washington a new study has shown that several common chemicals including pesticides ingredients in consumer products food additives and drinking water contaminants could increase the risk of breast cancer by causing cells in breast tissue to produce more of the hormones estrogen or progesteronethe findings of the study appeared in the journal environmental health perspectivesevery day people are exposed to a variety of synthetic chemicals through the products they use or the food they eat for many of these chemicals the health effects are unknown however this study has found the adverse effects of these chemicals and how it may increase the risk of breast cancerthe connection between estrogen and progesterone and breast cancer is well established said coauthor ruthann rudel a toxicologist and research director at silent spring instituteso we should be extremely cautious about chemicals in products that increase levels of these hormones in the body added rudelfor instance in 2002 when the womens health initiative study found combination hormone replacement therapy to be associated with an increased risk of breast cancer women stopped taking the drugs and incidence rates went downnot surprisingly one of the most common therapies for treating breast cancer is a class of drugs called aromatase inhibitors that lower levels of estrogen in the body depriving breast cancer cells of the hormones they need to grow said rudelto identify these chemical risk factors rudel and silent spring scientist bethsaida cardona combed through data on more than 2000 chemicals generated by the us environmental protection agency epas toxcast programthe goal of toxcast is to improve the ability of scientists to predict whether a chemical will be harmful or not the program uses automated chemical screening technologies to expose living cells to chemicals and then examine the different biological changes they causereporting in the journal environmental health perspectives rudel and cardona identified 296 chemicals that were found to increase estradiol a form of estrogen or progesterone in cells in the laboratory71 chemicals were found to increase levels of both hormones the chemicals included ingredients in personal care products such as hair dye chemical flame retardants in building materials and furnishings and a number of pesticidesthe researchers dont yet know how these chemicals are causing cells to produce more hormones it could be the chemicals are acting as aromatase activators for instance which would lead to higher levels of estrogen said cardona what we do know is that women are exposed to multiple chemicals from multiple sources on a daily basis and that these exposures add upthe silent spring researchers hope this study will be a wakeup call for regulators and manufacturers in how they test chemicals for safetyfor instance current safety tests in animals fail to look at changes in hormone levels in the animals mammary glands in response to chemical exposure and although high throughput testing in cells has been used to identify chemicals that activate the estrogen receptor mimicking estrogen the testing has not been used to identify chemicals that increase estrogen or progesterone