The Milwaukee Metropolitan Sewerage District has issued warning letters to a St. Francis industrial plant which discharges mercury in excess of legally-permitted limits. Mid-America Steel Drum plant has paid no fines and has reportedly continued the actions for at least four years. An investigative report by the Milwaukee Journal-Sentinel revealed the problem when local officials weren’t aware of the levels. The mercury discharges coming from the plant where industrial barrels are refurbished are not considered a health risk, but mercury can build up in the environment and cause health problems over time.