Arsenic in Water

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Arsenic is an incredibly dangerous, cancerous, and poisonous substance that is occasionally found in trace amounts in water supplies.

This glossary will discuss arsenic in drinking water, including how arsenic gets into water, the dangers of drinking this contaminant, and how to protect your family from arsenic exposure.

❔ What is Arsenic?

💡 Arsenic is a chemical element and a natural component of the earth’s crust. This widely distributed metalloid is found on land, in the air, and in the water. Arsenic comes in three common forms: inorganic salt, organic salt, and gaseous form. It also comes in four common valence states: As(o), As(III), As(V) and arsine gas.

In Water As**When pH = 6-10

As(III), arsenite as H3AsO3 and H2AsO31-
As(V), arsenate as H2AsO41- and HAsO42-
SourcesSurface runoff and soil seepage
Leaching into natural water resources
Smelting ores or mining
Wood preservatives, industrial deposits, pesticides
Contaminant Levels (MCLs)
US EPA: 0.010 mg/L; 0 (MCGL)
WHO Guideline: 0.010 mg/L
EWG: 0.000004 mg/L
Potential Health RisksEndocrine disruptor, causes serious skin problems
Skin & lung cancer risks
Developmental effects in children
Increased risk in cardiovascular & nervous systems
TreatmentsReverse Osmosis
Anion Exchange
Manganese Greensand
Activated alumina
Oxidation & Filtration
Coagulation & Filtration

🩺 What are the Potential Health Effects of Arsenic?

According to the CDC, if you’re exposed to elevated levels of inorganic arsenic in your drinking water, you’re at risk of the following health effects:

  • Nausea
  • Diarrhea
  • Vomiting
  • Shock
  • Dehydration
  • Other effects of acute arsenic poisoning, such as muscle cramping, and numbness and tingling of the extremities

Being exposed to high levels of inorganic arsenic in the long term is associated with the following medical conditions:

  • High blood pressure
  • Developmental effects (in children)
  • Increased risk of diabetes
  • Problems with memory and cognitive development
  • Pulmonary and cardiovascular disease
  • Adverse pregnancy outcomes and infant mortality
  • Skin & lung cancer risks
  • Skin disorders
Woman not feeling well after drinking water with arsenic

According to the World Health Organization (WHO), long-term exposure to arsenic in water typically first presents symptoms in the skin, such as hard patches on the hands and feet, skin lesions, and pigmentation changes. These symptoms may eventually lead to skin cancer. Lung cancer and bladder cancer are two other cancers commonly associated with drinking water with high arsenic levels.

Exposure to arsenic causes different symptoms in different populations, age groups, and geographical locations, which makes it difficult to properly assess the potential risk of arsenic or define the disease caused by this heavy metal.

☠️ Excessive arsenic exposure over a short or long period of time can cause death, making arsenic one of the most dangerous drinking water contaminants.

🚰 How Does Arsenic Get Into Drinking Water?

Because it is so widely distributed and naturally found in the environment, arsenic gets into water through surface runoff and soil seepage.

Most arsenic in drinking water is dissolved into water that flows through rock formations containing this metalloid. Water then carries arsenic into streams, rivers, and underground aquifers that are used as drinking water supplies. Arsenic tends to be a greater risk to private well owners than customers of public water systems because well water is often drawn from deep underground.

Some human activities cause arsenic to dissolve into natural water sources. Smelting ores or mining are two activities that release arsenic into the environment.

Several decades ago, arsenic was commonly used in agricultural chemical products like ant poisons, rat poisons, and weed killers, as well as commercial wood preservatives. Arsenic was banned as a wood preservative and agricultural compound by the Environmental Protection Agency for most uses in the 1908s, but it still exists in old agricultural soils and some treated woods today.

Water contaminated with arsenic

📉 Do Water Treatment Facilities Monitor Levels of Arsenic in Drinking Water?

Yes, water treatment facilities are legally obliged to monitor their arsenic levels and prevent arsenic contamination in drinking water.

📌 The Environmental Protection Agency (EPA) has a Maximum Contaminant Level (MCL) of 0.01 mg/l or 10 parts per billion (PPB). This MCL was revised from the original MCL of 50 PPB in 2001.

All public water systems in the US must adhere to the EPA’s Maximum Contaminant Levels for various listed contaminants, including arsenic. Facilities must monitor their drinking water quality and provide the EPA with records to prove that their water is safe to drink.

