Document 2JowMkGZQwY6N8dZMqmnXpeDb

verity nfhi pairs ttt siiht by snfw charcoal tub and 3M Brand passive vapor monitor samples were taken in 0,6 field and analyzed for 22 organic chemicals including trichloroethylene, benzene, toluene. MEK. m-. p-. and 8^lylnnes isnprnpannl. and several CS through C alkanes. Sixty-four pairs were personal and fourteen pairs re a>ea samples Linear regression analyses were performed for ten chemicals detected over a sufficiently large of concentrations Satisfactory correlation |r 0.90 and slopes not significantly different from 1 01 was l^und between monitors and tubes for n-hexane. methylcyclopentane. toluene. 2 methylpentane. 3-methyla no. nheplane. n-pentane, and isopentane. Tube and monitor results differed for methylcyclohexane and octane. Paired t tests were performed on the remainder of the chemicals, and no consistent significant differences (5% level) in the means were found. Field comparison of charcoal tubes and passive vapor monitors with mixed organic vapors JOHN L S HICKEY PhD. PE and CAROLYN C 0ISHOP Qnivt'fsily ill North Carolina. Occopahon.il Health Studies Group School ot Public Health, Cliapr-IH.il NC 27514 introduction Severn I brands ot charcoal-adsorption passive vapor moni tors have been marketed icecnily. I hesc monitors hold mm,It ailraclion lor measuring workplace vapor exposures hccausc thev are lightweight. require no power, pump, or I tithing. and aie not likely to interlere with wotkets' move* I imills I lie opctuling ptmoplcs ol ihcse momtois have been I'icsviihed. and then advantages ami hniilalions have been oimpated to (hose ol chart oal lube pump momlotmg svsU'tns ' I lie pel loiin.inee ol passive momtois has been o.i11lalcd lot v ai ioil' i belliiv als undo \ ai ions v onilitions ' Howev ei I u hl si mlies ol the perlot mauve ol passivc nioiiloi s m ass.i\ i np mi xeil organic v a pin s are lack mg. alt honeh in vs lensiv c 11eld v omparison o| passiv e monitors and elt.n eo.iI tubes is planned procedures Vv entv -eight sets ol simultaneous eh.uvoal tube and i\l ktaiuf It <500 oreattiv vapor monitor samples vveie collected "id analvzed loi 2d organic chemicals as part ol a survev ol :'re m a mi I ae i in me lavihties I lie chemicals, listed in I a hie I. j *vrc selected lor analv sis on the basis ol their piesencc in j Materials used in me manufacture ! Samples were collected during regular work shills m two j miauls dunng two 2-day periods in duly and August. Id7d i '"xiy-tour sets were personal samples and 14 were aiea ! 'Jinples I he sampling penods varied trom three to live hours ( hareoal lubes were usually changed during ihc sampling Period to reduee the possibility ol o\erlnailing: t lie monitors *v're not I hus. with tew exceptions, each pair of results sunsists ol the concentration Irom a single monitor and the "mic weighted average concentration Irom two ehateoal 'uhes chemical analysis \liet exposure to the solvent vapors, the organic vapor monitors and t hareoal tubes were capped and stored at - 7 C until lime ol analysis. Monitors were analyzed in accordance xvmh the manufacturer's instructions. using a Perkin* n.ih i g.ts ehi omatograph ( Model Sigma 11 equipped w nil a ilame umi/alion detector C oneenlialion data wen- I'aleulaivd vviih a I'erkm-f liner Sigma III data system I he ilc'oi pi ion el I iv leth v lor each so!v cut w as determined h\ our l.ihm.itoi v using the methovl icvommcndcd bv the YM ( ouip.iny t om vtitrations weie calculated m at v oul.uive ss 11 h mail ii I av i m el's instruct ions | he vlitl ii'ion laptops oi M/m/'///re 'M/i ' l.iualagous to ihllueuin voel lie lent' i u'v'vl ar v lisivil m I a hie I tor each client it a I Chart oal t u hes w ere dc-orhcd in the standard manner and analxzvd under the same pioteilures as the momtois' results I en ol the vhenneals were detected over a sufficiently wide i a nee ol tom durations m one or both plains lo permit a linear legression analysis ot passive monitor and charcoal i tibv sampling i esult s Slopes, mtereepis. cot re I ji ion voel 11eicnis and dY , vonlidenw intervals lor prediction ol indiv idual v .dues ai v giv en in I able 11. separately lor the l w o sin \ v v s ami lor the combined dala irom both groups ( hareoul lubes weie l\l values and monitors