New Evidence Implicates 2-Mercaptobenzothiazole as a Human Carcinogen

NEW YORK JAN 22, 2009 (Reuters Health) - A new study involving chemical production workers indicates that exposure to 2-mercaptobenzothiazole raises the risk of multiple myeloma as well as cancers of the large intestine and bladder.

"2-mercaptobenzothiazole is used as a vulcanizing agent in the rubber manufacturing industry, a corrosion inhibitor in auto radiator and metalworking fluids and a stabilizer in the manufacture of plastics," study author Dr. Tom Sorahan explains in the January 21 online issue of Occupational and Environmental Medicine.

In an earlier investigation into a high rate of bladder cancer at a chemicals production factory in north Wales, exposure to 2-mercaptobenzothiazole was considered to be a possible contributor. However, animal studies of the potential carcinogenicity of the chemical yielded equivocal results.

Dr. Sorahan, at the University of Birmingham, UK, investigated cancer risks among a sub-group of the original factory study involving 363 men exposed to 2-mercaptobenzothiazole during their employment.

Although the standardized mortality ratio (SMR) for all causes between 1955 and 2005 was "close to expectation," he reports, there was significant excess mortality for all neoplasms (76 deaths, SMR 141), for cancer of the large intestine (8 deaths, SMR 232), and bladder cancer (8 deaths, SMR 374).

Dr. Sorahan also detected significant excess morbidity (standardized registration ratio, or SRR) for the period 1971-2005 for all malignant neoplasms (97 cases, SRR 148), cancer of the bladder (12 cases, SRR 253), and multiple myeloma (4 cases, SRR 465).

Moreover, in analyses that included follow-up information for all 2160 employees included in the original cohort, there were significant positive trends for cancer of the large intestine and for multiple myeloma in relation to 2-mercaptobenzothiazole exposure. These trends could not be explained by exposure to other potential carcinogens.

Since this was a single-site study, the findings need to be confirmed in other populations exposed to 2-mercaptobenzothiazole. "In the meantime," Dr. Sorahan advises, "perhaps 2-mercaptobenzothiazole should be handled with increased care as it may be a human carcinogen."

SOURCE:

• Occup Environ Med 2009.



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