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1 Monitoring Exposures to Vinyl Chloride Vapor: Breath Analysis and Continuous Air Sampling EDWARDD. BARETTA* RICHARD D. STEWART, M.D. and JOHN E. MUTCHLERt , Department o/ Environmental Medicine, Marquette School of Medicine, Milwaukee, Wisconsin, and Environmental Health Section, Biochemical Restareh Laboratory, The Dow Chemical Company, Midland, Michigan An environmental survey was conducted to determine the time-weighted average exposure (TWA) of a group of chemical plant workers to vinyl chloride (VC1) vapor. This survey featured continuous multipoint air sampling and analysis using an infrared spectrophotometer. The inhalation exposure data were digitized and record ed on paper tape for subsequent computer analysis and derivation of daily TWA values for each worker. A breath sampling program was conducted concurrently with the environmental survey, and a series of breath decay curves relating pastexposure breath concentration to vapor exposure were derived from the data. To validate the bteath curves derived from on-the-job data, poslexposurc breath curves were also constructed from breath data obtained following exp--im-ntai human exposures to carefully controlled concentrations of VC1 vapor. The close agreement between postexposure breath concentrations at, the corresponding TWA'* obtained by each of the methods suggests that either continuous air monitoring or breath analysts is valid for estimating the worker's individual daily exposure to VCI, and provides further evidence that breath analysis is a useful industrial hygiene technique for evaluating vapor exposure. ork, AO provide designed especially for worrcn V 1 v the tough, attractive F5100 and * nodels. Or you can have metnl with | F5300 Safcmaster. ittachments amcs are made to take the extras, if d'4 -m. Like clear plastic semi-side shn: ' cher vented side shields. Even clear l ft.im.rt* tn Amn Ofiml C** Introduction "THE QUESTION THAT MAY ARISE *- following an environmental survey is whether the chemical vapor concentrations measured are truly representative of the ex posure being experienced by the workmen. Evaluation of the ranges of atmospheric con centrations and estimates of time-weighted average concentration (TWA) are all too often based on a few spot samples obtained under conditions which are not representa tive of all phases of a given operation. A more exact measurement of vapor exposure would have to be based on continuous moni toring of air in the workman's breathing lone during his entire work shift. Obviously this task is made difficult and often impossible This pjptr w>i presented t the American Inductriil yriene Conference* St. Limit. Missouri, May 13*17* 1968. 'Marquette School of Medicine, Milwaukee, Wisconsin. tThe Duw Chrmicat Company* Xhdland* Michigan, by the large number and variety of tasks per formed by today's modern chemical plant worjter. * Rqpent improvements in automatic moni toring and data processing equipment have provided a means for a more satisfactory so lution. Sequential samplers and automatic analyzers and recorders can now be used to continuously monitor several locations r operations to provide more valid data on which to base estimates of chemical exposure. Computers can be utilized to manage the large volume of data generated by continu ous monitoring.1 Meanwhile a technique has been under de velopment which more precisely defines the level of individual exposure. The realization that the total body burden of a volatile chem ical is directly related to its concentration in expired air led to the development of tech niques for collecting and analyzing breath samples useful in estimating the more indi- 537 VC2085 $38 Hovembrr-December, /9C'i tmcrican Industrial Hygiene A vidualized exposure experience of each work man. Studies by Stewart et al. *'* have shown that the excretion or "decay" of vapor in the bread) can be used to characterize the ex posure. Breath decay curves constructed for several chemical solvents have proved clin ically useful as an index to chemical expo sure. These breath decay curves, for the most part, were constructed from postexposure breath data obtained from experimental hu man exposures to carefully controlled and relatively constant vapor concentrations. However, breath decay curves have recently been constructed from breath data collected from workers whose work environment was being continuously monitored.