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Developing the SafeWater CBX Benefit-Cost Model


  • What are the cost and benefits of new drinking-water standards?
  • Abt developed the SafeWater CBX computer model to calculate estimates.
  • SafeWater CBX will estimate the cost-benefit of all future regulations.
The Challenge

More than 140 unregulated chemicals contaminate public water supplies in 42 states. The risk to consumers is unclear because researchers haven’t figured out the threshold for when they cause harm. To weigh regulatory options, the Environmental Protection Agency wants to be able to calculate how much any new drinking-water standards likely would cost and the likely benefits.

The Approach

Abt developed the SafeWater CBX computer model to estimate both costs and benefits. SafeWater CBX expands on two previous models—one a cost model, the other a benefits model, both called SafeWater XL—by incorporating variability across inputs and outputs for individuals and/or public water systems. It incorporates the known uncertainty in inputs with outputs that include both best estimates and confidence intervals reflecting the uncertainty of the results. In addition, SafeWater CBX can compare the effects of different standards in a single model run.

The Results

The flexible, customizable SafeWater CBX model can assess different combinations of maximum contaminant levels (MCLs) and other model parameters. The model can select from existing dose response functions or add new ones. It can estimate benefit-cost ratios and economic impacts for different contaminants. The model also can simultaneously consider two or more user-specified MCLs for easy comparisons. This model will be used by EPA to estimate the costs and benefits of all future drinking water regulations.