ABC of Safety in the Biological Sciences
Three types of epoxy resin form the basis for embedding media - these are Araldite (diglycidyl ether of bis-phenol), Epon (triglycidyl ether of glycerol) and Spurr and Ladd (vinyl cyclohexane dioxide).
The polyester resins consist of three components: an unsaturated low molecular weight polyester resin, a fluid monomer (either vinyl or acrylic) capable of radical polymerisation and a curing system such as a heat activated catalyst.
All acrylic monomers have the acryl group in common. The acrylates are generally avoided because of their strong odour, and therefore the methacrylates are used almost exclusively.
Health hazard data
Two monomers, vinyl cyclohexane dioxide and propylene oxide, have produced tumours in animals. The resin components can, in either liquid or vapour form, cause skin, mucosal and eye irritation. Resins are toxic and can be absorbed through the skin, inhaled or ingested. The effects of systemic poisoning can be many and varied and include sensitisation, heart dysfunction, chest spasm, neurological and blood disorders. Of these sensitisation is the most common problem and can, in extreme cases, result in the affected individual having to cease work in the resin laboratory. Many of the diluents used in conjunction with resins are volatile and most will produce aerosols during curing. These vapours and aerosols can cause headaches, lower the appetite, taint food and contaminate clothing with the vapour.9
Most of the resins are flammable and should never be used close to heat or naked flames. Benzoyl peroxide is potentially explosive when dry and is capable of violent reactions with amines.
Unpolymerised resins should only be handled beneath a working fume hood and whilst wearing full protective clothing including gown, mask, rubber gloves and a face mask as a minimum standard. Use disposable equipment wherever possible.
Polymerisation should be in an oven vented to the outside or in a small oven in a fume hood.
When handling polymerised resin dust should be kept to a minimum and collected with a disposable damp cloth, moist paper towel or vacuum cleaner.
Resins are disposed of by high temperature incineration or landfill burial. As incineration may lead to the production of hydrochloric acid, carbon dioxide, nitric acid and cyanides the incinerator must be fitted with a scrubber to remove toxic gases.121