* In this study of human exposure to vinyl chloride (VC1) vapor, breath decay curves constructed from data obtained during ex perimental exposures to the relatively uni form concentration within an exposure cham ber were compared with those derived at the theoretically equal, but broadly fluctuating, concentrations encountered in a chemical plant atmosphere. A measure of the validity of continuous monitoring data and the use fulness of breath analysis in assessing timeweighted average exposure was reflected by a close similarity betwren the two sets of breath decay curves. OUTSIDE AIR STATION I ______ ! f WORK AREA 1 STATION 3 station $ _____________9______ i1 STATION t {station 4 {stations 9 ------ 1------------ !--l -- -J - i r-~-j___i 3, Lie; INFRARED SPECTROMETER '''S^IGIGITlTIIZZIER LRECORDER'S,! computer EXPOSURE SUMMARY TIME-WEIGHTED MEAN EXPOSURE OlOI WAttt nitan (MctiitrtiiM *i $iIIm I P, pw am IMK IRpAI (I ImrIIm l ApriAR ppnppl Pk pei*ltj M Figure I- Schematic diagram o( the infrared continuous monitoring tyitem. Procedures ' Monitoring the Plant Atmosphere The chemical installation surveyed was a closed structure housing several separate chemical processing operations. First, a job survey was conducted for each of four job classifications to determine the work arej, frequented by the workmen and the time they spent in each area. For each job classification, five sampling probes were strategically placet! in the work area. A sixth probe was placet! outside the building, and charcoal and si!ir.i gel filters were placed in the sampling !in>to assure a clean air reference. The samplr probes were 5/16-inch I.D. Saran tubinc through which air samples were drawn by a vacuum pump at a rate of 17.5 liters/mie to a centrally located infrared spectrophotom eter, The spectrophotometer was equipped with a 10-meier parh-length gas cell sensi tive to 5 ppm of VC1 at a wavelength oi 10.63 microns. The VCI concentration wa* linearly related to absorbance up to approx imately 1000 ppm. A schematic diagram of the sampling Ex tern is shown in Figure 1. Sampling was ex ecuted sequentially with a set of six two-w.w solenoid valves controlled by a timer whit!: advanced the sampling location every 5 min utes. A visual account of transmittance warecorded on a strip chart recorder. Mean while the data were recorded in digital font, on paper tape by a tape punch and digitimprogrammed to record three equally spacit! transmittances during the last half of eat! 5-minute sampling period. The transmittance data furnished by tb-' spectrophotometer was converted to ab>d" ance and reduced to concentration according to Beer's law: n, (X,-XW) A L9|0(X,-X") v/here A X\ xm Xi i = absorbance -- base-line response. = response at total absorpiiu = response at location . - 2, 3, 4, 5, 6. finally, where C= KA K = a proportionality cc C -- concentration The taped data were processe i toughs 5500 computer at The 3 ,a) Company Computation Resei i .ory. The computer was used the mean and standard devtatioi i nations at each location for c j work shift- Finally, time-weigh 1 .oncentrations were calculated l ; classification using the time-do > Stained from the job surveys, t -Isewhere,1 the weighted percent ' Airing which concentrations ex -ral prechoscn levels was also cc 1 .tie in establishing exposure prof Figure 2 describes the expos , frequency distributions) for th classifications studied during t These profiles show the percent; hat concentrations exceeded (town. They summarize several ti -rndj of individually measured j nns and reduce them to single < } ire 3 shows the corrective tret ..bout by actions undertaken to ' '.rmospheric concentration of VC ; '-month period during which the inducted. Only two job dassific. anted extensive study, but men (ossifications were asked to par `he breath sampling program. 