Document 6b108d54n7dQ5wRDRZEBgojvo

Monitoring Exposures to Vinyl Chloride Vapor: Breath Analysis and Continuous Air Sampling EDWARD D. BARETTA,* RICHARD D. STEWART, M.D., and JOHN E. MUTCHLERf Department of Environmental Medicine, Marquette School of Medicine, Milwaukee, Wisconsin, and Environmental Health Section, Biochemical Research 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 postexposure breath concentration to vapor exposure were derived from the data. To validate the breath curves derived from on-the-job data, postexposure breath curves were also constructed from breath data obtained following exp-rimentai human exposures to carefully controlled concentrations of VC1 vapor. The close agreement between postexposure breath concentrations at. the corresponding TW.Vs obtained by each of the methods suggests that either continuous air monitoring or breath analysis is valid for estimating the worker's individual dally exposure to VC1, and provides further evidence that breath analysts is a useful industrial hygiene technique for evaluating vapor exposure. Introduction '"THE QUESTION THAT MAY ARISE E 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 ork, AO provide centrations and estimates of time-weighted ! average concentration (TWA) are all too often based on a few spot samples obtained designed especially for women. * 1 under conditions which are not representa y the tough, attractive F5100 and 1 * tive of all phases of a given operation. A nodeU. Or you can have metal with I t more exact measurement of vapor exposure F5.100 Safcmaster. j would have to be based on continuous moni attachments I toring of air in the workman's breathing amcs are made to take the extras, if d' 1 tone during his entire work shift. Obviously -mi. Like dear plastic semi-sideshi<' this task is made difficult and often impossible cher vented side shields. Even cleat | t'tlUltitffrt by Amem an Optical Thii p*pcr wu presented t (be Atnrriean Industrial Hyriefie Conference, St. Louis, Mi'Bfluri, May 1.1*17, 1968. Marquette Srhrol of Xfedicine, Milwaukee, Wisconsin. tThe Dow Chemical Company, Midland, Michigan, by the large number and variety of tasks per formed by today's modern chemical plant worker. * Recent 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 or 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 EC- 0201 Novembcr-Decembcr, 1%<) jwicrican 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 breath 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 bicath analysis in assessing timeweichtcd average exposure was reflected by a close siinilanty between the two sets of breath decav curves. OUTSIDE AIN STATION I ______g-- j WORK AREA 1 STATION 3 STATION 5 ____________9______ i STATION l {STATION 4 ! STATION C 01 !? t1 9 -- .1 tioit f INFRARED spectrometer ^OIGITIZER "* \ --1 RECORDER'v. I 1 COMPUTER Procedures Monitoring the Plant Atmosphere The chemical installation surveyed was a closed structure housing several separau chemical processing operations. First, a joh survey was conducted for each of four job classifications to determine the work arc\frequented by the workmen and the time thw spent in each area. For each job classification, five sampling probes were strategically placed in the work area. A sixth probe was placed outside the building, and charcoal and silic.i gel filters were placed in the sampling line to assure a clean air reference. The sample probes were 5/16-inch I.D. Saran tubing through which air samples were drawn by a vacuum pump at a rate of 17.5 liters/min to a centrally located infrared spectrophotom eter. The spectrophotometer was equipjx-d with a 10-meter path-length gas cell sensi tive to 5 ppm of VC1 at a wavelength oi 10.63 microns. The VC1 concentration was linearly related to absorbance up to approx imately 1000 ppm. A schematic diagram of the sampling sys tem is shown in Figure 1. Sampling was executed sequentially with a set of six two-wav solenoid valves controlled by a timer which 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 form on paper tape by a tape punch and digiti/ci programmed to record three equally spaced transmittances during the last half of eari 5-minute sampling period. The transmittance data furnished by thspectrophotometer was converted to absorb ance and reduced to concentration according to Beer's law; EXPOSURE SUMMARY a=L09'w|=F) TIME -WEIGHTED MEAN EXPOSURE * OOI ) C,R| In* Ci mi cmctntrelini l Sl*tl I P( P*t af liiM apant a< lacafiaa