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Water: Water Quality Standards Academy

Basic Course: Supplemental Topics - Health (v)

Exposure Assessment: Introduction

Human Health Ambient Water Quality Criteria

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The remainder of this module focuses on the portions of the three human health AWQC equations that address exposure to the chemical contaminant. (Remember that the particular equation used in conducting a quantitative risk assessment will differ depending on the chemical contaminant and the type of adverse health effect associated with that chemical.)

There are two primary exposure sources of concern:

  • Direct ingestion of drinking water. Assumptions apply to both direct ingestion of water from the source, as well as ingestion of treated water from the source if the contaminant is unregulated. (The inclusion of treated water covers situations where treatment may not remove the contaminant of concern. If the contaminant is unregulated, there is no way to know if it is being removed through treatment.)
  • Consumption of fish/shellfish. This component pertains primarily to fish ingested by subsistence fishermen and sports fishermen but can also apply to fish caught locally and sold to the general population. Fish/shellfish consumption estimates vary with the population of interest.

Other sources of exposure to a given contaminant are considered when deriving criteria for noncarcinogens and nonlinear carcinogens as part of the Relative Source Contribution (RSC) analysis. The RSC takes into account the portion of the total exposure that is contributed by drinking water and ingested fish/shellfish that originate from the ambient water body being evaluated.

For informational purposes only–Not official statements of EPA policy.

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