The substances are also known as PFAS and are sometimes called “forever chemicals,” and they are linked to human health problems. Elevated levels of the PFAS were detected in fish samples from the Police Athletic League Ponds and Fish Brook in Fairfield, Messalonskee Stream in Oakland and Waterville, Durepo Reservoir and Limestone Stream in Limestone, sections of Mousam River and Estes Pond in Sanford, Unity Pond in Unity, and the lower Presumpscot River in Westbrook.