Wednesday, May 02, 2007

What do nonstick pans, carpets, polar bears and newborn cord blood have in common? Perfluorinated chemicals in the news again

Once again, the “miracle” chemicals that coat most of our fry pans, raincoats and the ever-white (well maybe after 10 years of leg-sweat and black dogs - off-white) stain repellant couch in the living room are in the news. I’m referring to that most complex family of perfluorinated chemicals which includes perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) (and I promise not to mention the whole chemical name again in this entry!)

I wrote about PFOA and PFOS earlier, some of the legal loopholes that led to this current situation, and the ongoing phase-out of certain types of these chemicals, and now there is an excellent article summarizing the current research on the toxic effects of these chemicals written by Kellyn Betts and published in the Environews section of Environmental Health Perspectives.

After decades of use, these wondrous and now infamous chemicals are a part of us all. Scientists have measured the chemicals in the bodies and tissues of humans and wildlife around the globe. In fact, a recent study published in Environmental Science and Technology reported the presence of these chemicals in “99-100% of umbilical cord sera” of newborn babies tested in Baltimore, MD.

What I find most frustrating is that though these chemicals have been used (and released) by the ton for decades, once again toxicologists are playing catch-up. The great majority of toxicity studies about how a chemical behaves in a body, and its toxicity depends upon experimental exposures to laboratory animals. The difficulty lies in translating these effects to the “target” species; it may be humans or it maybe certain wildlife species that are at greatest risk of exposure (for example – Atlantic dolphins.) One key, among many, to extrapolating from laboratory animals to target species is understanding the similarities, and differences of how a chemical moves through the body. Where it goes, how long it remains and what happens to it (is it broken down, metabolized, excreted?) But according to EPA scientists interviewed by Betts, for chemicals like PFOA and PFOS there are very large differences in how long the chemical remains in the body, not only between species but between sexes, that they don’t understand just yet. For example while PFOA might be eliminated in a few hours from a female laboratory rat, it might be days for a male rat, and years for a human.

Among the findings reported in this recent Environmental Health Perspectives article are a summary of studies indicating that both PFOA and PFOS suppress immune function, in some cases at concentrations that occur in wildlife (some of the highest concentrations reported in wildlife have been found in Atlantic dolphins, according to the article,) in addition, researchers report impacts on growth and development of offspring born to exposed mothers, and neonatal morality. For more, read the article published in Environmental Health Perspectives Volume 115, Number 5, May 2007

Update Nov 1, 2007: Another study just published in Environmental Health Perspectives evaluates the relationship between PFOA and PFOS concentrations in cord blood with birth size and weight. Although the authors report a small negative relationship between PFOA, PFOS and birth weight and head circumference, the authors suggest "...cautious interpretation of this study until the findings can be replicated in other populations."