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Common chemicals linked to breast cancer

Of the 216 compounds, many are in the air, food or everyday items.

May 14, 2007|Marla Cone | Times Staff Writer

Because epidemiological studies are difficult to conduct and full of uncertainties, human data are "still relatively sparse," the researchers wrote. Only 152 studies worldwide have examined whether women exposed to contaminants are more likely to have breast cancer -- compared with nearly 1,500 that have explored the links between diet and the disease -- and most of the 216 carcinogens were not included.

"Despite this large remaining gap, research in the last five years has strengthened the human evidence that environmental pollutants play a role in breast cancer risk," the researchers wrote. They said the existing studies suggested "substantial public health impact."

Human evidence is particularly strong for PCBs, or polychlorinated biphenyls -- compounds widely used in the 1940s to late 1970s that still contaminate fish and other foods -- and for polycyclic aromatic hydrocarbons, or PAHs, found in diesel and gasoline exhaust.

Solvents in dry cleaning, aircraft maintenance and other jobs also may increase breast cancer risk.

Some of the chemicals named as breast carcinogens already are regulated to protect public health, but some, particularly those in consumer products, are not.

The scientists conducted the review hoping to lay the groundwork for new human studies, as well as to persuade regulators to use existing animal data to strengthen regulations and require more testing of chemicals.

"Animal models are the primary means of understanding and anticipating effects of chemicals in humans," they wrote. "All known human carcinogens ... are also carcinogenic in animals."

Emerging evidence suggests that the roots of breast cancer are in infancy or the womb. More animal and human research should focus on such early exposure, said Patricia Hunt, a Washington State University School of Molecular Biosciences professor.

But Hunt and Soto urged society not to wait for scientific proof to reduce exposure to the chemicals.

"When you look at their list of chemicals, we are exposed to all of it," Soto said. "We know humans are exposed to mixtures, and studying mixtures is very difficult. We will never have the whole picture, and it will take many, many years to collect epidemiological evidence, so we should take some preventive measures now."

Although virtually all women are exposed to the chemicals, some may be more susceptible because of differing metabolism or ability to repair DNA.

Breast cancer is probably triggered by an interaction of multiple environmental and genetic factors.

Experts have long suspected diet plays a role. But the new research found "no association that is consistent, strong and statistically significant" for any particular foods raising or reducing breast cancer risk. There is substantial evidence, however, that regularly consuming alcohol, being obese and being sedentary increase risk.

About 178,000 new cases will be diagnosed this year in the United States.

The reports are at www.silentspring.org/sciencereview.

marla.cone@latimes.com

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(BEGIN TEXT OF INFOBOX)

Chemical carcinogens

Researchers name 216 chemicals that cause breast cancer in animal tests. Here are some of the most widespread:

*--* Chemical Source/use 1,4-dioxane Detergents, shampoos, soaps 1,3-butadiene Common air pollutant; found in vehicle exhaust Acrylamide Fried foods Benzene Common air pollutant; found in vehicle exhaust Perfluorooctanoic acid Used in manufacture of Teflon Styrene Used in manufacture of plastics; found in carpets, adhesives, hobby supplies and other consumer products Vinyl chloride Used almost exclusively by the plastics industry to make vinyl 1,1-dichloroethane Industrial solvent; also found in some consumer products such as paint removers Toluene diisocyanate Used in foam cushions, furnishings, bedding Methylene chloride Used in furniture polish, fabric cleaners, wood sealants and many other consumer products PAHs Diesel and gasoline exhaust PCBs Electrical transformers; banned but still in environment Atrazine Widely used herbicide, particularly for corn

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Source: Silent Spring Institute

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