr. Stemer's 10-year study of workers exposure to butyl alcohol.2 There is a real need for more data based on industrial experience. The often-heard statement "the threshold limits are nothing but educated guesses" unquestionably re flects the wish at least that more data be firmly based on industrial experience to sub stantiate the choice of limits. As a member of the Threshold Limits Committee, I was concerned over the statement and took the trouble to review each substance in the threshold limit list for 1955 as to the basis for choice of the level. The results are shown in Table I. It is possible that everyone would not arrive at precisely the same figures, but I believe that their magnitude would not be much altered. Although the table shows that the educated guesses account for a relative ly small number, it does confirm the often expressed feeling of the need for more solidly based levels. Table I shows a number Table I. Basis for Choice of Threshold Limit Value* Study Typ* No. of Listings Ptrctat Total Liatlnta <sa> Animal Industry Animal ft Industry Man "Educated Guess" Animal ft Man 94 41 51 IS 23 10 26 11 21 4 Source uncertain S1 'Based in part on Cook* W. A., /uL 14:9U, 194, and from documented material of Threshold Limits Com mittee A.C.G.I.H. 1953-1655. of other interesting facts: (1) that most of the values have some sort of scientific basis; (2) that each level has been documented either by Warren A. Cook,3 or by the Com mittee on Threshold Limits; (3) that tbi values based on animal experiments account for the largest number, 42%; but (4) that values having some industrial basis account for 1/3 of the total. The values ascribed to the "man" cate gory arise from two sources--that of Nel son, et al,4 and those more recent publica tions of the Dow Chemical workers, Irish, Rowe, Spencer, Adams et al. The "Educated Guess" A few words should be said in defense of 1 the "educated guess." A review of the values described as guesses indicates in the instances in which sound information has later become available that the "guess" was remarkably good. Two prominent examples only will suffice--hydrogen fluoride and uranium. A safe exposure level for hydro gen fluoride was set at 3 ppm on the very limited evidence supplied by a study in ani mals by Ronzani in 1909.'* Last year a report'1 culminating many years of study of fluoride exposure in the aluminum industry, involving thousands of air and urine analy sis for fluoride and studies of roentgenographic changes in bone, showed without question that air levels double the accepted limit gave rise to perceptible changes in bone in only a few individuals, and only after many years of exposure, thus vali dating the wisdom of this "educated guess." In the case of uranium, an engineering bench-mark had to be "guessed" at early in the days of the Manhattan Project. After a ST0853698 286 September, 1956 review of the quite limited animal data on uranium then available, Dr. Stafford Warren suggested that the "safe" exposure level for uranium be the same as that for lead, 0.15 mg/cu.m. After ?500,000 and many years had been spent in research, the safe levels of exposure to uranium compounds were found to bracket this value very closely. Levels for Cancerigens '"There is still one group of substances for x which some method should be devised for establishing safe air standards--the indus trial cancerigens. How shall we establish the limits for this type of substance? Thus far the question has been sidestepped com pletely. As a result, with one exception, nickel carbonyl, limits taking into consider ation potential cancerigenicity have not been assigned. Several industrial substances are known or suspected cancerigens; many more are suspect on the basis of animal ex periments. As a suggested method of ap proach, the following is offered: To the level judged safe for other types of systemic in jury add a safety factor for carcinogenicity. The magnitude of the safety factor is sug gested to be from 100 to 500. This provides at least a second power of 10, which, from the well-known dosage-response hypothesis, provides at least a fourfold longer interval before effects may be expected to occur, or conversely at least a response with Vi the intensity. This manner of approach has been used for nickel carbonyl. A tentatively safe level for systemic effects from repeated daily exposure has been set at 0.1 ppm; one- hundredth this level, or 0.001 ppm was set for nickel carbonyl on the basis that nickel poisoning gives rise to a substantial in crease in the incidence of lung cancer. It is realized that unfortunately the safe lim its for all industrial cancerigens cannot be so readily resolved. This is especially true of dye intermediates, such as benzidine and naphthyl amines whose major route of entry is not commonly via the lungs but through the skin and gastrointestinal tract. These are laundry and protective equipment prob lems not solvable by air control. There are undoubtedly substances to which the suggested procedure may not strictly apply, but imperfect as it may be, the suggested method is felt to be a step in the right direction and serves better to curb exposures to industrial carcinogens than considering the problem too difficult to cope with at the present time. References 1. Wkbba. H. J.; Threshold Limits. A Panel DImui- Rion. AlHA Quart,. 16:U. 1968. a.2. Sterner, J. H.. Crouch. H. C., Brock nr**, F.. Cusack. M.: A Tcn-Ternr Study of Butyl AJeohol Ex- posture. AIHA Quart.. 10:63, 1949. Cook. W. A.: Maximum Allowable Concentration! of Industrial Atmospheric Contaminants. Ind. Med., M :93. 1945. 4. NkL3on, K. W., Ece, J. F.. Ross. M., Woodman, L. F.. Silvkrman. L.; Sensory Response To Certain Indus trial Solvents. J. Ind. Hyg. A Toxie.. 26:282, 1943. 5. Ronkani. E.: Uber der Einfluss der Einitmungen von reisenden Casen der Industrie!) auf die Schutxkraffe Her Organ ism us gegentiber Her infektiven Krankhelten. A rrh. f. Hyg.. 70:217. 1909. *>. Irwin, D. A.: Clinical Findimrs Which Can be An ticipated After Long-Continued Exposure to Fluorides. Presented before Symposium on Fluorine, Kettering Laboratories. Cincinnati. Ohio, May. 1964. Engineering and Chemical Application of Standards ALLEN D. BRANDT, Sc.D. Bethlehem Steel Company, Bethlehem, Pennsylvania The why and how of threshold limits for To engineers engaged in industrial hy air contaminants have been discussed by, giene, threshold limits provide the reference the preceding speakers. The logical nextline or bench mark upon which all considera and final consideration is the use or applica tions and calculations for the control of air tion of these limits in preventing occupa contamination are based. It is characteristic tional diseases, in avoiding complaints from of engineers and of others in the physical exposed employees, in maintaining employee sciences to want to reduce to numbers the efficiency, and in promoting good house problems with which they deal, because only keeping. then can they be attacked in a precise man- Industrial Hygiene Quarterly ST 0853699 887 ner. It has never been clear in my mind whether engineers enter this profession be cause of their love for and adeptness with numbers, or whether they acquire their de sire to work with numbers as a result of pursuing the engineering discipline. Nor Is it important to the subject matter of this paper to know which is the cause and which the effect Suffice it to recognize at this time that this quality is omnipresent in engi neers, and if industrial health problems arising out of environmental conditions are to be prevented or controlled, the physiologi cal responses of the industrial employees will have to be translated into some physical yardstick readily understood by engineers whose function it is to regulate the environ ment in the best interests of the worker and of production. Threshold limits serve several very use ful purposes in the industrial health picture. Through careful studies of the air at exist ing operations or in existing plants, they permit deciding whether a health hazard is present or not, and if present, how severe it is. They are quite useful to the discern ing physician in determining whether the health impairment of an exposed worker is attributable to his employment, and in this respect may exert significant influence on the disposition of occupational disease claims. Where a health hazard from air con tamination has been found to exist, thresh old limits frequently are the guidepost indi cating which avenue of control to follow to achieve a satisfactory solution to the prob lem. Having ascertained the avenue to fol low, the threshold limits provide the only scientific basis as to how far we must jour ney to arrive at the desired destination. Having alluded briefly to the principal roles played by threshold limits in industrial hygiene, let us now examine each one of these more carefully and consider their ap plication in industry. Evaluating Potential Health Hazards JN this age of mechanization and high speed production, there are many places in industry where some of the materials be ing handled, consumed, or processed escapes into the air. Whether this airborne