Agency for Toxic Substances and Disease Registry (ATSDR):
The principal federal public health agency involved with hazardous waste
issues, responsible for preventing or reducing the harmful effects of
exposure to hazardous substances on human health and quality of life.
ATSDR is part of the U.S. Department of Health and Human Services.
Comparison
value:
A concentration of a chemical in soil, air or water that, if exceeded,
requires further evaluation as a contaminant of potential health concern.
The terms comparison value and screening level are often used
synonymously.
Contaminant:
Any chemical that exists in the environment or living organisms that is not
normally found there.
Exposure:
Contact with a chemical by swallowing, by breathing, or by direct contact
(such as through the skin or eyes). Exposure may be short-term (acute) or
long-term (chronic).
Groundwater:
Water found underground that fills pores between materials such as sand,
soil, or gravel. In aquifers, groundwater often occurs in quantities where it
can be used for drinking water, irrigation, and other purposes.
Hazardous
substance:
Any material that poses a threat to public health and/or the environment.
Typical hazardous substances are materials that are toxic, corrosive,
ignitable, explosive, or chemically reactive.
Indeterminate
public health
hazard:
Sites for which no conclusions about public health hazard can be made
because data are lacking.
Media:
Soil, water, air, plants, animals, or any other part of the environment that
can contain contaminants.
Monitoring
wells:
Special wells drilled at locations on or off a hazardous waste site so water
can be sampled at selected depths and studied to determine the movement
of groundwater and the amount, distribution,
and type of contaminant.
No apparent
public health
hazard:
Sites where human exposure to contaminated media is occurring or has
occurred in the past, but the exposure is below a level of health hazard.
Plume:
An area of contaminants in a specific media such as groundwater.
Risk:
The probability that something will cause injury, linked with the potential
severity of that injury. Risk is usually indicated by how many extra
cancers may appear in a group of people who are exposed to a particular
substance at a given concentration, in a particular pathway, and for a
specified period of time. For example, a 1%, or 1 in 100 risk indicates that
for 100 people who may be exposed, 1 person may experience cancer as a
result of the exposure.
