Mercury is released to surface waters from rocks and soils and from industrial activities and wastewater treatment facilities. An indirect but significant source is the deposition of mercury emissions from power plants in rain to water surfaces and to soils. When mercury enters water, biological processes transform it to methylmercury, which is highly toxic and builds up in fish and animals that eat fish. For this reason, EPA sets a maximum contaminant level for mercury in drinking water and works with the states to issue consumption advisories. These advisories may be directed at the general population or at sensitive groups such as pregnant women, nursing mothers, and their children.

Recommended EPA Web pages

• Mercury: Environmental Effects
  Provides information about environmental effects of mercury.
• Mercury: Human Exposure
  Provides information about human exposure to mercury.
• Fish Advisories
  These advisories inform the public that high concentrations of chemical contaminants have been found in local fish and wildlife.

Drinking Water
Drinking Water System, Protection

Ground Water
Discharge, Hydrogeology, Protection, Runoff, Wells

Storm Water
Combined Sewer Overflows (CSOs), Industrial Storm Water, Permits, Sanitary Sewer Overflows (SSOs), Wet Weather Programs

Surface Water
Dumping, Marine Debris

Wastewater
Animal Feeding Operations (AFOs), Biosolids, Discharges, Effluent Guidelines, Effluents, Industrial Wastewater, Municipal Wastewater Treatment, National Pollutant Discharge Elimination System (NPDES), Permits, Publicly Owned Treatment Works (POTWs), Standards, Treatment, Wastewater Systems

Water Infrastructure

Water Pollution
Community Involvement, Cost Benefit Analysis, Data, Nonpoint Sources, Point Sources, Reporting, Testing, Transboundary Pollution

Water Pollution Control
Pretreatment, Remediation, Trading, Wastewater Treatment

Water Pollution Effects
Economic Effects, Environmental Effects, Health Effects

Water Pollution Legal Aspects
Compliance, Enforcement, Guidance, Legislation, Permits, Public Comment, Regulations, Standards, Total Maximum Daily Loads (TMDLs)

Water Quality Monitoring
Bioassessment, Criteria, Health Advisories, Models, Standards