Arsenic In Water (Everything You Need To Know)

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Arsenic In Water

Arsenic in drinking water is toxic even at low levels and is a known carcinogen. But we also know that Arsenic is one of the most common contaminants found in tap water. A recent USGS study detected arsenic in nearly half of the wells sampled across the U.S. at concentrations of 1 µg/L or higher.

Fear not! This guide will cover everything you need to know to reduce your exposure, including how to test for arsenic and how to effectively remove it from your water supply.

Key Takeaways:

  • The main source of arsenic in drinking water is rock and sediment components that naturally release into groundwater. It can also enter the water supply from its use in mining activities, wood preservatives, pesticides, and animal feed.
  • The EPA maximum contaminant level for arsenic in water is 10 ppb to protect children and adults from the negative effects of acute exposure to arsenic.
  • Since you cannot smell, taste, or see arsenic in your water, the only method to detect arsenic is to use a certified laboratory test that screens for arsenic contamination.
  • The most effective method to remove arsenic from drinking water is reverse osmosis (RO). The RO process forces water through a semipermeable membrane where arsenic and other contaminants are rejected and only pure H2O molecules pass through.

What Exactly Is Arsenic?

Arsenic is a naturally occurring chemical element (As) in Earth’s crust. The substance can be classified as organic (contains carbon) and inorganic arsenic (doesn’t contain carbon), with inorganic arsenic being the most problematic to human health. This is an important distinction because organic arsenic is relatively harmless whereas inorganic is highly toxic.

Since arsenic is a metallic element, it is classified as a heavy metal or metalloid. Metalloids like arsenic can lead to toxicity at even low exposure levels.

Arsenic can pollute foods grown in soil and in water such as rice. However, the most alarming arsenic levels are found in drinking water.

The World Health Organization (WHO) lists arsenic as one of the 10 chemicals of major public health concern. In the United States, the US Geological Survey (USGS) works to constantly identify, measure, and report arsenic contamination risks.

What Are The Sources Of Arsenic In Water?

Since arsenic is a naturally occurring element, most arsenic concentrations in drinking water come from groundwater sources. This can cause arsenic to contaminate our drinking water supply. Levels of arsenic in groundwater depend on a few factors like rock type, pH, irrigation practices, climate, and groundwater age.

Arsenic in drinking water is a problematic containment in over 100 countries. In the US, the highest concentrations of arsenic are in the southwest, where 16% of drinking water wells sampled exceeded the EPA maximum contaminant level. The USGS developed a map of arsenic concentrations throughout the country based on well water data.

Arsenic Concentration Map
USGS Arsenic Concentration Map

Public water systems primarily use surface and rainwater, so arsenic isn’t as much of a concern. Well water on the other hand is much more likely to come into contact with arsenic.

A 2017 research study in the US estimated 2 million people were using wells with arsenic levels higher than the standard set by the Environmental Protection Agency (EPA).

Though the practice was phased out in 2003, arsenic-treated wood is a contributor to arsenic exposure, especially in children. Wooden decks and playsets made from this wood increase the likelihood of absorption through the skin and ingesting arsenic through hand-to-mouth behavior. Also, over time, runoff from treated wood can leach into the surrounding area.

What Is The Safe Level For Arsenic In Drinking Water?

In 2001, the EPA lowered the arsenic maximum containment level (MCL) from 50 ppb to 10 ppb. The EPA’s limit of 10 ppb (0.01 mg/L) is the level by which all public water suppliers must abide. Of course, though, private wells are not regulated by the EPA.

The EPA’s maximum containment level goal (MCLG) for arsenic is zero. The MCLG is the level at which there are no associated health effects from a lifetime of exposure, including in vulnerable populations like children and the elderly.

Two states, New Jersey and New Hampshire, have a lower threshold for arsenic levels in drinking water at 5 ppb. The United States Department of Agriculture (USDA) funded research that led to this change in New Hampshire. The department also monitors arsenic levels in water sources and helps ensure safe drinking water standards nationwide.

The Food and Drug Administration (FDA) adopted the EPA’s MCL of 10 ppb for arsenic in bottled water.

What Are The Side Effects Of Drinking Arsenic?

Drinking Water Cup

Arsenic is a known carcinogen and containment that can lead to detrimental health effects if exposed to high levels or in smaller amounts over an extended period.

Organic arsenic has much less serious health effects whereas inorganic arsenic is highly toxic to humans. There are both short-term and long-term health effects from arsenic exposure.