con taminant constitutes a health hazard de pends upon its concentration in the air breathed by exposed persons as related to its inherent harmfulness. The concentra tion of the material in question in the breathing zones of employees is capable of rather accurate measurement. If the harm fulness of the contaminant is known, also, in terms of a safe atmospheric concentra tion (the threshold limit), the presence or absence of a health hazard is apparent. In this way threshold limits are applied widely in industry to decide where better control of the environment is needed and where it is not needed. Assisting in the Diagnosis of Illness "MiOT infrequently, there is a discouragN ing duplicity of symptoms manifested by persons suffering from different illnesses, especially in the early stages. If the symp toms exhibited by an employee are compati ble with those that might be produced by the air contaminant to which he has been ex posed as well as with several other stimuli of non-occupational origin, comparison of the concentration to which he actually was exposed with an accepted threshold limit for this same material is of inestimable value in arriving at the most probable cause of the illness. If the exposure exceeds the thresh old limit and the symptoms are indicative of illness from such exposure, the occupa tional hazard may well be the cause. If, how ever, the atmospheric concentration of con taminant in the breathing zone of the worker has been well below the threshold limit, it suggests to the examining physi cian that all other possible causes must be explored thoroughly before a diagnosis can be made. This application of threshold limits some times reaches out into the compensation courts. The employee's personal physician, having only the complainant's description of his job rather than factual data to guide him in the diagnosis, not infrequently will arrive at an erroneous conclusion. Contro versial medical opinions are introduced in evidence at the hearing, and the carefully measured atmospheric concentration of the material in question as compared to the threshold limit for this material is the only bit of uncontested scientific informa tion that the referee has available on which to decide the case. This is not to say that the controverted cases usually are decided on I ST 0853700 288 September, 1958 ;kV ' this basis. Qther factors, many of which are How much simpler it is with threshold not scientific in nature, play a part in the limits to provide a scientific basis for con adjudication of such compensation cases. sideration. Obviously the exhaust system Nevertheless, testimony of this kind has could be redesigned to capture all the vapor been helpful in arriving at the truth in Borne rising from the tank surface and from the cases, and there is hope that an increasing withdrawn parts. This would have the seri amount of importance will be attached in ous disadvantage of increasing markedly the . --'t y;- the future by compensation courts to evi consumption rate of the solvent, carbon dence of this kind, as more and more experi tetrachloride. Since methyl chloroform has ence is accumulated to support the threshold physical characteristics very similar to car !>: limits and as knowledge of this useful tool bon tetrachloride, if it were used instead of becomes more common in compensation carbon tetrachloride the atmospheric con v- circles. centration of vapor would be about the same, and since the threshold limit for methyl Control of the Hazard chloroform is 600 ppm, the problem would tt is in the control of atmospheric contami- be solved. However, this solution carries 1 nants that threshold limits find their most with it a substantial cost disadvantage, important application in industry. The methyl chloroform being more expensive judicious use of threshold limits in selecting than carbon tetrachloride. Therefore, let's and designing control measures and equip consider using trichloroethylene or per- ment will result in satisfactory working con chloroethylene in place of carbon tetra ditions at a minimum in cost and interfer chloride. It too costs more than carbon tetra ence with production. Possibly the best way chloride, but because of its lower volatility to add clarity and reality to this general ob the consumption rate will decrease if much servation is to implement it with conspicu of the loss takes place via the air entering ous examples. the exhaust system. But what about solving Given: a production type degreasing op the health hazard. The threshold limit for eration in which the parts are cleaned trichloroethylene and for perchloroethylene mechanically by immersion in a tank of car is 200 ppm and the vapor concentration was bon tetrachloride. The tank is provided with found to be in the order of 250 ppm when a local exhaust system, but is so wide that carbon tetrachloride was used. Because of considerable of the grossly contaminated air the lower vapor pressure of the proposed at the remote side is spilling into the work substitutes, the amount of vapor getting room air and nearby employees are exposed into the room air will be much less and the to vapor concentrations in the order of exposure of the workers will be reduced to 250 ppm. Problem: how best to correct this a value well below 200 ppm. Thus by em condition. ploying the yardstick of threshold limits, Obviously the condition can be corrected two easy and certain solutions are found to by rebuilding the exhaust system and in this problem without difficulty. creasing its capacity, or by changing to a It may be well to emphasize at this point less toxic solvent. Imagine how insecure that other important considerations must you would feel in facing this problem if not be overlooked. All factors must be borne ;r :r there were no threshold limits to guide you. in mind whenever one is faced with an air You would not have any idea how much re contaminant control problem. Sometimes duction in vapor concentration is necessary careful selection of a substitute will not to eliminate the health hazard. Even if a less not only bring the health hazard under toxic solvent were substituted, there would control but also will increase the op- be no way of knowing whether it alone will # erating rate, or decrease the consumption solve the problem or whether improved rate of a process ingredient thereby achiev process ventilation is needed, and if an in ing considerable cost advantage as a by creased exhaust rate is needed, how much product of the change. By way of illustra increase is required. To be on the safe side tion, the slower evaporation rate of per you probably would change to a safer sol chloroethylene as compared with carbon vent and redesign the exhaust system with tetrachloride not only minimized the poten 100% capture as your goal. tial health hazard at a specific gravity test- Industrial Hygiene Quarterly ST085370I 289 in? operation but also resulted in an an* nual savin? of about $3000 in the cost of the liquid consumed. This, in spite of the fact that perchloroethylene is much more ex pensive per unit of measure than is carbon tetrachloride. Criteria in Substitution 'T'KE application of threshold limits in the A control of health hazards by substitution is such a useful tool that several other ex amples will be cited. Solvent de?reasers and cleaners are used so widely, and frequently so erratically, that it is difficult to be certain that adequate control precautions are bein? observed at all times, especially if the solvent in ques tion is relatively toxic. For this reason in dustry is en?a?ed in a search for effective solvent cleaners which inherently are much lees toxic than those in common use today. Because carbon tetrachloride has qualities which make it an exceptionally satisfactory solvent from the functional viewpoint, it is in constant demand by all operating people who are not fully aware of its danger. How ever, reputable jobbers and vendors of pro prietary solvents of all kinds have become increasingly conscious of the health con siderations attending the use of their prod ucts and have been selecting their product ingredients on the basis of toxicity ex pressed in terms of threshold limits. It is heartening to note how commonly the sup pliers of solvent degreasers and cleaners are using the valuable yardstick of threshold limits to concoct ever safer products to sat isfy the complex degreasing and cleaning demands of industry. It appears to us that we are on the door step of a new era which will see great ad vances in solvent cleaning safety, thanks to threshold limits. It would be remiss at this time not to mention that methyl chloroform promises to be the carbon tetrachloride of tomorrow. If properly inhibited to prevent its corrosive action on certain metals, it appears to be the perfect answer for those cleaning and degreasing jobs on which only carbon tetrachiuride has been acceptable in the past. Threshold limits have played and continue to play a key role in the control of the hazard associated with abrasive blasting of all kinds. Originally, sand was used for all abrasive blasting. This created a serious health hazard on the part of the operators and