'h-the-Job Breath Sampling Three separate breath sampling rre conducted concurrently with omental plant survey, designate oxed portions in Figure 3. Ea< 'lireted three breath samples daily o his arrival home from work, t to 10 hours later, and a final s re returning to work the following ;oiple* were collected in pipets c on short lengths of 20-mtn soft gl "hich had been welded at eacl traded portion af a 2-dram (8-n VC2086 Novembcr-Decembrr, IOC'i American Industrial Hygiene Association Journal 539 Finally, the Plant Atmosphere nical installation surveyed was n nure housing several separate where C= KA ocessing operations. First, a job K = a proportionality constant. conducted for each of four job C = concentration s to determine the work area* >y the workmen and the time they 1 area. For each job classification. | probes were strategically placed area, A sixth probe was placed auilding, and charcoal and silica ere placed in the sampling line clean air reference. The sample 5/16-inch I.D. Saran tubinc ch air samples were drawn by a ip at a rate of 17.5 liters/min located infrared spectrophotonirectrophotometer was equipped ctcr p3th-length gas cell sensim of VCl at a wavelength of The taped data were processed by a Bur roughs 5500 computer at The Dow Chemi cal Company Computation Research Labora tory. The computer was used to calculate the mean and standard deviation of concen trations at each location for each 8-hour work shift. Finally, tiine-weighted average concentrations were calculated for each job classification using the time-location data obtained from the job surveys. As described elsewhere,1 the weighted percentage of time during which concentrations exceeded sev eral prechosen levels was also computed for use in establishing exposure profiles, s. The VC1 concentration wa< f Figure 2 describes the exposure profiles cd to absorbance up to approx- (frequency distributions) for the four job ppm. classifications studied during this survey. ic diagram of the sampling sysin Figure 1. Sampling was e.\- itially with a set of six two-way es controlled by a timer which sampling location every 5 min1 account of transmittance wa< a strip chart recorder. Meana were recorded in digital form by a tape punch and digitizerto record three equally spaced . during the last half of each pling period. littance data furnished by the These profiles show the percentage of time that concentrations exceeded the levels shown. They summarize several tens of thou sands of individually measured concentra tions and reduce them to single curves. Fig ure 3 shows the corrective trend brought about by actions undertaken to reduce the atmospheric concentration of VC1 over the '-month period during which the study was conducted. Only two job classifications war ranted extensive study, but men in all four j classifications were asked to participate in the breath sampling program. teter was converted to absorbiced to concentration according On-the-job Breath Sampling Three separate breath sampling programs were conducted concurrently with the envir (X,-X") Log 10 (X;-X) onmental plant survey, designated by the boxed portions in Figure 3. Each worker collected three breath samples daily--the first on his arrival home from work, the second absorbance base-line response, response at total absorption, response at location i. 2, 3, 4, 5, 6. 5 to 10 hours later, and a final sample be fore returning to work the following day The samples were collected in pipets constructed from short lengths of 20-mm soft glass tubing to which had been welded at each end the threaded portion af a 2-dram (8-ml) screw- cap glass vial (Figure 4). The overall length of the pipet was about 9 inches, so it could be conveniently and inconspicuously trans ported to and from work in a lunch bucket. The plastic caps were lined with six layers of Saran film identical to that used for the construction of Saran air sampling bags. A 3/32-inch hole predrilled through one of the caps provided an access for withdrawing samples. The Saran liners provided an ef fective gas barrier so that vapor losses were held to less than 10$) for a holding period of 3 days. When collecting a sample the subject was asked, to remove the caps, place the pipet to his lips, and breathe normally in through his nose and exhale through the pipet three Fioure 3. Weekly mean vapor exposure concen trations measured during the survey. Periods dur ing which breath sampling was conducted are rep resented by the boxed-in areas. VC2087 540 Novcmbcr-Deeembert 1%. imericen Industrial Hygiene Ass *GJ!32T3IM6ce mer infrared spectrophotometer equipp.,; ,,rre measured in the morning ant with a 10-mcter path-length gas cell. A sail, the afternoon exposure periods. pling probe, consisting of 5/16-inch I.D. S.i. Subjective and neurological resj ran tubing, was centrally located during tl,. rasured before the subject e Ficuse 4. Glass pipet (50 ml) used for collect ing breath samples. One cap has a prcdrilled hole for gas sampling. Both caps have Saran linen which se?-! 