The National Institute of Health (NIH) continues to research the effects of acute and long-term arsenic exposure at the population level. The Centers for Disease Control and Prevention (CDC) also collects biomonitoring data regarding arsenic in drinking water.

Long-term exposure can lead to:

  • skin lesions
  • hyperpigmentation
  • hardening of palms and soles (hyperkeratosis)
  • cancer (skin, bladder, lung, kidney, liver, nasal passages)
  • developmental effects
  • diabetes
  • pulmonary disease
  • cardiovascular disease

Short Term (acute) exposure may lead to:

  • vomiting
  • abdominal pain
  • diarrhea
  • numbness and tingling of the extremities
  • muscle cramping
  • death in rare cases

There is ongoing research that is investigating arsenic exposure in relation to cancer risk and other downstream health effects of arsenic exposure. Research indicates that early childhood exposure to arsenic can increase cancer risk later in life. The lung cancer risks are especially high for smokers who also ingest arsenic through their drinking water.

Much of this health data was established after over 19 million people in Bangladesh were consistently exposed to arsenic in drinking water from wells in the region. This was a horrific public health event and thousands of Bengali people are still suffering from the side effects, including cancer, today.

Because such serious health complications are associated with drinking arsenic, public health initiatives, and policies should encourage limiting as many arsenic exposures as possible.

How To Test For Arsenic In Well Water?

Arsenic is tasteless, odorless, and colorless, so it’s imperative to test water that is suspected of containing arsenic. If your drinking water comes from a private well, make sure your well is tested for arsenic at least once per year.

Since there is not really a good DIY method to test for arsenic at home, the recommended way is to use a laboratory test kit.

Certified Lab Test Kit

You can purchase a certified well water test kit where you collect a sample of your well water, send it off for testing, and receive a detailed analysis of your well water.

I recommend the Freshnss Labs Well Water Test Kit which screens for not only arsenic but also dozens of other harmful contaminants. The water sample is then analyzed in a certified lab by well water specialists. Within 3 business days, you will get a report with the exact arsenic concentrations, any health or plumbing alerts, and

If test results indicate arsenic concentrations higher than the EPA limit of 10 ppb, you should stop drinking it immediately and find a way to reduce arsenic in your drinking water supply as soon as possible. However, this water is fine to use for bathing, brushing teeth, and washing dishes and clothes, as long as it’s under 500 ppb.

Laboratory Water Test Kit

Tests for arsenic, lead, copper, and other harmful contaminants
Analyzed in a certified laboratory
Includes detailed report with EPA benchmarking and safety concerns

Since arsenic occurs naturally, it is unattainable to remove it from the water supply completely. This is why we must test for and monitor this contaminant in our drinking water.

How To Remove Arsenic From Well Water

There are a few treatment methods for arsenic removal in water systems. Reverse osmosis and ion exchange systems can be employed as whole-house filtration systems or as point-of-use filters.

Reverse Osmosis

Reverse osmosis (RO) is a popular and effective treatment to filter out contaminants from drinking water and is capable of removing over 99% of arsenic in drinking water. This technology works by using pressure to force water through a semipermeable membrane, leaving behind contaminants and allowing only pure H2O molecules to pass through.

The main disadvantage of RO systems is water wastage. Also because RO is so effective, it lowers healthy mineral content in water and lowers the pH, making it more acidic.

Ion exchange

Ion exchange is when unfavorable ions are traded for favorable ones through an ion exchange resin. Cations are positively charged ions that remove certain contaminants whereas anions are negatively charged ions that remove others. For arsenic, anion exchange is needed. Arsenic is removed when it passes through the resin and is replaced by a non-toxic substance from the resin.

Ion exchange water softeners can also help reduce small amounts of iron and manganese, and remove hard water minerals.


Distillation consists of boiling water at such a high temperature the water turns to vapor, the vapor is collected, and then it is chilled to turn back into water with the contaminants left behind at the boiling stage. The final product is free from all contaminants, including arsenic.

Frequently Asked Questions

Is it bad to shower in arsenic water?

As long as the level of arsenic in the water supply is under 500 ppb (0.5 mg/L), the water is fine to shower with. A very small amount of arsenic is absorbed through the skin.

Can boiling water remove arsenic?

No, since arsenic is a semi-metallic element, it has a very high boiling point. Boiling water with arsenic in it will only remove the water molecules and leave behind a liquid that has higher arsenic concentrations in drinking water.

Is arsenic in bottled water?

There may be small amounts of arsenic in bottled water since it is regulated by the FDA which adheres to the EPA’s maximum containment level of 10 ppb.

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