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FILE NAME: Union Carbide (UC) DATE: 1956 DOC#: UC334 DOCUMENT DESCRIPTION: Lecture from Scientific Journal - Improved Communication - Hygienic Standards for Daily Inhalation Improved communication --hygienic standards for daily inhalation* HENRY FIELD SMYTH, JR., Ph.D. Mellon Institute and Union Carbide and Carbon Corporation, Pittsburgh, Pennsylvania Experience convinces us that we humans are unique in the universe. Because of our ability to communicate, we may be well on the way toward emerging into a new level of biological existence. Each individual may eventually share completely all past and present experiences of the species. Each may act in concert with his fellows toward common ideals and goals, still retaining his own individuality. Real progress in this direction has been made during the past ten thousand years through developments of recording, duplicating and retrieval techniques. Despite briefback-sliding, there has furthermore been real spiritual progress, and an increase in the proportion of men of good will. The next ten thousand years should bring substantial achievements in communication upon higher levels, perhaps even through inarticulate contact of mind with mind. There are hints that what som e have called the world mind may come into being before the present human species evolves physically into whatever new species its body is tending toward. However, until the world mind develops, we are forced to depend upon more prosaic means of communication. Hot so many generations ago, a natural philosopher like Roger Bacon,whom today we call a scientist, could live a full life investigating the secrets of nature, feeling no need and finding no opportunity to communicate his discoveries and his conclusions to a living soul. He could bury his achievements in code, making them difficult for posterity to unravel. We do not have such people and such situations today. Each one of us benefits from current division of labor, of experi ence, and ofknowledge. Each one of us is a unique specialist, depending upon a multitude of other unique specialists for the achievement of our aims, for our very existence. If nothing else mo tivates us, simple self-interest should dictate that each one ofus ought to make public all that he has learned, in order that his fellow specialists may use it to help us all. Communication Ayear ago SternerTM expressed the situation in more concrete terms. We comprise persons sep arately trained in highly specialized fields, led after training to cooperate in the common aim of providing means by which technological develop ments in occupation may be utilized in a manner compatible with complete health. He said, "We must provide a fluid and effective means ofcommunication between the chem ist, the engineer, the physicist, the toxicol ogist, the physician, and the other specialists brought Into industrial hygiene. There must result from this Interchange of ideas not only an appreciation o f each team member's con tribution, but an ability actually to bridge the gap between the disciplines, to synthesize, from the offerings o f each of the fields, the solutions to the ever more complicated prob lems. Each m em ber specialist m ust not only contribute the Information he Is most quali fied to give, but also m ust encourage sym pa thetic, Intelligent, and mutual understanding." In this matter of mutual understanding, we are veiy much like the inhabitants of Looking Qlass Land. You remember that the White Queen told Alice, "How here, you see, it takes all the running you can do, to keep in the sam e place. Ifyou want to get somewhere else, you m ust run at least twice as fast as that" With the entry of new people into our profession and the recognition of new con stituent specialties such as health physics and atmospheric pollution control, each with a ten dency to keep to itself, are we running fast enough *The Donald E. Cummings Memorial Lecture presented at the Seventeenth Annual Meeting of the American Indus trial Hygiene Association, April 25, 1956, Philadelphia. Published in Am. Ind. Hyg. Assoc. Q. 17:129-136 (1956). Reprinted by permission of American Industrial Hygiene Association. Ann. Am. Conf. Ind. Hyg., Vol. 9 (1984) Page 93 lL(j^ T h irty -fiv e Y e ars o f TLVs even to stay in the same place? We all feel there are too many conferences and too many committees to leave us time to do our daily work. On the other hand, if we are to do our work as well as it can be done, we m ust be in constant communication with related specialists, because each one of us fully knows only one facet of his own problems. Communication is not a simple process. It re quires an informed speaker or writer who can express himself at the level of comprehension of his audience. Itrequires an audience which