Example Benchmark Dose Derivation

The BMD approach has been used for many years to identify acceptable surface water concentrations for exposure by fish and other aquatic species. The Ambient 

Water Quality Criteria (AWQC) adopted by the U.S. EPA are based on a series of laboratory tests that include identifying effective concentration levels for specific endpoints. These effective concentrations are then used to develop AWQC. 

The standardized approach for risk assessment discussed in chapter 8 is called deterministic because the outcome of the risk assessment is a single risk, and only specific values are used to develop that risk. These specific values include assumptions that everyone has the Scime body weight, lives in one place for the same length of time, contacts the Scime cimount of dirt, breathes the same amount of air, etc. In reality, individual variability exists that introduces uncertainty into the results obtained from using these simplifying assumptions. 

One way to quantify this uncertcunty is to develop a range of risks that corresponds with different likelihood of risk occurring across a population. This range of risks incorporates the known variability within the humcm population. Such an approach is called probabilistic because it is statisticcdly based. This is a fairly complex mathematical process and typically involves hundreds of thousands of calculations by a computer that essentially mimics human vcu iability. An overview of the process and its significance is presented here to familicu ize you with the approach. 

One probabilistic method that has become popular in recent years for use in risk assessments is called the Monte Carlo technique. Monte Carlo is the name of the mathematical formula used to generate the range of risks, and is not related to the location or gambling. This process is further discussed below. 

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