Polychlorinated biphenyls, or PCBs, are industrial chemicals so toxic that Congress banned them 40 years ago. Research has shown that they can cause a range of health concerns, including cancer and neurological problems such as decreased IQ. And yet, because they were commonly used in building materials for decades, they continue to contaminate classrooms in between 13,000 and 26,000 schools nationwide, according to Harvard researchers.
No one knows exactly how many schools are affected — nor how many children are being exposed to these toxic chemicals — because many schools don’t test for PCBs. Under federal law, they don’t have to.