Quote from Steve MacLellan on March 8, 2025, 7:44 pm

At the levels of uranium detected in some bedrock aquifers in Nova Scotia (>20 μg/L), long-term ingestion of well water from these aquifers can cause kidney disease. About 42% of Nova Scotians are supplied by private wells and these water sources are not monitored or regulated with respect to water quality. Effective communication of the health risks associated with the ingestion of uranium in drinking water from private wells is critical for reducing uranium exposure and protecting human health.

The relationship between uranium in well water, bedrock lithogeochemistry, and aquifer geochemistry was investigated to develop a new uranium in well water risk map, which will be used to communicate risk to well owners and inform groundwater supply development. Available uranium in well water data were compiled for bedrock wells and classified by the source aquifer (i.e. bedrock unit). The frequency of uranium in well water samples exceeding Health Canada’s maximum acceptable concentration (MAC) of 20 μg/L was tabulated for the province’s five major bedrock groundwater regions and over 65 individual bedrock units.

Bedrock geology was shown to be the most important provincial-scale control on the distribution of uranium concentrations in well water. Both the highest concentrations (i.e. >100 μg/L) and exceedance rates of the Health Canada MAC were associated with the plutonic (30.3%) and sedimentary (6.3%) groundwater regions of Nova Scotia, largely due to the higher content of uranium in aquifer materials. Well water samples from the South Mountain Batholith and Black Brook granitic suite plutonic aquifers, and from the Pictou Group sedimentary bedrock aquifers, were associated with the highest frequency of uranium exceeding the Health Canada MAC for uranium in drinking water.

The study highlighted other controls on uranium occurrence and mobility, including the influence of pH and total alkalinity (as CaCO3). It was generally observed that higher levels of uranium in groundwater were associated with alkaline pH and higher groundwater alkalinity.

Based on the relationship between uranium in well water and bedrock geology, a uranium in well water risk map was developed. Demographic analyses show that approximately 26,445 private wells are in high risk areas (>15% exceedance rate), and the overall percentage of private well water exceeding safe drinking water limits in Nova Scotia may be as high as 6.5% (~25,100 persons). |Read the 33 page report|