By Rita Rubin
WebMD Health News
Reviewed by Michael W. Smith, MD
June 24, 2015 -- Researchers have been testing individual chemicals for years to see if they can cause cancer.
Now, a groundbreaking new report suggests scientists should also be looking at how low doses of chemicals considered safe on their own might cause cancer when mixed together.
"We're swimming in this chemical soup ... and we really don't know what it's doing to us," says William Goodson III, MD, lead author of the report. "We're pushing for the idea that the chemical testing has to basically go back to step one. Instead of looking at individual chemicals, look at chemicals in mixtures. We live in a mixture every day."
Other experts agree with the report. It was written by a team of international scientists from 28 countries.
"We must take on the significant challenge of evaluating mixtures and not just evaluate one chemical at a time," says Linda Birnbaum, PhD, director of the National Institute for Environmental Health Sciences and the National Toxicology Program. She was not involved in writing the report, but her institute helped fund the work.
WebMD asked Goodson, a senior scientist at the California Pacific Medical Center in San Francisco, and Birnbaum about the need for such research and whether consumers should be concerned about encountering everyday chemicals.
Q. What percentage of cancers might be related to chemicals in the environment?
A. The report says that "credible estimates" by the World Health Organization's International Agency for Research on Cancer puts the percentage at 7% to 19%.
"We discussed this among ourselves," Goodson says. "Some people argued it is as low as 5% or 10%." But, he says, he suspects it could be higher than 19%.
Q. Are there certain cancers that are more likely to be linked to chemicals?
A. "The issue is that we don't know," Goodson says.
Q. Are there certain periods in life when exposure might be most harmful -- say, in the womb?
A. "The newest research clearly shows that biology is affected by low doses of chemicals ... and that these biological changes can be harmful, especially during periods of development," Birnbaum says.
She says researchers need to study how coming in contact with small amounts of chemicals affects people in all stages of life.
Q. What types of chemicals are we talking about, and what are some of the main ways we're exposed to them? Are they only manmade chemicals, or do some occur naturally?
A. "There are things that occur naturally, in water, for example," Goodson says, noting arsenic is found in groundwater. Then, he says, there are manmade parabens and phthalates, used in personal care products such as shampoo, food products, and food packaging.
Q. Since we come in contact with infinite combinations of chemicals, how can you figure out which combinations might cause cancer?
A. "It's going to be a huge project," Goodson says. "We don't underestimate how complicated this will be."
But there is research that shows the importance of pursuing this question, he says. For instance, British scientist Philippa Darbre, PhD, showed that exposing cancer cells to a mixture of parabens, but not individual parabens, spurred growth, Goodson says.
Q. Should we try to minimize our exposure to any particular chemicals?
A. "We sort of tried to stay away from specific chemicals, because then you start telling people to go throw this away or throw that away," Goodson says. "It's almost impossible to live a life that's going to get you away from these things."
But he says he has made a few changes.
"Probably the biggest thing I've done is stop drinking bottled water" because of the chemicals in the plastic bottles, Goodson says. "Whatever I decide to do is just my best guess." Still, he says, "if I go to a place where the only water available is bottled water, yes, I will drink it. I don't have a choice." Goodson says he'd prefer to buy milk in glass bottles, but it's hard to find.
Everyone, particularly pregnant women, children, and the elderly, should try to avoid coming in contact with chemicals known to be harmful, Birnbaum says. Also, she says, "people need to be aware of their environment, including the air they breathe, the water and food they consume, and the products they use in their home. All of these things even at low doses can impact a person's health."
The Environmental Working Group, an advocacy group focused on the environment and public health, recommends you drink filtered tap water rather than bottled water. Also, the group's Skin Deep cosmetics database looks at the safety of thousands of ingredients in personal care products. The FDA offers guidance on phthalates used in cosmetics, too.
A spokeswoman for the American Chemistry Council says the organization hasn't yet reviewed the report and has no immediate comment.
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SOURCES: William Goodson III, MD, senior scientist at the California Pacific Medical Center in San Francisco. Linda Birnbaum, PhD, director of the National Institute for Environmental Health Sciences and the National Toxicology Program. FDA: "Parabens." NIH "Tox Town," "Phthalates." Darbre, PD. Journal of Applied Toxicology, Jan.-Feb. 2004.
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