Step 2.2 Comparing Exposure Doses to Health Guidelines

Evaluating Noncancer Effects

Although health assessors evaluate all adverse health effects, the method of evaluation for cancer-related health effects differs from the methods used to evaluate noncancer health effects. When evaluating noncancer health effects, health assessors use health guidelines developed by ATSDR and EPA. ATSDR developed minimal risk levels (MRLs). EPA developed reference doses (RfDs) and rerference concentrations (RfCs).

minimal risk level (MRL)
ATSDR's minimal risk levels are doses of a chemical that are unlikely to result in noncancer health effects.

reference dose (RfD)
EPA's reference doses are estimates of ingested doses of a chemical that are unlikely to result in noncancer health effects.

reference concentration (RfC)
EPA's reference concentrations are estimates of daily exposures to a chemical that are unlikely to result in noncancer health effects. Reference concentrations apply to possible noncancer effects from breathing a chemical.

The health assessor compares the exposure dose (the amount of the chemical that people are actually contacting) to the minimal risk level (or another guideline). If the exposure dose is higher than the health guideline, the exposure is further evaluated. If the exposure dose is lower than the health guideline, noncancer effects are unlikely to occur, but if the chemical could cause cancer, the health assessor will evaluate the chemical further.

Where do health assessors find the most recent ATSDR and EPA health guidelines?

Up-to-date health guidelines may be found in the following sources,
ATSDR's toxicological profiles
ATSDR's Minimal Risk Levels (MRLs) for Hazardous Substances

EPA guidelines. Information about EPA's health guidelines is reported in EPA's Integrated Risk Information System database, which can be accessed at http://www.epa.gov/iris/index.html.

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