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An alternative hypothesis for bladder cancer among workers exposed to ortho-toluidine and aniline.

Acquavella JF; Wilson JD; Conner P; Bannister R; Ward EM; Roberts D; Streicher R; Boeniger M; Fajen J
J Natl Cancer Inst 1991 Nov; 83(22):1686-1687
The results of a study of bladder cancer in workers exposed to ortho- toluidine (95534) and aniline (62533) were discussed in a letter and a response. A NIOSH survey of workers employed at a chemical manufacturing facility in the 1950s and 1960s who were potentially exposed to ortho-toluidine, aniline, and other chemicals found an excess incidence of bladder cancer. The excess was attributed to exposure to ortho-toluidine. This finding was challenged. The findings of the NIOSH study were considered to be inconsistent with the results of two earlier mortality studies of workers exposed to aniline and ortho-toluidine that found no significant bladder cancer risk. It was suggested that the positive findings in the NIOSH study reflected the fact that aniline used in the 1950s contained 2- naphthylamine (91598) and possibly 2-aminofluorene (153786), known bladder carcinogens, as impurities. In the 1950s, aniline was made from benzene which was derived from coal-tar, which also contained 2- naphthylamine and 2-aminofluorene as impurities. The NIOSH response was that the two studies cited used mortality as the outcome. Using mortality as the endpoint in occupational bladder cancer studies frequently yields false negative results because bladder cancer is not a rapidly fatal cancer. Because of this, the two cited studies did not have the statistical power to detect an excess bladder cancer risk. Only cancer incidence studies, like the one NIOSH conducted, have the statistical power to detect an excess bladder cancer risk. Contacts with suppliers indicated that some supplied petroleum derived benzene in the 1940s and 1950s. A major producer of coal-tar derived benzene stated that during that period the benzene they supplied was 99.9% pure, containing only aliphatic compounds as impurities. The authors of the response conclude that the alternative hypothesis to explain the excess bladder cancer in its study is unlikely.
NIOSH-Author; Bladder-cancer; Epidemiology; Amino-compounds; Occupational-exposure; Chemical-industry-workers; Cancer-rates; Mortality-data; Chemical-composition
95-53-4; 62-53-3; 91-59-8; 153-78-6
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Journal of the National Cancer Institute
Page last reviewed: September 22, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division