Arsenic in Drinking Water

Arsenic is potentially a very harmful, sometimes fatal, contaminant that can cause damage with immediate consumption or over the long term. Across the U.S., more than 700 community water treatment facilities are not compliant with the regulations for arsenic reduction. There are several types of water treatment systems that can effectively reduce arsenic levels in drinking water. These include: reverse osmosis systems, specialty media, and distillation systems. You can choose from numerous tested and certified water treatment products available to reduce arsenic in drinking water.

Contaminant  In Water As Maximum Contaminant Level


Arsenic (As)

When pH = 6-10

As(III), arsenite as H3AsO3 and H2AsO31-

As(V), arsenate as H2AsO41- and HAsO42-


MCL* = 0.010 mg/L (or ppm)

MCGL** = zero

WHO† Guideline = 0.010 mg/L

Sources of Contaminant

  • Leaching from natural deposits
  • Wood preservatives, pesticides, industrial deposits
  • Petroleum production
  • Semiconductor manufacture
  • Coal power plants

Potential Health Effects

  • Serious skin problems, endocrine disruptor
  • Causes cancer - skin, bladder, lung, kidney, liver, prostate
  • Harms cardiovascular & nervous systems

Treatment Methods

Point-of-Entry (POE)

Point-of-Use (POU)


  • 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)

*Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

**Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.

WHO - World Health Organization


Click here to open WQA's Technical Fact Sheet on Arsenic.

Click here to access all of WQA's Technical Fact Sheets.

Click here for data on arsenic occurrence from the U.S. Geological Survey.