nearby employees, and not infrequently it posed a serious wear problem on nearby machinery which had not been protected during the blasting. The problem was soon brought under control for most productiontype blasting by housing such operations in well ventilated rooms, chambers or booths. In addition, steel grit was substituted for sand on most work of this kind if the grit was recoverable and reusable. Because of the high cost of steel grit as compared with sand, it was not readily accepted for work in which most or all of the grit was lost. More recently, however, several types of grit have been placed on the market which are by-products of the metal smelting and refining industry. While not as economical as sand, they are much leas expensive than steel grit. These substitute blasting grits came into use because the probable health hazard attending their use is much less than is the case with sand, in terms of the threshold limits of the ingredients and the amounts present. Selection of the particular by-product grit to be used on any blast cleaning job is made on the basis of avail ability and the probable health hazard as ex pressed by the threshold limits of the in gredients and the amounts present. But the application of threshold limits on abrasive blast cleaning jobs does not end here. Since most blast cleaning jobs are not done mechanically in well ventilated booths and require respiratory protection for the operator, threshold limits enter the con sideration as to the proper respirator to be worn. Supplied-air respirators or helmets require a supply of air of respirable quality under pressure. Consequently for isolated jobs where a separate blower or semi-com pressor would be required to furnish air to the respirator, conventional dust respirators of the mechanical filter type may provide adequate respiratory protection depending upon the harmfulness of the dust produced as determined by the threshold limits of the grit ingredient and those of the surface be ing cleaned. In reverse order, of course, sand may be used with safety if the blaster can conveniently wear a supplied-air helmet and a source of respirable air for the res pirator is readily available. It must not be inferred from the fore- ST0853702 290 September, 1956 going that threshold limits per se of a process material or the ingredients thereof determine the extent of a health hazard. The atmospheric concentration of the contami nant in the air to which the employee is ex posed is equally important. But when con sidering a type, or class, of operations in which the employee's exposure does not vary tremendously, as a rule, from one operation to another, substantial changes in the threshold limits of the process material in gredients overshadow the smaller variations that take place in atmospheric concentration of the contaminant. This is not to say that all abrasive blasting operations produce the same concentration of dust in the ambient air, but rather that, all other things being equal, a change in the nature of the blasting material will not affect the dust concen tration nearby as profoundly as it will the applicable threshold limit, if the sub stitute material is well chosen. For ex ample, it is extremely unlikely that steel grit or even a substitute grit pro duced as a by-product in the glass or in the smelting industry and containing less than 5% free silica would create as severe a hazard as does sand in blast cleaning of unpainted surfaces. Obviously, if painted surfaces are blast-cleaned, a new factor en ters the picture which may well overshadow the composition of the grit. However, here again threshold limits would be consulted in conjunction with the dust concentration to determine (11 the severity of the health hazard, (2) whether there is any advantage in using a more expensive substitute grit, and <3) what is required in the way of personal protection. Threshold limits are especially useful in designing for the control of air contami nants in all cases where the sources are of such nature, location and distribution as to permit effective control by general ventila tion. In the case of solvents or other liquids being used in a room, the required ventila tion rate can be calculated very easily if the consumption rate of the liquids is knowp. The same is true for particulate matter if the rate of dust generation is known, or if information is available as to the dust con centration and ventilation rate prevailing at a comparable operation elsewhere. By em ploying the threshold limit for the dust in question, the ventilation for the operation under consideration can be calculated readi ly, rather than guessing what it should be or following some rule of thumb. In all existing shops or rooms where air contami nants are present in objectionable concen tration, the threshold limit of the contami nants in conjunction with the current gen eral ventilation rate (which can be meas ured) permits calculating accurately what is needed in the way of fans to eliminate the objectionable or potentially harmful condi tions. Threshold limits remove much of the conjecture otherwise involved in problems of general ventilation for purposes of dust, fume and gas control. Classification of Material for Control Purposes jCVEN though it is desirable to consider each problem separately, not infrequent ly it is expeditious to set down rules govern ing the control of hazards created by many operations that differ considerably in type. In such instances the toxicity of the process materials and the by-products in terms of their threshold limits may be grouped and used in conjunction with similar groupings of the other variable factors influencing the hazard, to arrive at a set of relatively few rules to cover the whole gamut of operations in question. For example, let us consider open-surface tank operations of all kinds, whether they be pickling, degreasing, alkalicleaning, painting, plating or other treat ment. By dividing all the materials involved in these operations into three groups accord ing to their threshold limits and into similar groups on the basis of the other governing factors, it was possible to classify all possi ble types of open-surface tank operations into four classes as regards the ventilation rate required at the tank for adequate con trol of the contaminants released.12 With out threshold limits to serve as a guide it would have been well nigh impossible to develop these few rules governing so many different materials and operations. Similar codification is under considera tion by American Standards Association Committee Z-9--Exhaust Systems--for other groups of processes and operations having like industrial hygiene aspects, as, for example, bulk materials handling, sur face coating operations, mechanical cutting and abrading operations, and abrasive blast ing operations. Without threshold limits, Industrial Hygiene Quarterly ST0853703 m guch codification would be beset with un ending research, consultation and guesswork of such magnitude as to make consummation dubious and as to place the final result under serious suspicion. Experience 'T'HEBE is much merit in the proverb "the 1 taste of the pudding is in the eating." Therefore, past experience may well be ex amined in the use of industrial hygiene standards to prevent occupational illnesses. In this respect, the literature is most dis appointing, not because the experience has been unfavorable but rather because the literature contains few reports of first hand investigations into this relationship. The one which probably best demonstrates the use of threshold limits and the results achieved may be found in the report by Mc Connell, et al., on the occupational disease experience in the government-owned ord nance plants during World War II.1 Since it was my privilege to take part in this pro gram from its inception, I can speak of it with some feeling. When the United States first began am munition production at an increased rate about 1940, very little information was available on the toxicity of TNT of such na ture that would permit setting a threshold limit. TNT consumption in the U. S. in the period between 1918 and 1940 was es sentially nil and threshold limits were not nearly so common as they are now. That TNT is toxic was not questioned, for ac cording to the best information available about 17,000 persons in ammunition plants were poisoned, 475 of them fatally, during World War I. It was this sad experience coupled with the related problems of absen teeism, inefficiency and manpower shortage that led the War Department to undertake jointly with the U.S. Public Health Service an aggressive industrial health program in all ammunition plants. Inasmuch as the most serious potential problem was TNT, it was decided at the outset to conjure up a maximum allowable concentration for this substance, the standard to be based on the little information available as to its toxicity, comparative physiology, and the concentra tion that was known to be achievable by good engineering practice. This "educated guess" turned out to be 1.5 mg/m-1, a value still in common use. Reference to the report by McConnell, et al., shows