142
6 Risk Assessment and Management of Chemical Products
Keep in mind that there is a possibility that extremely sensitive species or persons
are not protected by the established no-effect levels.
• Limited validity of laboratory tests on aquatic organisms: An initial estimate of
environmental effects is often based on data for aquatic organisms (fish, daphnia,
algae). These findings have, for example, only limited significance for terrestrial
ecosystems.
• Variability of product quality: Especially in the early development stages of
a product, the variability of product quality can complicate a prospective risk
assessment.
• Not all effects covered: The concept of a safe effect threshold cannot be applied
to all effects. For genotoxic carcinogens, for example, a tolerable risk level has
to be established on the basis of the results from in vivo experiments.
• Low-dose effects: Remember that not all chemicals may follow the traditional
thinking of “the dose makes the poison.” Research is ongoing to understand
substances such as some EDCs that may have a wide range of adverse effects
that are greater at lower exposure levels.
6.6
Risk Characterization and Classification (Step 4)
In the next step of risk assessment, risk characterization compares the findings
of the exposure and effect assessments in order to assess the vulnerability of a
population or of an environmental compartment to the use of the substance. This
is often done deterministically in the form of a risk quotient, but it can also be
done probabilistically by using exposure and effect distributions. Risk classification
then aims to determine whether the characterized risk is acceptable or not. This
assessment step depends on set societal protection goals, but it still needs to be
conducted in a transparent manner and in agreement with established criteria.
As will be discussed more in this chapter and further in Chap. 9, a “subjective”
classification of the risk does not mean that it is “arbitrary.” If a risk is deemed not
to be acceptable, subsequent risk management actions will then need to be identified
and implemented in the next and final step of risk assessment (Sect. 6.7).
This section introduces a few of the fundamental calculation methods for
assessing risks using both deterministic and probabilistic approaches. For risks to
humans and the environment, a deterministic approach makes use of the margin of
safety (MOS) and the risk quotient (RQ), respectively. The basic methods to take
into account the toxicity of chemical mixtures are also introduced.
6.6.1 Deterministic Human Health Risk: Margin of Safety (MOS)
Assessing the risk posed to humans aims to consider the risks for all identified critical effects across all population groups and relevant exposure routes. A deterministic
description of this risk can be created by forming the quotient of the extrapolated
safety threshold for adverse effects (e.g., derived no-effect level in humans (DNEL))
6 Risk Assessment and Management of Chemical Products
Keep in mind that there is a possibility that extremely sensitive species or persons
are not protected by the established no-effect levels.
• Limited validity of laboratory tests on aquatic organisms: An initial estimate of
environmental effects is often based on data for aquatic organisms (fish, daphnia,
algae). These findings have, for example, only limited significance for terrestrial
ecosystems.
• Variability of product quality: Especially in the early development stages of
a product, the variability of product quality can complicate a prospective risk
assessment.
• Not all effects covered: The concept of a safe effect threshold cannot be applied
to all effects. For genotoxic carcinogens, for example, a tolerable risk level has
to be established on the basis of the results from in vivo experiments.
• Low-dose effects: Remember that not all chemicals may follow the traditional
thinking of “the dose makes the poison.” Research is ongoing to understand
substances such as some EDCs that may have a wide range of adverse effects
that are greater at lower exposure levels.
6.6
Risk Characterization and Classification (Step 4)
In the next step of risk assessment, risk characterization compares the findings
of the exposure and effect assessments in order to assess the vulnerability of a
population or of an environmental compartment to the use of the substance. This
is often done deterministically in the form of a risk quotient, but it can also be
done probabilistically by using exposure and effect distributions. Risk classification
then aims to determine whether the characterized risk is acceptable or not. This
assessment step depends on set societal protection goals, but it still needs to be
conducted in a transparent manner and in agreement with established criteria.
As will be discussed more in this chapter and further in Chap. 9, a “subjective”
classification of the risk does not mean that it is “arbitrary.” If a risk is deemed not
to be acceptable, subsequent risk management actions will then need to be identified
and implemented in the next and final step of risk assessment (Sect. 6.7).
This section introduces a few of the fundamental calculation methods for
assessing risks using both deterministic and probabilistic approaches. For risks to
humans and the environment, a deterministic approach makes use of the margin of
safety (MOS) and the risk quotient (RQ), respectively. The basic methods to take
into account the toxicity of chemical mixtures are also introduced.
6.6.1 Deterministic Human Health Risk: Margin of Safety (MOS)
Assessing the risk posed to humans aims to consider the risks for all identified critical effects across all population groups and relevant exposure routes. A deterministic
description of this risk can be created by forming the quotient of the extrapolated
safety threshold for adverse effects (e.g., derived no-effect level in humans (DNEL))