Safety Education for Chemistry Students Hazard Control Starting at the Source A. W. Zwaard, H. P. W. Vermeeren, and R. de Gelder Gorlaeus Laboratories, Leiden University, P. 0. Box 9502, 2300 RA Leiden, T h e Netherlands
Chemists and chemistry students in academic research laboratories generally make use of a tremendous variety of chemicals and other agents. New techniques and the application of new chemicals, radiation sources (lasers, ultrasonic devices, microwave equipment), radioactive materials end microorganisms make many research lahoratories complex working environments. This causes a need for some hasie knowledge in the field of hazard control. To realize effective hazard control procedures and practices, students in chemical
Waiter Zvaard was born in 1954 in Delft. The Netherlands, and studied chemistry at Leiden University. He obtained his PID in chemisby and has several years experience in chemical research. He s p ~ c i a l i z din hazard control and has much experience in giving courses an various aspects of halard conwal for both students and professionals. Since 1983 he has been the manager of Safety and Occupational Health at Gorlaeus Laboratories of Leiden University. Hans Vermeeren was born in 1949 in Rotterdam. The Netherlands, and started hiscareer as a researchassistantat Leiden University after graduating from Rotterdam Higher Technical School. Aner obtaining his MS in chamisby at Laiden University. he r e c e i v e d extensive training i n Occupational health and occupational hygiene as well as in policy research and development. He has several years experience as an advisw on Safety and Occupational Hygiene at a large research laboratory. Since 1983 he has wwked as Chief Inspector with the Dutch Directorat% General of Labor. R e d de Gelder was born in 1965 in Wissenkerke, The Netherlands. He studied chemistry a t Leiden University. specializing in crystallography. Recently he obtained his MS in chemistry. At the moment he is working on his PhD lhesis. which is about direct melhods using KarleHauptman matrices.
Laboratories should he provided with the necessary tools including equipment, provisions, and information. The necessary information can he provided by a program of safety education that has as the central theme a systematic and strategic approach to hazard control, following three steps: hazard recognition, hazard evaluation, and hazard control. This paper presents an outline of the contents of such a program. Throueh an inventorv and classification of onssihle hazards a oroerammed wav to ~. mercume specific hazards is then ohtarned preventing the dudent t'rom werkmking relevant (not directly recognized) hazards. Specific hazards as exposure to chemicals, radiation, radioactive compounds, light, sound, microbiological agents, fire, explo-
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Hazard recognition
Hazard evaluation
sions, and heat can be discussed. For each of these hazard types hazard control can be accomplished following t h e same hasie strategy.
A Basic Strategy To realize hazard control in an efficient way, it is not sufficient to teach a set of specific safety rules or prescriptions. Instead of teaching standard solutions to standard nroblems. students should be stimulated in $trategie thinking. Therefore asystematic and strategic approach should he presented that can in principle be applied to any laboratory situation (see Fig. 1). The basis of this approach is that hazards are as much as possible eliminated a t their source.
1 What is the hazard? What is its source?
What may be its consequences? Is the hazard acceptable to all parties involved?
Hazard control can be taken?
be taken? Figure 1. Stages in Ihe process of recognition to contral of hazards
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The different measures within the strategy may have different purposes: 1. removal of the origin of the hazards, 2. diminishing the hazards, or 3. limiting of the nossible conseauences of the hazards.
Which purposesuitra sperifirsituation best berumes clear from the harard evaluation and the moment the process of hazard control starts. In a new experiment or research program much more is possible than in a fixed setup that has been running for years. I t is therefore imnortant that the nracess of hazard control st& in an early phase, preferably when experiments are designed. When hazard control starts after accidents have taken place, it is only possible to diminish the consequences of the accident. To realize hazard control in a systematic way, use can he made of a basic strategy consisting of the following steps: 1. taking measures at the source, 2. isolation of the source, 3. adjustment of the surrounding, 4. isolation of people, and 5. use of personal protective equipment.
