PPG Industries' chlorine plant in Marshall County can discharge more than 10 times the mercury it currently emits under a new permit approved by state regulators.
PPG says the permit raises the cap on average monthly mercury discharges from the Natrium plant's main outlet from 12 parts per trillion to 143 parts per trillion.
It also gives PPG mixing zones for two pipes that discharge mercury. That allows the plant to meet water quality limits farther downstream instead of at the end of its outlet pipes.
The Department of Environmental Protection approved the permit earlier this month.
Mercury is a neurotoxin that accumulates in fish. Ingesting mercury can cause nerve and brain damage to pregnant women, women of childbearing age and young children. Mercury also can lead to kidney damage in children.