In the initial stage, a cumulative framework can start with a simple additive approach as a basis for the future development of more sophisticated, data-driven risk models.Additive risk methodologies have been effectively used for the cumulative evaluation of air quality within the EPA’s National Air Toxics Assessment, first developed in the 1990s .
The cumulative cancer risk estimates are aggregated via a simple addition of cancer risk levels for individual contaminants .
These cumulative values are commonly presented as a 10 and express the lifetime risk of developing 1 case of cancer in a population of 1 million, 100,000 or 10,000 people, respectively .
Applying the cumulative cancer risk framework to the 2011–2015 drinking water dataset for community water systems in California, we calculated that up to 15,449 lifetime cancer cases could be related to drinking water quality across the state (Table 1).
Our assessment is based on water quality data published by the California State Water Resources Control Board, and the data collected under the EPA’s Unregulated Contaminant Monitoring Rule.
We posit that the drinking water field would benefit from making the transition to a unified assessment framework for multiple contaminants that can overcome the long-standing challenge of treating cancer and non-cancer contaminants separately.
Here we present a cumulative risk methodology that combines a risk-based cancer metric with a weighted health indicator index for non-cancer contaminants and incorporates disability weights from the Global Burden of Disease study.The health risks of drinking water contaminants and the economic benefits of drinking water standards are typically assessed one chemical at a time, an approach that misses the health impacts of co-occurring contaminants in drinking water.In contrast, a cumulative risk framework has become common in air quality evaluations such as the U. Environmental Protection Agency’s National Air Toxics Assessment.In our estimate, the slow adoption of cumulative methods in drinking water assessments is at least partly due to the variety of health outcomes caused by drinking water contaminants.While acknowledging the scientific challenges of assessing the impacts of co-occurring chemicals on multiple body systems, we believe that the drinking water field can start with the application of existing cumulative risk methodologies established for air quality.Post-campaign, households encouraged to switch water sources have 46% higher rates of child mortality than those not encouraged to switch.Switching away from arsenic-contaminated wells also increased adult mortality.The EPA’s technical support materials for the National Air Toxics Assessment note that the true value of the cumulative risk is not known and that the actual risks could be lower than predicted .These risks could also be higher, for example, due to potential synergistic interaction among co-occurring carcinogens. 25729 Issued in April 2019 NBER Program(s): Development Economics The 1994 discovery of arsenic in groundwater in Bangladesh prompted a massive public health campaign that led 20% of the population to switch from backyard wells to less convenient drinking water sources that had a higher risk of fecal contamination.We find evidence of unintended health consequences by comparing mortality trends between households in the same village that did and did not have an incentive to abandon shallow tubewells.