Image
© drcorneilus/flickrUmbilical cord being cut.

New horizons in biomonitoring are identifying environmental exposures that may play a role in health problems, including cancer, neurological disorders and diabetes. At their fingertips, researchers already have precise measurements of nearly 150 chemicals in several thousand American adults and children. Now the Centers for Disease Control and Prevention is preparing to release even more extensive data, and expand its reach by testing 500 umbilical cords, which will allow scientists to determine which chemicals babies are exposed to in the womb. Biomonitoring "is a game changer in environmental health," said Thomas Burke of Johns Hopkins University. Nevertheless, actual use of the information hasn't yet fulfilled its potential.

For scientists, it's a treasure trove of data, one that might help unravel some of the world's most enduring medical mysteries.

New horizons in biomonitoring - which measures chemicals that people carry in their bodies - are identifying environmental exposures that may play a role in health problems, including cancer, neurological disorders and diabetes.

"We didn't have this lens 20 years ago," he said. "Not very long ago in my career in New Jersey, when we were trying to figure out if there were health effects from hazardous waste sites, we had very limited measures of who's exposed and to what they are exposed. This is a tremendous breakthrough. It could redirect environmental policy."

One recent government report concluded that too few chemicals are being assessed, and that the data are not being incorporated into regulations to protect people from exposure to toxic substances.

The Government Accountability Office report noted that there "are no biomonitoring data for most commercial chemicals." There are some 6,000 chemicals that the Environmental Protection Agency "considers the most likely sources of human exposure," the GAO report said.

In comparison, the CDC is getting ready to release its Fourth National Report on Human Exposure to Environmental Chemicals - due out by the end of the year - that will quantify 212 chemicals in the blood and urine of 8,000 Americans.

The CDC effort is the world's most comprehensive look at chemical exposure, including pesticides, ingredients in consumer products and industrial compounds. It will analyze 43 percent more chemicals than the 148 in the CDC's 2005 report, yet that remains a fraction of 1 percent of the ones that most people encounter.

The federal agency also is testing infants for the first time. In a pilot project, 500 mother-infant pairs will have their blood and cord blood tested.

Although cord blood has been tested before, the previous studies, including one released Wednesday by the Environmental Working Group, have tested only five to 15 babies at a time. In its latest report, the group found 232 chemicals in the cord blood of 10 newborns from racial and ethic minority groups.

Measuring cord blood shows what babies were exposed to before they even took their first breath - during the most sensitive period for chemical exposure.

"What we need to know are the levels of chemical exposure that occur in the mother and in the infant," said John Osterloh, chief medical officer at the CDC's Center for Environmental Health's Division of Laboratory Sciences. He is in charge of the CDC's exposure report.

The number of chemicals to be tested in the pilot project has not yet been determined. But officials said phthalates and perfluorinated compounds, which are used in consumer products and have been linked to disrupted fetal development, will be included.

Blood and urine samples of the newborns will be stored, providing a database for future research of disease patterns, said Mary Mortensen, a CDC senior medical toxicologist.

"You may have a group of kids with diabetes and a group that doesn't have diabetes, and an investigator says, 'Let's see if chemical x is more common in the diabetic kids than in the non-diabetic kids,'" she said.

Many scientists already have tapped into biomonitoring data to look for connections to disease.

Last year, a British team reported that people with higher levels of bisphenol A - a chemical found in polycarbonate plastic bottles and liners of food cans - in their urine are more likely to develop cardiovascular disease and diabetes. The findings were based on biomonitoring data from 1,455 Americans.

One goal is to use the data to prevent - not just identify - exposures that may cause health problems. But, according to an April report from the Government Accountability Office, the EPA needs to do a better job of using the data to reduce people's exposures.

The EPA, said the GAO report, "does not yet have a coordinated strategy for integrating biomonitoring research or for integrating biomonitoring data into its chemical risk assessment process."

Image
© roberrific/flickrSeconds after birth, the umbilical cord and cord blood are removed and the fluid preserved.
The report also notes that biomonitoring only reveals a person has been exposed to chemicals, with no information on how the chemicals arrive in a person's body - via food, air, water, or some other means. The absence of that information hobbles regulatory efforts.

A 2006 National Research Council panel noted that the ability to detect chemicals in the body has "outpaced the ability to interpret health risks." And the GAO report called for more data on whether the levels found in people are a cause for concern, yet it noted that EPA had little ability to compel chemical companies to provide it.

"It's an unfortunate reality that a number of products on the market contain chemicals for which there are little or no safety data. If biomonitoring shows that people are exposed to poorly evaluated chemicals, there's an obvious urgency to understanding their potential toxicity," says Ted Schettler, science director for the Science and Environmental Health Network, a research organization founded by environmental organizations.

But as valuable as biomonitoring is, there are limitations, notes Schettler. One major one is the inability to measure chemicals with short half lives, such as benzene, an ubiquitous toxic contaminant in vehicle exhaust.

Chemicals selected for the CDC testing are based on a couple of factors - including the seriousness of suspected health effects and how broadly the U.S. population might be exposed, Osterloh said.

The National Research Council report criticized the approach, saying "there has not been a coordinated and consistent public health-based strategy for selecting how chemicals are included and excluded from biomonitoring studies."

A 2006 National Research Council panel noted that the ability to detect chemicals in the body has "outpaced the ability to interpret health risks."But Burke sees improvement. He said at the CDC, "there has been a much broader opening and inclusion" of chemicals. Still, he said, "there always will be concerns there is not enough data on the public health concern of the day."

To help fill the void and spur political action, the Environmental Working Group and other environmental groups have conducted their own biomonitoring. The Environmental Working Group has detected more than 400 compounds in people, nearly twice the amount that the CDC has looked for. In 2005, the group asked the CDC to start testing cord blood, after its own testing of ten babies showed they were exposed to nearly 300 chemicals.

Some famous people, including members of the European Parliament and journalists Bill Moyers and Anderson Cooper, have undergone testing.

Scientists hope that the more data that are collected, the better they will be able to figure out the impact on people's health.

The chemical industry has stressed that finding traces of chemicals in people's bodies does not mean there are any health risks. Burke agreed, saying that people should not become alarmed at the mere presence of a chemical in their bodies.

But Theo Colborn, co-author of the book Our Stolen Future, said biomonitoring results are vital because a connection between low levels of exposure and health impacts already exists.

"We've had a lot of information from what is going on in wildlife and in the laboratory," said Colborn, a scientist credited with discovering in the early 1990s that environmental pollutants disrupt hormones. "We wouldn't even be looking for these chemicals if we hadn't gotten the signal from wildlife or laboratory animals that there is a problem when those chemicals are present."

The chemical industry has stressed that finding traces of chemicals in people's bodies does not mean there are any health risks.The CDC's biomonitoring data allows researchers to look for vulnerable populations by age and race.

For example, the 2003 report showed that Mexican Americans had substantially higher exposures to many agricultural pesticides than African Americans and non-Hispanic whites. And children had higher levels of many chemicals than adults, according to the 2005 report.

Collected from people dating back to 1999, the data also identify which chemical exposures are increasing and which are dropping.

But there is a lack of localized information.

"States don't have state-specific data nor community-specific data," said Diana Lee, a scientist with California's Environmental Health Investigations Branch, which is developing the state's biomonitoring program. California's program, which was signed into law in 2006, is designed to help fill that gap.

Although funding for the program is limited, Lee says the state is beginning pilot work. The goal, she said, is to provide information specific to California that "can be used in additional research studies that will then more definitively" determine risks to people's health.