how closely the in cidence of illness from TNT paralleled the exposure curve. Owing to the tremendous scarcity of the equipment needed for engi neering control of the fumes and dust, such as motors, fans, and sheet metal for piping and hoods, the weighted-average level of 1.5 mg/m-1 was not reached until the latter part of 1944. However, the fatalities from TNT were held to 22 for the entire period of the war4 and the total number of lost time cases was only 56 as of May 1, 1945, the end of the report period covered in reference 3. The incidence of early symptoms of TNT poisoning was quite high, and there is little doubt that the number of lost-time cases as well as fatalities would have been much higher if it had not been for the excellent periodic medical examination program then in effect in the ammunition plants, especial ly in the loading plants where the exposures were the worst. It is interesting to note that the case rate of early systemic effects was close to 500 per 1000 man years of exposure for the first six months of 1943 when the weighted average exposure to TNT was about 2.7 mg/m-1, and about 1/5 of this rate for the last six months of 1944 when the ex posure had been reduced to about 1.4 mg/m-1. The control program in the ordnance plants during World War II would have been inestimably more difficult, and there is little doubt in my mind that the final report would portray a different story, a much sadder one, from that told by McConnell, et al., if there had been no standard for TNT. In the face of the dire shortages of equip ment needed directly by the Armed Forces, and other equipment needed to produce the weapons of war, authorization to divert some of this material for dust control pur poses would have been out of the question in the absence of a threshold limit to indi cate how badly and where such equipment was needed. As in many other factors af fecting our daily life, standards are the very foundation of industrial hygiene. Without them the engineer in this field is placed in the same position as the boy who is sent to the hardware store by his father to buy a "big" bolt. The boy would have as good a chance of getting a bolt of the right size as an engineer would have of preventing the vast majority of occupational illnesses and .i 'ST0853704 298 September, 1956 complaints if there were no threshold limits. In conclusion a few remarks are in order dealing with the philosophy of and justifica tion for threshold limits, and are added here because they serve as* a reply to the criti cisms often leveled at Industrial hygiene standards. It is not unusual to hear that these limits are useless, if not even dangerous, because in the event that the atmospheric concen tration is measured inaccurately, reliance on the standards creates a false sense of se curity on the one hand, or needless alarm on the other, depending upon whether the measured result is in error downward or upward. It requires little mental gymnastics to realize that this is equivalent to con cluding that there is no sense in asking your grocer for a dozen oranges simply because he may make a mistake in counting them. By definition, threshold limits are those concen trations of contaminants which in the light of current knowledge will not cause harm to persons exposed continuously day in and day out during the normal working hours. Reference is to the concentration actually existing, not to some value that the investi gator might conclude exists. Concentrations can be measured accurately, but to do so re quires skill, understanding, patience and energy. It is rather discouraging to note how frequently conclusions are based on wholly inadequate data. It is not surprising either that the concentrations frequently "measured" have little relation to the true weighted average concentration. The philosophy of threshold limits is that each one represents a concentration of the substance in question that will have no demonstrable adverse effect on the health of exposed persons. Not all persons react the same to stimuli of this nature, but rather any given population follows approximate ly an average random distribution pattern as regards response to atmospheric contami nants. That is to say, there is an occasional person at one end of the curve who is un affected by relatively overwhelming concen trations and there is an occasional person at the other end who is affected by extreme ly low concentrations. To prevent any ad verse effect upon every last man may require such low concentrations as to be impractic able. The threshold limit is merely a con centration that intersects the random dis tribution curve at a very low point. How low this point is for any substance cannot be stated. That it is not the same for all ma terials is obvious, and that it serves to pre vent harm to all but a relatively few is obvious, also. Serious or irreparable damage to the occasional person who falls to the left of the threshold limit on the random dis tribution curve can be avoided by an appro priate medical examination program. References 1. American Standards Association: Safety Coda for Ventilation and Operation of Open 8urface Tanks. Z-9.1, New York. 1961. 2. Biandt. A. D.: Exhaust Systems. Electroplating Engineering Handbook, Chapter 27, Reinhoid Publishing Corporation. New York, 1966. Z. MoConnill. W. J., Funk. R. H., and Bpamot, A. D.: Occupational Diseases in Government-Owned Ord nance Explosives Plants. Oecup. Mod. 1:661-616. June. 1946. 4. McConnell. W. j., end Funn, R. H.: Summary of Twenty-Two Trinitrotoluene Fatalities In World War II. J. InduMt. H*q. & Toxic., 28:76-86, May. 1946. Prepared Discussion ARTHUR C. STERN, Chief Air Pollution Community Program Robert A. Taft Sanitary Engineering Center U.S. Public Health Service Cincinnati, Ohio IN an endeavor to safeguard the health of the worker and the public from exposure to harmful substances, two basically differ ent types of standards have evolved. One type--the threshold limit, or maximum al lowable concentration--is the performancetype of standard. The other, about which little has been said by the previous speakers, is the engineering type of standard. To make the distinction between the two types of standards more concrete, take the specific example of a stave-type tumbling mill (Fig. 1) in a ferrous foundry. Into it are placed castings with sand both clinging to their outer surfaces and in their internal cavities in the form of cores. The express purpose of placing these castings into the mill is to clean them of this sand. The mill is, therefore, by its very nature, a device designed and operated to cause sand to leave the castings and enter the ambient air. While it is true that most of this sand will Industrial Hygiene Quarterly ST0853705 293 Fig. I. Stm mill. fall to the floor under the mill, it is equally true that a tremendous number of free silica particles will become air-borne by the process. From the viewpoint of the perform ance standard, it is necessary to keep the atmosphere of the cleaning room below the threshold limit for free silica by whatever means the owner of the foundry may choose to employ. Engineering Standards ptOM THE VIEWPOINT of engineering standards, the reasoning is somewhat as fol lows: A. It is widely recognized in the foundry industry that stave mills are bad dust pro ducers and require enclosure. B. The industry, by trial and error, has developed a satisfactory type of ventilated enclosure (Fig. 2) which not only keeps the dust out of the workroom, but also keeps the floor below the mill free of much of the sand that would otherwise accumulate there and have to be carted away. C. This type of enclosure, having been adopted by mo3t of the industry, should therefore become the standard of the entire industry. D. An engineering standard should there fore be written so specifying this enclosure with respect to structure and ventilation that any foundryman building an enclosure meeting these specifications will achieve dust control of his stave mill (Fig. 3). Applicability of Standards J^et us explore some of the arguments for and against each of these approaches. Both aim at the same objective--the safe guarding of the worker. The principal ar gument in favor of the performance stand ard is that it is noboby's business except the owner's as to how he achieves control of the hazard, just so long as he does, in fact, suc ceed in so doing. The corollary argument against the use of the engineering standard is that there is no positive guarantee that once the owner has invested his money in an enclosure conforming to the standard speci fication, the exposure of the workers in the cleaning room will be below threshold limit. The same logic can be used to plead the case for the engineering standard. The dust load in the cleaning room air comes from many sources in addition to the stave mills (Fig. 4). If some of these sources remain uncontrolled after the stave mill has been enclosed and ventilated according to stand ard specification, it is entirely possible, even probable, that duBt concentration in the room will remain above threshold despite entirely satisfactory dust control by the stave mill