In this strategy the different measures are shown in order of decreasing effectiveness.
not possible it is sometimes possible to eon tain the source effectively. Containmenf i.e., isolation of the source, is possihle re gardless of the character of the source:
lsolatlon of the source. chemicals, radioactive compounds, radiation sources,or sound sources. Typical control measures can he found in the use of glove boxes, laboratory hoods, lead bricks, or sound insulating devices. The exact nature of the containment thus depends on the character of the hazard source. When isolation of the source is not fessible technically, more attention should he given to the surroundings of the source. General laboratory ventilation, local exhaust ventilation, or the use of explosion screens or black curtains (when working with certain light sources) are typical examples. Other examples are the use of special rooms for specific experiments or the application of warning signs. I t is dear that again the exact measures depend on the type of hazard involved. Although giving attention ta the direct surroundine of the hazard sources is important, it is generally less effective than measures a t the source or containment of the source.
Student and hazard source. The first step consists of taking measures a t the source. A very efficient way of reducing hazards is eliminating their source. In lahoratorv situations elirninotine the hazard source is sometimes possihle, eg., hy substituting rhcmirals by less hazardour ones. Sr
Adjustment ol the wrroundlngr The next step in the strategic approach is in a wav onnwite to isolation of the source and consists of isolatim of the person work. ing wlth the sources. In rnduxtry this is a well-known measure, as represented by the use of control rooms. In lshoratory situations it is less common. Limiting access to certain laboratory rooms (containment lahoratories) is, however, an example.
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Ellmlnatlon ot the source.
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In - manv cases however.. comolete elimination of the harard rource i~ not possible, bur odoptotion of the source is a goud alterna~3~~~
Personal protective equipment. Measures at the Source The examplesgiven illustrate that the basic strategy ran be applied to all types of harard: fire or explosions, working with toxic chemicals or radioactive materials, working with lasers or ultrasonic devices, etc. For chemistry students the hazards of working with chekicals deserve of course a hroad attention. In the following the strategic approach, especially the first steps, will he illustrated by some examples derived from that type of work. When the hazard sources are chemicals, an efficient way of reducing hazards is to eliminate the chemicals. This surely seems an impossible task in a chemical laboratory. Nevertheless, a critical choice of chemicals is a crucial ooint in realizine hazard control. Of course, when one has decided to investigate the brumination of phenol it ir hard to think of alternatives for bromine or phenol, but in many instances the use of specific chemicals is less vital. Some chemicals are of course chosen because of their specific molecular structure. Others are, however, selected on less clear grounds. For example, many syntheses are performed according to standard procedures taken from the chemical literature. In several cases the selection of chemicals (especially solvents) in these procedures is not based on extensive research but determined by availability, eeonomical factors, or nure chance. It has hecome clear, however, that many toxic wlvenw (henzene, carbon tetrarhloride, rhlon~form,hexane) can be substituted by less hazardous ones (toluene, dichloromethane, pentane) (see Fig. 2). As a more recent example hexamethylphosphorustriamide (HMPT) can be mentioned. The carA/V
CCl' CHCl3
0 [(cH~~N]~Po HMPA
lsolatlon ot man. Adaptallon ot the source. tive. Since in chemical laboratories the source often consists of a number of chemicals plus equipment, there are possibilities in adjusting the equipment. When control measures a t the source are
The last step in our strategy is the application of personal protective devices. It should be stressed that this is a last step. Many examples, safety gaggles, laboratory coats, and protective gloves, are well known from daily practice.
