A value applied to toxicity values (i.e. LC50 or
LOEC) to provide an estimate of the concentration that will cause no detrimental
effect on an organism. Sometimes referred to as an extrapolation factor or
a safety factor.
AS/NZS 4360: Risk Management is the Australian and New Zealand joint
Risk Management Standard.
It was published originally in November 1995 and substantially revised and
republished in April 1999.
Risk management is the culture, processes and structures that
are directed towards the effective management of potential opportunities and
Refers to common internationally used test species,
such as rainbow trout or cladoceran ‘water fleas’ for fresh waters,
or earthworms for soil.
Benchmark values are sometimes applied where regulatory
guidelines or standards to protect ecological receptors are not available
The degree to which a contaminant in environmental media can be
by an organism.
The bioavailability of a chemical to the
receptor will depend upon its chemical and physical characteristics, and the
characteristics of the media it is in. For example, hydrophobic compounds tend
to bind to organic matter present in the soil or water, making them less ‘bioavailable’
to the receptor. Reduced bioavailability means a lower exposure of the chemical
to the ecological receptor. To a certain degree, bioavailability also depends
upon the physiology of the receptor of concern and the route of exposure. For
example, if contaminated soil is ingested by a bird, its subsequent
bioavailability will be dependent upon its uptake through the gut wall of the
bird. In Level 1 ERA it is assumed that the total amount of chemical is
bioavailable, which in most cases adds considerable conservatism into the
abbreviation of benzene, toluene, ethylbenzene and xylene: volatile hydrocarbons
that are present as components of petroleum-based fuels but are also
common contaminants at a range of contaminated sites.
For more information on testing in New Zealand related
to BTEX follow this link.
abbreviation of copper, chromium and arsenic. The first two are metals and the last is a
metalloid. They are commonly used together in the treatment of timber.
Arsenic was historically also widely used as part of a sheep and cattle dipping solution.
The outcome of an event or situation expressed qualitatively or
quantitatively, being a loss, injury, disadvantage or gain.
"Any substance(including gases, liquids,solids
and micro-organisms) or energy (excluding noise), or heat, that either
by itself or in combination, with the same, or similar or other
substances, energy, or heat -
(a) when discharged into water, changes or is likely
to change the physical, chemical, or biological condition of water, or
(b) when discharged onto or into land or into air,
changes or is likely to change the physical, chemical, or biological
condition of the land, or air onto or into which it is discharged.
A contaminated site is a site where concentrations of
contaminants are above background concentrations, and an assessment suggests that the
substances pose a risk to human health or the environment.
Criteria (singular, criterion).
In the area of risk assessment, and more specifically, for the
setting of protective levels for contaminants in the environment, the term ‘criteria’
is often used in two separate, but related ways. How the term ‘criteria’ is
applied appears to be dependent upon both the discipline (i.e. aquatic or
terrestrial toxicity) and the country. The word ‘criteria’ in the context of
water quality in Australia and in Canada, for example in the ANZECC (2000)
guideline and in the Canadian water quality guidelines (CCREM, 1987), refers to
scientific findings that are used to derive guidelines or standards for water
use. For example, the finding that ‘half of a sample of test organisms dies
after a given time of exposure to a certain concentration of a toxicant’, is a
criterion. In the U.S. however, water quality criteria refer to values that
reflect available scientific information on the maximum acceptable
concentrations of chemicals in water that will protect aquatic life and human
health. This is similar to how the term ‘criteria’ is employed for soil
quality purposes, i.e. it is used to describe a protective level for a
particular soil contaminant based on the available scientific data.
Ecosystems, habitats, communities, populations and individual organisms that can be exposed directly or indirectly to
Ecological risk assessment
Ecological risk assessment is the application of risk assessment techniques
to assessing risks to plants, animals, and ecosystems.
Plants, animals, or ecosytems that are identified and
considered to be of significant societal relevance, ecological or economical
significance. Ecological values may be generic or specific to a
particular site or habitat.
EIL (ecological impact level)
The concentration of a contaminant which, if exceeded, may adversely
affect ecological values.
are identified during initial discussions between the
risk manager and the risk assessor, and are ecologically-relevant receptor/s
Assessment end points
Measurement end point is a measurable response to a stressor (measure,
metric or index) that is quantifiably related to the assessment end point. A
measurement end point is also known as an ‘effects measure’.
Although assessment and measurement end points may appear to be the
same thing, they are not necessarily so.
