Science & Policy
Glossary of Breast Cancer Exposures
When it comes to preventing breast cancer, did you know only 10% of breast cancers are attributed to genetics? Preventable causes of the disease include exposures to toxic chemicals and other environmental factors. We’ve summed up the science connecting the exposures with the strongest evidence linked to breast cancer for you here.
1,3-Butadiene | Alcohol | Alkylphenols | Aromatic Amines | Atrazine | Benzene | Bioidentical Hormones | Bisphenol A (BPA) | Bovine Growth Hormone (rBGH & rBST) | Cadmium & Other Metals | Chlorpyrifos | DDT & DDE | Dieldrin & Aldrin | Diethylstilbestrol (DES) | Dioxins | Ethylene Oxide | Fragrance | Glyphosate-based Herbicides | Heptachlor | Hormone Replacement Therapy (HRT) | Hormones in Personal Care Products | Ionizing Radiation | Night Shift Workers: Light-at-Night | Non-Ionizing Radiation (EMFs) | Oral Contraceptives | Organic Solvents | Pesticides & Herbicides | Parabens | Per- and Poly-Fluoroalkyl Substances (PFASs- PFOA and PFOS) | Phthalates | Phytoestrogens | Polybrominated Diphenyl Ethers (PBDEs) | Polychlorinated Diphenyls (PCBs) | Polycyclic Aromatic Hydrocarbons (PAHs) | Tobacco Smoke | Triclosan | Sunscreens (UV Filters) | Vinyl Chloride | Zeranol & Mycroestrogens
For more, see our full analysis of 23 factors that can influence breast cancer, which goes beyond exposures to include lifestyle factors like diet, exercise, and more.
What is an exposure?
We often come into contact with—or are exposed to—substances and other factors linked to breast cancer. These include chemicals as well as physical agents such as ionizing radiation and light-at-night. This glossary highlights certain exposures with the strongest evidence linked to breast cancer. For each, we describe what it is, where it’s found, the science linking it to breast cancer, who is most vulnerable and how to avoid the exposure.
1,3-butadiene has been listed as a human carcinogen by the National Toxicology Program and by the Environmental Protection Agency.
The more one drinks, the higher the risk, and even light drinking increases risk. Research on interactions between alcohol consumption and other lifestyle and demographic factors reveals more complicated results.
They are found throughout our indoor and outdoor environments and disrupt the body’s hormone system.
Many are carcinogens and endocrine disruptors that may increase the risk of breast cancer.
Atrazine is an endocrine disruptor, and exposure to atrazine has been associated with an increased risk of developing breast cancer.
Their effect on breast cancer development is unclear, due to conflicting evidence.
BPA can disrupt the hormone system, particularly when exposures occur during prenatal development and infancy.
Though research is mixed on the extent to which dairy consumption is linked to increased cancer risk, higher blood levels of IGF-1 have been linked to increased risk for pre-menopausal breast cancer.
Cadmium has been shown to demonstrate estrogen-like activity, which is known to increase breast cancer risk. Other metals such as nickel, chromium, zinc, lead and mercury have been shown to have similar estrogen-like effects.
Cadmium has been recognized as a human carcinogen by both the International Agency for Research on Cancer (IARC) and the National Toxicology Program.
Chlorpyrifos is a pesticide and insecticide widely found on produce and home pest control formulas that is an endocrine disruptor and breast carcinogen. Exposure to chronic low doses of chlorpyrifos leads to an increased risk of mammary tumors in lab studies.
Banned in the EU, California, New York, and Hawaii, several other U.S. states are considering a ban on chlorpyrifos.
To avoid consuming this pesticide, choose organic produce when possible and wash produce thoroughly. Also, wear synthetic protective clothing if you are exposed to this chemical in an agricultural or home setting.
As a result of consumption of and exposure to these sources, it can be found in blood samples of a majority of people.
They have been linked to both an increased risk of breast cancer and higher rates of mortality from breast cancer.