'he pipet chamber. exposure to represent the breathing zone . all subjects within the chamber. The proh was moved about prior to each exposure t. detect imbalance of vapor concentration, lumber, 15 minutes after entrai -hour intervals thereafter. Flar rdination and Crawford Manu: Tests were conducted at midm times. After expelling the fourth breath he quickly caps the tube, trapping a portion of alveolar air. The importance of writing the name, date, exact time of sampling, and the workshift most recently completed, on the label attached to each pipet, was stressed. Aliquots were drawn from the pipets with a 1-ml Hamilton gas-tight syringe and ana* K-ff-d ir. Aerograph A-600B gas chromato* graph using N2 carrier gas and a hydrogen flame detector. Separations we^e made with a 6-foot, J4-inch I.D. stainless-steel column packed with Carbowax 20M alkaline on Chromosorb W 60/80 mesh acid-washed. Exposure Chamber Operation within the chamber so that necessary cor. rections in the recirculating system could l> made. Air samples collected periodically within the chamber throughout the exposun day were analyzed by gas chromatography (or added assurance of analytical accuracy. Both the infrared spectrophotometer and the g.v chromatograph were calibrated before each experiment and at intervals throughout du exposure day. Each 7.5-hour exposure day included a 0.5-hour lunch period in an uncontaminaud area outside the exposure chamber. The TWA concentration was calculated on thr basis of 7.5 hours of exposure. jmin in the afternoon. Breath s. yin immediately after the subjc tposure chamber. A 24-hour p trine sample was collected and a -tie was drawn the following n >GPT, LDH, alkaline phospha creatinine, and bilirubin determir Analysis of Breath Data The decay curves for the breat}ride concentrations were construe wise multiple regression using a < outer. An empirical relationship Concentration = / (TWA, time) cd from a choice of several terms, on TWA and/or time. The resu Three experimental human exposures to VCl were conducted at nominal vapor con centrations of 50, 250, and 500 ppm. The exposure chamber was a room measuring" 41 feet by 6 feet wide hy 7.5 feet high. The room had a continuous positive air supply and exhaust system capable of maintaining a slight negative pressure within the cham ber. Continuous distribution of the cham ber air was achieved by recirculating the air with a squirrel cage fan through a series of inlet and outlet ducts spanning the length of Clinical and Laboratory Procedures Each subject had been under careful medi cal surveillance by the medical department for a number of years, and each was given a complete medical examination a few day. prior to the VCl exposures. Included wen a complete urinalysis and 24-hour urine for urobilinogen, complete blood count with sed imentation rate, reticulocyte count, 5GOT. SGPT, LDH, alkaline phosphatase, BUN. creatinine, and bilirubin. Each subject received a repeat physical sion equation best represents the utionship between breath vinyl c erntration, time-weighted averag and postexposure time. Each breath decay curve has a andard error of regression wf used to compute'the confidence t chosen level of significance, Th fidence band for the mean of a tervations was chosen in this case the statistical error associated wit! data and the regression technique the chamber. The VCl was metered into the duct carrying air exhausted by the squirrel cage fan and entered the room atmosphere via the recirculation system at a rate sufficient to maintain the desired atmospheric concen tration. The vapors were introduced from a pressurized storage cylinder through 6 feet of 14-inch I D. stainless-steel tubing into a rotometer prior to entering the circulating air duct. A heating tape wrapped around the stainless-steel tubing prevented condensation of the VCl and stabilized the flow of the vapor. The concentration of VCl in the chamber was constantly monitored with a Perkin-El- examination 1 hour before entering the ex posure chamber. This examination included measurement of temperature, blood pressure, and pulse rate, a neurological examination, and collection of blood and breath sampleA questionnaire noting the presence of am symptoms of illness (for example, headachenausea, dry throat) completed the pre-ex posure medical evaluation. After the subject entered the chamber, total expired breath samples were collect1'1^ every hour by having