ContaminantIn Water AsMaximum 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)
MCLG** = zero
WHO† Guideline = 0.010 mg/L

*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

Sources of ContaminantLeaching from natural deposits
Wood preservatives, pesticides, industrial deposits
Petroleum production
Semiconductor manufacture
Coal power plants
Potential Health EffectsSerious skin problems, endocrine disruptor
Causes Cancer –skin, bladder, lung, kidney, liver, prostate
Harms cardiovascular & nervous systems
Treatment Methods
Iron oxide/ hydroxides
Activated alumina
Iron based specialty media impregnated or coated with iron oxide/hydroxides
Titanium oxy/hydroxide
Anion Exchange (strong base anion exchange resins)
Manganese greensand
Reverse osmosis (RO)


In the United States the EPA, under the authority of the Safe Drinking Water Act (SDWA), has set the Maximum Contaminant Level Goal (MCLG) for arsenic at zero. This is the health-based goal at which no known or anticipated adverse effects on human health occur and for which an adequate margin of safety exists. The US EPA has set this level of protection based on the best available science to prevent potential health problems. Based on the MCLG, the US EPA has set an enforceable regulation for arsenic, the Maximum Contaminant Level (MCL), at 0.010 mg/L (10 ppb). MCLs are set as close to the MCLG as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies. In Canada, the regulated Maximum Acceptable Concentration (MAC) for arsenic in drinking water is also set at 0.010 mg/L.

This information is sourced from the Water Quality Association (WQA) of which WCC is a proud member. Complete reports are available via the links below. This material is shared with the objective of offering comprehensive, professional insights into relevant water quality standards and guidelines.

Arsenic Fact Sheet – Downloadable PDF