in the Chemical laboratory Edited by NORMAN V. STEERE, 140 Melbourne Ave., S:E. Minneapolis, Minn. 5541 4
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Health Hazards and Precautions for Epoxy Resin Systems in Electron Microscopy and Other Laboratory Uses* Catherine Leppert,? Scanning Electron Microscope Laboratory. Department of Geology and Geophysics, Space Science Center, University of Minnesota. Minneapolis. Minn. 55455
Although many laboratories use epoxy resin systems, laboratory personnel are often unaware of the severe hazards of certain system components. The need for special precautions is particularly great in laboratories where embedding of specimens in epoxy resin systems is a common and frequent procedure, as it is in electron microscopy laboratories. The history of industrial experience with epaxy resin systems provides a basis for concern about the increasingly common laboratory uses. Soon after initial industrial production and use of epoxy resins in the late 1950's. there were frequent outbreaks of contact dermatitis among workers handling epoxy resin components. In 1959 it was stated that epoxy resins had caused more cases of industrial dermatitis than any other chemical introduced in the previous ten years. (3) By 1969 epoxy resin components had become the second most common allergenic sensitizer in industry.(j) Epoxy resins with many versatile formulations and properties have found broad and increasing use for encapsulation, coatings, and adhesives. Epoxy resins have continued to be introduced in many small and diverse operations without accompanying knowledge of the precautions that are needed to protect users. Epoxy resin systems have been used. widely in electron microscopy laboratories since becoming the embedding media of choice in the 1960's. (5) The final cured epoxy resin tissue block is achieved by combining the uncured resin with hardeners and accelerators, and occasionally plasticizers, and heating for a specified period of time. Some of the components commonly used are: *This article is based an a paper Ms. Leppert presented on May 18, 1973, t o a meeting of the Minnesota Electron ~ i c r a s c o p ySociety. tCatherine Leppert received a Bachelor of Arts degree in 1966 from the University of Minnesota, majoring in zoology. She has done biological research from 1966 to 1973. working for the past :I?* years in electron microscopy facilities.
Epoxy resins: Araldite* 6005, an aromatic, highly viscous resin; Epon" 812, an aliphatic, undiluted, low viscosity resin: D.E.R. 736**, diglycidyl ether of propylene glycol; ERL-4206**, vinyl eyclohexene dioxide: Hardeners: Dodecenyl succinic anhydride; N a d i a methyl anhydride; Nonenylsuccinic anhydridee*; Accelerators: 2,4,6-Tri(dimethy1aminomethyl)phenol (available as D M P 30, or Thiokal EH-33W, an aromatic tertiary amine; Benzyldimethylamine (BDMA), an aromatic tertiary amine; Dimethylaminoethanol*'; Plasticizer: Dibutyl phthalate.
CONTACT DERMATITIS HAZARDS FROM EPOXY RESIN COMPONENTS Contact dermatitis is classified into two types: primary irritant dermatitis, and allergic sensitization dermatitis. The epoxy resin components with the greatest potential for causing dermatitis are the amine accelerators. The reaction between the epoxy resins and the aromatic amines is exothermic, and emission of heated vapors increases the possibility of exposure. The amines are capable of causing both primary irritant contact dermatitis and allergic sensitization contact dermatitis. The amines are also extremely caustic. Bath types of contact dermatitis are caused by epoxy resins which contain reactive diluents added to reduce viscosity, and by the reactive diluents alone. Undiluted epoxy resins are less likely t o cause bath types of dermatitis than other components, but the lower the molecular weight of the resin the greater is the potential for dermatitis. **These are the ingredients of Spurr's low viscosity medium, which is used increasingly. Far Spurr's comments on the toxicity of these components see his original paper in J. Ultrostruct. R m 26: 31, 1969.
