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Researchers report that exposure to ubiquitous household chemicals may lower children’s responses to vaccines.

The study, published in the Journal of the American Medical Association, suggests that perfluorinated compounds (PFCs), which are commonly used in Teflon coatings in pots and pans as well as in furniture, stain-resistant carpeting, rain gear and microwave popcorn bags, may hinder children’s ability to mount proper immune responses after they are vaccinated. The findings suggest that important gains made by immunization programs in the past century may be eroded by the emergence of these environmental chemicals.

In the report, Dr. Philippe Grandjean, chair of environmental medicine at the University of Southern Denmark, and his colleagues studied a group of 587 children born between 1999 to 2001 in the Faroe Islands. The researchers chose that population, located in the north Atlantic, since most residents rely on the sea to survive, and recent studies have recorded increasing amounts of PFCs in the drinking water and fish there.

All of the children received the diphtheria, tetanus and pertussis (DTaP) vaccine at 3 months, and a booster at 5. The scientists tested the children’s antibodies to diphtheria and tetanus at age 5, just before they received their booster shot, and again when they were 7. In addition, the team also drew the children’s blood to test for PFCs.

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When the researchers compared the participants’ antibody levels to the levels of PFCs in their blood, they were surprised to find that higher levels of PFCs were linked with a lower immune response. In fact, kids whose PFC levels were twice as high had half the amount of antibodies to diphtheria and tetanus, compared with children who tested lower for PFCs. At age 7, kids with a twofold increase in PFC levels were also two to four times more likely to show an immune response that was so low that it was no longer clinically protective.

“We were kind of shocked when we saw those numbers,” says Grandjean, who is also an adjunct professor at the Harvard School of Public Health. “This is the first study to say that by [exposing children to these chemicals], we are screwing up a major aspect of disease prevention in our society. I’ve been in the field for quite a while, and this is a very strong signal.”

Grandjean acknowledges that the study involved an isolated island population and needs to be confirmed, but he notes that he and his team took care to address many factors that could potentially confound the results, including the children’s birthweight, the time since their last vaccination, their age, sex and other parameters. Even after adjusting for these contributors, he says, the association remained strong. “We haven’t been able to explain it away,” he says.

Other studies have found similar effects on the immune system associated with environmental toxins such as PCBs and dioxin, but the PFC effect on immunity seems to be stronger, says Grandjean. That’s a particular concern since PFCs have a half-life in the body of at least four years, meaning that it takes four years to reduce by half the amount of PFCs absorbed at any given time.

The scientists also looked at how prenatal exposure to the chemicals might influence infants’ immunity, and found that a twofold increase of PFCs in an expectant mother’s blood was linked to a 39% lower concentration of antibodies in 5-year-olds (before their booster), compared with those whose moms had lower levels of PFCs.

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The researchers had expected PFC levels in the study participants to be higher than in kids elsewhere, because of their high fish consumption. But, in fact, their levels of PFCs were similar to those seen in American kids, who are exposed to PFCs through common household dust. In certain parts of the U.S., including West Virginia and Ohio, water pollution from decades of industrial waste has also led to unhealthy levels of PFCs in drinking water, meaning that residents may still be harboring the chemical from earlier exposures.

Avoiding the chemicals can be difficult, if not impossible. The Environmental Protection Agency (EPA) currently does not require companies to test for PFCs in industrial waste, noting that “to date, significant adverse effects have not been found in the general human population.” However, under the Toxic Substances Control Act (TCSA) the agency in 2002 limited the future manufacture and import of certain types of PFCs known as perfluoroalkyl sulfonates (PFAs), citing concerns that “these chemical substances may be hazardous to human health and the environment.”

For children who may have been exposed to enough PFCs to affect their immune system, Grandjean says there is a simple solution — get re-vaccinated. That’s what the scientists did for the children in the study whose antibodies levels fell below protective amounts from diphtheria and tetanus. But, he says “that can only put a Band-Aid on the wound. The problem is that those drops may not be the only deficit.” Grandjean and his colleagues are now analyzing children’s responses to other vaccines, to see if PFC exposure affects antibody levels for other childhood immunizations as well.

If they do, then the problem becomes a much bigger one. If the exposure to environmental chemicals is negating the effect of childhood immunizations, then the major public health gains made by vaccines in the past century in preventing infectious diseases may start to erode. And if the immune system is compromised enough to respond more sluggishly to vaccines, then what does that mean for its ability to fend off other pathogens, like the common cold virus and influenza? Further, is it possible that exposure to environmental chemicals plays a role in autoimmune diseases or conditions like type I diabetes and cancer that may in part be due to dysfunction of the immune system?

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There’s not much that we can do currently to cleanse ourselves of these compounds, says Grandjean. But if we’re aware of how potentially harmful they can be to our health, we might be more vocal about how we want our regulatory agencies to handle them. “When we see results like this, it’s clear we haven’t done our job well enough,” he says. “I think the next generation deserves better from us.”

Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.