For years, parents–as well as scientists–have worried that chemicals in common household products may pose a risk to growing children. We are talking about the sorts of things used to make modern amenities, such as non-stick pans, or say, stain-resistant fabrics. But definitive evidence is hard to come by. Now a new study suggests that a particular chemical may hinder a child's immune system.

A study of 600-children in the Faro Islands (in between Scotland and Iceland) found that those with the highest level of exposure to PFCs had the weakest immune responses to vaccines compared to those with lower levels of exposure. PFCs are not used as extensively in the United States as they had in the past (due to fears of such hazards), but they linger in the environment for years and years. Scientists and environmentalists have eyed PFCs for years, accrueing evidence of their dangers. Many of these findings, simliar to the recent study, have prompted manufacturers in the U.S. to limit their use. However, PFCs are still used widely in developing countries. 

Vaccines work by stimulating the immune system. A weak response, as this study found, suggests that vaccines would not be as effective among those children with high exposure. The findings, reported in the current issue of the Journal of the American Medical Association, lend further credence to speculations that PFCs harm children.
Listen to the full report by NPR's science writer Jon Hamilton.