A major survey found that the lead in the water supply in major Canadian cities exceeds the safety level of hundreds of thousands of households.
Some areas showed lead levels higher than those in the US city of Flint, Michigan, during its 2015 water crisis.
One-third of the 12,000 samples collected between 2014 and 2018 exceeded national safety guidelines.
Canada has the third-largest per capita freshwater reserve in the world.
Lead pollution is associated with low IQ in children and high blood pressure and heart disease.