PCBs are man-made chemicals that persist in the environment and were widely used in construction materials and electrical products prior to 1978. Although the manufacture and most uses of PCBs were banned and phased out in 1978, the EPA has evidence that many buildings across the country constructed or renovated between 1950 to 1978 may have PCBs at high levels in the caulk around windows and door frames, between masonry columns, mastics, expansion joints and in other masonry building materials. This caulk may be present inside and on the exterior of the building, as well as surrounding surfaces.

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