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Trying to understand our chemical exposure

CDC studies attempt to measure the presences of man-made chemicals in our bodies and begin to determine their effects.

October 11, 2010|By Jill U Adams, Special to the Los Angeles Times
  • CONTROVERSIAL INGREDIENT: These water bottles are made with bisphenol A, also used in food can linings. Its safety for humans has been questioned.
CONTROVERSIAL INGREDIENT: These water bottles are made with bisphenol… (David McNew / Getty Images )

Our modern-day environment is loaded with man-made chemicals. We breath car exhaust, gasoline fumes and secondhand smoke, and we eat food laced with pesticides and plasticizers and cooked in pans with nonstick coatings.

Biomonitoring: An article in the Oct. 11 Health section on traces of man-made chemicals in human bodies incorrectly named an environmental advocacy group. It is the Natural Resources Defense Council, not the National Resources Defense Council.

We use cosmetics on our skin, cleaning products in our houses and lawn products in our yards. We decorate our homes and clothe our kids with flame-retardant fabrics. And we drink municipal water that contains traces of pharmaceuticals and other chemicals.

What's the health fallout of this? In some cases, such as those for lead and mercury, the effects of environmental chemicals are clear. Not so much for others, such as bisphenol A and flame retardants. It's difficult to link disease to chemical exposure, partly because of the uncertainty of just who is exposed, to how much and for how long.

To get at part of the puzzle, since 1999 the national Centers for Disease Control and Prevention has been doing biomonitoring studies — sampling blood and urine from a broad swath of Americans to see what chemicals are regularly found in people.

"For the public, I think the basic point is just the understanding that chemicals … in our environment do in fact actually get into your body," says Dr. John Osterloh, the chief medical officer of the CDC's division of laboratory sciences. And with that information, he adds, scientists have a starting point for understanding the medical consequences.

The list of man-made chemicals now found in human tissue samples is long, encompassing 212 environmental chemicals. The latest report, published in 2009, added 75 chemicals to the list, including bisphenol A, found in many plastics; triclosan, found in antibacterial soap; a dozen perfluorinated chemicals, such as PFOA used in the manufacture of nonstick cookware; and 29 volatile chemicals, such as the gasoline additive MTBE.

The exposure report shows how pervasive many of these chemicals are in the environment, that they are found in a representative sample of Americans living in different communities across the country. Each of the surveys — there have been four so far — included about 2,500 people.

The CDC cautions that the mere presence of chemicals doesn't necessarily mean that they pose a risk. But scientists who study environmental health risks say that each widespread chemical is like a human experiment. "If you want to expose millions of people to something, just intermingle it with the food supply," says Thomas Burke of the Johns Hopkins Bloomberg School of Public Health, speaking about the bisphenol A in food can linings. (Burke chairs an advisory panel on risk assessment for the Environmental Protection Agency.)

Scientists and advocates alike hail the biomonitoring effort as a good thing because the data can be used in so many ways. Researchers can mine the data for associations between exposure and disease, regulators can monitor for new contaminants and policymakers can track changes in contaminant levels following regulations.

But some advocacy organizations wish the CDC had taken additional steps to be more user-friendly. "It's very stripped of interpretation, of how these chemicals may affect human health," says Sonya Lunder, senior analyst for the Environmental Working Group, a Washington, D.C.-based environmental advocacy organization.

For example, she says, chemicals such as PCBs are reported individually — and there are dozens — so you'd have to add them up to calculate the entire body burden for these pesticides. Ditto for the 11 brominated fire retardants.

Biomonitoring is not new, say Dr. Sarah Janssen, a public health doctor at the National Resources Defense Council. Screening lead levels in children, for example, has been done for decades because the substance is known to cause developmental and behavioral problems. Lead paint and leaded gasoline were banned in the late 1970s. "As the levels went down in those products, the levels in kids' bodies also went down," Janssen says.

The levels are still declining, according to the CDC biomonitoring reports. In children 1 to 5 years old, 1.4% have blood lead levels of concern — at least 10 micrograms per deciliter. This finding from the 1999-2004 reporting period is lower than the 4.4% seen in the period of 1988-1994.

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