An epidemiological study conducted at Baltimore's Johns Hopkins University focused on the health risks of exposure to electromagnetic fields. Involving over 50,000 male New York City telephone workers, the study showed a higher risk for leukemia for young workers who continued to be employed in the same profession. In particular, cable splicers—the group with the highest EMF exposure—showed high cancer risks in general, and seven times the risk of leukemia. However, when compared with New York males as a whole, the cable splicers actually had a lower rate of cancer.

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