edited by
MIRIAMC. NAGEL A w n High School A w n . CT OBOOl
How Much Is Too Much? Toxic Chemicals in High School Labs Mlrlam C. Nagel A w n High School
Awn. CT 06001
A high school laboratory where students have their first encounter with chemicals should be as safe an environment as possible. The big question is, "Which chemicals are toxic?" I t is important to remember that toxic is not always used with the word chemical and, even when appropriat& toxic is a relative term. In May 1982, a popular home and family magazine ( I ) published an article titled, "Dangerous Chemicals in High School Labs." In the article, under the heading, "Hazardous chemicals in high school labs," 37 chemicals were listed and classified as suspected carcinogens and suspected teratogens (chemicals capable of producing malformation in an embryo). The list follows: Suspected Carcincgens acetamide methylene chloride aniline hydrochloride nickelous ammonium benzene sulfate henzidine reagent nickelous chloride chlor,oform nickelous nitrate chromic acetate phenol chromium trioxide propanol dichloromethane pyrogallic acid dichlorophenal sodium chromate ferric oxide sodium dichromate formaldehyde tannic acid isoamyl alcohol thioacetamide isobutyl alcohol trichlorotrifluorokerosine ethane Chemicals listed in both categories cadmium chloride carbon tetrachloride colchicine diphenylamine ethylene dichloride lead acetate The Consumer Product Safety Commission which is now investigating high school chemistry labs was the source of information for the article. Twenty-two high schools in eleven states were asked to supply copies of their chemical orders for the 1981-82 school year. A list of 312 different chemicals was compiled and analyzed. According t o Chem. Eng. News (2). the NIOSHIOSHA "Pocket Guide to Chemical Hazards" and "Dangerous Properties of Industrial Chemicals" by N. Irving Saxe were the ~ r i n c i ~sources al for information on the toxic properties of 'the c'hemicals listed. Unfortunately, these sources are primarily geared to industrial users where exposures are measured in hours, weeks, and years. Ferric oxide would not have been included in the list bv anyone familiar with high school chemistry. Exposure hazards lor "ferric oxide fume" are discussed in the summarv of its toxicology in the OSHA guidelines (3) in terms of 6 to 10 years in the work place where permissible exposure limits of 10 mg/m3 are set for 8-hour work shifts. Occupations where ferric oxide dust exposure might be a genuine concern include Suspected teratogens lead chloride lead nitrate lithium chloride methyl ethyl ketone salieylamide
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Journal of Chemical Education
welding, foundry operations, and grinding and polishing operations. Ferric oxide is used in verv few traditional tirst-vear chemistry programs. This example is not intended to diminish the seriousness of exposing students to toxic hazards. Every conscious effort, obviously, must be made to protect them from unreasonable risks. T o do less would be negligent. The secondary teacher needs t o know where to find information that is useful and how to interpret it. Rather than disseminate a list of "Hazardous chemicals in high school labs" to parents in a family magazine, the Consumer Product Safety Commission could be more effective if i t shared its information directly with teachers. A very good reference for anyone involved with chemicals is the NIOSHIOSHA "Pocket Guide to Chemical Hazards" (4). Besides the Permissible Exposure Limits, PEL, which are based on time-weighted 8-hour work shifts, information is included on the concentration of many chemicals. Immediately Dangerous to Health or Life, IDHL, and on routes of entry into the body. IDHL probably provides the most useful data on toxicity for high school teachers. High school lab time is so short and the work so varied, exposure is more appropriately measured in minutes for students. and not much more than that for their teachers who usuallb shift from lab to classroom several times a day. Seldom is one activitv continued for more than about 90 min. the average length-of lab periods (5). The inevitable set:up and clean-UDtime must be subtracted from the 90 min. A teacher is fortuAate who can salvage 75 min. of productive work per week per class. The American Conference of Governmental Industrial Hygienists, ACGIH, produces an annual guide (6) for Short Term Exposure Limits, STEL, for common chemicals which would also be useful for teachers. The limits are based on 15-min exposures. ACGIH standards seem to be more stringent than NIOSHIOSHA. Threshold Limit Value, TLV, a term registered by ACGIH, has approximately the same meaning as PEL. Routes of entrv need to be considered in rev en tine exnosure. There are four important routes for toxic c h e m ~ c ato l~ enter the body: inhalation, skin absorption, skin and eye contact, and ingestion. Enforcement of good hygiene and firm rules for NO eatine. drinkine. or ni~ettinebv mouth in the lab will do much to minimizeyhe iniestio; hazard. The other three exposure routes are more of a problem. An eye wash, a shower, and a good hood are absolute necessities, or the chemicals used must be very low risk. Inhalation hazards can be minimized by the use of a good fume hood. That solution is not always as easy as it sounds in the high school setting, where there is generally one hood for 20 or more students. The hood is usually adequate for only two students a t a time. If a student exneriment is feasible but the hood must be used, staggering assignments will greatly ease congestion and make the work safer lor all. The layout of the
Safety TIPS" .s planned to be a source of safety ntarmaton and pranlcal ruggestlms lo mast Ve s+wc a1 negls of h ~ 1 cnernisby 1 teachers. It is also intended to be a forum for teachers to share their experiences and seek solutions to safety related problems.