were (Y) values, lhat is. vh.uvojl tube sample results were considered in relict i i/i/> ' e oneenl i at tons, as a basis lor comparison I he second column in lahle II indicates Ihe range ol concentrations loutul in ihe sample's Columns t and 4 are I he slope and 'i - intercept of the linear regression line, w hieh indicates how well the two methods agree -N slope ol I (land at S -intercept ol zero indicate close overall agreement I he correlation coefficient leolumn 5) reflects the degree ol :u 3M 106752 r- 1981 TABLE I Chemicals Analyzed and Sampling Rates Sampling Rales ImL mm)' j J )tiHi`thyltHilim' j Mfthytjirni.in*' 2 hvU`w't.ine ,, Cy, iupfiitiint" M,thvi<.v<'h`pf*nt&n*f n Heptane Cyclohexane Meihylcyclohexane o-Octane 11 1 Tru-hloroethane Methyl ethyl ketone tsopropanol Benzene Trichloroethylene Toluene Ethylene trichloride p Xyltma m Xylene o Xylene Reference 1*6 29 8 29 a 28 2 28 2 28 2 28 2 28 2 28 2 27 7 28 2 27 2 2) 8 28 1 31 2 35 9 33 0 28 0 30 4 32 1 23 7 25 6 25 7 departure of data-pairs from the repression line. An r value ot I 00 indicates near perfect correlation, and lower r \uiues indicate poorer correlation. The last two columns are the predicted 95C(. confidence limits of an individual passive moni tor sample, given some "true" concentration of X as indi cated bv charcoal tube samples. I he predictions were made lor concentrations at the top of the data range observed, I he other twelve chemicals were detected in coniparaiivclv lew samples or mostly at low concentrations | less than I ppm), so no linear repression analyses were pertormed Instead, the paired t-tesf ' was used to determine it the monitor and tube sample means were statistically dillerent at the () 05 probability level, assuming normal distribution No consistent difference in means was demonstrated except lor n-octane. discussion I he data in I able II show two trends. In C roup No, I, lor every chemical except n-heptanc the passive monitors show highci vapor concentrations than the charcoal tubes, as indicated hv iinear regression slopes greater than 1 I), In three cases (toluene, n-octanc and meihvleyclohexanc) the slopes were signdicantly different at the 95G confidence level Irom the ideal slope o! 1.0. The observation ol higher concentrations from passive monitors than from charcoal tubes is not unique. In one report..... acrylonitrile was moni tored with Ilf Gasbadges1'* and charcoal tubes side-hy-side; the badges averaged 2.73 ppm and the tubes 2.14 ppm, a mean difference of 25 percent. The second trend was that Y-intercepts tor nearly all chemicals in all groups were very close to zero (less than I ppm), and were m the main negative. Although a slight negative intercept is of little importance in monitoring sub stances with relatively large TLVs, it may indicate a detec- Jmeocjn mdosir'4* 4ssOC>4hon JOURNAL 4 HI I ion l hr cuboid or lac L ol 'etu it iv it v m t lie p.i"iv e moil not' at very low concentrations Such a condition, it continued should he considetcd in making decisions on the use ol passive monitors lor detection ol substances with 11 \ ' m the I ppm range or lower Correlation coclticienis n) lor several ol the substances were 0.94 ot highci. I he *45 percent prediction limit' on indiv idttal passiv c monitor sample concentrations are show n in I able II lor given chemical concentrations I lie predicted monitor concentrations are generally within 125 percent ol the reference concentrations, m Group No. 2 and the com bined data, but vary widely m Group No. I because ot the high slope values. I his predictability would be much improved by use of the regression curve to "calibrate" the monitors. However, tt ts presumed that ihecurvewill not be known u priori. If the slopes for any chemical had consist ently varied from 1.0 appreciably in both groups (as with n-octane and mcthylcyelohexane). an inaccurate "\amptinit raw" lor diffusion published by the passive monitor manu facturer might be responsible. For the statistical analysis, charcoal tube sampling results were presumed to reflect the true concentrations, and be subject to much less variation than the passive monitors. This is by no means a certainty. However, statistical analyses where both methods are subject to error arc rather compli cated"" and the method used here is considered to he satislactory lor this purpose."" sources of error Several possible sources of errors in the results of this study are discussed below. 