Division of Environmental and Community Health

Maine Center for Disease Control & Prevention

A Division of the Maine Department of Health and Human Services

DHHSMeCDCEnvironmental and Community HealthDrinking WaterDrinking Water Consumers Arsenic

Arsenic in Drinking Water

Arsenic is a semi-metal element in the periodic table. It is odorless and tasteless. It enters drinking water supplies from natural deposits in the earth or from agricultural and industrial practices. The health effects of Arsenic exposure can be severe, and include stomach pain, nausea, diarrhea and vomiting; thickening and discoloration of the skin; numbness in hands and feet; partial paralysis; and blindness. Prolonged exposure or exposure to large doses can be fatal. Arsenic has also been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver, and prostate.

The Environmental Protection Agency (EPA) has established a Maximum Contaminant Level (MCL) for arsenic in drinking water at 10 ppb (parts per billion/micrograms per liter, µg/L).


Treatment Technologies for Arsenic

EPA identifies the following treatment technologies as Best Available Technologies for removing Arsenic from drinking water:

  • Anionic Exchange
  • Reverse Osmosis
  • Iron Oxide Filters
  • Activated Alumina
  • Modified Coagulation/Filtration
  • Modified Lime Softening
  • Electrodialysis Reversal

The Drinking Water Program recommends that water systems and homeowners seek advice from a water treatment professional to determine the most effective treatment based on the characteristics of their specific water system. Public water systems should contact their Public Water System Inspector for approval before installing or making changes to any treatment in their system.

Arsenic Treatment Checklist

  • Have I had my water tested at a state certified laboratory?
  • Have I done a retest to confirm the results?
  • Have I also tested for iron and manganese? They are very common in Maine and can foul RO systems. They may also require removal.
  • Have I contacted a water treatment professional to aid in the analysis and the selection of an adequate solution?
  • Do I need whole house treatment or is point of use treatment adequate?
  • Have I checked references (other homes that he/she has worked in) for the water treatment professional I've selected?
  • Are there other problems with my drinking water system that should also be addressed?

Additional Resources

Updated 2/10/2023