CATEGORY*: IARC known carcinogen, NTP known carcinogen
FOUND IN: Tobacco smoke, gasoline fumes, diesel exhaust, industrial burning
THE GIST: Both the National Toxicology Program and the International Agency for Research on Cancer have designated benzene, which is one of the most widely used petrochemical solvents, as a known human carcinogen. Humans are exposed to benzene by inhaling gasoline fumes, automobile exhaust, cigarette smoke and industrial burning. It is sometimes used in fracking fluids. Occupational studies of men who have been diagnosed with breast cancer offer some of the best evidence of benzene’s link to breast cancer.
State of the Evidence on Benzene
Benzene is one of the largest-volume petrochemical solvents currently in production, and global production rates are expected to continue to grow over the next several years. Chemical industries estimated that over 42 million metric tons (over 105 billion pounds) of benzene would be produced globally in the year 2010 (Davis, 2006). Exposures to benzene come from inhaling gasoline fumes, automobile exhaust, cigarette smoke (primary and secondary) and industrial burning. Benzene presents a serious occupational hazard for people exposed through their work in chemical, rubber, shoe-manufacturing, oil and gasoline-refining industries. Both the National Toxicology Program and the International Agency for Research on Cancer have designated benzene as a known human carcinogen (IARC, 1987b; NTP, 2005c).
TIPS FOR PREVENTION
Stay far away from cigarette smoke, and avoid inhaling gasoline fumes as much as possible.More tips for protecting yourself and the environment >
Epidemiological studies of the effects of benzene on breast cancer risk are difficult to conduct, mainly because exposures to benzene occur in conjunction with exposures to other chemicals that are also released in combustion and manufacturing processes. Also, few of the occupational studies focusing on chemical and automotive industries have included women in numbers substantial enough to allow for meaningful conclusions. In one study that did look at relevant occupations among female Chinese workers, the occupations with elevated risks for breast cancer included scientific research , medical and public health, electrical and electronic engineering, teaching, library science and accounting. In the same study, looking across professions, benzene exposure was associated with an elevated risk of breast cancer (Petralia, 1998). Results from recent studies examining occupational exposures among enlisted women in the U.S. Army (Rennix, 2005) and women in various professions in Israel (Shaham, 2006) support these conclusions. A study of a fairly small sample of women for whom researchers have benzene exposure data from their work at a shoe factory in Florence, Italy, also supports a relationship between exposure to benzene and later development of breast cancer (Costantini, 2009).
The largest studies implicating benzene and associated chemicals in breast cancer risk are occupational studies of men who have been diagnosed with breast cancer. Men who had worked in professions that involved exposures to gasoline fumes and combustion had statistically significant increases in rates of breast cancer (Villeneuve, 2010). The effect was most pronounced among men who started their jobs before age 40 (Hansen, 2000).
Benzene administration to laboratory mice induces mammary tumors (Huff, 1989). Mice exposed to benzene have frequent mutations of genes that are responsible for suppressing the development of tumors (Houle, 2006).
*For chemicals that have been shown to be carcinogens, we provide classifications from two authoritative bodies: the International Agency for Research on Cancer (IARC, an international body) and the National Toxicology Program (NTP, a division of the U.S. Department of Health and Human Services). We have categorized endocrine-disrupting compounds where the body of peer-reviewed research indicates a strong foundation for doing so.