I Aariag aarmaf work wctMlf > Figure 1. Schematic diagram of the infrared continuous monitoring system. where A X, X* Xi i = absorbance -- base-line response. -- response at total absorption = response at location i - 2, 3, 4, 5, 6. finally, where C= KA K -- a proportionality cc C -- concentration The taped data were processe flight 5500 computer at The I Company Computation Resea jury. The computer was used die mean and standard deviatior orations at each location for t work shift. Finally, time-weigh -iMicentrations were calculated f< classification using the time-lex ibtained from the job surveys. I -lsewhere,* the weighted percentduring which concentrations ex< >ral prechoscn levels was also co ise in establishing exposure profi Figure 2 describes the expos* frequency distributions) for th classifications studied during t! These profiles show the percents .hat concentrations exceeded -hown. They summarize several te -uids of individually measured ions and reduce them to single c ire 3 shows the corrective tree bout by actions undertaken to : '.'.mospheric concentration of VC 'month period during which the inducted. Only two job classifier anted extensive study, but men i ^ossifications were asked to pari iie breath sampling program. '^n-the-Job Breath Sampling Three separate breath sampling `re conducted concurrently with 'mnental plant survey, designate 'Wed portions in Figure 3. Eac "Hected three breath samples daily his arrival home from work, tl to 10 hours later, and a final s; re returning to work the following ttiples were collected in pipets cc 'in short lengths of 20-min soft gl; which had been welded at each readed portion af a 2-dram (8-m EC- 0202 November-Decembcr, 1%'t American Industrial Hygiene Association Journal 539 the Plant Atmosphere nical installation surveyed was a cture housing several separate ocessing operations. First, a jo!) conducted for each of four jol> s to determine the work area' >y the workmen and the time thw 1 area. For each job classification. I 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 tubing ch air samples were drawn by a ip at a rate of 17.5 liters/min located infrared spectrophotonv jectrophotometer was equipped ctcr path-length gas cell sensin^nf VC! at a wavelength oi" VC1 concentration wa< absorbance up to approxppm. ic diagram of the sampling sysin Figure 1. Sampling was exitially with a set of six two-way es controlled by a timer which sampling location every 5 min1 account of transmittance was a strip chart recorder. Meana were recorded in digital form t by a tape punch and digitizerto record three equally spaced . during the last half of each pling period. littance data furnished by the teter was converted to absorbiced to concentration according Log 10 (X,--X") (X;-X) absorbance base-line response. r^^nse at total absorption. i^Hhse at location i. 2^,4, 5, 6. Finally, where C= KA K -- a proportionality -constant. C -- concentration 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 I use in establishing exposure profiles. Figure 2 describes the exposure profiles (frequency distributions) for the four job classifications studied during this survey. 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 7-month period during which the study was conducted. Only two job classifications war ranted extensive study, but men in all four classifications were asked to participate in the breath sampling program. On-the-job Breath Sampling Three separate breath sampling programs were conducted concurrently with the envir 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 5 to 10 hours later, and a final sample be fore returning to work the following day The samples were collected in pipets constructed bom 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- Ficure 2. Exposure profiles expressed as VCI vapor concentration versus the exposure frequency distribution for the lour job classifications. 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 tration! measured during the survey. Periods dur ing which breath sampling was conducted are rep resented by the boxed-in areas. EC- 0203 I 540 Novembcr-December, I jmerican Industrial Hygiene Asst mer infrared spectrophotometer equippl(_ .,rre measured in the morning and with a 10-meter path-length gas cell. A s.ui, :i the afternoon exposure periods. pling probe, consisting of 5/16-inch l.D. S,. Subjective and neurological resp Ficure 4. Glass p'ipct (50 ml) used for collect ing breath samples One cap has a prcdrilled hole for gas sampling. Both caps have Saran liners which seal the pipet chamber. 