NIOSH Testimony to DOL on the Occupational Safety and Health AdministrationProposed Rule on Occupational Exposure to Methylene Chloride by J. D. Millar, September 21, 1992

摘要

The testimony indicated that the present 500 part per million permissibleexposure limit for methylene-chloride is not adequate to protect worker health, and supported the attempts of OSHA to lower the standard. Laboratory animal studies have indicated the carcinogenic potential of the compound. Three areas of concern related to the pharmacokinetics section of the OSHA proposed rule were discussed: unproven mechanistic assumptions made in physiologically based pharmacokinetic modeling; the impact of the variability in human metabolic parameters on the risk estimates; and the interpretation of a recent mechanistic study relevant to methylene-chloride risk assessment. Also discussed in the testimony were central nervous system health effects (short term exposure limit and prolonged neurobehavioral effects), studies of workers exposed to methylene-chloride, indirect evidence related to cardiovascular risk, estimates of carboxyhemoglobin levels in relation to methylene-chloride exposure, comparisons between the results of the animal and epidemiologic studies, exposure monitoring, control technology, respiratory protection and other protective clothing and equipment. NIOSH recommends that the exposure limit be reduced to the lowest feasible level.