The more exposure children have to chemicals called perfluorinated compounds, the less likely they are to have a good immune response to vaccinations, a study just published in JAMA, the Journal of the American Medical Association shows.
The finding suggests, but doesn't prove, that these chemicals can affect the immune system enough to make some children more vulnerable to infectious diseases.
For decades now, PFCs have been used in nonstick coatings, stain-resistant fabrics and some food packaging. And because they persist in the environment for years, they have become common around the globe.
"You can find them in polar bears," says Dr. Philippe Grandjean, the study's lead author who works at both Harvard and the University of Southern Denmark.
Studies in animals have shown that PFCs can weaken the immune system.
Grandjean wanted to know whether this was happening in children. So he led a team that studied nearly 600 kids in the Faroe Islands, which lie about halfway between Scotland and Iceland.
The Faroese have levels of PFCs similar to those of U.S. residents. Grandjean figured if the chemicals were having an effect, it would show up in the way kids' bodies responded to vaccinations.
Normally, a vaccine causes the production of lots of antibodies to a specific germ. But Grandjean says the response to tetanus and diphtheria vaccines was much weaker in 5-year-olds whose blood contained relatively high levels of PFCs.
"We found that the higher the exposure, the less capable the kids were in terms of responding appropriately to the vaccine," Grandjean says. The results raise the possibility that "the immune system is not really developing optimally."
The health effects of PFCs are still poorly understood. But in the past decade, government scientists have become increasingly concerned about possible links to developmental problems in children.
As a result, the Environmental Protection Agency has taken steps that have resulted in some PFCs being phased out.
These chemicals aren't as frightening as some found in the environment, says Dr, Alan Ducatman from West Virginia University, which has been part of a large study of a PFC known as C8. "But they are clearly problematic," he says, adding that the C8 study also found some evidence of an effect on the immune system.
Consumers in the U.S. have reason to be concerned about PFCs, Ducatman says, even though exposure to some of them is falling.
The problem is that levels "are not going down in other parts of the world and in fact there are places where they may even be going up," Ducatman says.
One of those places is China, says Grandjean. And that's a problem for countries that buy products from China, he says.
"We may just be importing products with the same compounds," he says. "So I don't think that we have solved the exposure problem yet and I think it needs international attention."
That's beginning to happen. Some global treaties are beginning to include language restricting the use of certain PFCs.
MELISSA BLOCK, HOST:
A new study finds that chemicals known as PFCs can impair a child's immune system. PFCs are found in non-stick coatings, stain-resistant fabrics, food packaging and even some seafood. Their use is declining in the U.S.
But as NPR's Jon Hamilton reports, exposure to even relatively low levels seems to have an effect.
JON HAMILTON, BYLINE: In the past decade, scientists have become increasingly concerned about PFCs, which are known formally as perfluorinated compounds. Philippe Grandjean, who works at Harvard and the University of Southern Denmark, says one reason is that PFCs are just about impossible to avoid.
PHILIPPE GRANDJEAN: These compounds have been around for, like, 50 years. I mean, you can find them in polar bears and they are all over the environment.
HAMILTON: Also, PFCs tend to linger for years in the body and, in lab animals, they've been shown to suppress the immune system.
Grandjean wanted to know whether this was happening in children, so he led a team that studied nearly 600 kids in the Faroe Islands, which lie about halfway between Scotland and Iceland. The Faroese have levels of PFCs similar to those of U.S. residents. Grandjean figured that if the chemicals were having an effect, it would show up in the way the kids' bodies responded to vaccinations.
Normally, a vaccine causes the production of lots of antibodies to a specific germ, but Grandjean says that response was less pronounced in the children whose blood contained higher levels of PFCs.
GRANDJEAN: We found that, the higher the exposure, the less capable the kids were in terms of responding appropriately to the vaccine and some of the kids were more or less incapable.
HAMILTON: The study looked at the responses to vaccines for diphtheria and tetanus in children from five to seven years old. Grandjean says the result suggests these kids have a blunted response to other vaccines, as well, and perhaps bigger problems.
GRANDJEAN: Of course, we worry that something more serious is going on here, that the immune system is not really developing optimally.
HAMILTON: If so, children with higher levels of PFCs might be less able to fight off infectious diseases.
Alan Ducatman from West Virginia University has worked on something known as the C8 Health Project, which has been studying the health effects of one particular PFC in Ohio and West Virginia.
He says results from the new study are consistent with some of their own findings regarding PFCs and immune function.
ALAN DUCATMAN: PFCs have certainly undergone a transformation in our perspective on them over one decade.
HAMILTON: Ducatman says consumers in the U.S. have reason to be concerned, even though companies here have phased out some PFCs and some exposure levels have begun falling. Ducatman says PFCs are not the most frightening chemicals out there.
DUCATMAN: But they are also clearly problematic and something to think about and, to the degree that levels are going down in the United States, we should also acknowledge that they're not going down in other parts of the world and, in fact, there are places where they may even be going up.
HAMILTON: Grandjean says China is one country that appears to be using more PFCs these days and they are putting them in products that get sold in the U.S.
GRANDJEAN: We may just be importing products with the same compounds instead, so I don't think that we have solved the exposure problem yet and I think it needs international attention.
HAMILTON: It's getting some. Global treaties are just beginning to include language restricting the use of certain PFCs. The new study appears in the Journal of the American Medical Association.
Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.