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Vinyl Chloride


Janet Gray, Ph.D.
Janet Gray, Ph.D.

As author of our 2008 and 2010 State of the Evidence reports, Dr. Gray drives the science behind all our work.

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CATEGORY*: IARC possible carcinogen, endocrine disruptor

FOUND IN: Fully banned in the U.S. in 1993, persists in the environment even where it's not used.

THE GIST: This is an insecticide that was widely used in the United States prior to 1993 throughout the 1980s, and mainly used to control termites. It was restricted in 1988 and use was allowed until 1993 when it was banned. banned in the 1980s, but It continues to show up in food, water and soil. Heptachlor increases risks for breast cancer by accumulating in breast tissues, affecting the way the liver processes hormones, disrupting cell-to-cell communication in cells and damaging DNA.

State of the Evidence on Heptachlor

Heptachlor is an insecticide that was widely used in the United States throughout the 1980s, especially for termite control. In 1988, the U.S. Environmental Protection Agency restricted use of heptachlor to certain applications for controlling fire ants, but agricultural use continued until 1993 because growers were allowed to use up existing stocks (Siegel, 1995).


Since heptachlor is banned, there is little we can do besides ensure that similar chemicals are not allowed on the market in the future.

Join the Breast Cancer Fund in advocating for responsible chemical regulations >

Heptachlor use was particularly high in Hawaii, where it was employed extensively on pineapple crops and consequently contaminated both local agricultural crops and dairy supplies. At the same time, breast cancer rates in Hawaii have increased dramatically for women of all ethnic groups over the past four decades (Maskarinec, 2006). Research is needed to assess the potential relationship between heptachlor use and breast cancer rates in Hawaii.

Heptachlor still contaminates both soil and humans. Its breakdown product, heptachlor epoxide (HE), is known to accumulate in fat, including breast tissue. Levels are highest in women ages 20 and older, but HE is also found in the bodies of adolescents 12 to 19 years old (CDC, 2005). NHANES data examining levels in blood serum found HE in 60 percent of people in the United States age 12 and older (Patterson, 2009). Although HE does not act like estrogen, it affects the way the liver processes hormones, thereby allowing levels of circulating estrogens to rise and increasing breast cancer risk. HE also has been shown to disrupt cell-to-cell communication in human breast cells in tissue culture (Dich, 1997) and to increase production of nitric oxide, a chemical that is found naturally in cells and known to cause damage to DNA (Cassidy, 2005).

*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.