lab often makes demonstrations impractical if they require a hood. Teachers have to seek information on the hazards of chemicals that might be used for an experiment, then select the ones. When the risk outweirhs anv oossible benefit, ~ - - safest it is not reasonable to think a first-ye& student has to do that oarticular exneriment. Peonle varv considerablv in their response to chemicals, and even pubfished 'safe' v&es have to be considered as aidelines onlv. Young veoole often have very sensitive s k i , soyt would be wise to take extra care where skin contact or absorption is the hazard. Ninhydrin, a common chemical in biochemistry, was used by antagonists against the family of Donald Woods, an outspoken anti-apartheid and former editor of an influential newspaper in South Africa. He was under house arrest when a gift of tee shirts was sent to the family. His young daughter tried one on and began screaming, "My eyes are burning." Washing did not relieve the pain. The family doctor was called. He applied oil to the child's eyes and sedated her for relief. Purole blotches aoneared around her eves and skin wherever the shirt had touched her skin. The iiritation was traced to ninhvdrin soraved inside the shirt. This incident escape a i t h his family in Decemher 1977 drove Woods (7). Ninhydrin is used by police to trace fingerprints on paper. They are warned toavoid contact with the chemical because of the severe burning sensation it will produce. Teachers and students who must use ninhydrin in the lab are urged to take preventative measures to avoid physical contact with the chemical. Everyone should he aware that some chemicals will produce severe reactions in persons who have previously been sensitive to them. Chemicals which produce allergic sensitization might not cause any irritation on the first exposure, but due to an "antibody mechanism" (8) reactions might be severe and without correlation to amount of exposure on subsequent encounters. A chemical known to he an allergic sensitizer is TDI, toluene 2,4-diisocyanate. TDI is used in the dramatic polyurethane foam demonstration. Case histories of severe reactions are discussed in the Decemher 1974, J. CHEM. EDLIC.,pp. 5 W 1 . Some chemicalsare more toxic when mixed than they are singly. A familiar example of this combined effect is the increased liver damage that can occur in workers exposed to carbon tetrachloride while they have ethanol in their systems. In regard to the Consumer Product Safety Commission's list of suspected carcinogens, the questions we must ask our~
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selves is. "What really constitutes a safe lahoratory environment?" Again, not afi chemicals are toxic and, of those that are, only a fraction are carcinogens. In addition (9)
".. .experts don't agree on the criteria that should he used in labelling a substance carcinogenic. "Should a compound be called carcinogenic if it causes tumors that appear to be benign? Should a chemical he regulated as a carcinogen if it causes cancer in animals exposed to dwes hundreds or thousands of times greater than people would he exposed to? What percentage of experimental animals must contract what type of cancer before the evidence is sufficiently strong? Are the data from animal tests directly applicable to human situations, such as occupational exposure?" The high school teacher has a moral and legal obligation to demonstrate safe practices as an integral part of the first course in chemistry. It is equally important t o relate the academic exuerience to the world outside the lab. Kerosine, a chemical-on the Consumer Product Commission's list, is a common fuel. Ferric oxide is found in many common paints, including barn paint, in minerals, and in rust. Although the very hazardous properties of carbon tetrachloride and benzene have received considerable publicity, they still may be found outside the laboratory. Every exposure to a hazardous chemical involves some risk, wherever it occurs. Unfortunately, there is no easy formula to use to answer the question, "How much is too much?" Editor's Note
If you have had an unplanned experience with chemicals in the lab, or found an especially effective way of handling them, please share your thoughts on the subject with other readers of "Safety Tips."
Literature Cited (1) Good Housekeeping. 194(5), 236 (1982).
(2) Chem. & En& Near. 60(5). 5 (1982). (3) "NIOSHIOSHA Occupational Health Guidelines for C h e m i d Harards:'Publieation No. 81.123, Superintendent af Daumenfs, U. S. Government Printing Office, Washington, DC 20402. (Jsnusry 1981). (4) DHEW (NIOSH) Publication No. 78-210. Supuintendent of Daewnente. U. S. Government P ~ n t i n gOffice, Wwhiwgttt, DC 20402. . (5) ACS~NSTACooperative Chemistry Test in High School Chemistry Form 1973,Tsblps of Percentile Ranks. Choroctenslics 01th. Group. (6) ACGIH,Ine.,P.O.Box 1937,Cineinnsti,OH45201. (7) Woods, Donsld,"Aaking forTrouble,"Atheneum, New York, 1981,~'333. . 181 . . Steere.Norm V.fEditor):'CRCH~dbookof Lsbobotary Safety: 2nd E~.,CRCPPP 1nc.i B a s Raton. FL, 1971, p. 297. (9) "Cancer. Pollution, and the Workplsce," American Industrial Health Council, 1075 Central Park Avenue. Scsrsdale,NY 10583, p. 13.
Volume 59 Number 12 December 1982
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