Carcinogens and Chemical Causes

The known and suspected causes of human bladder cancer fall into four groups: industrial chemicals, metabolites of foodstuffs, tobacco tar, and chronic mechanical stimulation.

It has been known since 1895³³ that chronic industrial exposure to certain dye intermediates is associated with a high incidence of transitional cell bladder tumors. Occupational bladder tumors occur after a mean exposure time of 22.9 years and may involve 26% of the workers.³⁴ The commonest recognized cause of occupational bladder tumor is β-naphthylamine. A recently recognized cause of human bladder tumor is p-biphenylamine (xenylamine).³⁵ Benzidine, α-naphthylamine, and auramine³⁶ are also suspect. The common denominator of chemicals which cause human bladder cancer seems to be a structure embodying an aromatic amine which can be excreted as an orthohydroxylated urinary metabolite.³⁷ Agents which cause human transitional cell tumors are unique, since they appear not to be carcinogenic to other tissues. Experiments in