Navy Human Health Risk Assessment Web Site

Navy Risk Communication Web Site

Glossary

Select a letter from the list below to view other definitions.

A B C D E F G H I L M N O P R S T U V W

Habitat
Place where a population (e.g., human, animal, plant, and microorganism) lives and its surroundings, both living and non-living (ORNL 1999a).

Hazard Index (HI)
The sum of more than one hazard quotient for multiple substances and/or multiple exposure pathways. The HI is calculated separately for chronic, subchronic, and acute exposures.

Hazard Quotient (HQ)
The ratio of an exposure level to a substance to a toxicity value selected for the risk assessment for that substance (e.g., LOAEL or NOAEL).

Hazard Ranking System (HRS)
The method EPA uses to assess and score the hazards posed by a site that takes into account the nature and extent of contamination and the potential for the hazardous substances to migrate from the site through air, soil, surface water, or groundwater. The HRS scores are used to determine whether a site should be placed on the National Priorities List (NPL) (EPA 1999).

Hazardous Substances
Substances that would cause injury or adverse effects under specified conditions (EPA 1997).

Human Health Risk Assessment (HHRA)
The qualitative or quantitative appraisal(s) of the actual or potential impacts of stressors (i.e., contaminants) on humans at a site.

Last Modified: 02/27/2003

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