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Figure 2. Safe substitutes (rlght)for some chemicals (lelt). ., (Continued on page A114)
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cinogenicity of HMPT in rats caused the development of (possibly noncarcinogenic) alternatives, as, far example, tetrahydro1,3-dimethyl-2(H)-pyrimidone(DMPU). Also the control of fire or explosion hazards is possible by changing to other chemicals, e.g., by choosing less flammable solvents or reagents with a relatively high flash point. Several examples of this kind are described in the literature. A good example is the use of tetrduaraborate (BF4-) or triflate (CF3S03-) instead of perchlorate (CI04-) in certain metal complexes, removing the explosive properties. Sometimes it is possible to adjust the reagents used without influencing the required properties. Far example, dimethyl sulfate and henzylie chloride form complexes with crown ethers, still containing the desired reactivity but being less volatile thus reducing the exposure hazard. Another aspect that should be mentioned ia the scale of the exoeriment. Laree-scale experiments generally imply greater haz. ards than small-scale ones. Adjusting the scale of the experiment t4~its goal thus is certainly worthwhile. Syntheses that consist of several steps also deserve attention. Sometimes the choice of the reaction route influences the hazards involved. This is esoeciallv true in eases where carcinogenic intkrmediates can be farmed. For example, the synthesis of 2-naphthylamino-6,bdisulfonic acid from Pnaphthol is possible in two steps (see Fig. 3). In the
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Flgure 3. Synthesis of 2-naphlhylamlno-6.Wsulfonb add horn 2-naphthol. f i s t step the hydroxy group is transformed in a Btichecer reaction into an amino function. In the second step the intermediate 2aminonaphthalene is sulfonated with formation of the final product. The formation of the powerfully carcinogenic 2-aminonaphthalene can be circumvented hy first performing the sulfonation and then the Becherer reaction. It is clear that thinking about the chemicals used, experimental scale and experimental details (including the poasihility of elevated temperatures or pressures) becomes more important when the toxicity of the chemicals involved increases. This means in short that for carcinogens suhstitution by alternatives should be seriously considered. Furthermore, the choice of chemicals becomes more important when the laboratory experiment is meant to be scaled up, e.g., in an industrial process or in experiments in student courses. In a small-scale experiment the choice of chemicals may seem of leas importance; however, a careless choice may make hazard control in a later application very difficult or expensive. A114
Other Measures If measures at the source are not feasible, the second step of our strategy might be useful. Isolation uf the suurce implies in fact the screening, insulation, or containment of the source from its surrounding. The way by which this is realized depends on the experimental details and the type of hazard. A special, weU-known device is the laboratory hood. In fact using a lahoratory hood is a combination of containment of the source and adjustment afthe surrounding, depending on design and use of the hood. Any course on hazard control in laboratories should pay sufficient attention t o hoods, including their design and eonstruction, their location in the laboratory, and their proper use. Generally, laboratory hoods extract their air completely from the lahoratory. The air flow within the hood is then directly related to the exhaust ventilation of the lahoratory. This hrings us to the third step of our strategy: adjustment of the surrounding. In this respect the ventilation rate of the laboratory room (in cubic meters per hour) deserves attention. The desired ventilation rate of a laboratory depends on a number of factors such as the chemicals used, their emission rates, and the volume of the room. The fourth step in the general strategy was described as the containment of oeoole. This measure should be taken onlv" if mea-~~~~~~~ sums at the suurce or sufficient adjustment ctf the surroundings is impossible. It means in fact that the chemicals and their direct environment are accepted as they are and that we concentrate on separating the people from them. Application of this principle should be clear in the design and layout of the laboratory. It might be useful to limit access to certain hauvdous areas in the laboratory. Separate office spaces are another feature of importance. Personal protection i~ the last step in our basic strategy. It is of course important to teach chemistry students about the essentials of personal protection devices that are commonly wed in chemical laboratories such as laboratory coats, safety glasses, and protective gloves. Of equal importance, however, is information on their Limitations. Especially the use of protective gloves deserves sufficient attention in any program of safety education. It should be stressed that anvelove has alimited "breakthroueh time" fo; ihemicals, the value of which 2epends both on the chemical and the glove material involved. Concluding Remarks The outline presented gives an impression of the philosophy and structure of a course an hazard control that can be given in a relative short period of time. It teaches the basics of hazard control in a way directly manageable by chemistry students, as has been our experience. General References
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Fuaealdo. A. A,: Erliek. B. J.: Hindman, B., Ed$. Loborofory Safety: Theory ond Badice; Academia: Near York. 1980. National Research council; National Academy of scienws; National Academy of Engineering; Institute of Medicine. Pludont Ploetieea for Handlig Hosordous Chemicals in Lobomtories; National Academy Press: Waahingon. 1981. Steere, N. V., Ed. Hondbwk of Loboratory Safety; CRC: B- Raton. FL. 1979. Wa1ters.D. B.;Jameaon.C. W.,Eds.H~ollh~ndSafety for To~icityTosting;Butternorth: Bmton. I s .