him breathe out throtf*a Saran tube leading to a Saran plastic col lection bag located outside the chamlxi Tidal volume and total expiratory capacin Results Experimental Breath Curves A total of 13 men participated experimental chamber exposures concentrations of 50, 250, .and 5C ! during a total of 160 valid l , points. Five of the six subjects ex | ppm were re-exposed at 500 p } >ater. There was no measurable tt chloride detected on the breaths ' icets prior to the second expos ' breath sampling was initiated i after the subjects left the exposu ; and continued up to 20 hours fc I 'Xpotures. VC2088 November~Decembcr, ]%, American Industrial Hygiene Association Journal 541 ired spectrophotometer cquipp<,j meter path-length gas cell. A satne, consisting of 5/16-inch I.D. S.>. was centrally located during tino represent the breathing rone o; s within the chamber. The proUd about prior to each exposure m balance of vapor concentrations : chamber so that necessary cor. the recirculating system could be r samples collected periodically chamber throughout the exposure nalyzed by gas chromatography for rrance of analytical accuracy. Both :d spectrophotometer and .the gas raph were calibrated before each : and at intervals throughout the lay. 5-hour exposure day included a snch period in an uncontaminated de the exposure chamber. The tentration was calculated on the hours of exposure. d Laboratory Procedures jeer had been under careful mediance by the medical department >er of years, and each was given a nedical examination a few days e VC! exposures. Included were urinalysis and 24-hour urine for n, complete blood count with sedrate, reticulocyte count, SGOT. IH, alkaline phosphatase, BUN. and bilirubin. rject received a repeat physical t 1 hour before entering the ex* nber. This examination included it of temperature, blood pressure, ate, a neurological examination, on of blood and breath sample' laire noting the presence of anv f illness (for example, headache. throat) completed the pre-excal evaluation. : subject entered the chamber, d breath samples were collected >v having him breathe out throuah o leading to a Saran plastic col located outside the chamber le and total expiratory capacity .,rre measured in the morning and again late a the afternoon exposure periods. Subjective and neurological responses were Measured before the subject entered the hamber, 15 minutes after entrance, and at hour intervals thereafter. Flannagan Co ordination and Crawford Manual Dexterity Tests were conducted at midmorning and jgain in the afternoon. Breath sampling bepn immediately after the subject left the fxpefeure chamber. A 24-hour postexposure irine sample was collected and a blood samale was drawn the following morning for sGPT, LDH, alkaline phosphatase, BUN, creatinine, and bilirubin determinations. Analysis of Breath Data The decay curves lor the breath vinyl chlo ride concentrations were constructed by stepwise multiple regression using a digital com puter. An empirical relationship of the form Concentration = / (TWA, time) was select ed from a choice of several terms, each based on TWA and/or time. The resulting regres sion equation best represents the ordered re lationship between breath vinyl chloride con centration, time-weighted average exposures, and postexposure time. Each breath decay curve has an associated standard error of regression which can be used to compute the confidence band for any chosen level of significance. The 95% con fidence band for the mean of a group of ob servations was chosen in this case to describe the statistical error associated with the breath data and the regression technique. Results Experimental Breath Curvet A total of 13 men participated in the three experimental chamber exposures at nominal concentrations of 50, 250, and 500 ppm pro ducing a total of 160 valid breath data points. Five of the six subjects exposed to 50 ppm were re-exposed at 500 ppm 2 days later. There was no measurable residual vinyl chloride detected on the breaths of the sub jects prior to the second exposure. Serial breath sampling was initiated immediately dter the subjects left the exposure chamber ind continued up to 20 hours following the "tposures. Table I Experimental Human Exposure to Vinyl Chloride Clumber Cooctnlntie* (ppm) 51 S.D. MZ 4X93I 7 491 S fcftftfC (ppm) 6J~ 2*9 24J 511-471 SSS-47S TWA* (ppm) 41 24* 439 491* Humber of Subject* 6 4 4 7 Time-weighted ftvmfe fcooccatretioo based on 7.5 Kauri including a Q*$-hovr Juacfc period in aa uaeoaumiaated area. tCoatiauoui czpeeurt for 95 bin. Table I shows the analyzed concentration to which the subjects were exposed. Calcu lations of the mean and standard deviation of exposure concentration are based on chart readings from the infrared spectrophotometer taken at 5-minute intervals over the two 3-5hour exposure periods. The TWA is based on the total 7.5 hours which included a 0.5hour lunch period in an uncontaminated area. The final breath decay curves intended for use as'an index to VC1 exposures were ad justed to TWA concentrations of 50, 250, Fioube 5. Breath decay curvet bated on experi mental human exposures to 50, 250, and 500 ppm of VCI (7.5-hour TWA). VC2089 Novembcr-Decetnbtr, ]%>, \mefican Industrial Hygiene Association Journal 543 tfidcnce bands only slightly wid,, . detect a faint odor of VCI. One subject sc from controlled human expeti- ,iuld detect a faint odor on deep inspiration The close similarity between tlt->. d those constructed from controlky. data are further illustrated in Fiu- ,>r approximately 15 minutes after entering Ac exposure chamber. The exposure had no noticeable effect on /urological responses, nor did it produce sig- Responses ificant changes in the results of mental, co gnation, or manual dexterity tests conduct- subjective standpoint no significant afTects were noted at any of tinoncentrations. The only complaints r of two subjects who reported mild J during the exposure period. All clinical sboratory studies performed in the postsjrosure period were normal and not signifiantly different from pre-exposure values. and some dryness of their eyes and ng the 500-ppm exposure experi- Discussion The object of the environmental health r was detected by anyone enterin',' i uney is to identify the atmospheric contain- ivc chamber at 50 ppm. At 250 * nant, determine the exposure level, and re- jur subjects entering the chambci ate this to the health hazard it presents. If ported that they could detect a >ne is to judge hazard by ambient concen- odor of the chemical. Five of the :ration measurements, then those measure rets entering the exposure chani- ments must accurately describe the exposure ppm were able to detect the odot n a continuing individual basis. A carefully i after 5 minutes of exposure those nablc to detect it even with forced Three of the four subjects tv- j onducted survey combining continuous analds of the work room atmosphere with a omprehensive job study will provide data Figure 8. Comparison of breath decay curves derived from the on-the-job data ami the experi mental human exposure data. e chamber after lunch were ahl.- slid for estimating time-weighted average vposure. limited by the number of sampling probes, On the other hand, breath decay curves and these probes are not always capable (instructed from breath data collected dur- of accurately measuring the individual's daily ng continuous plant monitoring are in close exposure experiences, especially should these agreement with those obtained from exposure involve unusual incidences such as chemical hamber experiments with VCI. These curves spills or exposures outside the monitored hould therefore be useful as a second meth- area. * d for assessing exposure to VCI vapor. Breath analysis has the advantage of in The choice of whether one or both meth- dividualizing each worker's integrated daily <ds should be used depends on prevailing exposure. Breath decay curves, as an index' j ircumstances and on the thoroughness de- of exposure, offer a means of estimating the . `red. For example, data useful in describ average daily individual exposure on the basis es peak exposures are obtained from con- of a few breath samples taken serially in the "nuous monitoring. Concurrently, exposure postexposure period. Consequently breath :ends and concentration gradients may help analysis can be used to diagnose as well as kntify plant operational inefficiencies and quantitate an exposure which has already `luipment malfunctions by revealing specific occurred. It is a relatively inexpensive and ' "urces of emission. Correcting these prob- simple method which can be put into opera "ms not only restores a healthful work en- tion without extensive and costly preliminary ronment but often results in bonus savings preparations. y reducing losses of raw material and prod However, postexposure breath analysis does rosr exposure time, hours Breath decay curves derived *rrin illected from workers follou inc "i> yrs to VCI vapor (8*hour TWA1- uct j Continuous monitoring, however, is ex- "rnely costly both in time and in the cquip| "ent required. The scope of data acquired is not provide information on the daily fluctua tions of exposure, and the peak exposure con centrations are not made evident by breath data. Finally, breath analysis is not applica* VC2091 ? 644 Novftnber-Deeember, !%<, ble to all chemicals, and breath decay curves established for one chemical are not useful as an index of exposure to any other chem ical. The decay curves presented here are in tended to serve as an index of exposure to vinyl chloride vapor and are based on an exposure duration of 7.6 hours for the experi mental exposures, and 8 hours for the on-thejob study. The close agreement between the two sets of curves and the narrow confidence bands obtained in each case demonstrate the usefulness and accuracy of both methods for estimating TWA exposures and indicate the importance of breath analysis and the need for expanding its use in evaluating ex posures to other widely used volatile organic chemicals. 'References 1. PfcizjtsON, J. E., M. R. Hovu, ind E. J Scmhij.w, The Application of Computer Science to Industrial It, . Amir. ini. Uyg. Au*t. J. 27: )8<ME5 (kL.w \. 2. SnwuT, R. D., H. H. Cat, D. 5. Ealby, C. L. Ihn mud A. W. SciiArrut; Human Ei|>oure to TeUacfeWm' ethylene* Vapor: Relationship of Expired Air and lb,.,* Conrmtntioni lo Exposure and Toxicity. Artk. am*' Htilth 2: 516*322 (May 19(0* 3. Stiwait, R. D.. H. H. Cat, D. S. Eauy, C. L. Htii and J. E. Pbtzaion; Observation! on the Coi>ceatrtin, of Trichloroethylene in Blood and Expired Air fatt ing Expoture of Human*. Amtr. Imd. Hyg, Amt, 1'| 167*170 (April 1962). 4. InwAiT, R. D., and V. K. Rows: Quint* A*. d'Etude* but !e ll,l*TrirMoro*thane. Ant. MtUd,, Pre/#w. 28: 194-201 (19C7). 5- nw*tt, R. D. H. C. Done, E. D. Bauvta, A. W. ScHArm: Human Exposure to Styrene Vaa< Artk. titilth 16; No. } (May IWl). 6. Stiwaxt, R. D.t E. D. B/MtrrrA, H. C. Dow, awf T. R. Tobkelxon: Experimental Human Expatur* t* Teirachlorocthyleoe, AMA Artk. EntAm, Httlih, (In print). 7. SnwAtr, R. D., H. C. Douo, E. D. Baaam. A, Vi ScHArna, and J. E. Mutchua: Chronk Oveirxpourr to Benzene Vapor. Presented at the Sixth Annual Meet ing of the Society of Toxicology, March 23*23, l^>! Atlanta, Georgia. Received Stay 26,1*4 Exposure t DOUGLAS L. JOH: v Bumra of Occupational i and Wolfe As part of its study of cuing of fibrous mater ducting a cohort analysis c surveys to estimate the dei respirable indicated that ttrations of fibers in air ere tration ranges and averagi turing are compared with t implications. Notices and Deadlines It is the policy of the AIHA Journal to accept and publish notices and short items of import and interest to our readers subject to the limitations of available space. This is done as a sen-ice to our profession and no fee is charged for such announcements. Some notices are received too late to be carried to advantage in our Jour nal. Persons supplying announcements to us should keep in mind the time schedule of our publication. The Journal appears six times per year with the copies being mailed about the 20th of February, April, June, August, October, and December. While emergency or urgent notices can be inserted up to three or four weeks before the mailing date, such cannot be assured. Normally the announcements should be in the Editors hands at least two .months or more before the issue in which they should appear. Perhaps these guidelines will aid you announcement generators. Introduction he bureau of occu TSAFETY AND HEALTH Public Health Sen-ice is present! j cohort analysis of past workc orous glass industry. The perse I were obtained for the subject s j .ive of the oldest plants in the I j hat manufacture fibrous gla | Mortality data will be develo ' iroup of workers from records c ! of Retirement and Survivors Ir rial Security Administration. -Judy is being undertaken in conj . the U. S. Public Health Serv siortality rates in the asbestos pr :acturing industry. Since the -ions of industrial workers selr :wsed to two different fibrous m adjusted death rates by cause ( ared for possible relation to in j -xposures. An environmental survey of ;lass plants to estimate the expos Mention of commercial product* or coot* i*tt (idonrmHi by the U*5. public Hex VC2092