Maximum Contaminant Level


MCL – 0.010 mg/L or ppm

MCLG – zero

WHO Guideline – 0.010 mg/L

Arsenic is a naturally occurring substance in the earth’s crust and is typically found in groundwater sources. Wood preservatives, pesticides, industrial deposits, petroleum production, semiconductor manufacturing, and coal power plants have also been found to contribute to the presence of arsenic in water. Arsenic’s toxicity to humans is well known; the ingestion of as little as 100 mg can result in severe poisoning. The regular ingestion of low concentrations of arsenic can still lead to chronic symptoms over long periods of time. Arsenic has been linked to a number of cancers such as bladder, kidney, liver, lung, nasal passage, prostate, and skin cancer. In 2001, the EPA revised the MCL for arsenic from 50 ppb (parts per billion) to 10 ppb. The presence of elevated levels of arsenic (above 10 ppb) in groundwater is greater in the western United States than in other parts of the country. You can get information about the presence of arsenic in your drinking water from your local utility or state EPA. If you are a well-owner, you should periodically test for arsenic.

Treatments for removing arsenic include:

  • Iron oxide/ hydroxides
  • Activated alumina Iron based specialty media impregnated or coated with iron oxide/hydroxides
  • Distillation
  • Titanium oxy/hydroxide
  • Anion Exchange (strong base anion exchange resins)
  • Manganese greensand
  • Reverse osmosis (RO)