6.5 Effect Assessment (Step 3)
141
factor. Just as for human toxicity, the method of assessment factors is widely used
in practice to determine a PNEC given a level of uncertainty regarding an effect:
PNEC =
LOEC (or NOEC)
AF
(6.26)
• PNEC (predicted no-effect concentration): the concentration below which exposure to a substance will likely not have a toxic effect
• LOEC (lowest observed effect concentration): the lowest concentration of a
substance in a series of test concentrations that causes a statistically detectable
toxic effect on the studied organism
• NOEC (no observed effect concentration): the highest concentration of a substance in a series of test concentrations that does not show a toxic effect on the
studied organism
• AF: assessment factor
In addition to extrapolation to a PNEC value, another threshold value used in
practice for the environment is the maximum immission concentration (MIC). An
MIC value refers to the concentration of a substance in air, water, and soil below
which no damages to animals, plants, and humans are known to occur (in units of,
for example, µg/m 3 ). The focus of the MIC is on preventing the long-term effects of
chronic toxicity.
Within an effect assessment, not only direct but also indirect toxic effects from
the accumulation of substances in the food chain can be considered.
6.5.3.3 General Aspects to Consider
In the course of the effect assessment, it is important to keep in mind some
overarching aspects that can influence the assessment:
• Inadequate characterization of hazard: All available references and previous
studies regarding the effects, exposure pathways, and exposed organisms should
be considered.
• Well-defined evaluation endpoints: The determination of concentrations and
doses that do not cause adverse effects in test organisms depends on how adverse
effects are defined and on how they are investigated. In particular, the values
of the LOEC and NOEC depend on the test concentrations chosen. A different
selection of test concentrations generally leads to different LOEC and NOEC
values (Laskowski, 1995).
• Consider various methods: Scientists often use and develop a wide range of
methods to evaluate effects. While data accuracy and method transparency are
important to ensure, it is advantageous to not limit assessments to using only a
small set of previously established methods.
• Diversity, variability, and temporal dynamics of ecosystems: The resulting effects
determined during testing have to be extrapolated to the real situation in the
environment or in humans, and this is of course associated with uncertainties.
141
factor. Just as for human toxicity, the method of assessment factors is widely used
in practice to determine a PNEC given a level of uncertainty regarding an effect:
PNEC =
LOEC (or NOEC)
AF
(6.26)
• PNEC (predicted no-effect concentration): the concentration below which exposure to a substance will likely not have a toxic effect
• LOEC (lowest observed effect concentration): the lowest concentration of a
substance in a series of test concentrations that causes a statistically detectable
toxic effect on the studied organism
• NOEC (no observed effect concentration): the highest concentration of a substance in a series of test concentrations that does not show a toxic effect on the
studied organism
• AF: assessment factor
In addition to extrapolation to a PNEC value, another threshold value used in
practice for the environment is the maximum immission concentration (MIC). An
MIC value refers to the concentration of a substance in air, water, and soil below
which no damages to animals, plants, and humans are known to occur (in units of,
for example, µg/m 3 ). The focus of the MIC is on preventing the long-term effects of
chronic toxicity.
Within an effect assessment, not only direct but also indirect toxic effects from
the accumulation of substances in the food chain can be considered.
6.5.3.3 General Aspects to Consider
In the course of the effect assessment, it is important to keep in mind some
overarching aspects that can influence the assessment:
• Inadequate characterization of hazard: All available references and previous
studies regarding the effects, exposure pathways, and exposed organisms should
be considered.
• Well-defined evaluation endpoints: The determination of concentrations and
doses that do not cause adverse effects in test organisms depends on how adverse
effects are defined and on how they are investigated. In particular, the values
of the LOEC and NOEC depend on the test concentrations chosen. A different
selection of test concentrations generally leads to different LOEC and NOEC
values (Laskowski, 1995).
• Consider various methods: Scientists often use and develop a wide range of
methods to evaluate effects. While data accuracy and method transparency are
important to ensure, it is advantageous to not limit assessments to using only a
small set of previously established methods.
• Diversity, variability, and temporal dynamics of ecosystems: The resulting effects
determined during testing have to be extrapolated to the real situation in the
environment or in humans, and this is of course associated with uncertainties.