Step 2.2 Comparing Exposure Doses to Health Guidelines (Observed Effect Levels)

Introduction

Once the site-specific exposure doses have been estimated, they are compared to human health guidelines, such as ATSDR’s minimal risk levels (MRLs). If the estimated dose for a chemical is at or above the health guideline, then the exposure will be further evaluated.

The health assessor must keep in mind what health guidelines are and what they are not.

Health guidelines are doses at which harmful health effects are not expected. They are based on toxicologic and epidemiologic studies, and they are conservative estimates with built-in safety and uncertainty factors.

Health guidelines are not used to predict adverse health effects. They are based on site-specific data. Health guidelines are not clean-up levels.

Environmental guidelines versus health guidelines

An environmental guideline or comparison value is a level (concentration) of a chemical in air, soil, or water that is considered safe for human contact. A health guideline is the dose (amount) of the chemical entering the human body that is not expected to cause harm.