Joints around windows and between masonry panels in public buildings erected or renovated during the 1960s and 1970s were often sealed with a caulk containing polychlorinated biphenyls (PCBs). The oily PCBs kept the sealant pliable so that it could expand and contract with the weather. Although the Environmental Protection Agency banned PCBs' production in 1977 owing to the compounds' toxicity, some tainted caulk remains in place. Indeed, Robert F. Herrick of the Harvard School of Public Health in Boston and his colleagues have now found it at 13 of 24 Boston-area buildings they sampled.
In some cases, a caulk's PCB concentration was nearly 1,000 times the amount that would ordinarily trigger a material's immediate removal and, if necessary, the decontamination of the building containing it.