By Anne Harding
Certain vaccines may not work as well in children who have been exposed to high levels of perfluorinated compounds (PFCs), a family of chemicals used to make everything from microwave popcorn bags and pizza boxes to carpets and nonstick cookware, new research suggests.
In a study published this week in the Journal of the American Medical Association, researchers found that the higher the level of PFCs in a child's blood, the fewer antibodies the child produced after receiving vaccines for diphtheria and tetanus. In addition, kids with higher PFC exposure were more likely than their peers to have antibody levels too low to provide protection against those infectious diseases.
"The immune system is more sluggish when these kids are vaccinated," says lead author Philippe Grandjean, MD, an adjunct professor of environmental health at the Harvard School of Public Health, in Boston. "It doesn't respond as well ... and produces less antibodies," he adds.
The number of antibodies generated by a vaccine is an indication of overall immune system function, so the findings suggest that PFCs may have negative effects on the immune system that go beyond these two vaccines, the researchers say.
Although experts haven't identified all the ways that PFCs enter the body, contaminated food and drinking water and consumer products containing the chemical are believed to be the main sources of PFC exposure.
Research in animals has already linked PFC exposure to changes in immune function. To determine whether the chemicals might affect the human immune system as well, Grandjean and his team took blood samples from 587 pregnant women between 1999 and 2001 and tested the samples for five common PFCs. Then, when the women's offspring were 5 years old, they repeated the process using blood samples from the kids.
The researchers also measured levels of diphtheria and tetanus antibodies in the children's blood at two time points: at age 5, after the kids had received three doses of the diphtheria and tetanus vaccine; and at age 7, two years after they'd received a booster shot.
Higher prenatal levels of two PFCs were associated with having fewer antibodies at age 5. Likewise, kids whose blood revealed higher PFC exposure at age 5 had fewer antibodies at age 7. A 5-year-old whose PFC exposure was double that of another 5-year-old's could be expected to have roughly half as many antibodies at age 7, the study estimates.
The findings raise the possibility that health officials are overestimating the protection provided by childhood vaccines, Grandjean says. If the percentage of vaccinated children "includes kids who are exposed to PFCs and therefore not responding to the vaccine," he says, the likelihood of an epidemic may be higher than it would appear from vaccination rates.
All of the children and mothers in the study lived in the Faroe Islands, located between Iceland and Scotland. Faroe Islanders are exposed to an unusual dietary source of PFCs, whale meat from polluted waters, but average blood levels of PFCs in Faroese children are comparable to those in American children, the researchers say.
At the urging of the U.S. Environmental Protection Agency (EPA), the chemical industry agreed to phase out one of the PFCs examined in the study (known as PFOS) in most consumer products by 2002, and since then several companies have voluntarily agreed to stop using and emitting the other (PFOA) by 2015.
Thanks to these efforts, average PFC exposure in the United States has declined over the past decade, Grandjean says. PFCs take many years to break down in the environment, however, and they similarly remain in the body for years once people ingest them. "For that reason, we ought to be concerned that they may be causing some adverse effects over the long range," he says.
Marie Francis, a spokesperson for the American Chemistry Council, a trade association representing chemical manufacturers, said in a statement that the chemical industry is "carefully reviewing" the new study, and that more research is needed to replicate the results.
"It is important for consumers to know that our companies, working with the EPA, have made marked progress towards advancing new chemistries that are substitutes for the older chemicals evaluated in this study," Francis said. "These new fluoro chemistries have an improved environmental and toxicological profile while continuing to offer consumer benefits."
Margie Peden-Adams, PhD, a research toxicologist at the University of Nevada–Las Vegas, says it's impossible to entirely avoid PFCs because they are pervasive in the environment. PFC-free products (such as carpeting) do exist, she says, but they tend to be expensive and hard to find.
Steering clear of PFCs is difficult because the government does not require companies to state whether a product contains the chemicals, Grandjean says. To make matters worse, he adds, China -- the United States' second-largest trading partner -- has no restrictions on PFC use.
Both children and adults are likely exposed to PFCs in their diets through food containers, but it's not clear how much of the chemicals in these containers actually find their way into food, Peden-Adams says.
And young children may be especially vulnerable to non-food sources of exposure. "They spend much of their time, early on, playing on or near the floor, increasing their exposure to compounds in dust, soil, and on carpets," Peden-Adams says.