Comment on "Monitoring Airborne contaminants in the Laboratory"
Tu the Editor: T h e s t u d y of s t u d e n t exposure t o toxic vapors by F r e d Hertlein 111 (Safety Column, M a y 1979) represents a useful s t a r t o n a n i m o o r t a n t ~ r o h l e mwhich h a s been too lone .. ie.. norc,d. I~nfa,rtuniltely,Hrrtlein draws conclusions unich seem 1011.; not iuqrified hs his data. In oartirular. n,e du not he.ieve t h a t h e h a s shown t h a t s t u d e n t iahoratori& are generally in c o m ~ l i a n c with e OSHA standards. T h e r e a r e a 1arp-en u m b e r of unanswered questions raised by his results. Fo;example: 1) The only measurement whieh appears to directly exceed OSHA standards is one of only three chloroform samples. This is dismissed as "anomalous" without explanation or justification. However, the range of chloroform readings is only about 221, whereas the range of readings of other substances (acetone, hexane, benzene) is over 100:1, reaching400:l for hexane. It seems to us that in the absence of further information, all readings must beaccepted; the low readings have as gwd a chance as the high reading of being "anomalous." Furthermore, it is impossible to be certain from the textthat thechloroform samples were really measured for ceiling values (10 or 15 mi".), rather than as averages over the laboratory period. If they were averages, even the low values may conceal excursions which exceeded the OSHA
problems: isocyanates, TLVs generally 0.02 ppm, diazo compounds, typically of the order of 0.1 ppm, o r diphenyl (0.2 ppm). 4) We are told very little about the circumstances ofthe lahmatories that were monitored. The measurements were evidently taken during the summer in Hawaii. Were the laboratories air-conditioned, or were the windows open? How did this affect the general laboratory ventilation? Evidently all work was carried on in hmds. However, the 100:l ratio of exposure levels suggests some sort of major variation from student to student. Were all students doing the same experiments on nnv dav? Were there anv. soills . eiven .. . or other accidents? An exoericnced tcnchcr w u l u =,ant thc . m . r t r ; la, the,? and otlwr quc;r.cms I,rlil:t)~the . ir c . ~ l t < cot thi* ~ t t r l ytr, another laboratory situation. 5) Hertlein mentions methods af measuring other samples, including dusts and metal fumes. However, there appears to be no reason to surmise, as Hertlein does, that when measured these will he shown to be present a t safe levels. For example, mercury vapor, although not afume or dust, is an immediate problem; it iscommonly used. often soilled. and has a vaoor oressure exceedinzits TLV ivaoor contaminate a 300 m3 laboratory to this level requires the ev?poration of just 30 mg, or 2.2 $L, of Hg) .Other substances, such asBrpand IP, also can easily exceed acceptable limits. Measurements on an organic lahoratnry are notjustification for an assertion on the eeseof meeting OSHA standards in general. 6) Skin contact is not mentioned as a hazard. Impervious glwes are not eenerallv worn in student lahorataries: nevertheless. the Natimal kstitute ofbccupational safety and ~ e a l t h(NIOSH);criteria documents for chloroform and for benzene recommend impervious clothing. 7) Hertlein briefly refers to possible synergistic effects of multiple exposures. OSHA criteria assume that effects combine linearly (exposure to, say, half the TLV of one substance, plus one quarter that of two others, would add up to oneTLV exposure, as would any other combination adding up to one full exposure) .However, in general, all solvents, and many other substances, are detoxified in the liver. Students are exposed to a variety of substances, often simultaneously. The possibility of true synergism, in whieh the total effect is not merely additive, must he admitted. The OSHA assumption may well be too weak. Insufficient work has been carried out in this area toallow any firm conclusions. 8) Although Hertlein states that there is now nosafe level accepted for carcinogens, benzene, among the compounds he measured, is known to cause leukemia (in fact, this is the basis of the dispute over its standard.) Chloroform is a weak or doubtful earcinrBgen. However, carbon tetrachloride is a k n o w carcinogen in common use, and it does have a TLV. (Many special precautions are, however, required in handling carcinogens, but these are not discussed by Hertlein) 0~
to 1ppm. The mast recent court ruling, on a suit by the American Petroleum Institute,' was that the health benefits to workers donot justify the cost to industry, however, this does nothing to protect our students. (The matter is now on appeal.) If we assume, for purposes of cmnputing a time weighted average, that the laboratory period was 4 hours (we can only deduce from the text that it was less than 8 hours), then three of the henzene readings are in excessof ttie 1 ppm stsndard. Furthermore, this standard includes a 5 ppm ceiling (50 ppm on the standard Hertlein used) which may have been exceeded hy other students as well; it evidently was not tested, as it was not mentioned. 3) Other than benzene and chlorofbrm, the compounds which were monitored have very high TLVs, 100 to 1000 ppm. However, many mmuwnds have TLVs whieh are much lower. in the 1-10 DDm ranee.
substances sometimes found in organic laboratories are also paasible
910 / J n u m l of Chemical Education
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.I .h w e questions, while no1 all t h a t n n l l d In. r u ~ i t dalrearly , s 1 0 whet her Hertlein's ddla retluirt, 11s113 1 t . l ~e r~i o u ; d c ~ h t as m a k e i t possible t o d r a w conclusions w i t h regard t o t h e safety of s t u d e n t laboratories. N o t o n l y i s i t still a n o p e n q u e s t i o n as t o h o w generally OSHA s t a n d a r d s a r e m e t i n t h e s e l a h w ratories, h u t t h e s t a n d a r d s t h e m s e l v e s m a y n o t be a d e q u a t e . Often.. t h e "v a r e m a d e m o r e s t r i n "e e n t a s n e w d a t a b e c o m e available. S t u d e n t s use m a n y s u b s t a n c e s which h a v e n o t been sufficiently s t u d i e d t o h a v e s t a n d a r d s s e t a t a l l (e.g., h r o m a b e n z e n e i n Hertlein's s t u d y ) . T h e q u e s t i o n of synergistic effects r e m a i n s onen. Hertlein's conclusion would l e a d to complacency, which s e e m s t o u s t o t a l l y u n j u s t i f i e d at t h i s point.
Michael E. Green Amos Turk
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City College of the City University of New York New York, NY ID031
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Note added in proof: The U.S. Supreme Court has sinee ruled in favor of the AS'S.
Reply to Comment on Monitoring Airborne Contaminents in the Laboratory
G r e e n a n d T u r k raise 8 p o i n t s regarding m y arlicle i n t h e M a y , 1979 issue to which I n o w reply.
was obtained. How this failure can be related to s&h a high coneent r a t i m is not known. and no attemot was made t o sneculate. T h e
vapors were collected during a 10 ;,r 15-minute sampling period ( a highly unlikely situation). Of the substances monitored only chlurotirrm has an estahlished ceiling value, and the only instance where this was exceeded was in the case o f t h e "snomalws" value. Data shown in the article are averages (all of them), and when the worst possible assumptions are made t o calculate the ceiling value, it is evident that rmeealed OSHA limit excursims do not exist. 2) The official T1.V fI,k~-1,r h m ,211 the lh w t m w l h n
