Studies on the relation between bladder cancer and benzidine or its derived dyes in Shanghai.

Area of Science:

• Occupational Health
• Epidemiology
• Toxicology

Background:

• Shanghai has a long history of benzidine-derived dye production and application.
• Benzidine and its derived dyes have been linked to health concerns, necessitating epidemiological investigation.

Purpose of the Study:

• To investigate the carcinogenicity of benzidine and its derived dyes through epidemiological studies.
• To identify the primary causes of bladder cancer in Shanghai's industrial settings.

Main Methods:

• A case-control study involving 344 bladder cancer patients matched with controls.
• Two retrospective cohort studies were conducted in dyestuff factories and textile printing facilities.

Main Results:

• Occupational exposure to benzidine was strongly correlated with bladder cancer (RR 5.71), exceeding the risk from smoking (RR 1.53).
• A retrospective cohort study revealed a significantly elevated standardized incidence ratio (SIR) of bladder cancer (1918) in workers exposed to benzidine during dye synthesis, with some subgroups showing an SIR as high as 7500.
• No excess cancer incidence was found in workers using benzidine-derived dyes in textile factories.

Conclusions:

• Occupational exposure, particularly to benzidine during the presynthesis stage of dye manufacture, is the primary cause of bladder cancer in Shanghai.
• The risk of bladder cancer is concentrated among workers directly involved in handling benzidine, not those working with the final derived dyes.