The next time you make some microwave popcorn or cook a frozen pizza, consider this: The packaging of many of these products contains a chemical that the Environmental Protection Agency considers potentially carcinogenic and wants businesses to voluntarily stop using by 2015. Studies show that this chemical -- perfluorooctanoic acid, or PFOA -- is present in 98% of Americans' blood and 100% of newborns. It doesn't break down and thus accumulates in the system over time. PFOA ... is used to make Teflon pans, Gore-Tex clothing and to prevent food from sticking to paper packaging. The industry says that while the EPA's carcinogen concerns are based on animal tests, there's no evidence that PFOA is harmful to humans. Public-health advocates counter that the industry is being disingenuous. There's never been a chemical found that affects animals but has no effect on humans," said Bill Walker, vice president of the Environmental Working Group. PFOA is part of a broader constellation of substances known as perfluorinated chemicals, or PFCs. When PFCs are heated, they break down into compounds that can be absorbed into food and make it into the bloodstream. Federal investigators determined in 2005 that PFOA is a "likely carcinogen" and called for expanded testing to study its potential to cause liver, breast, testicular and pancreatic cancer. Walker at the Environmental Working Group said the voluntary phaseout supported by the EPA was insufficient. It wouldn't apply to Chinese companies, which are among the leading manufacturers of food packaging.