mfety in the
edited by MALCOLMM . RENFREW University of Idaho MOSCOW, Idaho 83843
Learning How to Run Safer Undergraduate Laboratories Jerry R. Mohrig Carleton College, N o r t h f i e l d , MN 55057
Virtually all teachers recognize the i m ~ portanee of safety in the design and implementation af laboratory exercises. We also know that focusing only upon traditional safety questions-good housekeeping, eye protection, fires, explosions, cuts, burns and acute toxicities-is no longer enough. Chronic toxicity, carcinogenicity and adequate disposal of hazardous wastes have become important safety considerations. Furthermore, i~~~-~~ t is not enoneh t o.orovide safer exneriments n for our students; we need also to teach the practice of sound safety principles in all lahoratory work. Chemistry and chemicals have gotten a bad name because of health and safety concerns. No one can doubt that there is a good deal of nuhlic anxietv about chronic chemical haz-
our profession would suffer. Nevertheless, providing safer experiments should he one of the goals of every author of laboratory manuals. Indeed, our textbooks should systematically teach safety principles and practice. Every experiment should point out any hazardous substances, along with the precautions necessary in their use (2). T h e now criteria being considered by the ACS Committee on Professional Training point t o the need for more e m ~ h a s i on s chemical safety.
would propose that low~level,chronic toxicity problems are unimportant in chemistry l a b oratories. An earlier column in this series has pointed out t h a t , with few exceptions, chemicals have properties that may make their use hazardous; however, it is possible to take precautions in their use t o prevent harm
A 1979 statement from the ACS C o m m i t ~ lgoes~further t byi advocating toxicology courses for (3)
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three areas: 1) Being effective teachers 2) Providing safe experiments 3) Teaching principles and prarticp of safety In our concern for lahoratory safety, we must not retreat to using trivial experimental exercises. T h e experiments in laboratory courses need to demonstrate sound chemical principles and important experimental techniques. They should be designed to catch students' imaginations and relate t o their experience. The importance of the aesthetic component of experiments-bright cuhirs, shining crystals, and intriguing odors-is too often overlooked. With less significant experiments, laboratory courses would become less important; our students' education and
"Toxicity of common chemicals and potential explosiveness of widely used substances need careful, forceful presentation and discussion in specific and systematic instruction of teaching assistants and students. Mere caution on their part is not adequate. They need to understand the chemistry, and the biochemistry, of the substances they handle."
teeon professional ~
"IL is no longer excusable that a chemist as a professional be ill aware of the p h y s i dogical hazards of his job. I t is r e c o m mended that every chemist should corn
ciety could well direct some of iti resources toward impressing this message upon the academic community. Toward this end, it is recommended that (a) every school offer a course in toxicology and safe handling of chemicals, available t o both undergraduate and graduate students of chemistry and chemical engineering and (111 t h a t every chemistry department include chemical safety as an important feature in every chemistry laboratory course." If these recommendations lead t o action, learning how to conduct safer laboratories will become a part of the education of all chemistry teachers. In the short run, though, we must face the fact that l'ew chemists who teach have received any formal education in the science of toxicology. The rub lor many teachers is not lack of intent but lack of exVolume
60
although short courses have become avail^ able; e.g., the ACS course "Toxicology for Chemists" and the J. T . Baker chemical safety course. In part, we are faced with the need t o pull ourselves up by our own bootstraps.
Learning About Safety
I am not an expert on safety, but over the past few years I have tried to learn as much as I could. Having worked on the development of numerous experiments for the undergraduate organic chemistry laboratory, I have been obliged to assess the safety of these experiments (5). Fortunately, learning ahout the toxicity of chemicals has become a good deal easier. Look back t o what seems the distant past tor a moment. In late 1976, I was developing a experiment, eal'feine from tea. ~ new ~ extraction ~ Both dichloromethane and chloroform are effective extraction solvents in this experiment. After a fair amount of searching traditional sal'ety references for their relative toxicities, I came t o the conclusion t h a t ehloraform he the safer solvent. One needed to use less of it and it was lessvolatile. ~,
as the extraction solvent, thus reducing the toxic hazard. Having an u p ~ t o ~ d a tsafety e resource
the latest editions be a t hand, since newtonieological data are accumulating a t a rapid
This article is based on a paper presented a1the Symposium on Teaching Laboratory Techniques far Organic Chemistry (in honor of Louis Fieser). 179th National Meeting of the American Chemical Society. Houston. TX. March 1980. Ched. 49.
