Cancer and Drinking Water Quality, funded by Canadian Cancer Society Research Institute
1. Investigators
Parker, Louise (PI)¹; Dummer, Trevor¹, Boxall, James², Dewar, Ron³, Murimboh, John⁴
¹Population Cancer Research Program, Dept. of Pediatrics, Dalhousie University,
²GIS Center, Dalhousie University,
³Surveillance and Epidemiology Unit Cancer Care Nova Scotia,
⁴Dept. of Chemistry, Acadia University
2. Funding, Budget and Timescales
Canadian Cancer Society Research Institute, $575,448, 3 years
3. Lay Summary
Project summary:
Arsenic is known to cause kidney and bladder cancer when consumed in large enough quantities. Arsenic is a material that occurs naturally in some rock types. Arsenic present in rocks can enter drinking water supplies, especially if drinking water is obtained from a drilled or dug well. This research will use a variety of techniques to estimate potential exposure to arsenic in drinking water in Nova Scotia. We will use this information to assess cancer risk in relation to this arsenic exposure.
Previous research:
Previous research shows that arsenic is a Class 1 cancer causing material. However, most studies that have investigated the risk of cancer in relation to arsenic in drinking water have looked at areas where arsenic exposure is very high. The risk of cancer in relation to arsenic levels in drinking water that are around the national acceptable limit guidelines of 10 micrograms per litre is not well understood. One particular problem associated with these types of studies is that measuring arsenic exposure and arsenic consumption is difficult.
Project description:
We will use existing cancer incidence and case-control data to provide an estimate of the geographic distribution of bladder and kidney cancer in Nova Scotia. We will use existing well water data in Nova Scotia to estimate arsenic exposure and use data on drinking water samples and toenail clippings from another study to estimate the relationship between arsenic in study participant’s bodies and their drinking water (from a a sample of Nova Scotian residents). We will link the cancer data to these different measurements of arsenic exposure in Nova Scotian residents to identify how much bladder and kidney cancer in Nova Scotia is influenced by arsenic in drinking water.
Impact and relevance:
Arsenic is known to cause cancer and it is a material that is commonly found in drinking water in Nova Scotia that is obtained from water wells. Other areas of Canada and elsewhere in the world that have the same geology as Nova Scotia also have problems with arsenic in drinking water. Public and environmental health policy requires accurate information in the health risks of environmental pollutants to ensure that legislation and environmental controls protect human health. In Nova Scotia private waters wells, that supply nearly half of the population with drinking water, are not regulated and do not have to be tested for arsenic. By establishing how high the risk of bladder and kidney cancer is in relation to arsenic in drinking water this study will impact on population health, by ensuring that government and health specialists are aware of the impact of this risk factor, a risk factor that can be dealt with by treating water supplies using appropriate technology.
4. Technical Abstract
Keywords/Technical Terms: kidney cancer, bladder cancer, population risk, arsenic, spatial analysis, GIS, case-control study
Background: Arsenic is a known class 1 human carcinogen that is causally associated with bladder and kidney cancer. However, although the risks associated with high levels of arsenic exposure are well described little is known about the effects on cancer risk of low to moderate exposure to arsenic. This is a particular problem across much of Canada because in many areas (including Nova Scotia) a large proportion of the population receives water from private water wells, and these wells are often in areas where arsenic naturally occurs in bed rock and hence leaches into drinking water.
Aims and Objectives: This study is concerned with estimating the risk of bladder and kidney cancer in relation to environmental exposure to arsenic in drinking water. Geographic indicators of arsenic exposure will be (i) arsenic in drinking water (derived from existing data on arsenic in drinking water wells in Nova Scotia) and (ii) arsenic body burden (derived from analysis of toenail clippings obtained from a sample of Nova Scotian residents). These estimates of arsenic exposure and arsenic body burden, and the relation between arsenic body burden and exposure in drinking water, will be linked to estimates of bladder and kidney cancer risk, at the population level, to estimate population risk of cancer in relation to arsenic.
Methods: Estimates of the geographic distribution of arsenic in drinking water and arsenic body burden for a sample of Nova Scotian residents will be produced using spatial interpolation techniques in a geographic information system (GIS). Bladder and kidney cancer rates will be mapped for Nova Scotia for the time period 1991-2006 and spatial cluster analysis techniques will be used to test for significant clustering of bladder or kidney cancer cases. Bladder and kidney cancer will be linked with the geographic estimates of arsenic exposure (arsenic in water well and arsenic body burden) using GIS. Multivariate logistic regression will be used to estimate population cancer risk in relation to arsenic.
Significance: Findings from this study will provide much needed quantitative evidence on the magnitude of the effect of low to moderate levels of arsenic in drinking water on bladder and kidney cancer risk. This evidence will help inform public and environmental health policy to ensure decisions are made to adequately tackle this modifiable environmental risk. The treatment of water supplies that are affected by arsenic is technically quite simple although it involves costs that currently have to be met in full by home owners. Data from this research will enable policy makers to decide if the magnitude of cancer risk warrants new approaches to financing water testing and remediation activities. |
