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Did You Know?
In Did You Know? the National Geographic magazine team shares extra information we gathered to expand your knowledge of our featured subjects.

PCBs were everywhere in the early 1970s, so popular as electrical coolants that they even found their way into the White House. In 1985 the Environmental Protection Agency (EPA) and the General Services Administration (GSA) carried out standard inspections and found these suspected carcinogens, which had been banned in 1976, in 19 electrical transformers within the White House complex. PCBs were also detected at NASA headquarters, the Department of Agriculture, the New and Old Executive Office Buildings, and the Smithsonian Institution.

Five of the White House transformers turned out to have leaks, and two were actually leaking the toxic chemicals. Electrical workers were called in to refill the transformers with nontoxic coolants at a cost of about $40,000 for each transformer. In the process workers tracked PCB-contaminated dust throughout the White House on their shoes and clothes. However, tests conducted by the EPA and GSA showed that the PCB levels stayed within acceptable limits.

—Agnieszka Siemiginowska