Arsenic is naturally occurring in Nova Scotia groundwater and exposure to arsenic in well water is associated with a range of adverse health effects, including skin and internal cancers. The Health Canada Maximum Acceptable Concentration for arsenic in well water is 0.01 mg/L.
Concerns over arsenic in well water first emerged in Nova Scotia in 1976 when a patient from Waverley, a former gold-producing area, was diagnosed with symptoms of chronic arsenic intoxication. The detection of elevated levels of arsenic in the patient's water well led to the formation of a provincial task force that investigated the occurrence of arsenic in water wells in Nova Scotia. Some of the key findings of the task force were reported in an Interim Task Force Report. A critical finding of the task force was that elevated arsenic in well water can also occur in areas not close to former gold-producing areas.
A review of historical research related to arsenic in Nova Scotia well water was published in 2016 by the Nova Scotia Department of Natural Resources as an Open File Report. The review found that bedrock geology was the dominant control on arsenic levels in water wells. A second Open File Report was produced to develop a province-wide arsenic in well water risk map based on bedrock geology. The purpose of the risk map is to communicate the risk of arsenic contamination in drinking water to private well users and to prevent disease. The risk map is available as a web map application and divides the province into low-, medium- and high-risk zones.
About 42% of Nova Scotians rely on private wells, and it is estimated that 1 in 5 of these private well users may have unsafe levels of arsenic in their untreated water. Testing your well water is the only way to find out whether arsenic is a concern in your well so it is important to test your water no matter where you live. Well water should be tested every two years for chemicals, such as arsenic, to ensure that it is safe for you and your family to drink. More information on arsenic and well testing and treatment for private well owners can be found here.