CATEGORY*: IARC known carcinogen, NTP known carcinogen
FOUND IN: Cosmetics, also used to sterilize surgical instruments
THE GIST: The National Toxicology Program classifies ethylene oxide, which is used to sterilize surgical instruments, as a known human carcinogen. It is also commonly used to manufacture popular brands of shampoo. Women who work in commercial sterilization facilities have an increased risk of getting breast cancer, and animal studies also indicate a link between the chemical and breast cancer.
State of the Evidence on Ethylene Oxide
A fumigant currently in use to sterilize surgical instruments, ethylene oxide was used in some cosmetics products in the past (ASTDR, 1999; IARC, 2008). Ethylene oxide is classified as a known human carcinogen (NTP, 2005b, IARC 2008) and one of 221 chemicals identified by researchers at the Silent Spring Institute as being associated with mammary tumors in animals (Rudel, 2007).
Scientists from the National Institute for Occupational Safety and Health (NIOSH) studied breast cancer incidence in 7,576 women exposed to ethylene oxide while working in commercial sterilization facilities. They found an increased incidence of breast cancer among these women in direct proportion to their cumulative exposure to ethylene oxide (Steenland, 2003). Although there are contradictory data in the recent literature, several other reports support the finding that exposure to ethylene oxide is associated with increased risk for breast cancer in women (Adam, 2005, Mikoczy, 2011).
Studies in which human breast cells grown in vitro were exposed to low doses of ethylene oxide demonstrated that the chemical exposure resulted in a statistically significant increase in damage to the cells’ DNA (Adam, 2005). These findings are supported by the results of a study examining gene mutations in mammary tumors induced in mice by exposures to ethylene oxide. Common mutations included those in the tumor-suppressor gene p53 and the cell-proliferation regulatory gene H-ras (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.