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 lyzed in an Aerograph A-600B gas chromato graph using Ni carrier gas and a hydrogen flame detector. Separations weje made with a 6-foot, '/g-inch l.D. stainless-steel column packed with Carbowax 20M alkaline on Chromosorb W 60/80 mesh acid-washed. Exposure Chamber Operation ran tubing, was centrally located during t),. exposure to represent the breathing zone all subjects within the chamber. The protv was moved about prior to each exposure t. detect imbalance of vapor concentration, within the chamber so that necessary coj. rections in the recirculating system could 1> made. Air samples collected periodical within the chamber throughout the exposun day were analyzed by gas chromatography for added assurance of analytical accuracy. Bo;!., the infrared spectrophotometer and the g:> chromatograph were calibrated before each experiment and at intervals throughout the exposure day. Each 7.5-hour exposure day included a 0.5-hour lunch period in an uncontaminau-i! area outside the exposure chamber. The TWA concentration was calculated on thr basis of 7.5 hours of exposure. measured before the subject et Ivamber, 15 minutes after entran .hour intervals thereafter. Flan .rdination and Crawford Manua' Tests were conducted at midme ,?ain in the afternoon. Breath sa ;an immediately after the subje. xposure chamber. A 24-hour p< irine sample was collected and a tie was drawn the following m SGPT, LDH, alkaline phosphat yreatinine, and bilinibin determin Analysis of Breath Data The decay curves for the breath ride concentrations were construct wise multiple regression using a d puter. An empirical relationship < Concentration = f (TWA, time) ed from a choice of several terms, on TWA and/or time. The resul Three experimental human exposures to Clinical and Laboratory Procedures sion equation best represents the t VC! were conducted at nominal vapor con Each subject had been under careful medi- iationship between breath vinyl ch centrations of 50, 250, and 500 ppm. The cal surveillance by the medical department eentration, time-weighted average exposure chamber was a room measuring'41 for a number cf years, and each was given a feet by 6 feet wide hy 7.5 feet high. The complete medical examination a few day and postexposure time. Each breath decay curve has ar room had a continuous positive air supply prior to the VCl exposures. Included very standard error of regression whi and exhaust system capable of maintaining a complete urinalysis and 24-hour urine for ' used to compute'the confidence b; a slight negative pressure within the cham urobilinogen, complete blood count with sed chosen level of significance. The ber. Continuous distribution of the cham imentation rate, reticulocyte count, SGOT. fidence band for' the mean of a gi ber air was achieved by recirculating the air SGPT, LDH, alkaline phosphatase, BUN. <ervations was chosen in this case with a squirrel cage fan through a series of creatinine, and bilirubin. the statistical error associated with inlet and outlet ducts spanning the length of Each subject received a repeat physical data and the regression technique. the chamber. The VC1 was metered into the examination 1 hour before entering the ex lUsulh 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 J4-inch l.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 VC1 and stabilized the flow of the vapor. The concentration of VC1 in the chamber was constantly monitored with a Perkin-EI- posure chamber. This examination included measurement of temperature, blood pressure, and pulse rate, a neurological examination, and collection of blood and breath sample' A questionnaire noting the presence of at" 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 collects! every hour by having him breathe out throne!: a Saran tube leading to a Saran plastic *'! lection bag located outside the chamlxi Tidal volume and total expiratory capacity Experimental Breath Curves A total of 13 men participated i experimental chamber exposures concentrations of 50, 250, and 50t I during a total of 160 valid b) , points. Five of the six subjects exj ) ppm were re-exposed at 500 p; j iater. There was no measurable ret chloride detected on the breaths i ' its prior to the second expost weath sampling was initiated it after the subjects left the exposur ; and continued up to 20 