wishes to receive communication, it m ust be carried on with words, those abstract symbols for reality, each of which has a different meaning to each individual, shaded by his entire past experience. Only a newly coined word is free from ambiguity, and it remains new for only a brief interval. Most important of all, successful communication re quires what is today known as feed-back. By this, the speaker hears his audiences' impressions. He can correct and amplify his words until he thinks his audience truly perceives his meaning. Aleisure ly conversation can be effective communication through feed-back; an article in ajournai is likely to be poor communication because feed-back is inadequate. The relatively new specialty of industrial toxi cology has already contributed to the equally new profession of industrial hygiene by means of communication. The toxicologists are doing an acceptable job for those people who recognize their need for toxicological information and opin ion. Thejob could be done better, but it is at least acceptable. Success is by no means as great in helping those people who do not recognize their need for help. Once more communication cannot succeed unless the audience desires to receive communication. . Acceptable concentrations The m ost important communication within in dustrial hygiene, and between our profession and others, may be the collection ofjudgments upon acceptable concentrations of contaminants in working atm ospheres. During what may be called the age of chaos, eveiy experienced industrial hygienist had a fewvalues uniquely his own, drawn from his own experience. For less familiar sub stances, he borrowed more or less judiciously from the values cherished by his professional colleagues. Some degreeof unanimitywas brought aboutwhen the United States Public Health Service values, based on its long-time collective experience in industrial hygiene,were published in a manual.(Z) Further unanimity followed publication of the values collected and extended by Cook.(3)In 1947 the American Conference of Governmental Indus trial Hygienists published its first list in the In dustrial Hygiene Newsletter.(i) In the next two years revised lists were privately circulated to the members of the Association/5'6'Then publication took place in a scientificjournal,(7) and each year thereafter a revised list of threshold limit values has appeared in the scientific literature, and has been generally accepted/812' The contributions ofCook<3)in unifying opinion, and in weighing threshold limit values then in use, judging new data and proposing a list of 129 values, are worthy of high regard. Among the 238 values for substances other than mineral dusts in the current list<13) of established and tentative threshold limit values are 54 of those which were first proposed in Cook's list, some as definitely established, others to be used cautiously until verified by actual experience. Hot since Cook has anyone published a sum mary of the data which serve as bases for the selection of specific threshold limits. The privately circulated documents^"16' which give some of these data cannot be considered to be publication, although they are freely available to any person. Threshold limits are, and m ust continue to be the products ofjudgment, important iftrue. Some fewtruly represent their definition and are approx imations of the maximum concentrations which can be inhaled continuously and repeatedly with out injury to health. These may possibily be fit parameters for incorporation into codes and reg ulations. Many of the threshold limits are well below concentrations which can injure health. They represent currentjudgment as to concentra tions to which, good practice dictates, men may be expected to subject themselves. These do not seem fit parameters for regulations. In a particular operation, if possible, it is dsirable to maintain concentrations below the bench-mark by reason able ventilation and precaution. It is always best to reduce exposure to chemicals to the lowest prac tical level. Page 94 Ann. Am. Conf. Ind. Hyg,, Vol. 9 (1984) Smyth: Improved Communication Previous suggestions for improvement During the riinth Annual Congress on Industrial Health, the writer was chairman of the Committee on Chemical Agents. The report of the 16-man committee(17) devoted considerable attention to praising the development of threshold limits, and to suggesting ways in which their presentation could be made more useful. Since that report, two developments have taken place along lines desired by the Committee. The annual table ofthe Thresh old Limits Committee ofthe American Conference of Governmental Industrial Hygienists is now pub lished in the Archives o f Industrial Health, re moving the earlier implication ofquasi-legal status arising from its appearance in the