Occurring over a short period of time. An acute exposure is one
which lasts for less than 2 weeks.
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.
Cancer Slope Factor:
A number assigned to a cancer causing chemical that is used to
estimate it's ability to cause cancer in humans.
Carcinogen:
Any substance that can cause or contribute to the production of
cancer.
Chronic:
A long period of time. A chronic exposure is one which lasts for
a year or longer.
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.
Dose:
A dose is the amount of a substance that gets into the body
through ingestion, skin absorption or inhalation. It is calculated
per kilogram of body weight per day.
Environmental Media Evaluation Guide (EMEG):
A concentration in air, soil, or water below which adverse non-cancer health effects are not expected to occur. The EMEG is a comparison value used to select contaminants of potential health concern and is based on ATSDR's minimal risk level (MRL).
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.
Lowest Observed Adverse Effect Level (LOAEL):
LOAELs have been classified into "less serious" or "serious"
effects. In dose-response experiments, the lowest exposure level
at which there are statistically or biologically significant
increases in the frequency or severity of adverse effects between
the exposed population and its appropriate control.
Media:
Soil, water, air, plants, animals, or any other part of the
environment that can contain contaminants.
Minimal Risk Level (MRL):
An amount of chemical that gets into the body (i.e., dose) below
which health effects are not expected. MRLs are derived by
ATSDR for acute, intermediate, and chronic duration exposures
by the inhalation and oral routes.
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.
No Observed Adverse Effect Level (NOAEL):
The dose of a chemical at which there were no statistically or
biologically significant increases in frequency or severity of
adverse effects seen between the exposed population and its
appropriate control. Effects may be observed at this dose but
were judged not to be "adverse."
Organic:
Compounds composed of carbon, including materials such as
solvents, oils, and pesticides which are not easily dissolved in
water.
Parts per billion (ppb)/Parts per million (ppm):
Units commonly used to express low concentrations of
contaminants. For example, 1 ounce of trichloroethylene (TCE)
in 1 million ounces of water is 1 ppm. 1 ounce of TCE in 1
billion ounces of water is 1 ppb. If one drop of TCE is mixed in a
competition size swimming pool, the water will contain about 1
ppb of TCE.
Plume:
An area of contaminants in a specific media such as
groundwater.
Remedial investigation:
A study designed to collect the data necessary to determine the
nature and extent of contamination at a site.
U.S. Environmental Protection Agency (EPA):
Established in 1970 to bring together parts of various
government agencies involved with the control of pollution.
Volatile organic compound (VOC):
An organic (carbon-containing) compound that evaporates
(volatilizes) easily at room temperature. A significant number of
the VOCs are commonly used as solvents.