hours fol I 'xposures. EC- 0204 November-Decembcr, /%>, American Industrial Hygiene Association Journal 541 tied spectrophotometer equipped meter path-length gas cell. A sajn, e, consisting of 5/16-inch I.D. S... was centrally located during th,. :o represent the breathing zone n; s within the chamber. The probe d about prior to each exposure m balance of vapor concentration chamber so that necessary cor. the recirculating system could be r samples collected periodically chamber throughout the exposuic nalyzed by gas chromatography for trance 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 inch period in an uncontaminated ie the exposure chamber. The tentration was calculated on the hours of exposure. aboratory Procedures ject had been under careful mediance by the medical department >er of years, and each was given a nedical examination a few days e VC1 exposures. Included were urinalysis and 24-hour urine for n, complete blood count with sedrate, reticulocyte count, SGOT. H, alkaline phosphatase, BUN. ind bilirubin. tject received a repeat physical i 1 hour before entering the exnber. This examination included it of temperature, blood pressure, "ate, a neurological examination, on of blood and breath samples tairc noting the presence of am f illness (for example, headache, throat) completed the pre-excal evaluation. subject entered the chamber. i breath samples were collected v having him breathe out throne!' c leading to a Saran plastic col located outside the chamber, pd total expiratory capncit' .,ere measured in the morning and again late n 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 Coirdination and Crawford Manual Dexterity Tests were conduoted at midmorning and jgain in the afternoon. Breath sampling be gin immediately after the subject left the exposure chamber. A 24-hour postexposure trine sample was collected and a blood sam ple was drawn the following morning for SGPT, LDH, alkaline phosphatase, BUN, creatinine, and bilirubin determinations. Analysis of Breath Data The decay curves for the breath vinyl chlo ride concentrations were constructed by step wise multiple regression using a digital com puter. An empirical relationship of the form Concentration = f (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 andard error of regression which can be used to compute the confidence band for any chosen level of significance. The 955b 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 Curves 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 after the subjects left the exposure chamber *nd continued up to 20 hours following the ^posures. ITable Experimental Human Exposure to Vinyl Chloride Chfember Co&centffetioft (ppm) X S.D. 59 2 261 S 493 7 491 5 Kant* (ppm) 65- 53 289 243 518-471 525-473 TWA* (ppm) 48 248 459 4916 Number of Subject* 6 4 4 7 *Time*weiphted fever*ft coocentntioo b**ed od 7.5 hour* including fe 04-hour lunch period in fen unconuminfeted nrefe. *Contiouou4 expofur* lor 34 hour*. 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, 5.Figure Breath decay curves based on experi mental human exposures to 50, 250, and 500 ppm of VCI (7.5-hour TWA). EC- 0205 542 NovrmbeT'Dectmbcr, J\%>, Ittlniran Industrial Hygiene Ass DAILY VARIATION IN EXPOSURE TO VCL VAPOR (8 hr TWA) Day* ot the Mwwh fMwBSMiiiB Figure 6. Variation in VCI vapor exposure (or three shifts. and 500 ppm (Figure 5). A 100-ppm decay curve was interpolated from the available data using regression analysis. These curves are presented wi*h the calculated 95% con fidence bands for the mean of a group of ob servations. On-lhc*Job Breath Curves Ten workmen participated in the on-thejob breath sampling program, producing a total of 91 usable sets of data. Ten percent of the breath samples collected were discard ed because of pipet leakage or poor sampling techniques. Ab'cluio breath levels ranged from about 20 ppm in one sample taken less than 1 hour after an 8-hour TWA of 250 ppm, to barely detectable levels (<0.05 ppm) in samples taken after exposures at TWA's below 50 ppm. The extremely broad variation in the TWA's experienced by workmen during one of the periods in which breath sampling was being conducted is demonstrated for three shifts of men bearing the job classification "coagulator operator'' (Figure 6). Minute, hourly, and daily fluctuations in the concen tration of a contaminant are most descriptive ly revealed by continuous monitoring. This method of sampling quickly points out the fallacy of