Measurement end points are usually more easily measured than an assessment
endpoint. An assessment end point must have ecological relevance, for example, an
impact at a population or community level. However, due to the high cost of
obtaining measurements of end point at this level, most toxicity tests measure an
end point at the level of the individual organism. Generally, measurement end
point data are extrapolated into corresponding assessment end point values.
Therefore, it is very important that the measurement end point is related to a
biologically significant response such as survival or fecundity of a population.
An example (from ASTM E 1848) is given below
- Assessment end point: Population-level effects on resident earthworms living in metal-contaminated soils
- Measurement end point: Toxic effects of site soils to surrogate species of earthworms in standard toxicity tests.
Relationship between assessment and measurement
end point: The higher frequency of death of earthworms in site soils compared to control soils or soils from reference sites in the standard earthworm bioassay indicates that mortality is likely to be elevated in populations of earthworms in the metal- contaminated areas of the site.
Guidelines that have statutory force to maintain a
desired quality of some part of the environment, such as ‘drinking
water standards’ or ‘soil quality standards’ Standards should be
based on sound scientific data, however the desired level of ‘quality’
is also a political and social decision. Therefore, environmental
standards provide the foundation for achieving the objectives of
Exposure assessment is used to estimate the magnitude, duration and frequency
of exposure of plants, animals or ecosytems to contaminants of concern.
Includes determining mechanisms or pathways of exposure.
Route by which contaminants enter an organism, e.g.,
via water and/or food.
Toxicity tests are conducted under specified and controlled conditions
that are not the same as the conditions that occur at contaminated sites. For
example, the test species may not be the species of concern, or the test
concentrations may be a lot higher than the likely environmental concentrations.
Extrapolation factors are applied to the toxicity data to ensure protection of
the ecological receptor under field conditions. These ‘factors’ are
applied to take into account such things as:
Extrapolating from a response at a high test concentration / short
duration exposure to a lower environmental concentration / longer
duration of exposure
- Extrapolating from laboratory to field data
- Extrapolating from a test species to the species of concern (factor may
be higher if species is threatened or endangered)
- Allowing for interindividual variation in sensitivity within a population
- Adding conservatism to poor-quality data
- Extrapolating from an effect level concentration (EC50, LC50
or LOEC) to a NOEC.
Individual extrapolation factors are often a number between 0 and 10, and the
value is usually determined according to a set of given criteria. For example,
to convert a LOEC to a NOEC for screening level (Level 1) assessments, a standard safety
factor of 10 is commonly used. In ERA, where the total amount of uncertainty can
be very high, overuse of application factors can lead to highly unrealistic
estimates of investigation levels or benchmark concentrations. It is quite
useful to have an understanding and knowledge of the extrapolation factors (if
any) that have been used to derive the benchmark or regulatory values for
Numerical or narrative statements whose application should
maintain a certain environmental use, for example a stated degree of protection
for aquatic biota. Numerical guidelines should be based on sound scientific
data. In effect, a guideline translates (eco) toxicity data into a form from
which a standard could, or should, be written. This may call for a value
judgement on acceptable risks or requirements.
The concentration of all metallic cations, except those of
alkali metals, present in water. In general, hardness is a measure of the
concentration of calcium and magnesium in water.
Hazard and hazard identification
A hazard is a source of potential harm or a situation with a potential to
cause adverse effect. Hazard identification looks at the source of the risk,or
the characteristics of the site that might lead to risk.
Human health risk assessment
Application of risk assessment techniques to assessing risks
to human health and safety.
Likelihood, Probability and Frequency
Likelihood is a qualitative description of probability or frequency.
Probability is measured by the ratio of specific outcomes to the total number
of possible outcomes. It is expressed as a number between 0 and 1, with 0
indicating an impossible outcome and 1 indicating an outcome is certain.
Frequency is the number of items occurring in a given category. Often
frequency is linked to time, for example, the number of events in a year.
Mechanism of action
Understanding the toxic mechanism of a contaminant helps evaluate the
importance of potential exposure pathways and selection of sensitive ecological
receptors. For example, a contaminant (like a vertebrate pesticide) may
selectively affect higher vertebrates by interfering with organ systems not
found in invertebrates, or a contaminant may be present at a level that may not
be toxic to most organisms, but which will threaten top predators through food
Qualitative risk assessment
Qualitative risk assessment is where the likelihood or the magnitude of the
consequences are expressed in qualitative terms (i.e. not quantified).
