Perfluorinated chemicals in U.S. population differ by race
A new CDC survey shows that white men have the highest levels of perfluorinated chemicals in their blood.
Levels of perfluorinated chemicals in the blood of U.S. residents, while low overall, differ by race, according to the first statistically representative survey of the U.S. population, published today on ES&T’s Research ASAP website (DOI: 10.1021/es0517973). Whites are found to have levels of perfluorinated chemicals in their blood that are two times higher than levels in blacks and three times those of Mexican-Americans.
Perfluorinated compounds are persistent and bioaccumulative and are widely found at low levels in the environment and in humans. In animal experiments in laboratories, some of the chemicals have been linked to adverse effects, including cancer and developmental problems, although at higher levels than those found in human blood. Companies are beginning to develop alternatives to perfluorinated compounds or ways to eliminate them or their precursors from products.
The new study, conducted by Antonia Calafat and colleagues at the U.S. Centers for Disease Control and Prevention (CDC), analyzed for selected perfluorinated compounds in 54 aggregated samples of blood that had been collected in 2001 and 2002 as part of the National Health and Nutrition Examination Study (NHANES). (Samples were aggregated because the perfluorinated measurements were not part of the original NHANES study and the researchers lacked enough material to run individual analyses.) Each aggregated sample contained serum from 34 people, grouped by race and age.
“Calafat and colleagues have done an excellent job with this, the first study to look at perfluorinated chemicals in blood and race or ethnicity,” says Geary Olsen, an epidemiologist who is with the 3M Corp. and who has written several papers on this subject.
In all three racial groups, men have slightly higher levels than women. White men have the highest concentration of PFOS (perfluorooctane sulfonate) in their blood, 40.19 parts per billion (ppb). PFOA (perfluorooctanoic acid) values in all the pools are lower—2 to 8 ppb—but again are highest in whites. Moreover, white adolescents have the highest levels of two perfluorinated chemicals associated with carpet stain protectors. In more than 75% of the blood samples, the CDC team also find PFOS precursors, which are thought to break down to PFOS in the body, and the presence of 9-carbon-long PFNA (perfluorononinoic acid). However, chemicals with chains composed of more than 9 carbon atoms are relatively scarce.
“These results are intriguing,” says Calafat. “But we really can’t explain the differences. That’s why we need more information about sources and pathways,” she adds.
Although earlier studies have detected PFOS and PFOA in blood, CDC’s report is the first designed to provide values representative of the U.S. population. The levels measured by CDC are similar to those reported in previous studies for people living in the U.S., Europe, and Asia, says Olsen.
Contamination levels in the U.S. are much higher than those in Peru, and perfluorochemicals are detected more frequently, Calafat notes, referring to unpublished work. Only 25% of Peruvians have PFOS in their blood, and even those have very low levels—about 0.5 to 1.0 ppb. This may reflect less exposure to mass-produced consumer items that contain perfluorinated chemicals.
“A question of fundamental importance is whether the occurrence of PFOS and PFOA in human blood arises primarily from a direct or an indirect source,” says University of Toronto chemist Scott Mabury, who notes that the observation of PFOS precursors suggests that indirect sources are important.
Calafat next plans to analyze individual samples from other years, including ones collected during 1999 and 2000, which predate the 3M withdrawal of PFOS-related chemicals.