In the late 1960s, doctors realized that there was a strong association between in utero exposure to DES and the incidence of rare vaginal and cervical cancer in young women and girls. It was later discovered that exposure to DES was also associated with an increased risk of developing breast cancer. DES was banned in the United States in 1971.
Dioxins have been linked to an increased risk of breast cancer.
During the 1980s, it is estimated that more than 270,000 U.S. workers were exposed to the chemical every year. The use of EtO has since decreased in the United States, though it is still used.
Glyphosate is a synthetic hormone-disrupting compound chemical widely used in herbicides, most notoriously in Monsanto’s Roundup. In fact, glyphosate-based herbicides (GBHs) are the most widely used herbicides globally.
Glyphosate exposures during critical periods of breast development (e.g., gestation, early childhood, adolescence, pregnancy) may lead to later risk for developing breast cancer.
HRT is a known carcinogen recognized by the International Agency for Research on Cancer (IARC) that has been associated with an increased risk of breast cancer, heart disease, stroke and blood clots. The components of BiCs, estradiol and progesterone, have also been determined by IARC to be either known or reasonably anticipated carcinogens and associated with numerous negative health outcomes.
Hormones in personal care products are listed as a known carcinogen by the International Agency for Research on Cancer (IARC) and the National Toxicology Program (NTP).
The International Agency for Research on Cancer (IARC) and the National Toxicology Program (NTP) classify it as a known human carcinogen.
Exposure to light-at-night has been linked to an increased risk of developing breast cancer. Recent data suggest that exposure to smartphone and computer screens into the evening, before heading to sleep, may also be an important source of LAN.
As of yet, there is no clear evidence linking breast cancer with non-ionizing radiation.
They have been classified as human carcinogens by the International Agency for Research on Cancer.
Exposure to these solvents may increase the risk of developing breast cancer.
Pesticides and herbicides are used to control insects and unwanted plants in agricultural fields. The chemicals in pesticides and herbicides can be inhaled or absorbed through the skin by those who work or live in close vicinity to the fields. When chemical residues remain on or in produce, meat, or fish, we may also consume these harmful chemicals.
Exposure to the pesticides and herbicides below, especially during critical periods of breast development such as prenatally and in early childhood, is associated with an increased risk for developing breast cancer.
Parabens are a group of chemicals that prevent the growth of mold, bacteria and yeasts. They are often added to cosmetics and personal care products to increase shelf-life and stability.
Parabens enter the body through dermal absorption, ingestion and inhalation, and can enhance the actions of the natural estrogen known as estradiol.
PFOA is a suspected endocrine (hormone) disruptor and possible carcinogen, and PFOS has been linked to fertility problems. Several PFASs, especially PFOA, have been linked to increased risk for breast cancer.
Phthalates are endocrine disruptors, and exposure to phthalates has been linked to breast cancer, developmental issues, decreased fertility, obesity and asthma.
Phytoestrogens, especially when consumed regularly during childhood, have been linked to a decreased risk of breast cancer.
They are endocrine disrupting compounds associated primarily with thyroid disruption. Some evidence also links them to breast cancer.
The EPA banned PCBs from new products in 1976. Due to their persistence in the environment, they are still found in soil, riverbeds and dust particulates in homes. They also remain in products manufactured prior to the ban such as paper, plastics and paints.
They contribute to indoor and outdoor air pollution and are harmful to humans.
The use of cigarettes has been linked to stroke, coronary heart disease, and many cancers, including lung cancer and breast cancer.
The chemical is a potential endocrine disruptor in humans. It can also have negative impacts on environmental health, including aquatic systems.
Vinyl chloride is synthetic and does not occur naturally.
Certain mycoestrogens, including especially zearalenone, may advance the growth of breast cancer cells. Zearalenone and zeranol mimic the natural estrogen estradiol. Both compounds can stimulate growth and proliferation of human breast tumor cells in vitro at potencies similar to the effects of estradiol.
Exposures we are monitoring
These are exposures that we frequently get questions about. Although we don’t consider them to be exposures of concern at this time, we continue to monitor the relevant emerging scientific evidence.
Additional research should continue to examine the safety of infertility treatments, particularly for women who are BRCA positive.