lower immune responses

A group of compounds used in a variety of products, including water-resistant clothing and microwave popcorn, may prevent childhood vaccinations from working properly, a new study says.

In the study, children who had higher concentrations of these compounds, called perfluorinated compounds (PFCs), in their blood had lower immune responses to diphtheria and tetanus vaccinations. An insufficient immune response to a vaccination can mean a child is actually vulnerable to catching a disease even though they've beenvaccinated against it.

Indeed, the levels of antibodies in the blood of some children exposed to PFCs indicated they were not protected against these diseases by age 7.

"When we take our kids to the doctor's office to get their shots, we expect that the vaccines are going to work," said study researcher Dr. Philippe Grandjean, of the Harvard School of Public Health in Boston. "What we found was that there was an increasing risk that they didn’t work if the kids had been exposed to the PFCs," Grandjean said.

The study is provocative, but the findings are not of immediate public health concern, said Dr. William Schaffner, chairman of the department of preventive medicine at Vanderbilt University in Nashville. Despite the link found in this study, vaccines have largely protected the public against diphtheria and tetanus over the same period of time that PFCs have accumulated in the environment, Schaffner said.

"These are illnesses that have been virtually eliminated from children," in the United States, Schaffner said.

However, Schaffner said investigations into the link between vaccines' effectiveness and PFCs, along with other potential environmental hazards, should continue.

The study will be published tomorrow (Jan. 25) in the Journal of the American Medical Association.

PFCs have thousands of uses in manufacturing, and most people have the compounds in their bodies, Grandjean said. They are slow to break down and persist for many years in the environment.

Studies in animals have suggested PFCs may lower the body's immune response, but their impact on people's health is unclear.

Grandjean and colleagues analyzed data from 587 children living in the Faroe Islands, in the northern Atlantic Ocean between Scotland and Iceland. These islands were chosen because their inhabitants frequently consume seafood, which is associated with increased exposure to PFCs. Still, overall,levels of PFCs in this area are similar to those found in other countries, including the United States, Grandjean said.

The researchers measured levels of PFCs in the blood of 5-year-old children, and tested the children's immune response to tetanus and diphtheria vaccinations at ages 5 and 7. The kids received complete vaccinations against these diseases, including a booster shot at age 5.

The higher the levels of PFCs were in the blood, the lower the children's response was to the vaccines.

A doubling of the exposure to PFCs was associated with a 49 percent lower level of blood antibodies in children at age 7, Grandjean said.

Children with some of the highest levels of PFCs were two to four times more likely to have antibodies in their blood at a level below what is thought to protect against these diseases.

The study "emphasizes the importance of making sure that the world does not pollute the natural environment," Schaffner said. "Clearly, greater efforts must be made to keep these perfluorinated compounds out of the environment," hesaid.

It's not clear exactly how people come to accumulate levels of PFCs in their body, so advice on how to avoid them may not necessarily work. But Grandjean said, "It would be prudent to avoid microwave popcorn [and] treatment of furniture, carpets, shoes and clothing with stain repellants," unless they are known not to contain PFCs.

Future studies into the health impact of PFCs should examine their effect on the immune system, Grandjean said. The researchers would also like to know if exposure to PFCs is associated with a reduced immune response to other vaccinations.