Exposure to Methacrylates
Technical Overview
There are no known major natural sources of methacrylate esters. To understand the possibilities for exposure it is important to understand the scope of the associated applications and products. In manufacturing/processing, chemical industry operators are responsible for the production of the esters or polymers, while downstream processors make the dispersions or other compounded or fabricated items. In professional/ commercial settings, applicators or technicians who may come into contact with the ester monomers or polymers include dental technicians, trained manicurists, paint and coating applicators, mechanics and auto repair technicians. Consumers could be the recipients of articles applied by professionals, like the dental appliances, artificial nails, etc, or could be the users of the products like latex paints, adhesives, or fabricated items.
Occupational exposure to short chain alkyl methacrylates is most likely to occur through inhalation and dermal contact during the production, transportation, or use of these compounds. The occupational exposures limits (OEL) that have been defined for methyl methacrylate, are generally in the range of 50 - 100 ppm as a time weighted average for an 8 hour workshift; OELs for ethyl methacrylate are generally in the range of 25 - 100 ppm; for the butyl methacrylate isomers they are generally in the range of 25 - 50 ppm. No OELs have been set for 2-ethylhexyl methacrylate. All of these materials are considered skin sensitizers.
Among the professional trades, trained manicurists use small quantities of EMA in the application of artificial acrylic fingernails. Artificial fingernail and nail-repair kits are also sold to the general public. In this application there is potential for inhalation exposure and for direct contact between liquid monomer and the nail, and sometimes the skin.
Small quantities of methacrylate esters are also used in the manufacture and repair of dental prosthetics by trained technicians. Polymeric dental products (dentures and denture prosthetic devices) will contain low levels (typically below 1%; ISO Standard 1567 specifies less than 2.2% for dentures) of total methacrylate monomers; hence consumer exposure to low levels of migrant monomers, via the oral mucosa, may occur.
Consumer exposure to methacrylate monomers, by skin contact with PMMA, or oral intake from use of PMMA articles, is regarded to be negligible. End-use consumer products contain low levels of methacrylic acid esters (as a result of polymerization) and their rate of migration from acrylic polymers is low.
As an example, exposure to BMA (isomer not specified) during use of methacrylate polymer based toners in facsimile machines has been reported as 0.045 ppm (0.21 mg/m3) (Fannick (NIOSH), 1981) and between 0.02 and 0.1ppm (0.14 and 0.6 mg/m3) (Raymond, 1996).
The Methacrylate Producers Association in the US and the Methacrylates Sector Group of the European Chemical Industry Council published a "Methacrylate Esters Safe Handling Manual" in 2007 for use by their customers. The manual provides information on characteristics, potential health effects, industrial hygiene, reactivity, shipping, storage handling and disposal, applicable to typical use scenarios.
