Dichloromethane (methylene chloride), with its degreasing properties, is used for a wide variety of purposes as a cleaning agent or solvent in various industries. Although only insufficient knowledge is available on the risks of dichloromethane exposure among the general population in Japan, a large number of industrial facilities have been taking measures in the recent years to reduce dichloromethane emissions under voluntary management programs on hazardous air pollutants implemented by industry associations. Such measures, however, should be imposed only in the cases where specific risks are identified.
The major purposes of the present assessment
are, therefore, to: 1) Conduct a comprehensive analysis of exposure to, and human health effects of, dichloromethane, and thereby to develop a detailed picture of current health risks among the Japanese population associated with environmental exposure to dichloromethane (excluding occupational exposure); and
2) Conduct a cost-effectiveness analysis of the measures being implemented at industrial facilities to date, with respect to reduction of dichloromethane emissions, and to provide the information critical to make a decision on whether or not to continue the current emission reduction measures.
The key features of the present assessment include a detailed risk analysis considering the distribution of atmospheric levels of dichloromethane and the corresponding distribution of the Japanese population. The distribution of dichloromethane levels has been evaluated at a spatial resolution of approximately 5 kilometers by the National Institute of
Advanced Industrial Science and Technology-Atmospheric
Dispersion Model for Exposure and Risk Assessment
(AIST-ADMER), with respect to the entire geographical area of Japan. Distribution of dichloromethane levels in the local vicinities of large-scale emission sources has been evaluated at a spatial resolution of 100 meters by the
Ministry of Economy, Trade and Industry-Low Rise
Industrial Source Dispersion Model (METI-LIS).
The results of the present assessment suggest that the current risks among the Japanese population associated with the estimated dichloromethane exposures are considerably low, and that the cost effectiveness of the measures currently taken by industrial facilities to reduce dichloromethane emissions is far from favorable, which indicates that higher priority should be given to other chemical
substance(s) in emission reduction programs of national level.