(Continuedon page A2561 Number 10
October 1983
A255
mfety pace. The resources which I have found to be most appear in first eight of these books constitute a core that, in my opinion, every college should have available for the use of faculty and students. Most universities have schools of public health or Table 1.
Books on chemical Safety
(1) "Safety in Academic Chemistry Laboratories? 3rd ed.. A~~~~~~~chemicsl societycommittee on chemical Safety, washingtun. D.C.. 1979. (2) ,,TLW T ~ I ~ ~ ~ ~ Oi I ~ values ~ i t for chemical substances and ~ h y s i c a~gents," l American conference of Governmental indurtrial Hygienists lACGIH1. C i ~ c i m a t i OH. . 1981, (Revised and publi~heda n n u ally). (31 Sax. N. L,"~angerousPropertierof~ndurtrialMsteruds," 5th ed.. van Nostrand Reinhold, New Yore, 1979. 14) he ~~~~k hdex: 9thed.. Merck& CO., Rahway, NJ. 1976. (51 Green, M . E, and Turk, A. "Safety i n Working with chemieats," ~ a c ~ i l l s n , ~~eowr k 1978. , (6) "Patty's Industrial Hygiene and Toxicoiopy," 3rd rev. ed., Vols. IIA. I I B , IIC, "Toxicology" wiiey-Interscience. New York, 1981. (7) "Safety in the Chemical Laboratory: Yolr 1-4, D i v i ~ siun ofChemical Education of the American Chemical Society, Esslon, PA, 1967ff. (81 :Prudent Practices for Handling HmdousChemicals in Laboratories", National Academy Press. Washington,D.C., 1981. 19) Fairchild, E. J.:'Suspected Carcinogens? U S UHEW. NIOSH. Castle House P u b i Ltd., Tunbridge Wells, Kent, Great Britain, 1918. (101 -Registry of Toxic Effects of Chemical Substances," U S . Department of Health and Human Services. NIOSH, cineinnati, OH. 1982 (Revisedand published annually).
A256
Journal of Chemical Education
111) "NIOSHIOSHA Occupational Health Guidelines for sidering the carcinogen situation may prove Chemical Hazards,"DHHS (NLOSHI Publication No instruelive (6), ~h~ OSHA list of regulated 81L123: NIOSH, Cincinnati. OH, 1981. 112) A ~ ~ ~ U ~ , Murowne.~. .A., ~ . , ~ ~ d wI.;,H~x~ i ~ , ~ .carcinogens is found in Table 2. A first step adous Chemicslr,"Deoarlment 01 Chemistry, l l a i is to amid their use entirely. This ran easily veisity of Alberta. Edmunlun, Canada. 1982. he done without impairing a laboratory pro(13) "Handling ChemicalsSafely 1980,"DutchAssocialiun gram. However, the OSHA candidate list of of safety experts, uutch chemical~~d~~~~~Associa. carcinogens has alti".. h t c h safety ~ n s i m t ~~ . ~ ~ he ~t e t ~h ~potential d ~ occupational ~ . eriands, 1980. most 200 entries ( 7 ) ;some of these appear in 1141 Rretherick.L.,"HazardsintheChamieslLaboratow~ ~ ~ 3, ~h~ b list l includes ~ any substanee 3rd. ed., Royal Society of Chemists. London. 1981.
which has been thought to cause an increased incidence of benign andlor malignant neoplasms in humans Or in One ex~erimental mammalian species as the result of any oral, respiratory, or dermal exposure. Although the legal requirements of OSHA apply only to employees, we cannot ignore the ethical obligation to consider OSHA guidelines with regard to our students. In this content, however, academic laboratories may be distinctly different from manufactlrring environments and shl,uld have a separate toxic chemicals policy (8). The conclusion of
departments of envinjnrnental hygiene which have toxicologists on the faculty. Getting to know a toxicalagist in a nearby department is invaluable. M~~~ wouldbe to talk with chemists who seek advice on the use of h a ~ a r d o usubstances. ~ Carcinogens and Chronic Toxicity
does One know if an experiment has a reasonable margin of safety, especially with regard to low-level, chronic toxicities? ConTable 2.
