Occurring over a short time [compare with chronic].
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 Risk Evaluation
Guide (CREG):
The concentration of a chemical in air, soil or water that is expected to
cause no more than one excess cancer in a million persons exposed over a
lifetime. The CREG is a comparison value used to select contaminants of
potential health concern and is based on the cancer slope factor (CSF).
Cancer Slope Factor:
A number assigned to a cancer causing chemical that is used to estimate its
ability to cause cancer in humans.
Carcinogen:
Any substance that causes cancer.
Chronic:
Occurring over a long time (more than 1 year) [compare with acute].
Comparison value:
Calculated concentration of a substance in air, water, food, or soil that is
unlikely to cause harmful (adverse) health effects in exposed people. The
CV is used as a screening level during the public health assessment process.
Substances found in amounts greater than their CVs might be selected for
further evaluation in the public health assessment process.
Contaminant:
A substance that is either present in an environment where it does not
belong or is present at levels that might cause harmful (adverse) health
effects.
Dose (for chemicals that are not
radioactive):
The amount of a substance to which a person is exposed over some time
period. Dose is a measurement of exposure. Dose is often expressed as
milligram (amount) per kilogram (a measure of body weight) per day (a
measure of time) when people eat or drink contaminated water, food, or
soil. In general, the greater the dose, the greater the likelihood of an effect.
An "exposure dose" is how much of a substance is encountered in the
environment. An "absorbed dose" is the amount of a substance that
actually got into the body through the eyes, skin, stomach, intestines, or
lungs.
Environmental Media
Evaluation Guide (EMEG):
A concentration in air, soil, or water below which adverse noncancer 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).
Environmental Protection
Agency (EPA):
The federal agency that develops and enforces environmental laws to
protect the environment and the public's health.
Epidemiology:
The study of the occurrence and causes of health effects in human
populations. An epidemiological study often compares two groups of
people who are alike except for one factor, such as exposure to a chemical
or the presence of a health effect. The investigators try to determine if any
factor (i.e., age, sex, occupation, economic status) is associated with the
health effect.
Exposure:
Contact with a substance by swallowing, breathing, or touching the skin or
eyes. Exposure may be short-term [acute exposure], of intermediate
duration, or long-term [chronic exposure].
Groundwater:
Water beneath the earth's surface in the spaces between soil particles and
between rock surfaces [compare with surface water].
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:
The category used in ATSDR's public health assessment documents when a
professional judgment about the level of health hazard cannot be made
because information critical to such a decision is lacking.
Ingestion:
The act of swallowing something through eating, drinking, or mouthing
objects. A hazardous substance can enter the body this way [see route of
exposure].
Ingestion rate:
The amount of an environmental medium that could be ingested typically
on a daily basis. Units for IR are usually liter/day for water, and mg/day for
soil.
Inhalation:
The act of breathing. A hazardous substance can enter the body this way
[see route of exposure].
Inorganic:
Compounds composed of mineral materials, including elemental salts and
metals such as iron, aluminum, mercury, and zinc.
Lowest Observed Adverse
Effect Level (LOAEL):
The lowest tested dose of a substance that has been reported to cause
harmful (adverse) health effects in people or animals.
Media:
Soil, water, air, plants, animals, or any other part of the environment that
can contain contaminants.
Minimal Risk Level
(MRL):
An ATSDR estimate of daily human exposure to a hazardous substance at
or below which that substance is unlikely to pose a measurable risk of
harmful (adverse), noncancerous effects. MRLs are calculated for a route
of exposure (inhalation or oral) over a specified time period (acute,
intermediate, or chronic). MRLs should not be used as predictors of
harmful (adverse) health effects [see reference dose].
Model Toxics Control Act
(MTCA):
The hazardous waste cleanup law for Washington State.
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:
A category used in ATSDR's public health assessments for sites where
human exposure to contaminated media might be occurring, might have
occurred in the past, or might occur in the future, but where the exposure is
not expected to cause any harmful health effects.
No Observed Adverse
Effect Level (NOAEL):
The highest tested dose of a substance that has been reported to have no
harmful (adverse) health effects on people or animals.
No public health hazard:
A category used in ATSDR's public health assessment documents for sites
where people have never and will never come into contact with harmful
amounts of site-related substances.
Oral Reference Dose
(RfD):
An amount of chemical ingested into the body (i.e., dose) below which
health effects are not expected. RfDs are published by EPA.
Organic:
Compounds composed of carbon, including materials such as solvents, oils,
and pesticides that 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:
A volume of a substance that moves from its source to places farther away
from the source. Plumes can be described by the volume of air or water
they occupy and the direction they move. For example, a plume can be a
column of smoke from a chimney or a substance moving with groundwater.
Reference Dose Media
Evaluation Guide
(RMEG):
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
EPA's oral reference dose (RfD).
Remedial investigation:
The CERCLA process of determining the type and extent of hazardous
material contamination at a site.
Route of exposure:
The way people come into contact with a hazardous substance. Three
routes of exposure are breathing [inhalation], eating or drinking [ingestion],
or contact with the skin [dermal contact].
Surface Water:
Water on the surface of the earth, such as in lakes, rivers, streams, ponds,
and springs [compare with groundwater].
Volatile organic
compound (VOC):
Organic compounds that evaporate readily into the air. VOCs include
substances such as benzene, toluene, methylene chloride, and methyl
chloroform.