Nothing better symbolizes public health in a community than the availability of clean and safe water. However, recent water quality tests in Newfoundland and Labrador found high levels of disinfection byproducts in the drinking water of 119 communities.
Unfortunately, these are not new concerns. In 1999, CBC first drew attention to the issue of chlorine and disinfection by-products in municipal drinking water. Since then, the number of affected communities has doubled.
Chlorine has been used to disinfect drinking water and prevent waterborne diseases since the early 1900s. It has been a great success, preventing millions of deaths and making drinking water widely available at low cost.
Although federal and provincial agencies say the benefits of chlorination outweigh the potential risks associated with disinfection byproducts, much of Europe has abandoned chlorine-based disinfectants and other similar chemicals for health reasons.
Canada has the opportunity to take an equally pragmatic approach.
Regulated drinking water systems, including municipal utilities, require a minimum level of treatment. Many water companies add chlorine twice during treatment. Primary disinfection kills pathogens present in raw, untreated water drawn from rivers, lakes and other sources. Secondary disinfection preserves the quality of the drinking water within the distribution system.
However, when disinfectants such as chlorine come into contact with natural organic matter, including algae, bacteria, soil, decomposed plant material or animal feces, they form compounds called disinfection byproducts, including trihalomethanes. (THM) and halogenated acetic acids (HAA).
Long-term exposure to disinfection byproducts is associated with an increased risk of bladder cancer. Asthma and other respiratory problems have also been linked to exposure to disinfection byproducts in swimming pools.
Many of the Newfoundland and Labrador communities are remote and their drinking water often comes from ponds and rivers with high levels of natural organic matter and is distributed over long distances. Newfoundland’s surface waters are also heavily affected by extreme and variable weather conditions, creating optimal conditions for the formation of disinfection by-products.
A problem throughout Canada
Minister of Environment and Municipal Affairs of Newfoundland and Labrador Graham Bed said municipalities should notify residents when THM levels exceed Health Canada’s 100 milligrams per liter standard and take steps to correct the problem.
For example, residents can install NSF-certified filters in water jugs or under the sink to reduce disinfection byproducts, or they can boil water or leave it in an open container in the refrigerator overnight. But these cannot remove all disinfection byproducts or prevent exposure to them while swimming, showering, or bathing.
An alternative approach is to use carbon or membranes to filter organic matter from the water prior to chlorination. Many municipalities do this, but it requires a large capital investment and well trained operators and engineers for ongoing maintenance. This may not be practical for small communities, nor does it eliminate the use of chlorine.