judging TWA and peak exposure concentrations on the basis of spot sampling or periodic surveys of brief duration. The remarkable correlation between breath concentration and corresponding TWA val ues made it possible to construct the series of breath decay curves shown in Figure 7, with confidence bands only slightly wide, than those from controlled human experiments. The close similarity between thr.curves and those constructed from cnntn|||.,| exposure data are further illustrated in Kieure 8. Human Responses From a subjective standpoint no significant untoward affects were noted at any of tl>,. exposure concentrations. The only complaint, were those of two subjects who reported mild headache and some dryness of their eyes and nose during the 500-ppm exposure cxjxii. ments. No odor was detected by anyone entering the exposure chamber at 50 ppm. At 250 ppm all four subjects entering the chamlx-i initially reported that they could detect a very slight odor of the chemical. Five of tinseven subjects entering the exposure chainber at 500 ppm were able to detect the odm of VCI, but after 5 minutes of exposure those* five were unable to detect it even with forced inspiration. Three of the four subjects re entering the chamber after lunch were able Figure 7. Breath decay curves derived h breath data collected from workers follow-inc the-job exposures to VCI vapor (8-hour TWA I , detect a faint odor of VCI. C j ,,,dd detect a faint odor on deep ,r approximately 15 minutes aft exposure chamber. The exposure had no noticeabl . ,-urological responses, nor did it p licant changes in the results of t 1 dination, or manual dexterity tes 1J during the exposure period. . .horatory studies performed in qiosure period were normal and jotly different from pre-exposurt j )cussion ' The object of the environmen itvey is to identify the atmospher ant, determine the exposure lev< ,:e this to the health hazard it p t ne is to judge hazard by ambiei ' ration measurements, then those irnts must accurately describe thi n a continuing individual basis, t inducted survey combining contin cs of the work room atmosphe unprehensive job study will pre jlid for estimating time-weighte rposure. On the other hand, breath dei j nstructed from breath data colli * continuous plant monitoring ai .Tcenient with those obtained fron Jinber experiments with VCI. Th 1 uuld therefore be useful as a sect 1 for assessing exposure to VCI va The choice of whether one or b Js should be used depends on -rcumstances and on the thoroug td. For example, data useful it peak exposures are obtained i -"nous monitoring. Concurrently, ends and concentration gradients 'ntify plant operational inefficie: wipment malfunctions by revealir, trees of emission. Correcting th to not only restores a healthful wnment but often results in bom reducing losses of raw material a ., L fontinuous monitoring, howeve 'ncly costly both in time and in t ( nt required. The scope of data a< EC- 02.06 Novembcr-Dccember, 1%; piifrifoii Industrial Hygiene Association Journal 543 ifidcnce bands only slightly wi<|, t ,i detect a faint odor of VC1. One subject sc from controlled human expt'ii. j otild detect a faint odor on deep inspiration The close similarity between tin- : <r approximately 15 minutes after entering d those constructed from controlled l jo exposure chamber. data are further illustrated in Fie- The exposure had no noticeable effect on :(-urological responses, nor did it produce sig- Usponses ificant changes in the results of mental, co ordination, or manual dexterity tests conduct- subjective standpoint no significant afTects were noted at any of tli. oncentrations. The only complains of two subjects who reported mild J during the exposure period. All clinical .iboratory studies performed in the postqxwure 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 entering I urvey is to identify the atmospheric contami ire chamber at 50 ppm. At 250 nant, determine the exposure level, and re Dur subjects entering the chamber ate this to the health hazard it. presents. If ported that they could detect a me is to judge hazard by ambient concen odor of the chemical. Five of the tration measurements, then those measure- rets entering the exposure chant- nents must accurately describe the exposure ppm were able to detect the odor n a continuing individual basis. A carefully : after 5 minutes of exposure those i inducted survey combining continuous analto detect it even with forced s:s of the work room atmosphere with a ree of the four subjects re- omprehensive job study will provide data e chamber after lunch were ablealid for estimating time-weighted average xposure. Figure 8. Comparison of breath decay curves derived from the on-the-job data and the experi mental'human exposure data. 