Quebec municipalities are waging an endless battle to improve the quality of their drinking water. Despite these efforts, more than 110,000 people were still served in 2022 by an aqueduct network that violated the standard for a group of contaminants — trihalomethanes — according to government data obtained by The duty.
The Rivière-Pentecôte sector, within the municipality of Port-Cartier, on the Côte-Nord, is at the top of the list. This village has been struggling for decades with a serious problem of trihalomethanes (THMs) in its drinking water. A concentration of 301 micrograms per liter (µg/L) was measured in 2022, while the Quebec standard is 80 µg/L.
“When you turn on the tap in the morning, the water is yellow, when it’s not downright brown,” laments Alain Thibault, the mayor of Port-Cartier, who himself lives in Rivière-Pentecôte. A boil water advisory has been in effect since 2003 in this hamlet of 150 inhabitants outside the city.
When you turn on the tap in the morning, the water is yellow
THMs are created when chlorine used to kill bacteria in water interacts with organic matter, such as dead leaves. These contaminants are part of the family of “disinfection by-products”, which includes hundreds of compounds. Since the 1980s, most municipalities in North America have managed to reduce the presence of these contaminants, but not all.
Prolonged exposure (“at least 20 years”) to a “high concentration” of THMs may slightly increase the risk of bladder cancer, warns the Quebec government. A specialist consulted by The duty (see below), however, is reassuring: the exceedances recorded in the province are probably too low to pose a health risk.
According to data provided to Duty by the Quebec Ministry of the Environment, 27 drinking water systems violated the THM standard in 2022. Besides Rivière-Pentecôte, the greatest excesses were observed in Belleterre in Témiscamingue (220 µg/L, 256 people served), at Les Bergeronnes on the North Shore (200 µg/L, 1357 people) and at Saint-Ulric in the Bas-Saint-Laurent (175 µg/L, 838 people).
Larger cities such as Shawinigan (115 µg/L), Sept-Îles (86 µg/L) and the Arvida sector of Saguenay (87 µg/) also reported non-standard, but lower concentrations. The declared values correspond to the average of measurements taken during each of the seasons. In Quebec, municipalities are responsible for compliance with this standard.
To lower the concentration of disinfection by-products, including THMs, it is necessary to reduce the presence of organic matter in the water, or else reduce chlorination as much as possible – without leaving the field open to bacteria, such as E.coliwhich pose an undeniable health risk.
Things are moving at Les Bergeronnes
Rivière-Pentecôte has been under an order from the Ministry of the Environment for more than 20 years to improve the quality of its drinking water. Successive municipal administrations have never been able to agree on a project. Mayor Thibault now hopes to break the impasse by improving water filtration by 2025. A call for contractors should soon be launched.
“As long as the file remains active, as long as the City moves in order to reach the standards, it is sure that there are no fines” from the Ministry of the Environment , says the mayor. The day the municipality stopped looking for options, it would become “at fault” and would be subject to penalties, according to him.
Over the past few years, several municipalities have invested millions of dollars to bring their drinking water plants up to standard, particularly with regard to THMs. Baie-Comeau — where THM concentrations of more than 300 µg/L were found in 2015 — is one of those that solved the problem with a new plant in 2018.
The municipality of Les Bergeronnes, where there is also a significant excess of the standard, is preparing to take action. Starting this year, it plans to install valves that will periodically purge the water at the ends of the aqueduct network, which will reduce the interaction time between chlorine and organic residues, and therefore THMs.
The administration of the north-coast village also plans to modify the source of its drinking water network in the next few years. She wants to move from a lake, high in organic matter, to an underground spring. This should definitely fix the problem. Hydrogeological studies have already been carried out.
“It has been a priority for our council since my election in 2021,” explains the mayor, Nathalie Ross. The work will cost millions of dollars. Even with a significant contribution from Quebec through the Municipal Water Infrastructure Program (PRIMEAU), the municipality of 650 inhabitants will have to scratch the bottom of the drawer to pay its share.
“bad water”
What are the health risks of THM concentrations reported in Quebec? Steve Hrudey, a professor emeritus of environmental toxicology at the University of Alberta who has dedicated his career to drinking water disinfection byproducts, insists on defusing any alarmism.
“It is highly unlikely that the concentrations measured in Quebec will cause cancer in a single person exposed,” judge Mr. Hrudey, a authority in the field. Small studies have already discerned an increased risk (twice as high) of bladder cancer in highly exposed populations, but their conclusions have never been confirmed by large epidemiological studies.
“Experts now agree that THMs themselves do not pose a cancer risk at the levels found in drinking water,” says Dr. Hrudey. Toxicological studies conducted on animals simply do not support this hypothesis. Other disinfection by-products created under the same conditions as THMs could pose a risk, however. “This is why we must apply the precautionary principle,” he recommends.
Notwithstanding the question of cancer, Professor Hrudey considers it intolerable for a municipality to fail in its responsibility to provide drinking water that meets the standards in force. THM concentrations above 80 µg/L are associated with water that is colored, tastes bad and suffers from “all sorts of problems”. “It’s bad water,” he sums up.