The chemical designation SO4 refers to sulfate. Sulfate is a molecule that combines one atom of sulfur with four molecules of oxygen. While sulfate occurs naturally in water, humans and animals should not consume large amounts.
Sulfate occurs in sulfite ores, shales and industrial waste and enters the water table from these sources. Water with a high proportion of sulfate, typically over 250 milligrams per liter, often has a bad taste and can cause diarrhea in humans or animals who are sensitive to sulfate. High sulfate levels in water are also corrosive and can damage copper and other metal pipes.