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 ing continuous plant monitoring are in close exposure experiences, especially should these ifreement with those obtained from exposure involve unusual incidences such as chemical hamber experiments with VC1. These curves spills or exposures outside the monitored hould therefore be useful as a second meth- area. <1 for assessing exposure to VC1 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 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 ng peak exposures are obtained from con- of a few breath samples taken serially in the nuous monitoring. Concurrently, exposure postexposure period. Consequently breath :nds and concentration gradients may help analysis can be used to diagnose as well as lentify plant operational inefficiencies and quantitate an exposure which has already (|uipment malfunctions by revealing specific occurred. It is a relatively inexpensive and -iirces of emission. Correcting these prob- simple method which can be put into opera 'fas 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 uct. not provide information on the daily fluctua Breath decay curves derived fren1 rllected from workers follow inc VC1 vapor (8-hour TW.'1- Continuous monitoring, however, is exI'mely costly both in time and in the equip;*nt required. The scope of data acquired is tions of exposure, and the peak exposure con centrations are not made evident by breath data. Finally, breath analysis is not applica- EC- 0207 M4 Navember-DectmbcT, ]%<t blc 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 7.5 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. Referancts 1. Piymson, J. E., H. R. Hovu, nd E. J. Sciinuihi The Application or Computer Science to industrial ll. gvrnp. Am*Tt Ind, Hyg. Alter. J. 27; IBO-IB) (fcLi.k 2. Snwur, R, D., H. H. Gay, D, S. Eouey, C. L, )|u, and A. W. Schaffer: Human Exposure to Tetr*chlort ethylene Vapor: Relationship of Expired Air and Conrmitrationt to Exposure and Toxicity. Artk. Emi-u*,* Health 2: 516*522 (May 1961). 5. SnwAtr R, D., H, H. Gay, D, S. Eiiiy, C. L, Htti and J. E. PttutsoN: Observations on the Concefiirat>(, of Trichloroethylene in Blood and Expired Air follth' in* Exposure of Humans. Amt*. Ind. Hyg. Ante. l_?i 167-170 (April 1962). 4. STtWAfcT, R, D., and V. K. Row*: Quinte A*. d'Etudes tur le 1,1,1-Triehloroethane. Anh. Atalnd,* Prajeaa: 28: 194*201 (I9G7), 5. Stewart, R. D.. H. C. Dodo, E. D. Baxtita. a*^ A- W. Schaffer: Human Exposure to Styrene Va* Arch. Environ. Health 16: No. 5 (May l9o8). , Sttwaht, R, D,. E. D. Baaftta, H. C. Dots, T. R, Torkelron; Experimental Human Exposure Tetrachloroethyleoe. AMA Arch, Environ, Health. (In print). 7. Stiwaxt, R, D,, H. C. Dot*, E. D. Baretta, a. \\ Schaffer, and J. E. Mutchler: Chronic Overexp^ut. to Benzene Vapor. Presented at the Sixth Annual Mrn in? of the Society of Toxicolofy, March 23-2), I9,* Atlanta, Georgia. Received May 26, Exposure tc < DOUGLAS L. JOHN: Bureau of Occupational Sa and Welfare As part of its study oi l cuing of fibrous materia ducting a cohort analysis of surveys to estimate the degr respirable indicated that th< trations of fibers in air are 1 tration ranges and averages turing are compared with thi 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 service 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 X'HE BUREAU OF OCCUP 1 SAFETY AND HEALTH o Public Health Service is presently i cohort analysis of past worker: brous glass industry. The person I were obtained for the subject w< ! nve of the oldest plants in the Ui j hat manufacture fibrous glass | Mortality data will be develop! : jroup of workers from records of ! of Retirement and Survivors Ins: rial Security Administration. Ti 'ttidv is being undertaken in conju the U. S. Public Health Servic mortality rates in the asbestos pro< :acturing industry. Since the t\ '.ions of industrial workers select :<osed to two different fibrous mat adjusted death rates by cause ca iared for possible relation to ind> ! tposures. An environmental survey of i .lass plants to estimate the exposu Mfmion of commercial product* or concern! -ute endowment by the ti.S. Public HealU ec- 020