Can PCB residues in old home insulation cause birth defects?

What's actually in it

Polychlorinated biphenyls (PCBs) were used in building materials from the 1930s through the 1970s. Old caulking around windows, insulation materials, fluorescent light ballasts, and some paints in homes built before 1979 can still contain them. PCBs don't break down easily, so they seep into indoor dust and air for decades.

If you're pregnant and living in an older home, you may be breathing in small amounts of PCBs without knowing it.

What the research says

A 2026 study in Environ Sci Technol combined human data and lab experiments to show how prenatal PCB mixtures cause neural tube defects (NTDs). Neural tube defects include conditions like spina bifida and anencephaly, where the brain or spinal cord doesn't form properly in the first weeks of pregnancy.

The researchers found that PCB mixtures disrupted folate metabolism, the very pathway that folic acid supplements are meant to protect. PCBs interfered with enzymes that process folate, reducing the amount available for the rapid cell division needed to close the neural tube.

They also found that PCBs increased oxidative stress in developing neural tissue, damaging DNA at a critical moment. The combination of low folate activity and high oxidative stress created a double hit on the forming nervous system.

If your home was built before 1979, consider getting it tested for PCBs, especially before or during pregnancy. Wet-mopping floors regularly and using a HEPA vacuum can reduce PCB-contaminated dust. Taking prenatal folate is more important than ever in these settings.