What is arsenic - and how are we exposed to it?

Arsenic is a substance found in rocks and soil that occurs naturally. You can be exposed to many forms of it. Arsenic is grouped into 2 categories:

  • organic (meaning that it is combined with carbon)
  • inorganic (meaning it is not combined with carbon)

Organic arsenic, such as that found in fish, is considered safe. Inorganic arsenic is not.

Arsenic in water

Canadians may consume arsenic from their municipal drinking water or private well water. Usually these levels are very low, but some areas of Canada have higher levels of arsenic in drinking water. Arsenic gets into drinking water either from natural sources, such as rocks and soil, or by contamination from certain types of mining, smelting or manufacturing plants.

Showering, bathing, swimming and other activities involving water are not believed to be harmful because arsenic is not absorbed through the skin.

Other ways you might be exposed
You may also be exposed to arsenic from some wood preservatives or by breathing in pollution from certain types of mining, smelting or manufacturing plants that release arsenic into the air. This exposure is usually at lower levels than drinking water that contains arsenic.
Person testing tap water in their home for arsenic

Arsenic and cancer

The International Agency for Research on Cancer (IARC) classifies arsenic in drinking water as a known cause of cancer. Drinking water that is contaminated with a high level of arsenic over a long period of time is known to raise the risk of several types of cancer, including lung, bladder and certain types of skin cancers.
Person testing tap water in their home for arsenic

The #1 thing to do if you have a private well

If you have a private well, test it for arsenic. The ministry of health or ministry of environment in your province or territory can tell you how to do this. If your arsenic level is above 0.01 milligrams per litre (0.01 mg/L) or 10 micrograms per litre (10 µg/L), stop drinking from the well and take steps to reduce the level of arsenic. You can get information about reducing the arsenic levels in residential water treatment systems from Health Canada.

If your water is contaminated with arsenic, you may have to use bottled water until the arsenic problem is fixed.

Learn more about bottled water safety.

Person filling up a glass with tap water

Should I drink bottled water instead of tap water?

The Canadian Cancer Society does not recommend using bottled water over tap water in Canada unless your tap water contains high levels of arsenic. There is no evidence that bottled water is safer than tap water that is treated by a municipality. In fact, current regulations for tap water are based on scientific information that is newer than the information used to regulate bottled water.
Person filling up a glass with tap water