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Solvents such as acetone remove oils and fats and make the skin more vulnerable to penetration of other components. The cured resin is considered to be nonirritating and nan-sensitizing. The primary irritant dermatitis is not distinguishable from allergic sensitization dermatitis by grass inspection alone. One can differentiate between the two types on the basis of the amount of exposure needed to elicit the reaction. In primary irritant dermatitis the same amount of skin contact with the chemical is required to elicit each reaction. In allergic sensitization reactions the inflammation will occur with significantly less exposure to the chemical than was necessary for the previous reaction. Primary irritant dermatitis may precede allergic sensitization dermatitis. It is also possible to show no reaction until allereic sensitization has taken olace. curred, progressively smaller amounts of the chemical which is now the allergen will elicit the contact dermatitis. The reaction has became a n immunologically-mediated response and the mast logical solution is to remove an individual from all oossihle fururr r m t n r t . Ilowwcr, the & \ r l q , m m t 01 idlerglc ~ ~ m ~ t . z a t 10 u mone chrm~cdl make one more readily susceptible to developing sensitization to other chemicals. The reactions to epoxy resin components can be varied. Any of these reactions can occur on exposed areas such as both surfaces of the hands, lower arms, face or
ARE EPOXY RESIN SYSTEMS USED I N YOUR LABORATORY? Even though this article was written for electron microscopy laboratories, the hazards are the same and the precautions should be the same in any laboratory using epaxy resin systems or any of the chemical components. The precautions recommended are probably more important in laboratories than in industry, hecause sensitized laboratory personnel can not be as easily replaced or "transferred ta another job" as sensitized factory employees can he. Substitution of less hazardous materials should be considered-either less hazardous epoxy resin systems, or other systems such as the acrylic resins. One reviewel suggested that the number of sensitized employees in electron microscopy laboratories may require the development and use of other embedding media far electron microscopy. Norman V. Steere, Column Editor (Continued onpageA448)
Volume 50. Number 9, September 1973
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Safety
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neck. A common reaction is small hives that itch. This reaction is usually seen on the upper surfaces of the hands on areas that have had contact with the resin and lasts from hours to days. Red swollen patches about the size of quarters can appear on the upper surfaces of the hands or the area around the eyes can become red and swollen. These areas itch and then scale as they heal. This reaction lasts a week or two. A third reaction involves redness with swelling and blistering. As the redness and swelling begin there is a sensation of tingling and burning. Then itching begins and the blisters appear on a spreading area for a period of three or four days. Instead of blisters the skin may form solid round elevations, papules, or may aooear lumov. ,~ , Then the inflammation subaidrs and either rrurtml: and prrling or scaling occurs. 'rhe w h d r reactwn 1% romplt.rcd in one to three u,eeks. The problems with the reactions are more than the inflammatory responses, since there is potential permanent damage to the skin of the involved areas.
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OTHER HEALTH HAZARDS FROM EPOXY RESIN COMPONENTS Epoxy resin components can cause health problems other t h a n , contact dermatitis. (1,4,7,11) Headaches, fatigue, gastrointestinal tract disturbances, and bronchial asthma have been reported. The bronchial asthmatic attacks are a result of respiratory sensitization from long term exposure to amine vapors. Symptoms of respiratory reaction include a feeling of dryness of the nasal tract. and a desire to take
Another serious problem with long-term ramifications is that some components, for example Epon'812, are carcinogens. (10)
PRECAUTIONS FOR USE OF EPOXY RESIN COMPONENTS The following precautions are recommended far handling of epoxy resin components to avoid health problems. These precautions are based on industrial experience, (1,4,7,8,9,11)with some modifications derived from laboratory experience. 1. Instruct all exposed personnel as to the potential health hazards and the precautions to be taken. 2. Eliminate skin contact with the components as completely as possible. a. If any skin contact occurs, interrupt work and immediately wash with soap and water. b. Adequate washing facilities should be available and washing should be done with a neutral or acid soap. c. Use latex* or polyethylene gloves (disposable or nondisposahle) with cotton liners and barrier creams. Wash the cotton liners daily to prevent imitation from toxic wastes in perspiration. Gloves should he taut over laboratory coat A448
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Journal ot Chemical Educaiion
cuffs. Barrier cream containers should be individual. d. If nandisposable gloves are used, they should be washed withsoap and water while still on the hands. e. All persons should wash thoroughly before putting on any harrier creams and gloves, and after the resin work is completed. f. Skin lotions should he used regularly after washing to maintain the skin in good condition: g. Wear goggles or a face shield. h. Wear protective clothing. If any . component contacts the laboratory clothing or other garments, remove them immediately and wash the skin under that area (unless the clothing is impermeable). Wash the clothing before wearing it again. 3. All epoxy resin work should he done in exhaust-ventilated enclosures or hoods. Ovens used for curing resins should have their vents exhausted to the outside of the building. 4. Handling of resin components should he minimized. Disposable containers (e.g. polyethylene-lined paper cups) and stirring rods (eg. wooden sticks or tongue depressors) should he used to mix and work with the resins. Disposable containers and stirring rods should be disposed of in closed containers as soon as they have been used. Any nondisposable item that is used with the resin components should he cleaned immediately after use to prevent contact with other personnel. 5. Each container with any epory resin component in it should be properly labeled to show the name, hazards, and recommended precautions. Obtain Material Safety Data Sheet for each component from the supplier or manufacturer before handling the chemicals. All precautions recommended on labels or data sheets should he strictly followed. 6. Limit the resin work and component storage to a small specified area. Establish meticulous housekeeping standards. Cover the work area with hrown paper (which shows spills) to facilitate keeping the work area clean. Keep adequate disposable towels handy so that spills or splashes can be wiped up immediately. Place soiled paper towels and hrown papers in a covered eontainer. After the resin work is finished, or at least twice a day, change the brown paper on the work area. The necessity of following all these precautions becomes apparent when one realizes that authorities consider 70% to 100% of any population capable of sensitization. (8) Each exposure brings one closer to his tolerance limit. Industry has attempted to mechanize as many operations involving epoxy resins as possihle. In electron microscopy, mechanization has recently been achieved for at least some steps of the embedding process. (6) *Latex is permeated by epichlorohydrin, which is one of the reactive diluents used with epoxy resin systems. If you are not certain your epoxy resin system is free of epichlorohydrin, check with the manufacturer and use their recommended means of skin protection. PLY No. 9 Gel Barrier Cream is reported to prevent penetration of epichlorohydrin.
