Arsenic in Drinking Water – Speciation, Human Exposure, and Health Effects

Principal Investigator - X. Chris Le, Professor, University of Alberta, 2001 - 2004

Challenge

Arsenic is a confirmed human carcinogen and has caused the largest environmental poisoning in the world.  However, it is not clear what level of arsenic in drinking water is acceptable because it is unknown how arsenic causes cancer in the body.  This information is crucial for developing better preventive measures to reduce human cancers that are induced via arsenic.  Nine million Canadians rely on groundwater as their main source of drinking water. In several areas of Canada, well waters contain arsenic levels above the Canadian guideline level. It is not known what arsenic species are present in these wells.  Information on exposure to individual arsenic species is far more useful than measurement of the total arsenic concentration because of the dramatic differences in toxicity among various arsenic species.   Finally, there exists a need to know how many Canadians are exposed to what levels of arsenic from drinking water.

The project team, led by Dr. X. Chris Le, investigates three knowledge gaps: 1) the effects of arsenic on DNA damage and repair, 2) characterizing new arsenic species, and 3) developing a map of Canada that characterizes how many Canadians are being exposed to arsenic in drinking water, and to what level.

Project

The overall goal of this project is to study arsenic speciation, human exposure, and health effects associated with exposure to arsenic species in drinking water. The projects specific objectives were to 1) study arsenic metabolism and the effects of arsenic species on DNA damage and repair; 2) characterizing new arsenic species of potential health concern; 3) developing a water arsenic exposure “map” that will fill a critical gap on how many Canadians are exposed to what levels of arsenic from drinking water.

Arsenic has been shown to increase the mutagenicity of human cells and may be exponentially more toxic when paired with cigarette smoking.  To better understand how arsenic causes cancer in the body this project investigated DNA. DNA damage and repair are key determinants in the early stages of carcinogenesis.  This project examined the effect of arsenic species on its own and when paired with benzo-a-pyrene, a carcinogen found in cigarettes.

A preliminary study of arsenic species in the Ottawa River found that 22% of total arsenic was unidentified.  Identifying all arsenic species is crucial in assessing the risk they pose on human health.  Therefore, this study sought to identify species, focusing on low dose levels.

Finally, with 9 million Canadians relying on well water, it is essential to identify where arsenic poses risk on human health.  This project has developed a map which overlays water arsenic concentrations and the populations exposed across Canada.

Outputs

• Development of a Canada Map of Arsenic in Drinking Water to overlay water arsenic concentrations and exposed populations
• Development of new analytical technology that enables differentiation and quantification of various arsenic species
• Circulation of techniques to other researchers and American Water Works Association subscribers
• Contribution of three review articles, summarizing arsenic speciation in natural water (Watt and Le 2002), describing various techniques for arsenic speciation analysis (Gong et al. 2002), and documenting recent advances in arsenic speciation research (Le et al. 2004)

Outcomes

• Collaboration with Canadian government agencies on health and environment which facilitates knowledge transfer and influences public policy with sound science.  An example is the partnership with the Federal-Provincial-Territorial Committee on Drinking Water, which re-evaluated the Canadian interim guideline for arsenic in drinking water.
• Increased knowledge on arsenic metabolism, DNA damage and repair, speciation of arsenic, and how many Canadians are exposed to different levels of arsenic.  This knowledge is essential for regulatory agencies of health and environment to develop evidence-based guidelines that protect public health.
• This work provides mechanistic insight to understanding the carcinogenic effects of arsenic, having measurable impacts on the way risk assessment is conducted.
• Water utilities and engineers will benefit from the characterization of arsenic in water, allowing them to implement the appropriate technology for the removal of arsenic from drinking water.  New techniques will lead to substantially improved understanding of arsenic speciation.
• This project has helped train three graduate students, a Postdoctoral Fellow, and a Research Assistant, creating future leaders in the field.
• The networking and partnership resulting from this project will leverage resources for further research and transfer of knowledge and technology. Researchers have successfully obtained additional support from several Canadian and U.S. funding agencies.