It is well known that cigarette smoking and genetic predisposition are potent risk factors in the development of cancer of the bladder. Cigarette smokers can increase their risk of contracting this cancer by as much as four times. Lesser known, but still important, is the risk posed by exposure to certain chemicals found in industry.
Of particular note are three chemicals known as benzidine, β-Naphthylamine and ortho-toluidine, all of which are known human bladder carcinogens. These chemicals were widely used in the manufacture of dyes and pigments for textiles, paints, plastics, paper and hair dyes. These chemicals were used in dyes and pigments in drugs and pesticides, and also as antioxidants in the rubber industry. Exposure to these chemicals also occurs in the printing industry, particularly in businesses that worked with azo dyes, such as Disperse Orange. These dyes, and others with known carcinogenic potential, have largely been replaced but were still widely used during the mid and late 20th century. This is important to note due to recent findings related to latency. Previously, it had been thought that the latency period for bladder cancer in occupationally exposed workers would expire after thirty years. However, recent research shows that even after a thirty year period, clinical cases related to occupational exposure were still arising.
The rubber industry is another area of concern for worker exposure. A particularly potent example in Western New York is the Goodyear Plant in Niagara Falls. For years, employees at the Goodyear Plant were exposed to unsafe levels of ortho-toluidine. This caused many of them (as much as three times the expected amount for the area) to develop bladder cancer. Much of this could have been prevented had the workers been provided with adequate and timely warning.
This kind of situation was not uncommon in the twentieth century. Increasing knowledge of human carcinogens and occupational exposure prompted government agencies, such as OSHA, to impose new and stricter regulations on chemicals. The suppliers, manufacturers and distributors of these chemicals were ordered to place warnings on the products to ensure that workers knew of their toxic nature. However, many companies refused to comply with these new regulations for fear that they would suffer economically if users knew of the dangers.
Because use and production of known bladder carcinogens (ortho-toluidine, benzidine and β-Naphthylamine) has been significantly withdrawn in the United States, current potential for industrial exposure and occupationally related bladder cancer should be low. However, both ortho-toluidine and β-Naphthylamine are byproducts of several industrial processes where nitrogen-containing organic matter is heated and burned. Included in these processes are carbon and graphite electrode manufacture, foundry coke production and roofing and paving. Coal tar pitch, a black or brown residue left by the distillation or heat treatment of coal tar, can release coal tar pitch volatiles (CTPVs), which become airborne when coal tar pitch is heated.