Chemicals in Food
Modern food-production methods have opened major avenues of exposure to environmental carcinogens and endocrine-disrupting compounds. Pesticides sprayed on crops, antibiotics used on poultry, and hormones given to cattle expose consumers involuntarily to contaminants that become part of our bodies. Some of these exposures may increase breast cancer risk.
In some ways, our ancestors had it easy. Because they didn't have chemically treated food and chemically enhanced kitchenware, their diets and cooking practices exposed them to fewer toxic hazards.
Following are some of the harmful chemicals commonly found in our food and food containers, along with descriptions of what they are, where they're found and why they're bad. And check out our Tips for Prevention section to learn how to avoid them.
Today, it's not just the food itself that you have to watch, but the containers they're stored in, which can leach toxic chemicals such as BPA, styrene and vinyl chloride. Not only do they sound unappetizing, they're actually bad for you.
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Bisphenol A (BPA) can be found in reusable plastic food containers and the lining of food and beverage cans. Research shows that BPA exposure is linked to breast cancer, and has been shown to interfere with chemotherapy treatment for the disease.
Phthalates can be found in some plastic food containers and are considered endocrine disruptors. 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.
Styrene can leach from polystyrene – a component of Styrofoam food trays, egg cartons, disposable cups and carryout containers – when heated, worn or put under pressure. Styrene is an animal mammary carcinogen and is possibly carcinogenic to humans.
Polyvinyl chloride (PVC) is used to produce food packaging. When PVC is made, vinyl chloride may be released into the air or wastewater. It was one of the first chemicals designated as known human carcinogen and has been linked to increased mortality from breast cancer and liver cancer among workers involved in its manufacture. After disposal, PVC can break down, and if it is incinerated or catches fire, it can form dioxins.
Some pesticides and herbicides used on the food we eat have been identified as human or animal carcinogens and many are also found in water supplies and indoor air and dust. Pesticide exposure is of particular concern for agricultural workers. Studies have shown that some herbicides and pesticides stimulate growth of breast cancer cells or cause mammary cancer in rats.
More than 75 million pounds of atrazine are applied annually to corn, sorghum and other crops to control broadleaf weeds, which leads to high levels of the herbicide in groundwater and drinking water every spring and summer in areas that grow these crops. Atrazine disrupts the body's own hormone systems in a number of ways and has been linked to a number of reproductive changes in wildlife. Experimental studies suggest it may disrupt mammary gland development.
These three pesticides were associated with increased risk of breast cancer in a study of Latina women recently diagnosed with the disease. The risks were highest in young women and those diagnosed with breast cancer early in life.
Young children of farmers where this pesticide is used have higher levels of 2,4,5-TP in their urine shortly after the pesticide is applied. In addition, a large study of farm women in Iowa and North Carolina found elevated rates of breast cancer in women exposed to 2,4,5-TP.
While DDT has largely been banned for agricultural use worldwide, it is still used in some countries for malaria control and shows up in humans and animals even where it has not been used for decades. Evidence continues to mount regarding DDT's health effects, including evidence that earlier exposures to the chemical may affect risk of breast cancer risk decades later. This serves as a cautionary tale regarding our use of other pesticides without full safety data.
Dieldrin and Aldrin are two additional banned pesticides that persist in the environment. Dieldrin has linked to breast cancer in women exposed to the pesticide and both pesticides have hormone disrupting effects.
Heptachlor was used in high quantities on pineapple crops in Hawaii, which led to contamination of crops and the local dairy supply. Research is needed to see if this exposure is associated with the dramatic increase in breast cancer incidence in Hawaii.
Natural and Synthetic Hormones
Some plants and fungi produce compounds that mimic estrogen or alter naturally occuring hormones in other ways. In addition, some synthetic hormones are given to farm animals to increase milk production or increase growth.
Zearalenone is a naturally occurring chemical compound produced by a fungus that grows on grains such as corn. Studies have found higher levels of zearalenone in people who frequently consume popcorn. The synthetic version of zearalenone is zeranol, which is given to cattle to promote growth. Both compounds mimic estrogen, and in vitro studies show that they can stimulate the growth of breast cells.
The U.S. and Canadian beef, veal and lamb industries have used synthetic growth hormones since the 1950s to hasten the fattening of animals. Zeranol is one of the most widely used chemicals in the U.S. beef industry. It is of special concern since it mimics the hormone estradiol. Scientists recently exposed cancer cells to zeranol-treated beef and the results showed significant increases in cancer growth. Economic and health concerns have led the European Union to ban use of these hormones in their own meat-production systems and to ban imports of hormone-treated beef, including meat from the United States, since 1989 (Hanrahan, 2000).
Since its introduction in 1993, bovine growth hormone (rBGH/rBST) has proven controversial because of its potential carcinogenic effects. Several studies have shown an association between dairy consumption and breast cancer in pre-menopausal women. rBGH has also been shown to raise insulin-like growth factor levels in the body, associated with an increased risk of breast cancer.
Phytoestrogens are estrogen compounds fround in many plants and plant products, including soy food products. Although scientific evidence suggests that plant-based estrogens offer nutritional benefits, the data is more conflicting when it comes to breast cancer risk. Some studies suggest phytoestrogen consumption during adolescence may help reduce later risk of breast cancer, but other studies suggest it may cause oxidative DNA damage and interfere with breast cancer drugs.