1 I he "sampling rates" used with the monitors may be imprecise I hese sampling rates are analagous to diffusion coefficients. Published sampling rates were used where available, the others were estimated on the basis ot chemical similarity. Isc ol loo low a sampling rate would increase the slope (hi ot the regression line in inverse proportion to the sampling rate error, hut would not affect the correlation coef ficient 1 his result was observed with methvlcvclohexane. raising the possibility that the estimated "sampling rate" used (27.2 ml, min) was loo low. I sc ol too high a sampling rate would tend to depress slopes in inverse proportion to the error Dus type of systematic error could account for regression line slopes lending to he consistently greater than I 0. 2 there may have been interference Irom unknown chemicals. Many small unidentified peaks were present in some of the chromatograms. Such inter ference would have affected tubes and monitors similarly 3 On-site temperature and pressure departures Irom 24x C" and 760 mm were not corrected. They were presumed to alieci monitors and tubes equally except for the temperature correction1 1 to the sam pling rate!T J K. 29K)1 \ This could cause differences in monitor results ranging Irom -3 to +5 percent, as 3M 106753 2CS > TABLE II Companion of Results of Simultaneous Sampling by Paifiva Monitors and Charcoal Tubas Chemical Range of Data (ppm) Linear Regression Slope & Y Intercept 95% C L Ippm) Correlation Coefficient <0 ft'. Prediction Interval tot Passive Monitor Sampla at True Concentration X Monitor Sample * tppmt (ppm) Group No 1 (30 umplt pairs) ft He*ane 0-37 Meiltylcyclopemane Toluene n Ociane 2`Methylpentane 3-MelZiylpenlane n Heprane 0 17 0-18 0-10 0-18 0 30 0-7 Methylcyeloheiane n-Pemane Isopentane 07 0-6 0-13 Group No. 2 (48 umpl pairs) n-He*an 0*27 Methyicyeiopeniane Toluene 0-20 0-20 7-Methylpcntane 0 16* 3 Meihylpeniane n Heptane 0 30 0-25* Merhylcyeloht..,ane n Pentane Isopentane 0-20 0-30* 0-40** Combined Datt (78 umplt pairs) n-Hesane 0*37 Methylcyclopemane 0-20 Toluene 2-Methyipentane 0-20 0 18 3 Meihylpeniane n Heptane 0 30 0 25 Meihylcyclohe*ane 0-20 n Pentane 0 30 Isopentane 0 40 1 02 0 12 111 0 13 1 31 * 0 12 141 *0 15 1 10 ` 015 113 * 0 16 0 94 .* 0 13 1 33 t 0 30 1 23 t 0 47 112 t 0 68 091 I 0 10 0 99 * 0 11 0 97 t 0 10 0 92 * 0 07 0 91 * 0 05 109 t 013 1 39 e 013 0 93 t 0 07 1 06 T 003 0 97 * 0 07 1 03 - 0 08 1 09 * 0 08 0 99 0 07 1 01 * 0 06 1 07 0 10 l 38 - 0 1 1 0 92 - 0 07 1 06 - 0 08 0 50 0 72 0 36 0 01 0 50 0 61 0 31 -0 04 0 01 0 92 -0 11 0 26 0 16 004 0 02 -0 56 0 IS 0 05 -0 17 0 26 0 38 0 06 0 09 0 15 0 53 0 12 0 15 0 31 0 96 0 96 0 97 0 96 0 94 0 94 0 94 0 86 0 73 0 54 0 94 0 94 0 97 0 97 0 98 0 93 0 96 0 97 0 99 0 95 0 95 0 95 0 95 0 97 0 93 0 94 0 95 0 94 40 33 8 to 46 6 io 18 3 to 24 6 20 23 2 io 28 6 10 12 0 lo 16 2 70 17 7 to 25 5 30 27 0 te 39 5 10 7 3 to 10 9 10 9 7 to 16 9 10 7 9 to 17 9 10 3 4 io 20 9 25 17 9 to 27 6 20 16 1 to 22 9 20 16 6 to 22 4 20 16 2 to 20 6 30 24 6 to 30 0 25 22 2 to 31 0 70 24 3 io 31 0 30 24 1 to 31 3 40 40 4 to 44 2 40 33 5 to 43 9 20 17 6 to 23 6 20 19 0 to 24 6 20 17 1 to 22 5 30 26 4 to 33 8 25 22 7 io 29 7 20 24 4 to 30 6 M 24 3 io 31 3 40 37 2 to 47 9 'Only 21 pairs 1 ppm ' 'Only 15 pairs 1 ppm 2H l the temperatures at sampling sites were judged to ranyc from 5 C below to 10 JC abuse 25 t'C Overloading ol lubes and monitors could cause errors Charcoal tubes sampled Irom 90 to 190 liters ol air. averaging 130 liters, at I l. min Only two charcoal tubes showed concentrations over 100 ppm total organic vapors assayed (120 ppm and 150 ppm) These two tubes indicated 2K and 45 ppm total vapor respectively in their hack charcoal sections. For other tubes, the total collected in the back sec tion was less than 25 percent of that in the tront section F.ach monitor was exposed as long as both tubes in a set. Any significant overloading of moni tors would result in regression line slopes suh>.iantially below' I 0. This did not occur The back section of a tube was analysed w henever the chromatogram of the front