Arsenic in Drinking Water

HealthLinkBC File Number: 
49c
Last Updated: 
March 2021

Arsenic exists naturally in rocks in the earth’s crust. It also exists in some drinking water supplies and wells. Drinking water containing arsenic can have serious short term and long-term health effects.

How does arsenic get into drinking water?

Arsenic can get into drinking water from natural deposits or runoff from agriculture, mining and industrial processes.

In B.C., natural minerals are the most common sources of arsenic in drinking water.

The amount of arsenic in groundwater supplies like wells is usually higher than in surface water supplies such as lakes, streams and rivers.

What are the health effects of arsenic exposure?

Short to medium term exposure to very high levels of arsenic in drinking water over days or weeks can lead to arsenic poisoning.

Exposure to high levels of arsenic may cause stomach pain, vomiting, diarrhea and impaired nerve function. Impaired nerve function may cause a ‘pins and needles’ sensation or numbness and burning in hands and feet.

Arsenic can also cause skin changes, which include skin darkening as well as wart-like or corn-like growths. They mostly occur on the palms of the hands or bottoms of the feet. Other symptoms can include skin flushing and rashes.

As children tend to drink more water per unit of body weight than adults, they may have more exposure to arsenic in drinking water. As a result, children may be at greater risk of illness when higher levels of arsenic are present.

Long-term exposure to even relatively low amounts of arsenic in drinking water over years or decades can increase your risk of developing certain cancers, including:

  • Skin
  • Lung
  • Kidney
  • Bladder
  • Liver

The risk of cancer is the reason for developing the Canadian guideline for arsenic in drinking water. For more information on The Guidelines for Canadian Drinking Water Quality, see www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-guideline-technical-document-arsenic.html.

What amount of arsenic causes health effects?

Health Canada has set a Maximum Acceptable Concentration (MAC) of 10 micrograms per litre for arsenic in drinking water. This amount reports as 10 µg/L or as 0.010 milligrams per litre (mg/L).

This level was set based on how feasible it is to treat water to this level. This amount still imposes a higher risk than the level considered minor. For this reason, consider taking precautions with your drinking water even if the arsenic levels are slightly below the guideline. Data collected in Canada show that levels of arsenic in drinking water are usually less than 0.005 mg/L, but concentrations may be higher in some areas.

How do I know if there is arsenic in my drinking water?

Public drinking water systems are monitored regularly. In drinking water, arsenic has no odour or taste. Only a chemical test can detect the presence of arsenic.

Most private wells do not have routine testing for water quality or contaminants. Any well may contain arsenic or other contaminants. It is the well owner’s responsibility to test the water for arsenic. Test your private wells regularly for water quality.

For more information about private well water testing, see HealthLinkBC File #05b Well Water Testing.

Contact your local public health unit or environmental health officer for more information on the testing process in B.C.

What can I do if there is arsenic in my drinking water?

Water with arsenic is only a concern if you use it for drinking or preparing food.

Exposure through breathing and skin contact is not harmful. For example, there are no known health effects from hand washing, bathing or washing clothing in water with arsenic.

If an initial test detects arsenic, even at levels below the guideline, it is important to have a second test done to confirm the results. If your water tests positive for arsenic above the recommended level, use another source for drinking water or treat the current source.

Arsenic can be present in two forms: trivalent and pentavalent. Most treatment options are only effective for pentavalent arsenic, so you may need pre-treatment of the water.

There are several treatment devices and options to remove arsenic, including reverse osmosis filters, distillation and some specialized media filters. Chlorination and mechanical filters do not remove arsenic from water. Boiling water may increase the concentration of arsenic.

There is no regulatory control over treatment devices for private homes. Owners must be careful and select an appropriate treatment device. The device should be certified for the removal of arsenic. For a list of filters and systems certified for arsenic, see www.nsf.org/knowledge-library/faq-water.

Consider getting a certified treatment device from an organization that is Standards Council of Canada (SCC) accredited. The treatment device should meet the following standards:

  • NSF/ANSI Standard 62 on drinking water distillation and adsorption systems
  • Standard 58 on reverse osmosis drinking water treatment systems
  • Standard 53 on drinking water treatment units  with specific designation for the water quality parameters you are trying to remove (arsenic)

Certification assures that a device works as the manufacturer or distributor claims. Find an up-to-date list of accredited organizations by visiting the Standards Council of Canada at: www.scc.ca/en/accreditation/product-process-and-service-certification/directory-of-accredited-clients.

For more information on drinking water and treatment options, contact your local environmental health officer.

For More Information

For more information about arsenic and drinking water, see:

B.C. Ministry of Environment - Arsenic in Groundwater www2.gov.bc.ca/assets/gov/environment/air-land-water/water/water-wells/as020715_fin3.pdf (PDF 1002KB)

Health Canada - Arsenic in Drinking Water www.canada.ca/en/health-canada/services/healthy-living/your-health/environment/arsenic-drinking-water.html

Is it an emergency?

If you or someone in your care has chest pains, difficulty breathing, or severe bleeding, it could be a life-threatening emergency. Call 9-1-1 or the local emergency number immediately.
If you are concerned about a possible poisoning or exposure to a toxic substance, call Poison Control now at 1-800-567-8911.

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