Industrial Hygiene newsletter of the Division of Industrial Hygiene, U.S. Public Health Service. In 1954, the Committee on Threshold Limits ofthatAssociation began to supplement its table of accepted values with a list of tentative values. Three other suggestions of the Committee on Chemical Agents deserve reiteration and discus sion. It was urged that the bases for the selection of each value should be published, that the name should be changed to hygienic standard, and that the particular concept of permissible human response behind each value should be clearly indicated. There is such a multitude of factors involved in the protection ofhealth in our complex civilization that no one person or group of persons is com petent to weigh them all with assurance. Ho oracular or ex cathedra statement on health deserves serious attention. Only when the facts upon which a decision are based are furnished for general scrutiny and evaluation can the decision be considered even tentatively sound, and only after there has been adequate opportunity for criticism and modification can it be considered established. All toxicological facts should be pub lished, and all decisions upon the facts should be accompanied by a summary of the reasoning under which they were derived, before anyone should be expected to act upon the decisions. Any publication ofstandards for maintenance ofhealth ought to include reference to the underlying data. The second suggestion referred to the name by which the values are known. Semantics is more than a sport for the idle. Ho matter how thoroughly a concept is originally presented, it always be comes known and referred to by a brief name, a catch-word. Most persons who learn ofthe concept hear the catch-word name, and do not go back to the original presentation. The meaning they attach to the name comes from their previous experience with the particular words. It may be, but is usually not, exactly what the originator of the idea in tended. The more carefully one chooses the name he assigns to a concept, the more likely are others to interpret the concept as he himself does. The values now known as threshold limits are usually identified by phrases containing the words allowable or permissible. These two words have connotations of legal regulations. Such connota tions cannot properly attach to thejudgment of a voluntary professional association. The identify ing phrases may also contain the words maxi mum, threshold and limit. These words all imply that below the concentration specified, human response is negligible, above the concentration it is dangerous. Actually, it is more than an implica tion. It is definitely stated. In the introduction to its 1956 list the Committee on Threshold Limits says, "Values are given . . . for the maximum average atmospheric concentrations of contaminants to which workers may be exposed for an eight-hour working day without iryury to health."<13)Careful study of the data which support the currently accepted values suggests that no such description can be truthfully attached to most of them. Indus trial hygienists recognize this. They are accus tomed to emphasize that the values should be regarded simply as bench-marks, guides to good practice. Indeed, the Threshold Limits Committee itself confusingly warns "Threshold limits . . . should not be regarded as fine lines between safe and dangerous concentrations. "(13) The term maximum acceptable concentration being used in revisions of standards by the American Standards Association Z-37 Committee is objectionable only because itwill be abbreviated MAC. Many will interpret this abbreviation as maximum allowable concentration, and nothing will have been gained by the change from allow able to acceptable. I conclude that the names maximum allowable concentration and threshold limit are misleading. They convey a wrong impression to those who are not already familiar with the concepts behind the values. The name suggested in 1949, hygienic Ann. Am. Conf. Ind. Hgg., Vol. 9(1984) Page 95 T h irty -fiv e Y ears o f TLVs standard, is not misleading. Standards of good practice are familiar to all of us in many fields. Looking toward the future provision of a variety of hygienic standards, a series of values should be selected, to be known as hygienic standards for daily inhalation. The third suggestion is more far-reaching. The Committee on Chemical Agents pointed out that there has been no simple or uniform relation between the effects ofa substance and the numer ical value chosen for tabuIation.(17>The Committee concluded that concentrations have been selected on the basis of one of four concepts of the level best suited to hygienic control of inhalation, the choice having been governed by the nature of the toxic response and by the degree of organoleptic response. The Committee's four concepts follow: a. Plus or minus: The maximal time-weighted average concentration which produces only minor injury, and that in a very small proportion of exposed workmen. b. Safe: The maximal time-weighted average concentration which sound evidence leads one to believe will cause no demonstrable illness or other symptom of toxic effect in anyworkman during a lifetime ofindustrial exposure. c. Bench-mark: A concentration based on the belief that any unnecessary exposure is undesirable -- a concentration lower than that of a or b, one as low as is con sistent with practical engineering control. d. Comfort: A concentration lower than a or b, representing the maximum which in a short time is not objectionable to 9 out of 10 of a group of persons not accustomed to inhalation of the substance. Note well that these four concepts werejudged to be those already used for the selection ofhygienic standards for daily inhalation. All four werejudged consistent with the goals of industrial hygiene. Hygienic standards for daily inhalation The subject of hygienic standards for daily inhalation should be re-examined, the concepts represented by the values should be restated in more realistic toxicological terms, and more con sistent and more informative standards should be prepared. Such a step will not undo any of the accomplishments of the profession of industrial hygiene or of any organization. Rather, it will supply informative standards to supplement the accumulation of naked numbers now accepted, some ofwhich have not been criticallyre-examined for a decade. It is certainly imperative that the inhalation of substances during the working day shall not be allowed to result in any injury to the physical well-being ofworkmen. Itis furthermore imperative that inhalation shall not increase the probability of accidents through the mental distress occasioned by objectionable eye, nose or throat irritation, transient though it may often be, nor through the impaired judgment and delayed reaction time of light narcosis. It is desirable that inhalation shall result in no degree of discomfort whatsoever. On the other hand, when it is impractical to avoid all discomfort, then such inhalation is certainlyjusti fied, provided there results no injury to workmen and no increase in the probability of accidents. Tables of hygienic standards do not now carry indications of the nature and of the magnitude of the effects to be expected from inhalation of greater concentrations. It is only by a rather thorough study of the available data that one can decide whether or not a particular substance can safely be inhaled at a greater concentration. With most substances, it is quite practical to set two standards, one an inoffensive level, another a con centration which cannot safely be exceeded under any pressure of practicality. Administrative expediency may be served by a table of numbers which constitute a part of official regulations. Regulations need not be defended, they need not cite justifications. However, it is a minority of the profession of industrial hygiene who have regulatory responsibilities. Most of our colleagues act through obtaining voluntary co operation with their judgments. They would be aided by a greater degree of explanation in a tabulation of standards. They could then show that their recommendations are quite defensible, that they are not arbitrary decisions having no regard for the realities of competitive industrial existence. A hygienic standard for daily inhalation should specifytwo concentrations, together with a descrip tion of the human response to be expected from Page 96 Ann. Am. Conf. Ind. Hyg., VoI. 9 (1984) Smyth: Improved Communication inhalation of each. One concentration should be low enough so that no injurious effect can be expected in any workman, but it may cause a detectable odor, it may cause a detectable eye, nose or throat irritation. The second concentration should produce somewhat more severe, but still reversible and non-progressive effects. From these two concentrations, one can at once see how strictly the standard should be observed, the steepness of the dosage-response curve, the breadth ofthe plateau ofnon-injurious concentra tions. Despite the wide range in individual sus ceptibilities of workmen, such values can be selected for most, if not all, substances. Adequate data for preparing this sort ofstandard consist of appropriate human experience, or re peated medical examinations of workmen in at mospheres whose concentration has been fre quently estimated. Sterner11' discussed this point in detail. Experiments upon animals, verified by biochemical and physiological studies in humans, may demonstrate conclusively that a substance has an effect during one period ofinhalation which does not progress during oft-repeated inhalation. For