Quantitative risk assessment
Quantitative risk assessment is risk assessment where the probability or
frequency of the outcomes can be estimated and the magnitude of consequences is
quantified so that risk is calculated in terms of probable extent of harm or
damage over a given period.
A plant, animal, or ecosystem exposed to a stressor.
A standard chemical used to measure the sensitivity of the
test organisms in order to establish confidence in the toxicity data obtained
from the test material. In most instances a toxicity test with a reference
toxicant is performed to assess the sensitivity of the test organisms at the
time the test material is evaluated, and the precision of results obtained by
the laboratory for that chemical.
Risk is defined as the chance of something happening that will have
a (generally adverse)
impact on plants, animals, or ecosystems. It may be an event, action, or lack of action. It is
measured in terms of consequences and likelihood.
Risk identification is the process of determining what can happen, why
and how. Identifying risks requires looking at all possible sources of risk
and the elements at risk.
A physical, chemical or biological entity that induces an
adverse response in a plant, animal or ecosystem.
Mechanism of exposure of a receptor to a stressor.
Toxicity to plants
A statistical procedure used to analyse data from toxicity tests.
The overall process of evaluating the type and magnitude of toxicity caused
by a hazardous substance. It involves determining the toxicity of the
contaminants, and establishes the sensitivity of the ecological receptor(s).
Toxicity of mixtures:
is where the toxicity of a mixture of
contaminants equals the summation of the toxicities of the individual component;
e.g. for a mixture of compounds A + B: if the toxicity of compound A = 1,
and toxicity of compound B = 1, then the additive toxicity would be 1 + 1 = 2.
is where the toxicity of a mixture of contaminants
is significantly less than the summation of the toxicities of the individual
components, e.g. 1 + 1 = 1.
is where the toxicity of a mixture of contaminants
results in a potentiation of toxicity where the total toxicity is far greater
than the summation of the toxicities of the individual components, e.g. 1 + 1 =
Toxicity tests are used to determine the toxicity of contaminants to one or
more species. A toxicity test measures the degree of response produced by
exposure to a specific level of contaminant (i.e. concentration or dose)
compared to an unexposed control.
are most commonly used in risk assessment. An acute
test generally involves an exposure to a single chemical at a high concentration
over a short time duration. A ‘short time’ is defined relative to the
life-span of the test organism. The types of effects or ‘end points’ which
are measured in an acute test are lethality (e.g. the LC50). However,
sub-lethal end points that illustrate adverse effects (e.g. the EC50),
such as changes in the behaviour of physiology of the test organism can also be
Acute toxicity tests
In aquatic toxicity tests, an acute test will usually have a duration of
between 48 and 96 hours. The test duration should always be reported with the
ecotoxicity value (e.g. 96-hour EC50). In soil toxicity tests the terminology ‘acute’
and ‘chronic’ are infrequently used. Standard test durations may vary
between 4 and 28 days.
Acute toxicity values are often converted to estimates of
chronic toxicity values using extrapolation factors.
Chronic toxicity tests are usually low-level exposures and conducted over
a longer time interval. For example, they may be conducted over the entire life
cycle of an organism. Chronic toxicity tests are more realistic reflections
of a real environmental exposure. Longer-term tests tend to be more complicated
and hence more expensive than acute tests. The types of effects generally measured include reduced growth or reproductive changes. Ecotoxicity
values such as the NOEC and the LOEC are mainly generated from chronic data.
Where chronic data are not available, LOECs are sometimes derived by applying
extrapolation factors to an acute end point such as the LC50. When
scanning the toxicity literature for ecotoxicity values, the risk assessor
should take care to understand exactly how the values were obtained.
Measures of the level (i.e.concentration or dose) of a chemical stressor at
which a specific level of toxicity is observed in a receptor (e.g. LC50).
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LD or LC Lethal Dose or Lethal Concentration
The dose or concentration that produces a specified level of
mortality in the test population within a specified time, e.g. LC50
is the median lethal concentration or the concentration of a substance
at which 50% of the test population are killed. Typical levels are LC10,
LC25, LC50, LC75, LC100.
ED or EC Effective Dose or Effective Concentration
The dose or concentration that produces a specified level of effect in
the test population within a specifed time, e.g. EC50 is the median
effective concentration or the concentration of a substance at which 50%
of the test population are affected. Typical levels are EC10,
EC25, EC50, EC75, EC100.
No observable effect concentration
Lowest observable effect concentration
Uptake, distribution, metabolism and excretion of toxic chemicals within