Carcinogens Regulated by OSHA
2 . ~ ~ ~ Acryionitriie Chminabiphenyl Inorganic arsenic
t
Asbestos
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l ~ ~ i ~ ~ E~~~~~~~~~~~~ Methyl chloramethyi ether ~Naphthylamine CNaphthyiamine
Benridine 4-Nitrobiphenyl Bis-chloromethyl ether N-Nitrosodimethyl1,2.~ib~~~~.3.~hl~~ amine ~. propane 3.3'-Dichlorabemidine
&Propiolactone Vinyl chloride
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Table 3. Some Common Chemicals from the OSHA Candidate List of Potential ~ ~ ~ Occupational ~ ~ ~ Carcinogens
Aniline Benzene
1.4-Dioxane Formaldehyde
Carbon tetrachloride Chloroform
Hexamethyl phosphoramide
C e n a i n chromium (VI) compounds 1.2-Dibromoethane
Hydraline Methyl iodide o-Toluidine
1.2-Dichloroethane Dimethyl sulfate
1.1,2-Trichloroethaoe Trimethyl phosphate
4-Dimethy1aminoazobenzene
(Continued o n page A258)
the authors of the National Kesearch Council laboratory safety study is pertinent (9). "Although there is currently a justifiably strong interest in chronic effects, particularly carcinogenesis,we believe that acutely toxic, explosive, and flammable substances constitute a t least equally important and immediate risks to laboratory workers. In addition. ~recautiansthat reduce exuosure
It should also be painted out that the OSHA candidate list contains the two insecticides, aldrin and dieldrin. These two compounds have been judged to be carcinogenic by the EPA; however, in Britain they were judged nut to he carcinogenic,based upon the same evidence (10). This fascinating story points out again that we must learn to live with ambiguity in dealing with possible carcinogens. The Threshold Limit Values (TLVse) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) provide an up-to-date list of hazardous volatile chemicals, including carcinogens (11). The TLVa entries may differ from the OSHA list. A recent comparison showed that five entries from Table 2 and four entries from Tahle 3 were not listed as recognized or suspected human carcinogens in the ACGIH tables. A further complication is seen when -
comparing the TLVo guidelines of the ACGIH with OSHA standards (12). The values often differ. In addition, NIOSHI OSHA publishes a list, with no legal standing, which offers still different guidelines (13). The many problems involved in the quantitative estimation of cancer risks have been described recently (14). We are also exposed to and ingest carcinogens every day outside chemistry laboratories (15). We are faced with a measure of uncertainty in assessing the risks. What does one do when experts disagree? It seems clear that the use of some chemicals should be avoided in undergraduate laboratories. These include the carcinogens regulated by OSHA (Table 2), as well as bydrazine and benzene and probably chloroform and carbon tetrachloride (16). Nevertheless, if we are to teach effective chemistry laboratories, we will need to use some h a z ~ ardous materials. How does one know if an experiment has a reasonable margin of safety? For many substances the ACGIH values are a good starting point, along with a prudent pmgram of monitoring the laboratory atmosphere. Having a quantitative sense of the atmospheric levels of volatile haaardous chemicals in our laboratories can save a good deal of worry. Some experiments may have to be discarded; many others may he tolerably safe. Constant monitoring is not necessary; it need be done only when a serious safety question arises, Individual instructors will have to decide their own margins of safety when "what is safe" hasnot been defined by statute or by widely accepted practice. I am happy when the levels do not exceed a third of the ACGIH TLV-Short Term Exposure Limit
(STEL). For example, in a recently-developed experiment which I consider safe, the oxidation of cyelohexanol with hypochlorite bleach, measured C12 levels never exceeded 0.2 ppm; the ACGIH STEL is 3 ppm, whereas the OSHA limit is 1ppm. (Several companies market inexpensive gas detection equipment. These include NationalIDriger, MathesonKitagawa, Gastech, Auer and Mine Safety Appliances. For a few hundred dollars, NIOSH-recognized sampling devices are available. Calibrated reagent tubes must he purchased separately for each gas; current prices are $1-2 per tube.)
Teaching Laboratory Safety When I began systematic presentation of chemical hazards to students in the introductory organic chemistry laboratory, I wondered if this would open Pandora's box. Would students develop paranoid fears? I soon learned that they did not. Instead, they developed a healthy respect for the suhstances they handled. Whenever the laboratory atmosphere was monitored, students were interested and asked numerous questions, but they did not become fearful. The presentations stressed good housekeeping, splash protection, toxicities and routes of entry, fire dangers, and adequate waste d i s ~ p o d . Most experiments were designed to he done a t the lab bench. hut it was minted out that the hoods were effective a i d available when there was a doubt about the hazard. Gloves were provided when skin protection was necessary. Lab quizzes often included safety questions. Explicit directions were given to students when experiments or parts thereof had to be done in the hood (17). Ex(Continuedon page A260) ~-
amples are the use of thionyl chloride, pyridine and dioxane in the synthesis of derivatives from "unknowns." At Carleton, systematic discussion of safety reference works is part of the junior-year advanced laharatorv seauence. This includes approach of a separate laboratory safety course has been described in this column (18).