such a substance, satisfactory data can be obtained from objective study and secretly re corded subjective effects of a group of humans inhaling known concentrations for substantially eighthours. Anylesser body ofdata should result in a hygienic standard being designated as tentative. Categories of objectionable action Judgments should be made to determine which hygienic standards for daily inhalation must be carefully observed, and which may be exceeded when it is impractical to observe them. These judgments will be most consistent ifwe first decide for each substance what objectionable action we are guarding against by the standard. Every toxi cologist will realize that the action at a lowconcen tration which it is most important to guard against, may not be the sam e as the menace to life to be expected at a high concentration. In a tentative fashion, the writer has made these decisions for the 238substances, exclusive ofthe mineral dusts, included in the 1956 tables ofproposed accepted and tentative stan d ard s/13' The decisions can be divided into the following nine categories on the basis on the nature of human response. Chronic toxicity The most dangerous effect of some substances is a progressive systemic injury, increasing in severity with continuing inhalation. Benzene, car bon disulfide, carbon tetrachloride arid lead are the m ost familiar examples. The lower standard for these substances should be a concentration believed not to produce any effect in anyworkman, and no considerations ofpracticality are sufficient to justify inhalation in excess of the standard. Close medical supervision is required for safe use ofthese toxic substances. The standard for chron ically toxic substances should refer to the timeweighted average concentration throughout a working day. Brief peaks of a few times the stan dard have no significance, save as they increase the average. Acute toxicity Some substances do not produce an injuiy progressing with repeated inhalation. Such sys temic injury as they may cause takes place as the result of one excessive inhalation, or not at all. Familiar examples are carbon monoxide and hygrogen cyanide. The standards for acutely toxic substances should be interpreted in the same light as those for chronically toxic substances. narcosis The most dangerous effect of some substances is narcosis, which becomes anesthesia in its extreme state. At a rather low concentration they induce accidents by impairing judgm ent and de laying reaction time. Familiar examples are ethyl alcohol, ethyl ether and gasoline. The lower stan dard for a narcotic substance should be a concen tration which produces no detectable effect upon judgment and reaction time after eight hours in halation. It should refer to the average concentra tion existing during some appreciable period of time, the length of which can be estimated from absorption and elimination data. No considera tions of practicality can justify exceeding the stan dard for a narcotic substance. Irritation The m ost dangerous effect of some substances is irritation. Eye, nose and throat are irritated at a lowconcentration, the bronchi at a higher concen tration, and fatal lung edem a may be the result of inhaling an extreme concentration. The aldehydes, Am. Am. Conf. Ind. Hyg.. Vol. 9 (1984) Page 97 T h irty -fiv e Y ears o f TLVs halogens and acids are familiar examples. Highly odorous substances may also be considered in this catagory. The lower standard for an irritant substance should be a concentration which is detectable, but is not objectionably irritating to the majority of unhardened subjects who are exposed for a substantial part of a working day. The higher standard should be set a t a concentration which is well under one injuring bronchi or lungs, and which is justifiable when it is impractical to keep concentrations at the lower standard. Standards for irritating substances should refer to concen trations existing for even a brief period during a work day. . , Asphyxiation Some substances are inert in the body and can injure only by asphyxia at extremely high concen trations, excluding the oxygen of the atmosphere. Familiar examples are the fluorochloro refriger ants. The lower standard for these asphyxiants should be a nominal bench-mark of good en gineering practice, such as the 1000 ppm concen tration now quoted. The inert nuisance dusts like iron oxide might well be placed in this same catagory, and the currently used bench-mark of 15 mg./cu.m. seem s an appropriate level. The stan dard should refer to the concentration existing during anybriefperiod, but it should be recognized that higher concentrations are justified when it is impractical to keep below the standard. Fume fever The m ost important effect of som e substances is a transient influenza-like condition known as