Cumulative Risk from Waterborne Contaminants

Climate strategies – both in mitigation and adaptation – can alter the loading of waterborne contaminants into waterways and drinking water supplies. To date, the process of assessing risk from such changes has tended to focus on one contaminant at a time, comparing the risk posed against regulatory limits.

Above: A representative result from application of the Cumulative Risk Project methodology when 50 contaminants are all present in a water supply at their US regulatory limits. DALY values for (i) morbidity (blue bars), (ii) cancer mortality (red bars) and (iii) total (yellow bars), by compound. Compound 51 is the Total Weighted DALY across all compounds in the assumed water supply. Note the very significant differences in DALY values associated with regulatory limits, due in large part to quite large differences in the treatment of uncertainty and precaution for different contaminants.

The Cumulative Risk Project has developed a methodology, rooted in epidemiological meta-analysis and Disability Adjusted Life-Years (DALY), to calculate the total risk from 100+ contaminants that might be affected by changes to a catchment area. Results suggest that conventional approaches to risk assessment significantly mis-state the cumulative risk of such changes due to very different levels of conservatism built into the risk assessment process for different contaminants. The Cumulative Risk Project removes these problems by separating clearly the exposure-response and uncertainty considerations in risk assessment, placing diverse contaminants onto a common metric of public health impact so cumulative risk can be calculated.

Outputs: D. Crawford-Brown and S. Crawford-Brown, Cumulative Risk Assessment Framework for Waterborne Contaminants, Journal of Environmental Protection, 3, 400-413, 2012

Funding: American Water Works Association Research Foundation

Project Partners: Stratus Consulting and Jacobs Consulting

Duration: January 2011 to June 2013

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