enclosure. Engineering standards thus have the inherent capacity to allow a step by step orderly approach toward the ultimate goal of achieving below-threshold concentrations in all parts of the plant at all times. New Construction A ssume that a new foundry is being dex signed. To apply performance standards, ST0853106 29i September, 1956 the foundry muat first be built, placed in cleaning room equipment and applying them operation, and then subjected to air sam to the best of his ability. In this situation, pling and analysis. No reputable and well- argument arises, not as to the need for such informed engineer would design this new engineering standards, but rather as to plant without seeking the engineering their accuracy. Should the opening for air standards for the control of dust from the be 3%' or should it be 4"? If the standard says 900 cfm, and the de signer is firmly convinced that 450 cfm are sufficient, he Bhould be prepared to back up his independence of judgment by later proof that concentrations are be low threshold in the com pleted workroom when the lower value of cfm is em ployed. But what if the designer reluctantly makes the ca pacity 900 cfm to conform TUS46LER to the standard? Is there Cuct vetocty '30CDFPM Entry toss `20b 40VPfdetmstt on deign) Duet idtocdy 3300FFM mermen Entry toes term mthlctt-cR025(UDVP Sguore mil side thorn in t* to 24 met 25 MX " EXHAUST VOLUMES Romdedl t.D. netches L9M 24 nctuded 24 - X X -X CFM Tntueon Store* 4X 660 990 600 SCO 960 equal necessity for the sponsors of the standard to guarantee compliance with the threshold limit? The difficulty of so doing in the possible presence of ex traneous sources of the con taminant that have alreadybeen mentioned almost in SitoX ` X - 42 I3X BX variably makes it impossi 37to 42 m 42 46 1750 I7X ble for the sponsor to un 43 to 46 ` 46 - 54 2200 2200 dertake such guarantees. 49 to 54 " X - 60 27X 27X 55 to 60 ' 60 - 66 3300 3300 Double Jeopardy 6! to 66 " X 72 67to 72 ` MFor lengths over 70", increase CFM ttropornonotety 3920 4E00 39a 4600 WfHERE the engineering standard is a tool in the hands of an enforcement Tig. 3. agency, the user of such Tumbling mills. standards frequently fears that he is placed in double jeopardy. He has to comply with engineering standards with which he may dis agree, and then, having em ployed all such standards in every operation, may still be not in compliance with the performance standards. The wise enforcement agency will let it be known that it will not permit such double jeopardy to occur, and that any factory owner Floor plan showing layout of equipment including stava mills. who adheres throughout to Industrial Hygiene Quarterly ST0853707 S95 the best aiiucaim standards known to the agency will not be asked to re-do the job. What, then, is the plight of the working man caught in the middle? Is he likely to become a pawn, farced to work in an unhealthful atmosphere because the sponsor ing agency is unwilling to admit a mistake as to the effectiveness of its engineering standards? We are indeed fortunate that the quality of our engineering standards is so high that such cases occur infrequently. Where they do occur, they are almost always borderline cases with respect to the thresh old limit and are well within the factor of safety built into the threshold limit itself. Euiifdan Standards *t*he gELSTioKSHir between performance x and engineering standards for in-plant atmospheres has its counterpart in that be tween atmospheric and emission standards in the field of air pollution. A major dif ference is that, whereas there are a large number of accepted threshold limits for inplant atmosphere, there are almost no stand ards caamnooly accepted for the outside atmosphere. The emiaskm standard is very much in the same position as the engineering stand ard for in-plant controls in that adherence to it by one specific stack does not guarantee the cleanliness of the air of the surrounding community. Thousands of factories have put in-plant engineering standards to the test and proven that when every source of contaminant release is controlled as specified by the applicable engineering standard, the result has been to maintain the factory atmospheric contaminant concentration be low the threshold limit. Such beautiful demonstrations, which are easy when the atmosphere in question is confined by four walls and a roof, became almost impossible to find in the open air over cities and towns. However, it is reasonable to believe that what works in a small confined space will also eventually work in the largest of con fined spaces, that having the inevitable in version ceiling as a roof and four topo graphical or meteorological side walls. Standard for the Opan Air J^et us uxml once again at the principal argument for performance standard in the in-plant situation, i.e., that it is no body's business but the plant owner's as to how he achieves control of the hazard--so long as he does so. Is this doctrine equally applicable to the air over a city? It hardly seems so. No individual owner or group of owners could or would be willing to take the responsibility for the maintenance of a specified level of contamination of the air of the community in which they operate. They would quickly recognize the many factors over which they do not have the same measure of control that exists inside the factory building. For them, the emis sion standard is a boon. Here the argument is not with the con cept of the emission standard, but with its numerical value for a particular installa tion. One of the most interesting develop ments of the past decade along these lines has been the fact that public utility power plant designers have consistently specified equipment for fly ash control to meet emis sion standards much more stringent than public regulatory bodies have required. In dustrial foresight and conscience is in this, and a number of other industrial hygiene and air pollution control fronts, well ahead of public regulatory demands. Conclusion JN BOTH these areas, this is the hope of the future. The dictum of a Massachusetts court of many years ago that the best plants in an industry may reasonably be used to set the standard for the entire industry provides the real key to future progress. America is blessed with real industrial leadership and statesmanship. Neither in dustry's leaders and statesmen nor the pub lic will tolerate the acceptance of stand ards which are below the best that industry can, by example, provide. Summary 'J'here are two general types of standards --performance type standards and engi neering standards. The former specify threshold limits. The latter specify the per formance of a particular piece of equip ment. Arguments are given pro and con as to the relative merits of these two ap proaches to the same objective--the safe guarding of the worker. The engineering standard approach is particularly valuable in new construction where no equipment ST0853708 296 September, 1956 exists at which to measure atmospheric con centration before designing safeguards. The similarity of engineering standards for the in-plant situation to emission standards for atmospheric pollution control is noted. lead to unfortunate problems of administra tion to which brief reference may be made. Under the constitutions of the various states and the powers granted to state De partments of Health and state Departments of Labor, there exists adequate authority Prepared Discussion for such departments to effectively control any hazardous condition injurious to health. As a practical matter, there is no THEODORE C. WATERS, L L.B. Baltimore, Maryland legal need for the adoption of codes prescrib ing maximum allowable concentrations. It is fair to state that state Departments of Health and state Departments of Labor This comment and discussion of the ex administering divisions of industrial hy cellent paper presented by Dr. Brandt giene have enjoyed the confidence of the will be directed to the legal aspects of thepublic, including both management and application of threshold limits in the form labor, and our several state departments of maximum allowable concentrations for have been and are doing excellent jobs in the control of air contamination. the administration of their affairs. There May I identify myself as one who has fore, the use of maximum allowable concen served as counsel for industrial organiza trations should be in the nature of serv tions ; and while my views may be prejudiced ing as a guide to industry with particular on their behalf, I feel that the industrial reference to engineering standards. Indus point of view is important in our discussion try has and will continue to seek the of this matter. advice of proper state departments to con It is needless to say that today industry is trol hazardous conditions effectively, and prepared and wishes to accept full responsi the desired objectives will be obtained bility for the control of potential hazards through education and dissemination of in incident to employment. Simply stated, it formation through the cooperation between is good business both from the financial state divisions of industrial hygiene and