fume fever. A familiar example is zinc oxide fume. The lower standard for a fume fever producer should be a concentration which will not produce that distressing but not menacing condition in any workman, and it should apply to an appreciable period, such as half an hour. No considerations of practicality can justify exceeding the standard for fume fever producing substances. Eye pigmentation The m ost important effect of two substances, quinone and hydroquinone, appears to be a slowly developing pigmentation of the sclera, which may reduce visual acuity, or even lead to blindness. The lower standard for these substances should be a concentration which produces no pigmentation after years of exposure, and it should refer to the time-weighted average concentration throughout the day. For a few days at a time, conditions of practicality should justify exceeding the standard. Cancer One substance is reasonably well established as a cause ofrespiratory tract cancer. This is nickel carbonyl. It appears probable that the minimum cancerigenic exposure will never be defined. At this time it is prudent to set the standard for a cancerigenic substance substantially at zero, as has already been done for nickel carbonyl, and no considerations can justify allowing the inhalation of any concentration which is avoidable. Allergy Some substances are known to sensitize an appreciable proportion of exposed workmen. They may produce distressing and menacing asthma like attacks when a sensitized person inhales a lowconcentration. Examples are ethylene diamine and the diisocyanates. At this time there is no rational experimental basis for defining a concen tration which will not sensitize a susceptible work man, or one to which no previously sensitized workman will respond. Control of exposure to allergenic substances must rely heavily upon in dustrial medicine. After experience has allowed withdrawal of workmen susceptible to sensitiza tion, the remaining resistant individuals can be protected by a hygienic standard for daily inhala tion based upon irritation or systemic injury. Until it has been demonstrated that a particular group includes no susceptible workmen, no considera tions canjustify allowing inhalation ofany concen tration which is avoidable. (E ditor's note: The table which lists the 238 values as well as the discussion that followed this portion of Dr. Smyth's paper is not reproduced in this publication due to space limitations. The interested reader may find the table along with the discussions and references cited on pp. 136-185 of the Am. Ind. Hyg. Assoc. Q ,, Vol. 17. The 1956 recom mended threshold limit values appear in this volume. The Documentation of the Threshold Limit Values, 4th ed., provides more up to date information regarding the pre dicted effects of a given substance. This publication is available from ACG1H, Publications Office, 6500 Qlenway Ave., Bldg. D-5, Cincinnati, OH 45211.) Page 98 Ann. Am. Conf. Ind. Hyg,, Vol. 9(1984) Smyth: Improved Communication References 1. Sterner, J.H.: The Experimental Animal -- Man -- in Industrial Hygiene. Am. Ind. Hyg. Assoc. Q. 76:103-107 (1955). 2. U.S. Public Health Service: Manual o f Industrial Hygiene, p. 264. W.M. Gafaler, Ed. Saunders, Philadelphia (1943). 3. Cook, W.A.: Maximum Allowable Concentrations of Industrial Atmospheric Contaminants. Ind. Med. 74:936-946 (1945). 4. ACGIH: 1947 MAC. Values. Ind. Hyg. newsletter 7:15-16 (August 1947). 5. ACGIH: Threshold Limit Values adopted at April 1948 meeting (privately circulated) (1948). 6. ACGIH: Threshold Limit Values adopted at April 1949 meeting (privately circulated) (1949). 7. ACGIH: Threshold Limit Values for 1950. Arch. Ind. H yg.& O ccup. Med. 2:98-100 (1950). 8. ACGIH: Threshold Limit Values for 1951. Ibid. 4:398-400 (1951). 9. ACGIH: Threshold Limit Values for 1952. Ibid. 6:178-180 (1952). 10. ACGIH: Threshold Limit yalues for 1953. Ibid. 8:296-298 (1953). 11. ACGIH: Threshold Limit Values for 1954. Ibid. 9:530-534 (1954). 12. ACGIH: Threshold Limit Values for 1955. AMAArch. Ind. Health 77:521-524 (1955). 13. ACGIH: Proposed Threshold Limit Values for 1956, presented April 23,1956 to Philadelphia annual meeting. Privately circulated in advance of publication. 14. ACGIH: Privately circulated document giving support for many earlier adopted threshold limits, and those proposed in 1953 (1953). 15. ACGIH: Privately circulated document giving support for threshold limits newly proposed in 1954 (1954). 16. ACGIH: Privately circulated document giving support for threshold limits newly proposed in 1955 (1955). 17. Committee on Chemical Agents: Report of the Panel of Environ mental Agents, Minth Annual Congress on Industrial Health, Chicago, January 18-19, 1949. Arch. Ind. Hyg. 8t Occup. Med. 7:601-624 (1950). Ann. Am. Conf. Ind. Hyg., Voi. 9 (1984) *5 Page 99