mfety in the chemkol loboratory
edited bv MALCOLM M. RENFREW University of ldaho MOSCOW, ldaho 83843
What's in the Air? How Much Is Too Much? Measurement of Toxic Gases, Vapors, and Particulates-Limits
of Exposure
Milton Freifeld Chemical Manufacturers Association, Washington, DC Here is a quotation from a favorite author, Lewis Carroll. In "Through the Looking Glass" Alice says to the White Knight,
mice on the horse's back." "Not very likely, perhaps," said the Knight: "but if they do come, I don't choose to have them running all about." "You see," he went on after a pause, "it'sas well to be provided for everything. That's the reason the horse has all those anklets round his feet." "But what are they for?" Alice asked in a tone of great curiosity. "To guard against the bites of sharks," the Knight replied. "It's a n invention of my own. And now help me on. 111 go with you to the end of the wood..
. ."
AS Associate Drector. Health. Safetv, and Cn?nlcil Pcg.xons at tne C ! e n ? ? Ma i.lacl.rers Assocmtron. Mr + e f e o s C O ~ C C ~ F AO tn satel, an0 hea In n tne w0rrpa;e ne 8s ?.lati eAec.1 ve lor m e Occ-pat onai Safetyand nea th Cammmee. ~h ch deal* wth sues relalea la toxc l y . accident prevention, and a variety of immediate and long term hazards. FTeviousIv. Mr. Freifeid held manaoement 005 I ~ n Sresearch andtecnntca Eervrce veal ng H th polymers and SJlfaCtanfS He uas employed o) Monsanto Company GAF Corporation. and Tenneca Chemicals. He received a Bachelor of Chemical Engineering degree Cam C.C.N.Y. in 1943and Master of Business Administration from Xavier University in 1960.
This exchanee demonstrates the need to k n ~ wrhe true hnzard5 In awuatiuch a< thruuzh the skin or lw inyr5tmn. I want to emphasize that measurement of airborne contaminants should be only one aspect of a n overall safety program. A good safety and health program will also include training, internal audits, the use of protective clothing, and many other elements. When
to Monitor
One of the first questions to be answered about monitoring in the laboratory is "when should it be done?" A goad answer may be found in "Prudent Practices far Handling Hazardous Chemicals in Laboratories," [National Academy Press, Washington, DC, 1980j. T h e authors of this National Academy of Sciences report believe that for most laboratory environments regular monitoring of the airborne concentrations of a variety of toxic materials is both unjustsified and impractical. They do stress the need for a wellfunctioning ventilation system, proper pratective clothing, and the use ofgood hygiene a n d safety practices among laboratory workers. They conclude, "If a specific substance that is highly toxic is regularly and continuously used (ex., three times a week) then instrumental monitoring of that substance may be appropriate. This is especially true if a relatively largeamount of the material is being stored or used in the laboratory." T h a t is a sound approach in my view, but I would leave to the laboratory managers' judgment when air sampling should be done; t h e example of using a n exposure of three times a week as a trigger may be misleading.
sieves, and porous polymer beads. Following the samoline . ...oeriod (usuallv a work shift) the tut>plare r e r n w ~ ~aud l , the < o n u m i u a waw decwled and annlynrd. 'l'he anrtl!tral rurrhod used for ;anal)z~n:: samples of gases varies with the material being detected. Far example, to analyze organic vapors, gas chromatography (GC) with various adjuncts may be used; for halogenated eomoounds. GC with electron caoture ur imiratnm detatur.; fur :nOrgdtliC y a w . ( X ' uith lhermal w n d w t i ~ i t vdttrctur\; L,r m r l , m munuu~deand rartm d ~ u x l d .n~. frared gas spectrometers. T h e range of materials in the air that can be detected and quantified in this way is wide indeed and encompasses organa-sulfur compounds. sulfur dioxide, hydrogen sulfide, nitrogen oxide, and ozone among others. (Continued on page A352)
Malcolm M. Renfrew draws on varled industrial and academic emeiiences in his
Methodology When the measurement of materials in laboratory air has been decided on, personal sample collectors should be used rather than area monitors. There are two types of personal air sampling collectors; sampling heads used with pumps and dose badges. In the first type, a constant flow of air is maintained through a sample tube containing solid sorbents such as charcoal, Silica Gel, molecular Volume 59
Safety &d the new division of Chemical Health and Safety. He now is professor emeritus of chemisby and is patent director of his University's Idaho Research Found* tion. inc.
