Benzene
CATEGORY: IARC known, NTP known
USED IN: Tobacco smoke, gasoline fumes, diesel exhaust, industrial burning
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 estimate that over 42 million metric tons (over 105 billion pounds) of benzene will 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 NTP and IARC have designated benzene as a known human carcinogen (IARC, 1987b; NTP, 2005c).
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 substantial numbers to draw meaningful conclusions. In one study that did look at relevant occupations among female Chinese workers, the occupations in which elevated risks for breast cancer were found included scientific research workers, medical and public health workers, electrical and electronic engineers, as well as teachers, librarians and accountants. 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 study implicating benzene and associated chemicals comes from an occupational study of men who have been diagnosed with breast cancer. Men who had worked in professions that involved exposures to gasoline fumes and combustion had significantly increased rates of breast cancer. The effect was most pronounced among men who started at 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).
