The trend in airborne asbestos concentrations at plants manufacturing asbestos-containing products in Japan.

In Japan, chrysotile is still permitted to use under the Ordinance on Prevention of Hazards due to Specified Chemical Substances. In recent years many countries have introduced a policy of prohibiting the use of asbestos, based on clinical and epidemiological studies. In light of this, it is important to evaluate the airborne asbestos concentrations in workplaces and also estimate the number of related disease cases in order to discuss the ban of asbestos use. The survey covered 528 workplaces in 145 plants and included 2795 asbestos handling workers from 1985 to 1998. These plants were belonging to the Japan Asbestos Association (JAA) as member companies. In Japan, nearly all of the asbestos using manufacturing companies are members of JAA. In our study, all of the workplaces were divided under each separate manufacturing process and classified into 3 categories of Control Classes. Of the 454/528 (86.0%) workplaces classified as Control Class 1 are improved to 376/378 (99.5%). Though in the cases of small enterprises, other factors such as a shift in product lines, and the economic recession, as well as efforts, contributed to improvements in working conditions. JAA recommended self-administered concentrations of 1.0 f/ml (compatible to <0.3 f/ml in personal exposure level) in 1991 to promote further improvements of the work environment. From this point of view, exposure limits can almost be technically achieved in Japan, and it is expected that asbestos related disease could be expected to decrease in 20 to 30 years later. This survey will become basic material for verifications whether we could control asbestos related diseases enough in such well-controlled work environment.