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IDEM > Your Environment > Risk Assessment > Risk Assessment Definitions Risk Assessment Definitions

Absorption
The process of taking in, as when a sponge takes up water. Chemicals can be absorbed through the skin into the bloodstream and then transported to other organs.
Acute effects
Any toxic effect that occurs within a short period of time (minutes to a few days) following an exposure.
Acute exposure
A dose (or exposure) occurring within a short time relative to the life of a person or organism (24 hours or less in humans).
Atmospheric pressure (1 atm)
The normal pressure of the air.
Air toxic
Any air pollutant that causes or may cause adverse health effects in humans.
Bioaccumulation
The accumulation of a chemical in an organism (plant, animal, etc.) which takes place when the rate of intake is greater than the rate of excretion of that chemical.
Cancer
A group of related diseases characterized by the uncontrolled growth of abnormal cells.
Cancer risk estimate
The probability of developing cancer from exposure to a chemical or mixture of chemicals over a period of time.
Carcinogen
A chemical capable of inducing cancer.
Chemicals
A substance with a distinct molecular composition that is produced by or used in a chemical process.
Chronic effects
An effect that occurs as a result of repeated or long-term exposure (years to lifetime).
Concentration
The amount of a chemical present in a medium (i.e. water, air) compared to the volume of the medium.
Dispersion
Pollutant or chemicals mixing with the medium around it (i.e. water, air).
Dose
The concentration and length of time that a person is exposed to a chemical.
Dose-response assessment
A determination of the relationship between the magnitude of a dose and the biological response.
Dry deposition
The removal of airborne substances to available surfaces that occurs as a result of settling due to gravity, diffusion, and thermophoresis (temperature differences) without precipitation (rains, snows, etc.).
Emission
A substance or chemical being discharged into the air.
Evaporation
When water or a chemical leaves water and goes into the air.
Excretion
When the body gets rid of a chemical from the body. This can be through the pores in the skin, breathing or by the kidneys.
Exposure
Contact made between a chemical and a person.
Hazard
Anything that has potential to cause harm. The likelihood of experiencing a non-cancer health effect is called hazard.
Health effect
A change that occurs to human health as a result of a chemical.
Health-protective assumption
When faced with two equally scientifically defensible inputs during risk estimations, selecting the input that is more protective of human health.
IDEM
Indiana Department of Environmental Management
Ingestion
Swallowing, such as eating or drinking.
Inhalation
Breathing.
Intake
The process where a chemical crosses the outer boundary of a person without being absorbed, for example, through ingestion or inhalation.
Micrograms per cubic meter (µg/m3)
Unit of measure for air concentrations. How many micrograms (unit of weight) are contained in a theoretical cube of air one meter tall by one meter wide by one meter deep.
Parts per billion (ppb)
Unit of measure for concentration. How many parts of a chemical are contained per billion parts total in a medium (air, water, land).
Parts per million (ppm)
Unit of measure for concentration. How many parts of a chemical are contained per million parts total in a medium (air, water, land).
Probability
The relative frequency with which an event occurs or is likely to occur. For example, the odds of a coin landing heads up.
Reentrainment
When a chemical evaporates from water but is then reabsorbed by the water body.
Risk assessment
The cumulative combination and results from the scientific method of evaluating the toxic properties of chemicals and how humans and the ecosystem are exposed. A risk assessment generally determines the likelihood, to what extent, and/or characterizes how humans and the ecosystem are adversely affected.
Risk characterization
The last phase of risk assessment where all information from toxicity and exposure are combined to calculate estimates of risk. This will include all the assumptions and scientific information used to estimate risk, the uncertainty associated with the assessment, and any other information that may be useful to decision makers.
Risk factor
A measure of how toxic a chemical is at a certain dose. Sometimes referred to as a dose-response value.
Threshold
The lowest dose of a chemical at which a specified measurable effect is observed and below which it is not observed.
Toxicity
The amount to which a chemical or mixture of chemicals can harm humans or the environment.
Transformation
When a chemical changes from one chemical to another.
TRI
Toxics Release Inventory. A collection of emissions information from industries in the United States.
U.S. EPA
United States Environmental Protection Agency
Uptake
The process where a chemical is absorbed into the body. This usually refers to absorption through the skin.
Volume of air
A defined amount of air. In most situations, a cubic meter is used for air concentrations.
Wet deposition
The removal of airborne substances to available surfaces that occurs as a result of settling due to gravity, diffusion, and thermophoresis (temperature differences), with precipitation (rain, snow, etc.).