A: Sulfur is not regulated as a primary drinking-water contaminant, so there is no official level of sulfur that represents a threshold between healthy and unhealthy concentrations. Sulfur is required by all living things as part of their normal metabolism, so the body needs a certain amount of sulfur just to live. Any adverse effects of sulfur in drinking water appear to be related to the following issues:
1. Hydrogen sulfide (H2S) is sometimes present in well water. A few tenths of a milligram of hydrogen sulfide per liter can cause drinking water to have a rotten-egg odor. A high content of Hydrogen Sulfide gas may have health consequences and it it recommended to have a water test to determine the amount of this gas present in your water. Hydrogen sulfide gas is flammable in high concentrations so, knowing the amount in your water is a recommended safety precaution. There is no government agency regulating the amount of hydrogen sulfide gas in drinking water through MCL's because it is not an issue for municipal water treatment plants and is generally driven off through the digestion process if present.
2. High concentrations of sulfate (SO4--) may be associated with diarrhea or intestinal gas. For this reason, and for aesthetic reasons related to taste and odor, the Environmental Protection Agency currently has a secondary drinking-water standard of 250 milligrams per liter (mg/L) sulfate.
3. Some waters with elevated sulfate also tend to have low pH (as in acid mine drainage). The pH of water is usually checked when well water is tested. A pH in the range of 7 - 7.8 is most desirable by most consumers.