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

Chronic
Having a slow onset or lasting long-term. A chronic stimulus induces a response over a long-term. The word chronic can be used to define either the exposure or the response to an exposure (effect). For example, the duration of a chronic aquatic toxicity test could be 96 days or more, and mortality is the response usually measured (EPA 1997).

Class
A major category in biological taxonomy ranking above the order and below phylum or division (e.g., Mammalia or mammals).

Community
An assemblage of populations of different species within a specified location and time. It is a broad term that may be used to designate natural assemblages of different sizes (e.g., organisms inhabiting a rotting log, organisms inhabiting a forest or stream).

Complete Exposure Pathway
All links in the physical and chemical pathways involved in getting a contaminant from the primary source (e.g., waste site) to the assessment endpoint receptor.

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
Cleanup Program focuses on human health and environmental concerns related to human health. The Cleanup Program is primarily carried out by the EPA, working with states, on sites designated for cleanup on the NPL. Cleanup Program emphasizes local source contact and prevention of further spread from sources. Cleanup Program is prohibited from restoring natural resources, although cleanup may prevent injuries to natural resources (ORNL 1999a).

Conceptual Site Model (CSM)
An integral part of a site investigation and/or ecological risk assessment, as it provides the framework from which the study design is structured. It follows contaminants from the media, through transport and fate pathways (air, soil, surface water, and groundwater), to the ecological receptors. It is frequently created as a site map or flow diagram that describes the potential movement of contaminants to site receptors (EPA 1997).

Conservative Assumptions
Used to estimate exposure parameters for which sound site specific information is lacking or difficult to develop. Examples of conservative assumptions include: the area used by the biotic receptor is only the contaminated area, the bioavailability of the contaminants is 100 %, the most sensitive life stage is present, minimum body weight to maximum ingestion weight, and 100 % of the diet consists of the most contaminated dietary component.

Contaminant
Harmful or hazardous matter introduced into the environment. Contaminants can be a food chain threat, a lethal threat, a direct non-lethal toxicant, an indirect toxicant, or some combination of the four.

Contaminant Bioavailability
see Bioavailability and Contaminant.

Contaminant of Ecological Concern
A substance detected at a hazardous waste site that has the potential to affect ecological receptors adversely due to its concentration, distribution, and mode of toxicity (EPA 1997).

Contaminants of Potential Concern (COPCs)
A substance detected at a hazardous waste site that has the potential to affect receptors adversely due to its concentration, distribution, and mode of toxicity (EPA 1997).

Critical Habitat
Habitat essential for the survival of a species (e.g., required for a key life stage or for obtaining prey). For example, a large body of water with fish is critical for the bald eagle. There are also designated critical habitats that are specified habitat areas required for the survival of a federally listed threatened or endangered species.

Last Modified: 02/27/2003

This website complies with the Electronic and Information Technology Accessibility Standards set forth in U.S. Section 508 of the 1998 Rehabilitation Act Amendments