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April 2007 Drinking Water Information About arsenic in drinking water What is Arsenic? What are the sources of Arsenic contamination in water? Arsenic is a naturally occurring element found in the earth’s crust, and is classified as a semi- As a natural component of rock and soil, arsenic metal or “metalloid.” Arsenic can enter lakes, can be introduced into groundwater through the rivers or groundwater when mineral deposits or natural dissolution of arsenic containing rocks containing arsenic break down and are minerals. As a result, drinking-water systems dissolved in water. that receive water from underground sources may draw water containing small amounts of Arsenic is common in both surface water and arsenic. groundwater aquifers. Dissolved in water, arsenic has no colour, taste, or odour and can Arsenic concentrations are generally higher in only be detected by chemical analysis. Arsenic is groundwater than in surface water sources (e.g. normally found combined with other elements to lakes and rivers) and higher levels of arsenic can form both inorganic and organic compounds. be found in groundwater sources in the Canadian Shield. How might I be exposed to Arsenic? Does Ontario have a Drinking-Water Quality Inorganic arsenic occurs in the environment in Standard for Arsenic? several forms. In natural waters and therefore drinking water, it is found mostly as trivalent Yes. The Ontario Drinking Water Quality arsenite [As(III)] or pentavalent arsenate Standard (ODWQS) for arsenic is 0.025 mg/L [As(V)]. Organic arsenic is abundant in seafood (25 ug/L). In May 2006, Health Canada lowered and much less harmful to health as it is readily the CDWQG to 10 ug/L based on recent eliminated by the body. information on the carcinogenicity of ingested arsenic. Ontario is currently reviewing the The most common route for general public adoption of a more stringent ODWQS of 10 ug/L exposure to total arsenic is through food for arsenic. followed by drinking water containing arsenic. Absorption of arsenic through skin is minimal Is my drinking water monitored for Arsenic? and thus hand-washing, bathing, or doing laundry, etc. with water containing arsenic does The Ontario Drinking-Water Systems Regulation not pose a significant human health risk. 170/03 requires that regulated drinking-water systems (municipal and non-municipal year- round residential drinking-water systems and all PIBS 6275e other systems serving designated facilities i.e. http://www.ene.gov.on.ca/en/water/sdwa/license school, children and youth facility, health-care dlabs.php facility, social care facility) monitor for arsenic. Frequency may vary from once per year to once For individual, private residences, there are two every five years based on the category of the possible points where treatment can be carried drinking-water system and whether the source is out; point-of-entry (POE) to treat all of the water surface water or groundwater. entering a household or point-of-use (POU) to treat the water from a single tap used for the The Ministry of the Environment also monitors purposes of drinking or cooking. Typical prices arsenic at a number of municipal drinking-water for POU devices range from a one-time unit cost systems through the Drinking Water Surveillance of $100 – $400 plus the cost of replacing the Program (DWSP). filters, which ranges from $100 - $200 per year, depending on the device as well as household How does arsenic affect my health? use. Maximum acceptable concentrations are very In small communal systems, the two devices conservative and the limits are set very low. most suitable for individual household water Exposure to drinking water every day for your supplies are based on reverse osmosis and lifetime at or below the limit is unlikely to cause adsorption/ion exchange. While both efficiently illness. The International Agency for Research remove arsenic from water, the choice of an on Cancer considers arsenic to be a human appropriate system depends on the carcinogen. Health effects of arsenic vary characteristics of the source water. depending on the compound. Inorganic arsenic compounds are generally associated with Residents living in areas with elevated levels of arsenic’s toxic and carcinogenic effects. arsenic should consult a water treatment specialist before purchasing a treatment unit to Consuming water with concentrations of arsenic determine which system is best suited to their well above the limit for long periods of time, may needs. increase the risk of cancer of the skin, lungs, urinary bladder, and kidney, as well as other skin If you would like other guides and fact sheets changes such as pigmentation changes and related to drinking water, please contact the thickening (hyperkeratosis). Short-term Ministry of the Environment’s Public Information exposure (days/weeks) to very high levels of Centre at: 1-800-565-4923 or visit the Ministry of arsenic, well above the limit, can result in the Environment’s website at: abdominal and muscular pain, diarrhea and www.ene.gov.on.ca vomiting, skin rash and numbness. References: How is arsenic removed from drinking water? Health Canada (2006) Guidelines for Canadian There are several technologies available to Drinking Water Quality communal drinking-water systems for the http://www.hc-sc.gc.ca/ewh-semt/pubs/water- removal of arsenic from drinking water, including eau/doc_sup-appui/index_e.html activated alumina absorption, conventional treatment (coagulation/filtration), lime softening, Health Canada (2006) Arsenic ion exchange and manganese greensand http://www.hc-sc.gc.ca/ewh-semt/pubs/water- filtration. eau/doc_sup-appui/arsenic/index_e.html If your residence relies on water from a private well as a source of drinking water, the first step you should take is to have your water tested for arsenic. This testing can be done by any private laboratory at a cost ranging from $25 to $50 per sample. A list of the laboratories in your area can be found on the Ministry of the Environment web site at: