4,4'-Methylene-bis(2-chloroaniline) (MOCA, CAS#101-14-4) is a substance used as a curing agent in waterproof materials. It is associated with the development of bladder cancer as seen in 5 workers in a Japanese chemical plant. On Sep 21, the Japanese Ministry of Health, Labour and Welfare (MHLW) issued an official notice to Japan Chemical Industry Association (JCIA), Japan Dyestuff and Industrial Chemicals Association (JDICA) and 2 other industry associations requiring:
Rigorous implementation of measures to prevent worker exposure to MOCA as stipulated in relevant regulations; and
Immediate bladder cancer diagnostic tests and related health checkup for current and former employees who are involved in MOCA-related work
It was first reported in Dec 2015 that exposure to o-toluidine was associated with the development of bladder cancer in workers in a chemical plant in Fukui Prefecture, Japan. In the following investigation of workplaces using o-toluidine, MHLW found that 7 workers (among whom 6 had retired) of a chemical plant were diagnosed with bladder cancer. 4 of them had never handled o-toluidine and had instead been involved in work using MOCA (One of the remaining three workers had been exposed to both MOCA and o-toluidine).
MOCA has been classified as a Group I carcinogen by IARC since 2010. In Japan, it is designated as a Group II Specified Chemical Substance under the Ordinance on Prevention of Hazards due to Specified Chemical Substances (Ministry of Labour Ordinance No.39 of 1972), though bladder cancer diagnostic tests are not required in the Ordinance.
MHLW’s notice to the 4 associations is an emergency response and interim measure. Once sufficient epidemiological evidence is collected and clearer association between MOCA and increased risk of bladder cancer is substantiated, the authority will issue new regulations or revise the existing ones to enhance supervision and control over the production and use of MOCA in the future.
