They found kids with more perfluorinated compounds, or PFCs, in their blood stream were less likely to respond to routine vaccines.

"When the PFC concentration increases in the body, the immune system gets more sluggish and is less capable of maintaining a defense mechanism against microorganisms," said Dr. Philippe Grandjean of the Harvard School of Public Health in Boston, who led the study.

Although the findings don't prove the chemicals themselves are harming the immune system, Grandjean said he thought that is "very likely" to be the case.

"I don't feel comfortable with the compounds for myself and my family and would rather eliminate them," he told Reuters Health.

PFCs are used worldwide in food packaging and the treatment of textiles. Because they don't break down easily, they are found throughout our environment and in both humans and animals.

According to the Environmental Protection Agency, they are toxic to laboratory animals, causing reproductive, developmental and other health problems.

But so far, they haven't been shown to pose a significant threat to the general human population.

The new study, published in the Journal of the American Medical Association, is the first to link PFCs to immune problems in children.

The researchers tracked a group of nearly 600 children from the Faroe Islands, in the North Atlantic Ocean, from before birth until they were seven years old, and linked their blood levels of PFCs to their response to routine diphtheria and tetanus vaccines.

Grandjean and his colleagues found that a doubling in mothers' blood levels of a common type of PFC -- called perfluorooctane sulfonic acid, or PFOS -- corresponded to a 39 percent drop in the diphtheria antibody concentration of their children at age five.

Similar results were found for antibodies against both tetanus and diphtheria based on blood samples from children themselves. At age seven, for instance, a doubling in a child's PFC levels corresponded to a halving of antibody levels.

And many kids had fewer antibodies than are considered necessary to protect them against infections.

"Already at age seven, that is two years after the last immunization, almost 10 percent of the kids were below that level, so they definitely aren't going to be protected in the long term," Grandjean told Reuters Health.

The Foodservice Packaging Institute, which represents the industry, was not available to comment on the findings.

But independent toxicologist Dr. Anthony Dayan, who has worked as an industry advisor, criticized the new study.

In a statement provided by the London-based Science Media Centre, he said it had failed to consider intake of polyunsaturated fatty acids (PUFAs), which are found in oily fish like tuna and mackerel, and may also suppress the immune system.

"So, as eating is claimed to be the source of PFCs and it is the source of the immunosuppressive PUFAs, the study proves nothing," he said.

Grandjean said that was unlikely, however, given that his team found no effect of mercury and certain other chemicals that are also found in fish.

Another researcher, Alastair Hay of the University of Leeds, said the new study was well conducted.

"The implication of this work is that everyday exposure to these chemicals makes us more vulnerable to infections," he said in a statement. "We cannot afford to ignore the research, but equally we should not panic. What we need is a measured response to test the findings in a robust way and assess their implications for our health and particularly that of our children."

The EPA is currently considering regulation of PFCs and Grandjean said his findings should be taken into account.

He added that parents might want to avoid microwave popcorn, and treatment of furniture, carpets and clothing with stain repellants to reduce their family's exposure to PFCs.

SOURCE: bit.ly/zouGRc JAMA, January 24, 2012.

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