A major settlement announced this week brought an end to a lengthy battle between chemical manufacturer Monsanto and students, parents and staff of a Monroe school who were exposed to toxic PCBs for years. PCBs, or polychlorinated biphenyls, are human-made chemicals that the Environmental Protection Agency has linked to some cancers and other illnesses. They festered at Sky Valley Education Center, an alternative school in Snohomish County, where fluorescent lights and building caulking were contaminated. The preservatives were once widely relied upon for building durability, but the EPA has since banned their use. More than 200 people from Sky Valley blamed their serious illnesses on exposure to the toxicant. This week's announcement marks the largest, and only significant, PCB personal injury settlement since Monsanto was acquired by Bayer Pharmaceuticals in 2018 And it appears to be among the largest, if not the largest, PCB settlement stemming from a single site containing the pollutant. The terms of the settlement, including the dollar amount, are confidential. But in July, before the agreement, Germany-based Bayer informed its investors that it had set aside 530 million euros, or about $618 million, for Sky Valley settlements and litigation costs. Sky Valley students, staff and others ... described devastating diagnoses, including various cancers, brain damage, autoimmune diseases and miscarriages. Some, including children, reportedly died.