section showed rather high peaks. In essence, the backs were analyzed if total organic vapors assayed exceeded about 50 ppm, which occurred in roughly half the samples. It ts possible that a portion of vapors collected in the lubes ujs r. in analyzing samples from areas with low vav-r ;onccniraiions. This would tend tv' increase re*-*,, ,n line slopes slightly and give sub stantially r- A.j,.; Y intercepts 1 he latter did noi occur. I ubes vh monitors interim *- zed 12 weeks alter sampling, and s-.rss All were kept ai -7 C in the ;?av may have resulted in loss of collected <- - One could speculate that migration ol vapor pack sections of charcoal tubes during o - jht account for some loss in tubes whose be i --- -,ns were not assayed Losses in the monitor. f -e )ess the vapors would have no alicrnao crease r - jeh migration would tend to tn* inc slopes slightly It is the iudg~ - -e authors that the potential errors did not signify.- ;*. the results. significance c4 5e/Srgs Since obscrvec ,, -anons of substances were generally far below T1A t-,' -c-missihle exposure limits (PEL s). no 4/n >P3 it*?) Apr.! 199 3M 106754 ,,uJli -ml*' i jli hi .llaWll I i ii(|| these il.ll.l IVgilllllllg cmiclj- ,n i>l .nut iuIh's mi iiinccniratiunx approaching I \ i. without j'lMimiii)! Iiucuiiiv hcvoiul the observed data However, onee one o| the anticipated values ol the passive giniiitor is hi rouiine niotninrmg. it is mipniiani to demon strate that (hc> can reliably measure low exposures as well as hit'll ones. I he results ol tins study indicate that the passive monitor rcliuhl) assayed low concentrations ol mixed sapors ol 20 ol the chemicals mentioned equally as well as charcoal tubes, under the conditions encountered. Charcoal tube and passive monitor results dittcred significantly tor mclhyleyelohe.xane and n-oetane. I he tendency toward negative Y-intereeptsl l able II) may indicate a sub-ppnt detection threshold in the monitors for some chemicals. More such comparative studies are needed to build a body ol literature on which to establish the appli cations and limitations ol the passive monitor. research support This research was supported by United Rubber Workers Union, firestone I ire and Rubber Co., I he General lire and Rubber Co.. Goodyear lire and Rubber Co., and IJniroyal. Ine. references 1 Tompkins. F C.. Jr. and R.L Goldsmith: A ew Persona: Dosimeter fur lire Monitoring of Industrial Pollutants Am Ind Hyg Assoc J 3$ 371 (1977) 2 Bamberger. R.L , G G Esposito. 8.W. Jacobs. G E Podolak and J F Marur A hevs Personal Sampler lor Organic Vapors Am Ind H\g Assoc J 39 701 >19781 3 Woebkanbarg. M l Current NlOSH Research on Passive Dosimeters InPrur of theSymposiumonthe De\eU'pn>enl arid Usage ol Persona/ Momln>> I,it Exposure and Health Meets Studies US Environmental Protection Agency Research Triangle Park NC777IT Publication EPA 600 9 79 032 (June 19791 A Hirayama. T and M Ikeda Appln nlutuy ot Activated Car bon Felt In llie Dosimetry ol Solvent Vapor Mixture Am hid Hyg Assoc J A0 1091 (1979) 5 3M Brand Organic Vapor Monitor Product Information and Usage Guide Occupational Health and Safety Products Div i$ion. 3M Cummpany (undated) 6 Compound Guide lor3M *3500 Organic Vapor Monitor 3M Company (Feburary. 1979) 7 Remington, R.D. and M.A. Schork: Statistics with Apph cations to the Biological andHealth Sciences Prentice Hail. Inc. Englewood Cliffs. NJ(1970) 8 Matrelta. M.G.: tupe/intenlalStatistics National Bureau of Standards Handbook 91 (1963) 9 U.S. Environmental Protection Agency: Guidance tor Selectrng TSP Episode Monitoring Methods Research Tri angle Park. NC 2771 1. Publication No. EPA-450-4-79-007 (February. 1979) 10 Silverstein. L.G.: Validation of Abcor GASBADGE1" for Acrylonitrile and Improved Desorption Efficiency Am Ind Hyg Assoc J 38 412(1977) 11 Acton. F .S.: Analysis of Straight Line Data John Wiley and Sons. Inc . New York. NY (19S9I 12 Netar. J. and W. Wasserman; Applied Linear Statistical Models Richard D Irwin. Inc . Homtwood. !L (1974) 13 ACGIH: Threshold Limit Values lor Chemical Substances and Physical Agents m the Workroom Environment with Intended Changes lor 1979 Am Con( ot Governmental Industrial Hygienists. Cincinnati. OH 45201 (1979) Arnencin Induifrui A-ujoilion /Ol/KNAl -V 4 3i 3M 106755