standpoint and also in the promotion of industry rather than the attempted enforce industrial relationships for employers to ment of a given code as a matter of law. concern themselves with the protection of Dr. Brandt and Mr. Stern have discussed employees from all types of industrial in in detail the practical uses of threshold lim juries, be they accidental or resulting from its with the purpose of eliminating or con occupational disease. The ultimate cost of trolling occupational hazards. With all of compensation for such injuries may well ex the information presently available to ceed the cost resulting from installation of science, it is seriously to be questioned effective methods for engineering and medi whether the present schedule of recom cal control, aside from the fact that the em mended maximum allowances of concentra ployer's relation to his employees is pro tions are scientifically correct. True, they moted when employees know that the em represent the best thinking of those scien ployer is doing everything practical to effect tists who have studied the problem; how protection. ever, it is a fact that from day to day, indus Question arises to the propriety and ad trial processes are changing, new chemical visability of the adoption of codes of in compounds are coming into commercial use, dustrial hygiene defining maximum allow and tomorrow some new problem may be able concentrations of toxic materials. The presented to industry and to public ad word ``code'' is defined as follows: "A* ministrative agencies entirely different from body of law established by the legislative any that may have been presented before. authority of the state, and designed to regu Industry welcomes technical information late completely, so far as a statute may, the with respect to the existence of occupational subject to which it relates." The adoption of hazards. They will continue to welcome codes having the full force and effect of law technical advice as to practical methods of is unnecessary, inadvisable, and may well control. It must be remembered that in- Industrial Hygiene Quarterly ST0853709 297 dufltry seeks the maximum production of its materials at minimum cost; and if our competitive system is to be retained and business is to succeed, bureaus of industrial hygiene must assist in the attainment of this goal by the simplest and most inexpen sive methods possible. No one would contend that it is the duty of the hygienist to tell the manufacturer how to run his business. Many industrial processes are so secretive and complicated and developed over an extended period of years that it is frequently impossible for an industry within a limited period of time to rearrange that production process to give effect to all of the methods of control that the hygienist would recommend. What is needed is cooperation between state depart ments and manufacturers, not additional laws on our statute books that may be used to the prejudice of state departments as well as manufacturers. There is one other thought which is worthy of consideration. Assuming that threshold limits of maximum allowable con centrations are established by law, the ad ministration of such codes may prove to be embarrassing to state departments charged with their administration and to industry at the instance of organized pressure groups of representatives of the public, labor unions, or possible competitors. Assuming the adoption of codes, it is a fact that oc casional violations may occur resulting from breakdown in machinery or equipment. Im mediately the manufacturer is placed in the position of having violated the law although such violation may be absolutely uninten tional and may be readily corrected. State Departments of Health and Labor do not need to be told by any organized group as to what they can or should do in the adminis tration of their functions. Therefore, a bet ter result will be obtained if use is made of the information developed by our scientists as to permissible concentrations not be cause some law requires this be done, but because it is simply good business to comply. Encyclopedia of Instrumentation for Industrial Hygiene ndustrial hycienists and workers in allied fields will be interested to know that I the heralded encyclopedia on industrial hygiene instrumentation is now generally available. The book is divided into seven sections, each of which includes a compre hensive review of instrumentation in the area being considered, technical papers on special problems or types of instruments used, .and descriptions of available instru ments, mostly commercially available. The sections include the seven areas of instrumentsfor measuring air contaminants in occupied spaces; for use in labora tories; for air pollution and meteorology; for air velocity and metering; for sound and vibration; for ionizing radiations; and for ultra violet, visible and infrared energy. This Encyclopedia brings together in one place a fund of specific information on instruments within the scope of the book. It was produced through the combined efforts of personnel of the University of Michigan, manufacturers' research directors and designers, authorities in the several areas of instrumentation, and a staff of ex perts assigned by the U. S. Public Health Service to assemble and edit the contents of the book. The comprehensive reviews include progress in the individual field of instrumentation, problems presented, limitations of present instrumentation, and needs not met by instruments now available. The descriptions of available instruments in clude the name of the instrument; name of the manufacturer; intended and special uses and adaptations; operating principle; physical description; performance data, such as sampling rate, range, sensitivity; inteferences, limitations and safety hazards; price; operating instructions; calibration instructions; maintenance instructions; photographs, line drawings or wiring diagrams; bibliography. The material in the book comprises some 1243 pages, 9 x 12 inches, with 1400 il lustrations, charts and diagrams. Copies may be obtained through the University of Michigan Publication Distribution Service, Ann Arbor, Michigan. The book is priced at 130.00. ST08537 I 0 Recent Industrial Hygiene Developments -A SYMPOSIUM-- The following papers were presented at tary Engineering Services consists of tech the Joint Session of the American in nical assistance, training, and demonstra dustrial HYGIENE association and thetions related to engineering and is carried American Conference of Governmental In out at the Robert A. Taft Sanitary Engi dustrial Hygienists, at the 1956 Industrial neering Center. The Division of Special Health Conference in Philadelphia, April 24, Health Services has the responsibility for 1956. the determination of the health effects of air pollution. The technical studies, particu In the Field of Air Pollution larly as they relate to toxicology and medi cal effects, are being performed at the Oc- cupational Health Field Headquarters. The HENRY N. DOYLE, Chief primary objective of the toxicologic studies Occupational Health Program is determination of the toxic effects of such U.S. Public Health Service Washington, D.C. air pollutants as ozone, nitrogen oxide, and sulfur derivative hydrocarbons on test ani mals. Much of the medical research is being carried out through contractual arrange- Probably the most significant development ments with universities and private organi in the past year in air pollution as it may zations. These relate primarily to studies of affect industrial hygiene or any of thethe biologic effects of air pollution on health. health-related sciences is the passage of Included are studies of the feasibility of us Public Law 159. Public Law 159, which was ing tissue culture and tissue enzymes to signed by the President on July 14, 1955, evaluate the toxicity of different air pollu authorized a comprehensive program of tants. A third project at the National Insti community air pollution research and tech tutes of Health involves the statistical de nical assistance to the States, communities, termination of geographic variations in the and other organizations. The act declares leading causes of death. This information, ``the policy of Congress to preserve and pro when correlated with environmental find tect the primary responsibilities and rights ings, will provide leads for community of States and local governments in control epidemiologic studies of air pollution. ling air pollution, to support and aid techni Because of the diverse interest of many cal research, to devise and develop methods federal agencies in air pollution, an inter of abating such pollution, and to provide Federal technical services and financial aid to State and local government air pollution control agencies and other public or private agencies and institutions in the formulation and execution of their air pollution abate departmental committee on community air pollution has been organized. The Depart ments of Agriculture; Commerce; Defense; Health, Education, and Welfare; and In terior; and the Atomic Energy Commission and National Science Foundation are rep ment