Benzidine and dyes metabolized to benzidine

ROC STATUS: Benzidine, known human carcinogen since 1980; dyes metabolized to benzidine, known human carcinogens since 2000

ALSO KNOWN AS: Direct Blue 6, Direct Black 38, Direct Brown 95

RELATED CANCERS:Bladder cancer, and less frequently cancer of the stomach, liver, kidney, central nervous system, and pancreas

DEFINITION: Benzidine is an organic compound used to make dyes. It is usually found in the form of a powder that is white, reddish gray, or grayish yellow.

Exposure routes: Benzidine can enter into the human body in many ways. If air containing molecules of benzidine is inhaled, the benzidine can enter into a person’s system. Benzidine can also be ingested, either directly or in contaminated drinking water. It is also possible for benzidine to enter the human body through the skin if direct contact is made with benzidine or a benzidine-based dye.

Where found: For many years, benzidine was used in the production of dyes and dyeing compounds. It was also used occasionally in some clinical and laboratory settings, for example, in blood detection. Dyes that metabolize to benzidine were used in many different dyeing applications. Benzidine was used especially often to dye paper products, textiles, and leather goods. Plants manufacturing dyes were likely to contain large quantities of benzidine or dyes that metabolize to benzidine, as were plants that produced goods using such dyes. Beginning in the late 1970s, use of these dyes was phased out.

Because of long usage, there remains the possibility of benzidine contamination in areas around industrial plants and factories that once used benzidine or related dyes. Benzidine that is released into or makes its way into rivers or streams generally settles quickly on the bottom of the riverbed or streambed. Benzidine that was released into the environment through accidental contamination or as a waste product that ends up in the soil bonds strongly to particles found in the soil. It is not likely to seep into the groundwater and contaminate drinking water sources because of these strong bonds. Because its use in dyeing was phased out, benzidine and related dyes are used in only very small quantities in mostly research and laboratory settings in the United States.

At risk: People who worked in industries that manufactured dyes or regularly used dyes in the production of other goods before the late 1970s were at risk of exposure to high levels of benzidine and dyes that metabolize to benzidine. According to the Occupational Safety and Health Administration (OSHA), in 1979 there were sixty-three separate occupations in which workers were at risk for benzidine exposure. Also at risk are people living near factories or plants that manufactured or used benzidine or benzidine-based dyes, especially if by-products of the plant were released into the air or water. Some residual benzidine may continue to exist at such locations. Benzidine and related dyes have also been identified as existing at many hazardous waste disposal sites and people who live near such areas may be at risk of exposure.

Etiology and symptoms of associated cancers: Benzidine and related dyes have been shown to cause cancer in laboratory animals. Studies of humans who have a history of working with benzidine or related dyes have also shown that prolonged benzidine exposure is a significant risk factor for developing bladder cancer. Scientists do not clearly understand all the complex mechanisms involved in how benzidine causes cancer, but benzidine is believed to interfere with normal cellular processes.

Bladder cancer is the cancer most commonly associated with benzidine exposure. The first signs and symptoms of bladder cancer are usually changes in bladder function or habits. This may include a person’s often feeling the urge to urinate without actually being able to do so. Needing to urinate much more frequently than usual is also a possible symptom of bladder cancer, as is blood in the urine. Researchers also believe that benzidine can affect other organs, such as the stomach, kidney, brain, mouth, esophagus, liver, gallbladder, bile duct, and pancreas.

History: Benzidine has a long history as an important industrial dye. It was first made in 1845. Its first use as a dye was in 1884, when a dye named Congo Red was created for the first time. Benzidine and related dyes were extremely useful in dyeing because of the way they adhere to cotton and cotton products. In the 1920s, some physicians and researchers began to suspect a relationship between exposure to benzidine and the development of bladder cancer. It was not until 1976, however, that major commercial production of benzidine and benzidine-based dyes ceased in the United States. There are no major manufacturers of benzidine for the purposes of dyeing or of benzidine-based dyes in the United States; however, because it has some research and laboratory applications, it may be imported. It is considered an occupational carcinogen by the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA). The EPA added benzidine dyes to its list of chemicals of concern in 2010. Personal protection is required for work with benzidine and related products, and it is necessary to take precautions to ensure that no benzidine is released into the environment. Benzidine is also considered a hazardous substance that requires special labeling and precautions when it is transported.

Bibliography

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