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Researchers Say Children May Be Exposed to Chemicals Through Dust and Food
By Brenda Goodman
WebMD Health News
Reviewed by Laura J. Martin, MD
April 15, 2011 -- Children in California have high levels of flame-retardant chemicals in their bodies, and they appear to be exposed to these chemicals through household dust and food, a new study shows.
The study found that Mexican-American children, whose mothers emigrated from Mexico before they were born, had blood levels of polybrominated diphenyl ethers (PBDEs) that were seven times higher than children of the same age who were born and grew up in Mexico.
"The only levels that we've seen in the literature that are higher than the California children blood levels are children living on a hazardous waste site in Nicaragua," says study researcher Brenda Eskenazi, PhD. Eskenazi is director of the Center for Environmental Research and Children's Health at the University of California, Berkeley.
By comparing children of the same ethnicity who came from roughly the same socioeconomic classes, and whose mothers all came from the same states in Mexico, researchers were able to better pinpoint where the exposure was happening.
And Eskenazi says that because California children's PBDE levels were higher than those of their mothers, the chemicals don't appear to be coming from the mothers' breast milk, as previous studies have shown.
More likely sources of exposure for American children, she thinks, are household dust and food.
Independent experts agree.
"The chemical essentially just evaporates and comes out of your household furniture and your household plastics and so it's actually dust exposure to children that's causing these high levels," says David Andrews, PhD, a chemist and senior scientist with the nonprofit Environmental Working Group in Washington, D.C.
Health Effects of PBDEs
PBDEs are chemicals that are used to keep things from burning.
In the mid-1970s, California created one of the highest standards for furniture flammability in the country. As a result, millions of pounds of flame retardant chemicals have been used in furniture foam, clothing, upholstery, electronics, and in the insulation for electrical wires.
Even though standards in other states aren't as strict, product manufactures often conform to California's flammability standards so their products can be sold there.
As a result, studies have shown that Americans have levels of PBDEs in the bodies that are 20 times higher than levels in Europeans. Government health surveys have found that some of the highest blood levels of PBDEs in California residents.
PBDEs have become so pervasive that a 2010 study documented their presence in butter.
Though their health effects are still being investigated, studies in children have linked high blood levels to problems with brain development, learning, attention, and behavior. In adults, high exposures have been associated with difficulty conceiving, menstrual cycle irregularity, low sperm counts, and altered levels of thyroid hormone.
Production of two kinds of PBDEs ceased in the U.S. in 2004. A third kind, deca-BDE, is being phased out, but it isn't expected to be off the market until 2014.
"Even though the ones that we have the highest concerns about are no longer being produced, they can still break down into these other forms," says Andrews.
And PBDEs appear to take a long time to break down, which means that they may persist in the environment for years.
WebMD called an industry group for comment, but an answer was not received in time for publication.
Tracking Exposure to PBDEs
Between 1999 and 2000, Eskenazi and her team enrolled pregnant women from a population of low-income, Spanish-speaking farmworkers in Salinas Valley, Calif.
In 2006, the researchers recruited similar low-income women and children in Mexico from the three states that had been home to most of the mothers in the California group.
There were 264 children from California, and 283 children from Mexico, included in the study.
The children all had access to health care and were receiving government food aid.
Almost all the children in both locations were breastfed, though the mothers in California breastfed their infants for a slightly shorter period of time, about nine months compared to 11 months for the mothers in Mexico.
Researchers found that the California children had a greater variety of PBDEs in their blood, as well as higher blood levels, than the children in Mexico.
The average serum concentration of all of the different kinds of flame retardants tested for in the study was 87.8 nanograms per gram of fat in the children in California, compared to 12.3 nanograms per gram of body fat for the children in Mexico.
Researchers also tested the children for levels of another chemical, the pesticide DDT. Though DDT was banned in the U.S. in the 1970s, it continued to be used in Mexico until 2000.
In contrast to the results of the PBDE testing, children in Mexico had markedly higher levels of DDT compared to Mexican-American children. This suggests, again, that environmental exposures to these two chemicals had more to do with where the kids were living than with maternal exposures through breastfeeding and pregnancy.
"This research has important policy implications, as it illustrates how halogenated flame retardant use in the U.S. is responsible for the higher concentrations of PBDEs measured in Mexican-American children in California compared to their Mexican counterparts," says Julie B. Herbstman, PhD, ScD, an assistant professor of environmental health at Columbia University's Mailman School of Public Health, in New York City. Herbstman is studying the health effects of PBDEs, but she was not involved in the current research.
"Given the potential health implications associated with this exposure, this study underscores the need for us to carefully consider the effectiveness as well as the unintended health consequences that may result from policy intended to reduce fire-related mortality," she says.
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