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Step 1.5 Using Comparison Values

Selection Process

The selection of comparison values takes into account the conditions at the particular site.

Consider aspects of the selection process:

Initial selection
The health assessor organizes the environmental sampling data by media: air, soil, and water. The health assessor initially selects the lowest comparison value for the chemical in each media table and compares it to the highest level of the chemical found in that medium at the site. If the amount found in the sample is higher than the comparison value, the health assessor selects the chemical for further evaluation.

Site-specific considerations
The assessor might use a different comparison value if exposure conditions warrant.

No comparison values are available
The assessor either selects the chemical for further evaluation or confers with toxicologists to develop a conservative comparison value.

Advanced exercise on comparison value selection.

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