Number 11
November 1982
A351
drwloped in thr rarly 19:03.'l'hcy replacrd rhe more wmhenomr hand-crankrd pumps used with impingers (shown in Fig. 6) employed two decades ago. Area monitors may be portable or fixed and models are available for measuring all of the materials named above plus many others. It seems as though there isan instrumenton the market for even imoortant air contaminanr in the workplace. Howerer, the 0 w u . pational Safety and Health Adlniniitration IOSHAJprefers that evidence ol contplianw with regulations be hased on personal sampling data. Hence, I will give little attention to area monitors. You may also obtain information about oersonal exoosure throueh oassive samolers ~ , rdcae hadyrs. 'These consist ol a sorhent material lrellit~dad~ffusiongapor permrat,lr membrane in a highly porou5 case. 'The p d . lutant diffuses through at a rate which can be calculated and reacts with impregnated paper or is trapped on sorbent. In some instances a stain develops immediately, which can be quantified by comparison with standard stains or by scanning reflectance spectroscopy; in others, set analytical procedures are necessary to develop the stain. Dose badges, the second type of air sampling collector, are a relatively recent development; their limitations and capabilities have not vet been evaluated fullv. Because of however, thrlr cunwnieme nnd ~ffrrt~wness, thry arr ronsrnnrly brmg uwd murr w~dely ~nthr wurkplare. Inderd, the I' S.En\,ironmental Protection Agency is underwriting a proiect to extend the sensitivity of such per-
. .
-.
A352
Journal of Chemical Education
Figure 2.
Typical sampling heads used with low flow pumps are shown in Figure 2. They include charcoal, Silica Gel, and long term detector tubes. Most National Institute for Occupational Safety and Health (NIOSH) recommended sampling procedures for organic sonal dose badges to monitor ambient air vapors utilize the charcoal tube. Silica Gel outside the workplace. and other paekings are used in certain cases. I will use the followine series of fieures to drmonatarr and rrpl:iiu the use ~ f < m s t a n t These rely on desorption and analysis of flow air pumps and pni.ivr iamplcrs. contaminant. Detector tubes, like the long-term type Figurr 1 i, a picture ois hn~tcry-c,perarrd shown at the right of Figure 2, depend on the low flow pump. It accurately controls the rate appearance of a stain or color change upon of air flow (10 to 200 ccimin., depending on exposure of contents to a contaminant. They model) through the sampling system for up may be calibrated far direct reading or comto ten hours. The total volume of air sampled oared with standard charts. hate X time) and the amount of material Iktw tur t u l m we a recent drvrlopment, drwrhed t n m the ample ruhe muit tw harinl: been i n ~ r d w r dahuu~five yewsnyo. nieawred todetermine th~conwntratimof contaminant. 'Their n u wavy i i qurstiunahlr since t h q are Light-weight, constant flow pumps comsensitive to variations in humidity and temhined with charcoal sampling tubes were perature. Even the short-term detector tubes
circle NO.
21 on ~ r a d e r r Inquiry ' Card
Figure 8
Human Resources, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, OH 46226; 2) "AIHA Analytical Guides," American Industrial Hygiene Association, Executive Secretary, 475 Wolf Ledges Parkway, Akron, OH 44311 Figure 5 Figure 3.
spirable dusts of roughly 0.5 to 5.0 p diam-
.+.,
can vary from theactual level as much as plus or minus 25%. Figure 3 shows a low flow pump being worn by a worker. Note that the sampling head is dipped to the wearer's collar, near his breathing zone. T h e sampling head is connected to the hip-mounted pump bya flexible tube.
Figure 6
Fgure 9.
Impingm may be u,rd I.,, :,~,r. a< rcl. zs particulates. bur nrr falhny out ot f,mor *IIICP they are awkward.
Figure 4
Figure 4 is a picture of a high-flaw pump having an operating range up to 4,000 cclmin. It is frequently used with jumbo sorbent tubes for relatively short times, usually only a fraction of a n eight-hour work day. However, if the contaminant level is low, sampling time may be increased up t o a full work shift with the jumbo tube. The multi-flow pump, used for dusts as well as gases, is a modified version of the hiah-flow pump. The multi-flow Dump, being worn by ~a woman, with sampling head clipped to her collar is demonstrated in Figure 5.
Figure G h o w the sampling heads th.4 ma) 1~ used with f h r m o l t , - t l ~ ~pump. u They
~ n i l . ~ df ne r rhar,ual 2nd .'.il;iaCcl ruhe5 fur gases and impinger plus nuisance dust samplers for dusts. There are over 400 substances for which OSHA has oublished oermissible exoosure I h r n t t ~11'El.s~(ifthi> tur31. nppnfl~innawlgSfi 3 w parli(u131~~ that occur In the lorn1 o f drat.,, mirt.,, and A~mrs.I ' a n ~ c ~ ~ l\amplint: ntr requires the use of various filter mem. branes. The nuisance dust sampler is sometimes employed with a miniature cyclone upstream to knock out coarse particles above about 5 g diameter.. This allows measurement of re-
T h e best source of information I have found for currently available monitoring equipment is Industrial Hygiene News, a Rimbach Publication, 8650 Babcock Blvd., Pittsburgh, PA 15237. It carries advertisements for detection and protective equipment but does not contain descriptive articles.