However, because arsenic is particularly difficult to remove from drinking water, the EPA’s MCL for this heavy metal is designated as provisional.

This means that, if resources are available, public water systems should make every effort to reduce arsenic exceeding the EPA MCL in their water according to the Drinking Water Standard.

On such occasions, states may develop overall strategies to progressively reduce arsenic exposure in water, taking local circumstances into account.

🔎 How Can I Tell if Arsenic is in My Drinking Water?

Arsenic has no taste or odor in water, so there’s no way to know that it’s in your drinking water by drinking or smelling it. The only way to tell if arsenic is in your water is to review testing data.

A simple way to learn about your water’s arsenic concentrations is to check your annual Water Quality Report. This report is made available to all customers of community water systems, either via email or post. Contact your local water treatment facility or search for your report online.

Owners of drinking water wells will need to test for arsenic in their well water. Private wells aren’t regulated by the EPA, and it’s the well owner’s responsibility to test for certain contaminants and treat their water if necessary. If you own a private well, we recommend using a laboratory test to get an accurate reading of your water’s arsenic concentrations.

Well owners can contact their local health department to discuss the local geology and arrange a geological survey. You could also speak to other owners of private wells in your region to discuss local contamination and learn your risk of well water arsenic exposure.

Arsenic in groundwater map
Source: United States Geological Survey

👩🏽‍⚕️ How Can I Protect My Family from Arsenic in Drinking Water?

Exploring arsenic removal water treatment methods is the best way to protect your family from this metal.

Not all water filters are designed to remove arsenic. Standard activated carbon filters won’t work against heavy metals like arsenic. Some of the most capable water filtration methods to reduce arsenic levels are:

Activated Alumina

Activated alumina filters use adsorption to grab onto arsenic particles and bind them to their media. These filters can remove more than 95% arsenic from drinking water, greatly reducing arsenic exposures. Activated alumina can also reduce fluoride.

Reverse Osmosis

Reverse osmosis uses several stages of filtration and a semi-permeable membrane to virtually eliminate arsenic concentrations in tap water. Up to 95% of arsenic is filtered out by an RO membrane. Reverse osmosis can also remove or reduce bacteria, fluoride, pesticides, VOCs, and other contaminants that are known to have public health risks.

reverse osmosis system

Check out the Top 6 Reverse Osmosis Systems Worth Buying this Year 👈

Oxidation & Filtration

Oxidation involves oxidizing certain contaminants, then filtering them out of water. In this two-step process, water is oxidized with chemicals like potassium permanganate, before flowing through a media made from birm or a similar material. This process is highly effective, but only if water has a relatively low pH and an iron-to-arsenic ratio of at least 20:1.

Coagulation & Filtration

Coagulation and filtration involves using a coagulant to bind to contaminants like arsenic, producing large particles that can be easily filtered out of the water. Common coagulants used for arsenic removal are ferric sulfate or chloride.


A distiller boils water until it evaporates, then sends water down a cooling corridor to condense in a separate container. Any impurities and contaminants that have higher boiling points than water (including arsenic) are left behind in the boiling chamber, limiting consumption of arsenic in drinking water.

Imber isla distiller on countertop table

👉 Here are our 10 Recommended Water Distillers for Arsenic Removal

Anion Exchange

Anion exchange attracts arsenic particles in water to a resin bed, then releases equal numbers of chloride ions into the water to balance the charge. Chloride is an ideal replacement for arsenic because it doesn’t have any known adverse health effects in water. Anion exchange is best suited to removing arsenic V.

⚠️ How Else Can I Be Exposed to Arsenic?

Aside from drinking water contamination, other forms of arsenic exposure are:

  • Using contaminated water to prepare food
  • Consuming foods that have been watered or treated with contaminated water
  • Eating foods or drinking beverages contaminated with arsenic, such as rice and some fruit juices
  • Smoking tobacco
  • Using wood items that have been preserved with arsenic compounds
  • Having contact with contaminated dust or soil

The biggest current exposure to high arsenic levels is drinking water. You can reduce exposure to arsenic by getting your water tested and treated, limiting your intake of foods that may contain arsenic, and throwing out any arsenic-treated wood products in your home.

📝 Where Can I Get More Information?

Find more information about arsenic pollution and contamination in water, and the health risks of short-term and chronic exposure to arsenic, in the below sources.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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