Toxicity Testing Glossary

acute toxicity

The ability of a substance to cause severe biological harm or death soon after a single exposure or dose. Also, any poisonous effect resulting from a single short-term exposure to a toxic substance.

Related terms: chronic toxicity, LC50, toxicity
Americamysis bahia

Americamysis bahia Small shrimp-like crustaceans found primarily in the Gulf of Mexico and the eastern coast of Florida; currently the primary estuarine species in toxicity testing; used in both acute and chronic tests; also known as mysidopsis bahia, opossum shrimp, mysid shrimp, and mysids.

Related link: Americamysis bahia

Analysis of variance; used in conjunction with NOEC to determine if statistically significant differences in a response occur among two or more groups.

Related terms: NOEC
aquatic indicator

Commonly referring to an organism used in bioassay testing.

Related link: aquatic indicator
Related terms: bioassay

A test to determine te relative strength of a substance by comparing its effect on a test organism with that of a standard preparation.


Any biological species or group of species whose function, population, or status can be used to determine ecosystem or environmental integrity.


The use of living organisms to test the suitability of effluents for discharge into receiving waters and to test the quality of such waters downstream from the discharge.

Ceriodaphnia dubia

Ceriodaphnia dubia Water flea, occurs in littoral areas lakes, ponds, and marshes throughout most of the world; EPA recommended freshwater invertebrate used in both acute and chronic toxicity testing.

Related link: Ceriodaphnia dubia
chemical oxygen demand (COD)

A measure of the oxygen required to oxidize all compounds, both organic and inorganic, in water.

chronic toxicity

Long-term poisonous health effects in humans, animals, fish, and other organisms.

Related terms: acute toxicity
coefficient of variation

The normalized measure of dispersion of a probability distribution. It is defined as the ratio of the standard deviation to the mean.

Related link: coefficient of variation
composite sample

A series of water samples taken over a given period of time and weighted by flow rate.

confidence limits

The lower and upper boundaries of a confidence interval. The upper and lower bounds of a 95% confidence interval are the 95% confidence limits.

Related link: confidence limits

an otherwise identical replicate within a test without the variable being tested.

control chart

A graph of the results of a process over time and against established control limits.

Cyprinella leedsi

Cyprinella leedsi (bannerfin shiner) a freshwater fish known to inhabit sandy runs of medium to large rivers. the EPA-approved vertebrate species for freshwater acute toxicity tests, in which one to 14 day-old organisms are used.

Related link: Cyprinella leedsi
Daphnia magna

Daphnia magna small, planktonic crustaceans approximately 5mm in length; lake dweller and is restricted to waters in northern and western North America.

Related link: Daphnia magna
Related terms: Ceriodaphnia dubia

DMR-QA evaluates the analytical and reporting ability of the laboratories that routinely perform inorganic chemistry and whole effluent toxicity self-monitoring analyses required by their NPDES permit.

Related link: DMR-QA

wastewater discharged into surface waters.

Related link: effluent
general permit

General permits are written to cover a category of dischargers instead of an individual facility. Application for coverage under a general permit is by submitting a "notice of intent" and is much less rigorous than applying for an individual permit. General permits may place limits on the quanity and concentration of pollutants allowed to be discharged and typically require operational conditions called Best Management Practices.

grab sample

A single sample collected at a particular time and place that represents the composition of the water, air, or soil only at that time and place.

Related terms: composite sample
industrial wastewater

Wastewater generated in a commercial or industrial process.

Related link: industrial wastewater
Related terms: effluent, wastewater
inhibition concentration (IC25)

IC25 is a point estimate of the toxicant concentration that would cause a 25-percent reduction in a non-lethal biological measurement, such as growth or reproduction.

ion imbalance toxicity

Acute or chronic toxicity caused by inorganic ion imbalance and/or the ion concentration of the effluent, common where process streams are concentrated.


A standard measure of toxicity; tells how much of a substance is needed to kill half of a group of experimental organisms in a given time.

Related terms: acute toxicity
Menidia beryllina

Menidia beryllina Inland silverside; Silversides occur in estuaries along the Atlantic, Gulf, and Pacific coasts. Menidia beryllina are the current EPA-approved marine vertebrate used in both acute and chronic toxicity testing. In acute toxicity testing, one to 14 day-olds are used and survival is recorded. In chronic toxicity testing, seven to eleven-day olds are used and survival and growth are recorded.

Related link: Menidia beryllina
Mysidopsis bahia

See Americamysis bahia.

Related terms: Americamysis bahia

National Environmental Laboratory Accreditation Conference

Related link: NELAC

National Environmental Laboratory Accreditation Program

Related link: NELAP

No Observed Effect Concentration; exposure concentration at which there are no statistically or biological significant differences in the frequency or severity of any effect in the exposed or control populations.


NPDES National Pollutant Discharge Elimination System; the NPDES permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States.

Related link: NPDES
Pimephales promelas

Pimephales promelas Common name - fathead minnow; the fathead minnow is a freshwater fish widely distributed in the United States and it is usually found in brooks, ponds, and small lakes. Pimephales promelas is the EPA recommended vertebrate species for freshwater chronic toxicity tests.

Related link: Pimephales promelas
Pseudokirchneriella subcapitata

Formerly Selenastrum capricornutum. Freshwater algae used as Daphnid food.

Related link: Pseudokirchneriella subcapitata
receiving water

A river, lake, ocean, stream or other watercourse into which wastewater or treated effluent is discharged.

reference toxicant

toxicant used in performing toxicity tests to determine the sensitivity of a test organism and to demonstrate the laboratory's ability to perform the test correctly and consistently.

reverse osmosis reject water

Wastewater produced by reverse osmosis; this reject water may require monitoring.

Related link: reverse osmosis reject water
Selenastrum capricornutum

See Pseudokirchneriella subcapitata.


water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt or runoff water from overwatering that enters the stormwater system.

Related link: stormwater

The degree to which a substance or mixture of substances can harm humans or animals.

Toxicity Identification Evaluation

TIE; series of toxicological studies to characterize and identify causative toxicant(s).

Related link: Toxicity Identification Evaluation
Related terms: TRE, toxicity reduction evaluation
Toxicity Reduction Evaluation

TRE; systematic evaluation of operations and effluent characteristics to determine the source(s) of toxicity and so that the toxicity can be controlled sufficiently to allow a discharger to comply with their permit limits.

Related terms: TIE, toxicity identification evaluation
toxicity testing

Biological testing, such as a bioassay with an invertebrate or fish to determine the adverse effects of a compound or effluent.

Related link: toxicity testing
Related terms: acute toxicity, chronic toxicity, toxicity

Water that has been contaminated with liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture.

Related link: wastewater
whole effluent toxicity tests

WET tests; measure wastewater's effects on specific test organisms' ability to survive, grow and/or reproduce.

Related link: whole effluent toxicity tests