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Clear Science

• Chemicals Linked to Breast Cancer
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  • BPA in Food Packaging
  • State of the Evidence 2010
  • Pollution in People
  • Breast Cancer Endpoints
  • The Falling Age of Puberty
• Chemicals Glossary

Chemicals in Health Care

Advances in health care have been extraordinarily helpful in prolonging our lives and providing better quality of life. But some medical advances have a downside: they can sometimes inadvertently expose us to risk factors that could lead to cancer or other illnesses.

Following are some of the health-care related risk factors. Check out our Tips for Prevention section to learn how you might reduce your risk.

Ionizing Radiation

Ionizing radiation (X-rays and gamma radiation) has long been known to cause breast cancer, both by directly damaging DNA and by disrupting normal cellular and intra-cellular processes. There is no safe dose of radiation and the genetic damage caused by radiation accumulates over a lifetime.

Hormone Replacement Therapy (HRT)

The International Agency for Research on Cancer (IARC) has listed estrogens as known human carcinogens since 1987, and the National Toxicology Program (NTP) added HRT and estrogens used in oral contraceptives to the list of known human carcinogens in 2002.

Oral Contraceptives

Oral contraceptives have been shown to increase breast cancer risk, especially among current and recent users who have used them for more than five years, premenopausal women, and those with a family history of breast cancer. However, postmenopausal women who have discontinued use for at least a decade show no significant increase in rates.

Diethylstilbestrol

Diethylstilbestrol (DES) offers the clearest evidence that a synthetic estrogen can increase risk of cancer. It was prescribed until 1971 to prevent miscarriages but was banned when daughters of women who took the drug were found to have higher rates of an extremely rare cancer.

Phthalates

Phthalates are a group of endocrine-disrupting chemicals found in PVC or #3 plastic, including plastic medical tubing. Phthalate exposure has been linked to early puberty in girls, a risk factor for later-life breast cancer. Some phthalates also act as weak estrogens in cell culture systems.

Ethylene Oxide

Ethylene oxide is used in the sterilization of medical equipment and is commonly used to manufacture popular brands of shampoo. It is classified as a known human carcinogen and is one of the 48 chemicals that the National Toxicology Program (NTP) identifies as mammary carcinogens in animals.

BPA

Bisphenol A (BPA) is one of the most pervasive chemicals in modern life. It’s a building block of polycarbonate plastic and epoxy resins, and is used in medical devices and as a dental sealant. Research shows that BPA exposure is linked to breast cancer.

Mercury

Mercury is found in some dental fillings. Higher accumulations of mercury and other metals have been found in cancerous breast biopsies as compared to biopsies taken from women without breast cancer. Lab studies have shown that methyl mercury can disrupt hormone-regulated cellular processes.

• Metals and breast cancer risk