Dear EarthTalk: Is there any proof linking
human breast cancer to exposure to chemicals in the environment?
do researchers think most cases of breast cancers are genetically
— Bettine Carroll, New York, NY
A groundbreaking research study coordinated by the nonprofit
Silent Spring Institute and recently published by the American
Cancer Society found that synthetic chemicals have likely played
a large role in the rising incidence of breast cancer throughout
the world over the last half-century. The study identified
216 man-made chemicals—including those found in everyday
products like pesticides, cosmetics, dyes, drugs and gasoline
(and diesel exhaust)—that have been shown to cause breast
cancer in animals. Researchers believe these substances, many
of which “mimic” naturally occurring hormones once
inside the body, are also to blame for the increasing prevalence
of human breast cancer.
According to epidemiologist Devra Lee Davis of the University
of Pittsburgh’s Graduate School of Public Health and
one of the lead researchers on the new study, the more hormones
cycling through a woman’s body during her lifetime, the
more likely she is to develop breast cancer. Synthetic chemicals
that mimic hormones magnify the risk, as the body doesn’t
know the difference between its own real hormones and other
introduced chemicals. One in 10 women who develop breast cancer
inherits a defective gene from their parents, Davis adds, meaning
that in 90 percent of breast cancer cases studied, external
nongenetic agents (e.g. synthetic chemicals) contributed to
the development of the cancer.
Women can prevent cancer by buying and eating organic foods,
avoiding pesticides and other synthetic chemicals whenever
possible, and supporting government regulation and more research
on synthetic chemicals and their effects.