research programs." The law author resented on the committee. This committee izes the expenditure of funds not to exceed will provide liaison between and coordina55 million per year for a period of five years. tion of federal activities relating to air pol- In 1956, $1,722,000 was appropriated. For fiscal year 1957, $3,000,000 has been re quested. lution. It will review from time to time the policies and programs related to community air pollution of the federal agencies, the The community air pollution program general status of technical knowledge con within the Public Health Service is carried cerning air pollution, particularly with re out by the Divisions of Sanitary Engineer gard to the area and scope of needed re- ing Services and Special Health Services. search and other technical activities and The technical work of the Division of Sani advise the Surgeon General thereon. At the , j i ! j ; ! : ' j i Industrial Hygiene Quarterly ST08537I I SSI - first formal meeting of the committee, held in November, 1955, the areas of interest and responsibility of each of the participating agencies were determined. Public Law 159 t vesta the primary authority for air pollu'4+ tion studies in the Public Health Service but authorizes it to cooperate with and / finance studies of other federal departments. $ In addition to research--both through 5 direct operation and contracts--another im^ portant activity has been technical consulta tion to the States and communities. Person nel were assigned to the California State Department of Public Health to aid in a special study of the Los Angeles problem and to assist in the development of a state wide program. Other personnel have been assigned by the Sanitary Engineering Cen ter to the Los Angeles Air Pollution Control District to assist in the conduct of a special ized aerometric survey and oil refinery studies. Another cooperative effort involving special studies of air pollution in the Louis ville, Kentucky area has been initiated to study the source and character of air pollu tants in that area. This study, which is ex pected to be completed in two years, was initiated in January, 1956. Direct research operations at the Sanitary Engineering Center included extension of the national air sampling network to a total of 45 cities and 74 sampling stations. Anal ysis of the material being collected includes determination of the weight of material col lected, identification of 17 metals, certain anions and organic fractions as well as the radioactivity levels. Twenty-six research projects are under way at the Sanitary En gineering Center. These include research to establish the relationship between atmos pheric pollution and meteorologic variables, studies of the performance and design fac tors involved in controlling air pollution from incinerators, and development of con trol devices utilizing fabric filters. Eight studies are under way to develop methods for determining the composition of air pol lutants and for the development of instru ments for air pollution measurement. Work also includes a detailed examination of cer tain air samples, studies of economic costs of air pollution, and studies of control in several industries. In addition to its directly conducted re search activities, the Public Health Service is supporting air pollution studies in other federal agencies. The U. S. Weather Bureau, U. S. Bureau of Mines, and National Bureau of Standards are ail undertaking important studies. The Weather Bureau, for instance, is studying the meteorologic parameters contributing to the severity of air pollu tion. The Bureau of Mines is investigating the incineration of combustible wastes, evaluating sulfur dioxide removal processes, and studying the effluents from automobile exhausts. The Bureau of Standards is devel oping methods for sampling and analysis of air pollutants and is studying the inter reactions of air pollutants at the source and in the atmosphere. Negotiations have also been completed with the Library of Con gress to provide a continuous abstracting service and to compile an annotated bibli ography covering all phases of the air pol lution literature. Utilizing the grants mechanism of the National Institutes of Health, to date, 20 air pollution research grants, totaling $481,359 have been awarded. Of these, six are in the field of physical science and engi neering and the remaining 14 are concerned with the health effects of air pollutants. Training will be eventually another maj or activity under Public Law 159. To date, the Sanitary Engineering Center has held several seminars for State and local person nel. The fact that 95 people from 31 States, 14 cities, and five countries attended the September, 1955 seminar indicates the widespread interest in air pollution. An other technical seminar was held in 1956 which concerned itself with atmospheric sampling, analytic procedures, sampling theory and techniques, and air pollution meteorology. A third seminar is planned for May, 1956. These developments, all related to the pas sage of federal legislation in the air pollu tion field, will probably stimulate expanded research activities in air pollution, not only by federal agencies but by private organizatiops as well. In passing this legislation Congress recognized that the Federal Gov ernment had a responsibility in research and development but it left the control of air pollution in the hands of local authori ties and private enterprise. The research being stimulated by this law promises to have the same beneficial effect in the air ,i i 4 .1 1 4 ST08537 I 2 336 September, 1956 Affecting Fly Ah Collector Performance on Large Pul verised Fuel-Fired Boilers. Air Repair. No. I, 5:27, 1966. 12. White. H. J.: Effect of Fly Ash on Collector Per formance. Air Repair, No. 1. 5:17, 1965. 13. Bmith. J. L.. Ja. and Goolla. M. J.: The Mech anism of Separation in the Louver-Type Dust Separator. Air Repair, No. 1, 5:61. 1956. U. VlNASLE. F. 8.: An Industrial Hygiene Program for a Benaane Extraction Plant in a Petroleum Re&nery. AlHA Quart.. 16:45, 1965. 16. McAldust. K. J.: The Sale of Uranium Contami nated Scrap Carton Steel to Commercial Channels. AlHA Quart.. 16:73, 1966. 16. KSAUCE. I. It., end Goldwatee, L. J.: Investment Csstlng by the Fmsen-Mercury Process. AHA Arch. Ind. Health. 13:29, 1966. 17. SiLvxaMAN, Leslie. Connees. E. W,, and Ficar. M. W.: Resistance Characteristics of Flexible Exhaust Hose. In press. Presented at the Sixteenth Annual Meeting of the A useican Industrial Hygiene Association. Buf falo. New York, 1956. 18. Dsinkex. P.. and Hatch, T.: Industrial Dust, 2nd Edition. McGraw-Hill Book Co., New York. 1964. 19. Humm, W. C. L.: Plant and Process Ventila tion. Th Industrial Pru Nw York, 1955. 20. MALLrrrs, F., editor: Problems and Control of Air Pollution. Keinhold Publishing Corp., New York. I06i. 21. Gsaiiam. A. K.: Electroplating: Engineering Hand* book. Reinhold Publishing Corp.. New York, 1955. In the Field of Noise preparing such a manual. Subjects covered by this manual will probably be: (1) Physics of sound. (2) Measurement of sound. (3) Man's physiological reaction to sound. (4) Hearing conservation. (5) Engineering control of sound. Second drafts of each chapter of this manual have already been completed and it is expected that the final draft will be com pleted for the 1957 annual meeting. It is not too late to include suggestions or data to help make this manual of maximum useful ness. K. M. Morse, of the U. S. Steel Corporation, chairman of this committee or any committee member as listed in the current issue of the Quarterly, will be glad to accept any contribution. Of particular interest would be examples of noise control treatments tried and found successful. No one of us has had experience with all types of noise problems but by pooling our ac complishments all should benefit. VAUGHN H. HILL E. I. du Pont de Nemours & Co., Inc. Wilmington, Delaware More Information Now Available Qrganizations outside our own AlHA have been active during the past year in making available recent technical and prac tical information on noise control. Many or Noise control is demanding an increas ganizations are involved but time permits ing portion of the Industrial Hygien the mention of only a few. ist's time and, therefore, justifies an over Associated industries of new york all look at recent developments. state, in their annual meetings on noise Management Acceptance control, present papers on practical solu tions to noise problems. These papers are QNE of the most significant developments presented by representatives of various in the past year has been the acceptance companies and are published in the AIHA by management of the facts that (1) they Quarterly. Each year these meetings in have a noise problem, (2) it is serious crease in value as the activity in noise con enough to warrant action, and (3) the re trol increases. sponsibility of protecting employee health and safety from excessive noise belongs to management. In most cases we no longer The national noise abatement sym posium held yearly at the Illinois Institute of Technology presents a similar program need to spend valuable time