Figure 7.
A dose badge is shown in Figure 7, clipped to a worker's collar, near his breathing zone. Figure 8 is a schematic view of the DuPont organic vapor air monitoring badge. Note that a diffuser is located on either side of the charcoal strip and the whole unit is encased in a cover. A similar unit with back-up section, containing a second strip of charcoal is shown in Figure 9. This second section allows one to determine whether breakthrough of t h e first section has occurred. Air flow through the front and back-up sections are illustrated in Figure 10. Sources of information on analytical techniques are 1) "NIOSH Manual of Analytical Methods," U S . Dept, of Health and
Volume 59
Figure 10.
Sale Limifs T h e American Conference of Gavernmental Industrial Hygienists (ACGIH) a t 6500 Glenway Ave., Cincinnati, OH 45211 annually publishes a list of "TLVs, Threshold Limit Values for Chemical Substances and Phvsical Aeents in the Workroom Environlows: "Threshold limit values refer to airborne concentrations of substances and represent (Continued on page A 3 5 4
Number 1 1
November 1 9 8 2
A353
conditions under which it is believed that nearly 311 wurkeri m;,). he repeatedly rxpcnecl day after day witht~utadvrnr effect. Hecause of n wide variation in indwdual susceptibility, however, a small percentage of workers may experience discomfort from some substances of concentrations at or below the threshold limit; a smaller percentage may be affected more seriously by aggravation of a pre-existing condition or by development of an occupational illness." The ACGIH recognizes three types of TLVs as follows: a) Threshold Limit Value-Time Weighted Auerage (TLV-TWA)the time weighted average concentration for a normal eight-hour work day or 40-hour work week to which nearly all workers may he repeatedly exposed day after day without adverse effect; h) ThresholdLimit Value-Short-Term Exposure Limit (TLV-STEL)--the maximal concentration to which workers can be exposed for a period uo to 15 min continuouslv without
addition the TLV-STEL may not exceed four excursions per day, with a t least 60 min between exposure periods and provided that the daily TLV-TWA is not exceeded; and, c) Threshold Limit Value-Ceiling (TLVW-the concentration that should not be exceeded even instantaneously. The ACGIH further states that "The TLV-TWAs should be used as guides in the control of health hazards and should not be used as fine lines between safe and dangerous concentrations." The Occupational Safety and Health Act, passed in 1970,incorporated the 1968ACGIH TLV list and in effect made it mandatory. OSHA uses the term permissible exposure limits (PEL) to describe allowable contaminant concentrations in the worknlace. OSHA has modified PELS for some individual sul,ztances through its rulrmakma pnnwlure. Those PE1.s published by OSHA haw the forcr of law in ~ e n e r ainduilry l workplaces. Thr PELS have not been widely oppl~edin research laboraror~eshut the TLV-TWAs should be used as guidelines. Charts of current OSHA concentration limits for gases are published annually by a number of companies such as the Foxboro Company, P.O. BOX5449, South No~walk,CT 06856. OSHA is now considering how best to protect people working in laboratories. In 46 Federal Reeister 21785.. A n d 14. 1981. the A g m q requested rtiponces questions d~alingwith the possilrle h u a n c e of guideline.; ur rcgulathm* pertaining solely to Inh-
.
proneness, impair self-rescue, or materially reduce work efficiency. In
A354
Journal of Chemical Education
oratories. The deadline for comments was August 15, 1981. OSHA still has not taken final action on this matter. Whatever action the Agency does take will affect academic laboratories that have employees, as defined by the Internal Revenue Service. Laboratory managers in industry prefer guidelines or rules designed for the workplaces they supenise so that they may he relieved of the burdens of excessive monitoring and recordkeeping required by OSHA's general industry standards.
Summary Monitoring need not be employed often in the laboratory since potentially hazardous materials areused in smallquantities, on an irregular basis by trained personnel. When a toxic material is used fairly frequently for some time, monitoring the concentration in laboratory air may be appropriate even though ventilation and protective equipment are in use. In those cases, personal samplers rather than area monitors should he used. Personal samplers include the constant air flow type as well as the passive monitor badges. In any event, monitoring must be recognized as only one part of the total safety program, which should include training relating to potential hazards in the laboratory and how to protect one's self against them.
Presentedat me Svmwsium on Chemical Healdl . . and Safe?,. ESpecmlly n the Academ c Laboratory a1 !he New York Cow ACS Meet8ng. Aug~st28,
