TUESDAY, Jan. 24 (HealthDay News) -- Exposure to high levels of a group of common household chemicals may impair children's immunity, a new study suggests.

The team of researchers, from the United States and Denmark, showed that elevated exposures to perfluorinated compounds (PFCs) in early childhood was associated with a reduced immune response to two routine immunizations.

"We found that PFC pollution is apparently making the immune system more sluggish, so that it doesn't react as vigorously to vaccines as it should," said study author Dr. Philippe Grandjean, an adjunct professor of environmental health at the Harvard School of Public Health in Boston.

The findings appear in the Jan. 25 issue of the Journal of the Medical Association.

PFCs are commonly used in a wide range of household products including nonstick cookware, carpets, upholstery and food packaging such as microwave popcorn bags; previous research has found that the chemicals are present in most people's bloodstreams.

Other recent studies have linked increased exposure to the chemicals with early menopause and elevated cholesterol levels. But Grandjean said this is the first study in humans to find an association between high levels of PFCs in the blood and an impaired immune response.

"What we don't know is whether this association represents a general immune system dysfunction, and if it has implications in regards to infections, allergies or even cancer," Grandjean said. "We are looking at something that appears to be just the tip of the iceberg, and we'd very much like to know what the rest of the iceberg looks like."

For the study, Grandjean and his colleagues followed 587 children born in the Faroe Islands between 1999 and 2001. In the Faroes, located in the North Atlantic Sea between Iceland and Norway, frequent intake of seafood is associated with increased exposure to PFCs.

To examine the chemicals' effects on immunity, the research looked at antibody levels to the tetanus and diphtheria vaccines, which children in the Faroes are given at 3, 5 and 12 months of age, with a booster shot at 5 years of age. The children's prenatal exposures to five kinds of PFCs were measured by conducting blood tests on their mothers in the last weeks of their pregnancies. Postnatal exposure was assessed through blood tests at age 5. The researchers then measured serum antibody concentrations against tetanus and diphtheria vaccines at ages 5 and 7.

Grandjean's team found that all of the five PFCs measured showed negative associations with antibody levels. In children who had twice the average levels of PFCs in their blood at age 5, their immune response to the tetanus and diphtheria vaccines at age 7 was only half of what it should have been, Grandjean said.

The researchers noted that most levels of PFCs measured in the children studied at age 5 were lower than the levels found in a group of 3-year-olds to 5-year-olds in the United States studied in 2001 and 2002.

Another children's environmental health expert said the findings were concerning. "It's one more thing, along with a number of other findings about perfluorinated chemicals, that suggests we should all be concerned about them in general and try to decrease everybody's exposure to them," said Dr. Jerome Paulson, medical director of the Child Health Advocacy Institute at Children's National Medical Center in Washington, D.C.

Grandjean said that in addition to avoiding products made with PFCs such as microwave popcorn and nonstick cookware, parents who want to reduce their young children's exposure to PFCs should vacuum their rugs and upholstery more frequently "to control the levels of house dust."

More information

The U.S. Centers for Disease Control and Prevention has more on exposure to PFCs.