Get rid of your vinyl shower curtains to avoid DEHP, a chemical on the new list of possible cancer-causers.

RODALE NEWS, EMMAUS, PA—When the President's Cancer Panel released its recent report, stating that environmental chemicals were a "grossly underestimated" cause of cancers in the U.S., the American Cancer Society (ACS) responded by saying the report put too much weight on environmental causes and not enough emphasis on known cancer risks, such as tobacco smoke and obesity. However, the ACS still believes that chemicals in our environment can have a profound impact on our health, says Elizabeth Ward, PhD, vice president of surveillance and health policy research at ACS. "We've always recognized that there are potential carcinogens in the human environment," she says, but "cases of cancer caused by chemicals have always been harder to measure."

Hoping to bring a little clarity to the field of chemicals that may trigger cancers, the ACS, three government agencies, and the International Agency for Research on Cancer published a list of 20 chemicals so far not officially linked to cancer but still in widespread use that have the strongest evidence against them that they may cause cancer.

THE DETAILS: After reviewing the existing research, the authors picked 20 chemicals that showed enough evidence of causing cancer in laboratory tests and in animals that there was a strong likelihood that they could also cause cancer in humans, says Ward. "What we were looking for were the chemicals for which there was a lack of definitive data that they caused cancer in humans as well as evidence of widespread human exposure," she says. And many of these chemicals, such as nanoparticles, are so new that there's very little evidence of safety or harm, yet hundreds of new products containing nanoparticles are being introduced every month.

Most of the chemicals on their list are industrial chemicals, for instance, carbon black (a substance used to make synthetic rubber) and welding fumes, but others are much more common and can crop up in everything from our sunscreen to our water supply:

• Atrazine: a widely used pesticide on corn that's so hazardous it's banned in Switzerland, the home country of the company that manufactures it.

• Chloroform: a water-disinfection by-product that can wind up in your tap water

• Diesel engine exhaust

• Diethylheyxl phthalate (DEHP): a chemical used to keep vinyl plastics, like your shower curtain, soft and pliable

• Formaldehyde: already a known human carcinogen that causes pharynx and nasal cancers, this chemical (used in hundreds of building products) was added to the list because of suspicions that it might cause leukemia

• Lead and lead compounds

• Polychlorinated biphenyls (PCBs): banned since the 1980s, these industrial flame retardants still linger in our food supply

• Styrene: used to make polystyrene foam coffee cups and takeout containers

• Perchloroethylene: the commonly used dry-cleaning solvent

• Titanium dioxide: used as a colorant in paints but also as an ingredient in sunscreens; the researchers were particularly concerned about nanoparticles of titanium dioxide, which are already suspected of causing brain damage

And, not a chemical, but definitely on the cancer-research radar screen:

• Shift work: a growing number of studies are suggesting that workers who don't stick to regular schedules are at an increased risk of cancer.

WHAT IT MEANS: Ward's study was meant to help researchers identify priorities for occupational cancer research, she says, because "our understanding of what causes cancer in the general population has come about in large part because of studies on occupational exposures." But, she adds, it can take anywhere from 10 to 30 years from the time a chemical is introduced to the time scientists have adequate evidence that it causes cancer in humans, which is why it's important to take the precautionary principle and protect yourself now.