News and Comments about Life
A new study finds evidence that people may be exposed through drinking water to a persistent nonstick chemical at levels approaching those that trigger adverse effects in laboratory animals.
Most of us are familiar with those pans whose cooking surface is covered with a nonstick layer designed to protect our food from excessive cooking and burnouts
This layer is a fluorine-based chemical, PFOA or perfluorooctanoic acid. Developed by DuPont more than 50 years ago and used to launch the company’s Teflon line of nonstick products, it is now part of our everyday cooking. Successful as it is, it does represent a potential threat to our health. Not for harmful effects on the food we cook in these pans, rather because he nonstick agents…sticks around a very, very long time. Potentially forever.
Actually, PFOA is used not only in teflon pans production, but also in carpeting, popcorn bags and, more generally, in everything we might use to cook or conserve hot food.
The chemical appeared in roughly two-thirds of some 30 public water systems sampled by New Jersey’s Department of Environmental Protection between 2006 and 2008, researchers report online and in an upcoming issue of Environmental Science & Technology.
In five of the sampled water systems, PFOA concentrations exceeded safety limits developed by the researchers by a factor of two or three. In each of those instances, says toxicologist Keith Cooper of Rutgers University in New Brunswick, the affected water came from groundwater or from well water. However, he adds, where contaminated water entered a water-treatment plant, “concentrations in the intake water and the output water were basically the same.” So it looks like the treatment plants didn’t remove the pollutant.
Values found in the New Jersey water systems are thought to be representative of water supplies all over the USA.
How PFOA gets into water remains largely unknown.
Human data have shown that blood concentrations of PFOA tend to be 100 times higher than the values in drinking water. To gauge whether these were likely to pose health risks, researchers applied a common practice used in lab tests when toxicologists need to extrapolate between animals or human life stages. As a result, though effects on our health are not determined yet, researchers propose a drinking water limit of 0.04 micrograms per liter.
On January 8, the Environmental Protection Agency proposed a “provisional health advisory” for PFOA that was 10 times higher. At the time, EPA explained it was issuing the advisory “in response to an urgent or rapidly developing situation” involving unregulated pollution.
One explanation for the difference: EPA’s value was set to deal with short-term emergencies such as a spill, Cooper says, whereas “ours was designed to deal with chronic exposure over a lifetime.”
Abby D. Benninghoff, a PFOA toxicologist at Oregon State University in Corvallis, finds the proposed New Jersey safety limit for PFOA pretty convincing. “I looked through the math pretty carefully and I am familiar with most of the studies that they based it on. So the proposed limit strikes me as reasonable.”
But the implications are a bit unsettling. She’s been studying PFOA activity in trout, a surprisingly good model for testing the chemical’s human cancer risk (SN Online: 5/21/08), and in human cells. These data show that the 8-carbon PFOA molecule and its 9- and 10-carbon analogs — which also show up in the environment — all bind to and activate the estrogen receptor. In trout, this estrogen action promotes the development of liver cancer.
Concentrations of any of these chemicals needed to turn on this hormone mimicry in human cells are fairly low, she reported at a toxicology conference last November. Indeed, she now notes, such levels are in the same ballpark as what would likely develop in the blood of people drinking water from the more contaminated sites described by Cooper’s team.