convincing man except of a more technical nature. The pro agement, but are at liberty, in fact, encour ceedings of these meetings are published in aged, to pursue methods of controlling .Voi.se Control. noise. The MASSACHUSETTS INSTITUTE OF TECH AlHA Noise Manual NOLOGY sponsors a conference on noise con trol about every two years and the one this 'J'he aiha recognizes the need for a practi past year was exceptionally good in that an cal manual to guide Industrial Hygienists attempt was made to provide the Industrial in controlling industrial noise. To fill this Hygienist with practical data for field ap need they have formed a noise committee plication. Proceedings of this conference and charged it with the responsibility of were also published in Noise Control. Industrial Hygiene Quarterly ST08537I 3 337 Since the magazine Noise Control haa been already mentioned twice, it might be in order to say that this quarterly publica tion has established itself during the past year as a valuable reference for Industrial Hygienists who are concerned with con trolling industrial noise. It provides tech nical and practical data on all phases of the problem. Machinery Noise Specifications TN OUR haste to get existing noise problems A under control we must not overlook the preventive side of the problem as far as new construction or machinery replacement is concerned. Manufacturers are awakening to the fact that noise production characteris tics of a machine are important specifica tions. Some are taking steps to provide such data. It is quite generally accepted that noise power output is the best specification for predicting the noise production charac teristics of machines, for specific conditions of installation. Most acoustical engineers agree that the echo-free room, i.e., anechoic chamber, provides the best environment for making measurements of sound power out put. However, few manufacturers feel they can afford such facilities. As a result, or ganizations such as the American Institute of Electrical Engineers (AIEE), National Electrical Manufacturers Association (NEMA), American Fan Manufacturers Association (AFMA), Industrial Unit Heater Association (IUHA) and the Ameri can Society of Heating and Air Condition ing Engineers (ASHAE) are investigating less costly means of measuring sound power output. There is indication that this might be accomplished in the next year or two. In the meantime, some companies are using some adaptation of the American Standards Association (ASA) Apparatus Noise Meas urement Standard together with some noise criteria to identify excessively noisy equip ment. By bringing this to his attention, the manufacturer is rapidly being made to realize that noise is a competitive problem. It is interesting to note how readily other manufacturers can get in line as soon as one solves the noise problem. The manufacturer of electric motors provides a good example. As soon as one manufacturer proved that quiet motors were practical, others found they could also meet the demand. As a re suit, you can now select a motor that will not create a noise problem. Our job is to warn our companies against buying new noise problems. The first step in preventing this is to supply Design and Purchasing Departments with noise speci fications for machinery. Automatic Audiometer 'TO ASSIST in hearing conservation pro*" grams where large numbers of hearing tests must be made, a new audiometer has been developed called the automatic audio meter. With this device the patient takes his own audiogram after having been given a few simple instructions. One operator can supply the instruction necessary to keep three automatic audiometers in operation. Indications are that to justify automatic audiometry, enough tests to keep three ma chines in operation are required. Impact Meter J7VEN though less is known about the rela tion between hearing damage and ex posure to impact noise than for steady state noise, fairly accurate field measurements of impact noise is desirable if we expect to develop damage risk criteria or evaluate cor rective measures. Until recently, field meas urements of impact noise was too com plicated to attract widespread use. The General Radio Corp. now has available an instrument called the Impact Noise Ana lyzer which gives promise of improving this condition. This instrument is simple to oper ate, easily portable, relatively inexpensive, can be used with frequency analyzers and provides fairly accurate measurements of impact noise. It is hoped this instrument will be valuable in the study and control of impact noise which has been sadly neglected up to now. To summarize these recent developments: 1. Management is accepting the noise problem and is looking to us for the an swers. It is our move now to get the job done. 2. Aiha will soon have available a manual on noise control which should be a guide in solving industrial noise problems. This should considerably reduce the necessity of searching through many sources for the answers to your problems. 3. Organizations outside the aiha are ST 08537 I 4 338 September, J.9.W also active in this field. While it is prac atomic energy, Part 20 will be among the tically impossible to cover them all, it is first Federal occupational health codes to wise to keep an eye on a few to provide as be enforced by a Federal agency. Many in broad a coverage as possible. teresting new concepts in radiation protec 4. Don't buy new noise problems. Pro tion are included in the AEC's proposed mote the use of machinery noise specifica code. It is expected that a revised draft will tions to emphasize the importance of the be forthcoming shortly. noise problem. Many papers on radiation protection were 5. If you have many audiograms to take, submitted to the International Conference consider the automatic audiometer; it might on the Peaceful Uses of Atomic Energy, save you money and provide more uniform which was held in Geneva in August, 1955. data. The legal and administrative aspects of the 6. If you have impact noise problems, you problem received a great deal of interest. should consider the use of an Impact Noise In December, 1955, the American Stand Analyzer. ards Association called a National Confer Only a few of the recent and important ence on Standardization in the Field of developments in the field of industrial noise Nuclear Energy to review its program in control fas far as the Industrial Hygienist this area and to obtain the thinking of a is concerned) have been discussed. The in large cross-section of industry, government, terest shown in this field today indicates labor and others on the need for additional that new and significant developments will American Standards Association activities. be forthcoming in increasing numbers. If As a result of this meeting, a Planning one is to keep abreast of this new and rapid Committee was established to review the ly developing field, constant vigilance of present status of standards and recommend current literature will be required. appropriate action. This Committee met in full session on February 15, 1956, and this In the Field of Radiation meeting was followed by meetings of the various subcommittees. Reports of these SAUL J. HARRIS Atomic Industrial Forum, Inc. subcommittees were analyzed on March 15, 1956, at a meeting attended by the subcom mittee chairmen and the Chairman of the New York City Planning Committee. The major recommen dation was for the American Standards As IT is not possible to cover all the develop sociation to establish a nuclear standards ments in the field of radiation in the board. course of this paper, but after discussing In December, 1955, the National Bureau the subject with several persons in this of Standards issued Handbook No. 61 on field, I have concluded that the following the regulation of radiation exposure by are probably the most significant. legislative means, which contained the Many developments have been primarily recommendations of the National Commit "administrative," that is, they deal with the tee on Radiation Protection concerning the development of regulations, codes and stand development of acts and regulations on the ards and the matter of agency jurisdiction part of state government. over health and safety. In March, 1956, the New York State Jn June, 1955, a conference was held on Health Department and the New York State the subject of health physics, and as a result Labor Department radiation protection of that conference, a preliminary organiza regulations became effective. tion of professional health physicists was This same month, the United Nations formed. Radiation Committee had its first meeting In July, 1955, the AEC published its pro and elected officers. The next meeting will posed standards for protection against radi be in about five months. This Committee was ation as part of Article 10 of the Code of established in December, 1955, by the Federal Regulation. Although other parts United Nations as a committee of specialists of the same Title may also be based upon a from 15 nations to collect information on need to consider the hazardous aspects of radiation levels and radiation effects on man ST0853715