Light ballasts are the electrical components that regulate fluorescent light fixtures. The ballast is usually located within the fixture under a metal cover plate.
Most fluorescent light fixtures made before July 1979 have ballasts containing small amounts of PCBs (polychlorinated biphenyls), a highly toxic substance. When these ballasts fail, the PCBs can leak out.
Ballasts made after 1978 are usually marked "non-PCB." These may contain a PCB replacement, called DEHP, which has been linked to cancer.
Businesses must dispose of light ballasts using specially-certified firms, depending on the type of ballast. Households may take ballasts to household hazardous waste facilities operated by the Local Hazardous Waste Management Program in King County for free recycling.