Waste disposal practices will depend upon local situations since different states have different hazardous waste disposal regulations. The practice in my labs is that only appropriate aqueous solutions and small quantities of wash acetone are normally put down the sink drains and then with copious flushing. Other materials go into waste or recycling bottles in the hood. An earlier eolumn in this series pointed out that t h r e e i m ~ partant strategies for effective waste disposal are minimizing quantities of chemical reagents, segregating different kinds of wastes and recycling when possible (19). Experimental design is crucial to successful recycling. In some experiments complex solvent mixtures result, making recycling difficult. In other experiments it is straightforward. One example is the recovery of dichloromethane from the extraction of caffeine from tea. Students pour their distilled solvent into the recycling bottle. This solvent is used and reused bv subseauent lahoratorv sections.
A260
Journal
of Chemical Education
The consumption of CH2C12 is thereby considerably decreased. We often recycle the diethyl ether used in the Grignard reaction. Here the motivation is mainly financial. The ether is treated with acidic ferrous sulfate to remove any peroxides and distilled for use as the extraction solvent in following Crignard experiments. Naturally, the recycling must be done carefully by a qualified person and the storage time must be restricted, but our EtiO consumption and waste have been cut substantially. The organic products, which the students hand in, are sametimes recycled as starting materials in advanced laboratory exercises. One such open-ended project provides an upper class student with 500mL of a ehemical prepared in the introductory organic chemistry laboratory, with the goal of purifying the chemical and demonstrating its purity by two independent analytical methods. The student decides upon themethod of purification and the analytical criteria. The purified chemicals can he reused in subsequent introductory experiments. In many cases, chemical disposal problems can be avoided by using different experimental methods. For example, oxidation of a secondary alcohol can be done with hypochlorite bleach rather than Cr(VI1; this replaces the troublesome Cr(1II) waste with salt water. Summary Although safety in the undergraduate laboratory has become a more complex issue, there is no reason to despair. We will need to live with a measure of uncertainty about chronic toxicities, hut excellent resources are available through which one can learn and subsequently teach all aspects of laboratory
safety. A prudent monitoring program can diminish the anxiety about chronic taxieity. Acknowledgment I wish to thank Dr. Fay M. Thompson of the University of Minnesota for her generous help in introducing me to the literature of toxicology. Literature Cited 11) Young, J. A . J. CHEM EDUC.,59, A265-A268 (1982). (2) Wawzonek, S., '"Safetyin the Chemicd ~aboratory." Vol.IV. 11 (1981). 13) Cham Enp. News. 3 6 3 7 ISepl. 17,19791, 14) Fitngeiald. J. J., J. CHEMEDUC..59, A85, ASS. A90 (1982). ( 5 ) Muhrig J.R., andNeckers. D. C. "Laboratory ExperiL mento in O~ranicChemistry: 3rd ed.. D.van ~ o s trand.New York, 1979. (6) Melnikow, J., Keeffe, J. R., and Bemstein, R. L.. J.
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I111 "TLVse Threshold Limit Values for chemical substances and Physical Agents in the Workroom En% rmmont," American Conference of Governmental Indurtrial Hygienists, Cincinnati, OH, 1981. (12) "Geneial Industry Standards and Interpretations: 1910-Subpart 2, Occupationd safety and ~ d t h Standards. OSHA, Washington. D.C. (13) Muckison, F. W., Stricoff, R. %and Partiidge, L. J.. Jr.. (Editom), "Occupational Hpalth Guidelines for Chemical H a s ~ d s ?Yo1 1.Summaru. NIOSHIOSHA. Washington. D.c.; 1981. 1141 "Carcinogen Identification Policy: A Statement of Science As a Basis oiPolicy: St& of California DP. Cartment oi Health Services, Sacramento, CA. 1982. (15) Ames, B. N.. Department ni Biochemist~y.U. California, Berkeley, personal communiestion.
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