At the “Workshop on Lead in Drinking Water” held at École Polytechnique de Montréal on June 8-9, Canadian and international speakers presented key findings on the engineering, regulatory and health aspects of developing a comprehensive strategy to reduce lead in tap water in Canada.
The amount of lead measured in the blood of the general population has significantly decreased over the last 20 years thanks to the successful reduction of lead in paint, dust, soil, food cans and gasoline.
However, the presence of lead in drinking water at the tap in some Canadian cities and the recent evidence that the current guideline of blood lead levels (BLL = 10µg/dL) may not be safe, especially for children, have triggered new investigations. Research is being conducted into the sampling and measuring of lead at the tap, the impact of exposure on blood lead levels, and corrective actions and costs.
With the cost of replacing lead service lines (LSL) estimated to reach $300 million in some large Canadian municipalities, and the growing evidence that only partially replacing a LSL can increase lead leaching caused by galvanic corrosion, the workshop’s multidisciplinary research project, which was funded by the Canadian Water Network, provided insights to decision-makers for developing a comprehensive strategy to reduce lead at the tap in Canada.
Partial lead service line replacement can worsen the problem
Since water leaving treatment plants has almost no lead, can we target efficiently which components of the infrastructure are contributing to lead concentration at the tap? This was a key question for Dr. Michèle Prévost’s research team of the NSERC Industrial Chair on Drinking Water at École Polytechnique de Montréal, who presented their findings at the June workshop.
Clément Cartier, Ph.D. student with Dr. Prévost [ 1] reported that: “Under moderate/high flow rates (8 to 32 L/min) in our laboratory setting, partial replacement of LSL with copper pipe released about three times more lead than a 100% lead pipe. Results showed that placing a copper pipe in front of a lead pipe is much worse than a situation with a lead pipe in front of a copper pipe, possibly due to deposition corrosion.”
Cartier suggested that the accumulation of rust on an old lead pipe created by galvanic corrosion from a new copper pipe placed upstream becomes a reservoir of potentially mobile lead, and the fate of this reservoir is a long-term concern.
Results of a Montreal study
A well documented Hamilton study that showed tap water lead concentration median of 5.3 µg/L has raised concerns at the municipal level. At the City of Montreal results from water sampling campaigns (2005 to present) have shown a high concentration of LSL in some areas of the city, specifically in wartime houses. The number of LSL was estimated at 75,000.
Concentrations of lead in drinking water at the tap in houses with LSL were significantly higher than houses without such lines. The guideline of lead concentration in tap water (10 µg/L) was exceeded in a proportion of more than 50% in wartime houses with a LSL (although none were exceeding the previous guideline of 50 µg/L), and 10% of the children were exposed to more than 9 mg/L of lead at the tap.
Water sampled from the bathroom tap showed a significantly higher concentration of lead than the water sampled at the kitchen tap. For Montreal residents having a LSL, the recommendations from the public health authorities are to let the water run for few minutes after the water becomes cold, especially if the water was stagnant for few hours, or to use filter devices connected to the tap, or pitchers.
Effects of Lead
Why is it necessary to investigate lead in tap water in Canada? Here are some reasons:
* Lead is a neurotoxin and probable carcinogen
* Health guidelines apply to blood: 10 µg/dL
* The 2010 guideline for lead in drinking water is 10 µg/L
* Children under 6 years and pregnant woman are the most vulnerable. Effects can be: loss of IQ in young children, learning disabilities, cognitive and executive dysfunction
* Early exposure may be associated with disruptive social behaviour.
* Men and post-menopausal women can also have health effects.
* Canadian Water Network – Developing a comprehensive strategy to reduce lead at the tap in Canada: http://www.cwn-rce.ca/research/core/eswi-01/
* NSERC Industrial Chair in Drinking Water Treatment – École Polytechnique de Montréal: http://www.polymtl.ca/recherche/rc/en/unites/details.php?NoUnite=34
* Triantafyllidou S, Edwards M. (In Press). Lead (Pb) in Tap Water and in Blood: Implications for Lead Exposure in the United States, Critical Reviews in Environmental Science and Technology
* Blood Lead Study BOH08012 (City Wide) – City of Hamilton: www.hamilton.ca/…/May27BOH08012RevisedBloodLeadStudy.pdf
Nathalie Ross, Ph.D., RAC is a scientific, technical and medical writer based in Montreal.