Exposure to common chemicals during critical periods of breast development may affect breast growth, the ability to breast-feed and breast cancer risk, a new report contends.
Some of these chemicals are found in ordinary household products such as certain types of plastic water bottles, canned foods and laundry detergents, the researchers noted.
With this in mind, the study authors called for chemical test guidelines for industry requiring that scientists test the chemicals' effects on early mammary gland development.
Scientists from the US National Institutes for Environmental Health Sciences, the Environmental Protection Agency and the Silent Spring Institute collaborated on the report, published online in the journal Environmental Health Perspectives.
"If we try to figure out what causes breast cancer, we have to look at the breast when we do the chemical safety tests," said Ruthann Rudel, research director at Silent Spring.
Breast feeding and breast cancer
Currently, protocols for testing don't require looking at mammary tissues, Rudel said, so it is rarely done. "We could be missing a lot," she said.
Experts believe these early disturbances in mammary glands due to chemical exposure may boost the risk of harmful effects later in life. These could include impaired lactation (secretion of breast milk), abnormal breast growth in men and breast cancer.
One impetus for the study, in fact, was an increase in early breast development in girls, which is linked to an increased risk of breast cancer.
The report also noted that although experts recommend that all infants be breast-fed exclusively for six months, millions of women are unable to produce milk or have difficulty breast-feeding each year.
The scientists interviewed 18 experts, reviewed research and discussed the issue at a workshop in late 2009. They are submitting a request to the Paris-based Organisation for Economic Co-Operation and Development (OECD), asking it to add mammary tissue testing to its guidelines.
The international organisation develops guidelines for testing of chemicals for safety, human health effects and environmental effects. "It's a call for government agencies that develop policy to make sure mammary gland assessment is required," Rudel said.
Findings of the review
Industry representatives said they welcomed the review.
"This workshop, which provided a forum for scientific discussion, did not produce data or outcomes relevant to consumers, and thus comments from the meeting should not cause undue concern," said Kathryn St. John, spokeswoman for the American Chemistry Council. "Based on their review of animal studies conducted by the participating scientists, the group considered ways to change chemicals safety testing, and discussed the relevance of potential scientific outcomes to human health."
According to Rudel, the three main findings of the review were:
Rodents are a reasonable test models and should be used to test for dangers to humans.
The breast can be more sensitive to the chemical exposure than other tissues, and in some cases the male mammary tissue was most sensitive.
Chemical exposure to the developing mammary gland can alter susceptibility to cancer-causing agents.
In the report, the experts concluded that early life environmental exposures can alter milk gland development, disrupt the secretion of breast milk, and increase susceptibility to breast cancer. "Assessment of mammary gland development should be incorporated in chemical test guidelines and risk assessment," they added.
Among the chemicals known to affect breast development and cancer susceptibility in animal studies, according to the report, are pesticides such as atrazine, used in agriculture; dioxins, an industrial pollutant found in some fatty foods; bisphenol A (BPA), found in some water bottles and canned foods; polybrominated diphenyl ether (PBDE) flame retardants, and nonylphenol (a breakdown product found in certain laundry detergents).
While efforts are being made to curb some of these chemical exposures, the experts said required testing is crucial. Rudel speculated that women with genetic predispositions to breast cancer might be at higher risk from these exposures.
The study authors declared no financial conflicts of interest.
The review is "raising a necessary red flag," said Olga Naidenko, a senior scientist at the Environmental Working Group, an advocacy organization in Washington, DC. She reviewed the report but was not involved in it.
Naidenko agreed that there has been a gap in studying the effect of chemical exposure on the mammary gland. "For many chemicals, researchers have not looked at it."
Meanwhile, she said, while some exposures are difficult to avoid, there are steps to take to minimize exposure.
Avoiding the plastic BPA in bottles (which some manufacturers have discontinued using) is one step. Buying organic produce whenever possible may also help consumers avoid the pesticide atrazine.
Avoiding canned foods (which can also have BPA in the liners) and the chemical DEHP by focusing on a fresh food diet can also reduce the levels of those chemicals in the body, according to the Silent Spring Institute.
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