J Oeeupalionol M d 5 Ill. 17 to Health Associated with the Use of E p x y Resins.'' (51 Glauen. Audrey M.. J. RoyalMicmsropid Soc. RO (41. 269 (19621. "A Survey of Embedding Media for Elsefron MiemseopyI' (61 Haudenschild. D., snd Tschirky, H.. Exprrianlm. 28 1111, 1389 (1972). "Automated Specimen Processing tor Eleenon Microscopy: A New Apparatus." (71 Key, Marcus M.. J. Point Tech.. 11 (5311. 304 (19691, "Control of Epory Dermatitis in Indus~ I41 Dernehl, Carl U.,
LABELING OF HAZARDS OF EPOXY RESIN COMPONENTS A means of identifying the hazards inherent in epoxy resin components has been established in the "American National Standard Guide for Classifying and Laheling Epoxy Products According to Their Hazardous Potentialities." (2) The guide was developed by a committee under the procedures of the American National Standards Institute and published in 1972. Secretariat of the committee was the Epoxy Resin Formulators Division of the Society of the Plastics Industry. The guide establishes classifications of flammable and pressure-generating properties, and six classifications for health hazard potentialities. The classifications for health hazard potentials include skin irritating, sensitizing, toxic, and carcinogenic. However, the section on labeling does NOT recommend t h a t labels include the full description of the hazard potentials listed in the six classifications. Specifically, the recommended labeling does not include any use of the terms "Sensitizer" or "Carcinogen." Present labels on epoxy resin eamponents for laboratory use do not include the classifications of health hazard potentials. If manufacturers and chemical supply houses that repackage epoxy resin components would use the health hazard classification ratings on their labels i t would be of great assistance in dealing with the problem of protecting the people who use the chemicals.
HEALTH PROBLEMS I N ELECTRON MICROSCOPY LABORATORIES The health problems in electron microscopy due to improper handling of epoxy resin components may be apparent sooner in laboratories with larger amounts of embedding heing done and a greater degree of laxness in handling than in average laboratories. With continued improper handling of epoxy resin components, contact dermatitis is only a matter of time. In a limited survey conducted among people working in electron microscopy, twenty-two have had what they thought were skin reactions from working with epoxy resins. Fourteen of these individuals reacted while working in the MinneapolisSt. Paul area in Minnesota. A survey of all members is planned by the Minnesota Electron Microscopy Society t o identify those who have experienced health problems with epoxy resin components.
REFERENCES i l l Adamr. R. M.. "Occupational Contact Dermatitis." J. 8 . Lippineoft Co., Philadelphia. 1969 (21 American National Standards Institute. "American National Standard Guide for Classifying and Labeling Epoxy ProdueU According to Their Hazardous Poientislities," American National st an^ darda Institute. New Yolk. 1972. (3) Birmingham, D. J.. A . M A Arch. lad. H d l h . 20. 490 (19591. "New Causes of Oeeupatiolal D e r m r ~ fa.er."
(19631, "Hazards
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181 Lee. Henrv. and Neville. Krii. "Handbook of Eooxv ~ ~ i i n n ; ; ~ ~ G ~~ ~n c~ . -, '~~ iYoik, e lwl , 1967. (91 Nation4 Safety Council, "National Safety Council Data Sheet 533. Rev. A, E w r y Resin Systems: National Safety Council. Chicago. 1970. I101 Shell Chemical Co., "SPI Classificat~on of Shell Epon Rsrinr. Shell Chemical Company Industrial Hyeiene Bulletin SC W:37." 1968. I111 U.S. Department of Health. Education and Welfare. Public Health Service. National Institute of Oeeupafionsl Sstety and Health. "Preventing Dormatitis if You Work with Epoxy Resine.). Pub. ri040. 1963.
CHROMATOGRAPH LABORATORY, JAN. 19, 1973 A gel-permeation chromatograph was used for the analysis of molecular weights of polymers. Materials to be analyzed are dissolved in a solvent contained in a 3 gal. closed reservoir in the base of the machine. The solvent used was tetrahydrofuran which has a closed cup flash point of 6°F. The solvent reservoir is filled by attaching a 5 gallon container to the top of the unit. The solvent is then gravity fed through filters into the reservoir. The reservoir is not equipped with an automatic fill shut-off or a fill level indicator. On the day in question an employee attached a 5 gal container of solvent t o the machine, started the refilling process and left the room. When the emolovee re, ~ u r n e d ,ahour or, hour lorcr, he diicuvered the F O ~ V P D I reiervoi? hod overflc~wrd.The employrc rernovrd the fill can then bit rhe laboratory for protective breathing apparatus. He then returned to clean-up the area. Upon his return he noticed that the solvent had dissolved the insulation on the electric wiring to a small electric pump adjacent to the chromatograph. Shortly thereafter he heard a snap as the electric wires shorted and ignited the spilled solvent. Both the fire department and the laboratory employees attempted t o fight the fire using COz. The COz was ineffective in that the solvent keot reienitine. ". and twenty minutes later dry chemical was used toextingish the fire. Damage $26,000.
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Reported t o the National Fire Protection Association and reprinted with permission.
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