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6 Risk Assessment and Management of Chemical Products
In the treatment of emissions, care should be taken to avoid shifting a problem
from one environmental compartment into another. For example, in a wastewater
treatment plant, a problem shift could occur if a substance is not degraded rapidly
enough (e.g., where the biodegradation rate constant k b < 10 −3 s −1 ):
• A shift into exhaust air for volatile substances (log K H > −5) 2
• A shift into waste (biomass) for substances with low polarity (log K ow > 3) 3
Environmental exposure assessment involves using models on two different
scales:
• Local: Calculation of the local predicted environmental concentrations (PEC local )
using emission rates and considering immediate dilution. This includes emissions
from point sources (e.g., from a single factory) and from population-related
sources (e.g., from municipal wastewater treatment plants).
• Regional or continental: Calculation of predicted environmental concentrations
for a specific region (PEC regional ) or an even larger area (PEC continental ) using
emission rates and information about the distribution and transformation of the
substance in the environment. This includes emissions from area-related sources
(e.g., from large farming operations) or from many point sources that are lumped
together.
6.4.2.1 Local Exposure (Point and Diffuse Emission Sources)
Exposure assessment on a local scale focuses on the immediate entry of emissions
into the environment and intends to determine the local exposure levels (PEC local ).
To estimate local exposures, several models exist with different degrees of
accuracy to describe the entry, dilution, and fate of chemicals released into water,
air, and soil (van Leeuwen and Vermeire, 2007). Regardless of the exact choice of
the model, the following approach can generally be used to estimate the PEC local :
1. Determine the upper and lower bounds of the emission flows and the annual
amount of product used.
2. Analyze the potential emission sources and the maximum emission; this analysis
should result in describing the quantity, concentration, and dynamics of the
emission.
3. Estimate the removal of the substance by means of environmental technology
(e.g., wastewater treatment plant (WWTP), exhaust air purification plant, etc.).
4. Identify the exposed environmental compartments.
5. Estimate the amount of substance entering each environmental compartment.
2 K H : Henry’s law constant [Pa m 3 mol −1 ].
3 K ow : octanol-water partition coefficient [−]
6 Risk Assessment and Management of Chemical Products
In the treatment of emissions, care should be taken to avoid shifting a problem
from one environmental compartment into another. For example, in a wastewater
treatment plant, a problem shift could occur if a substance is not degraded rapidly
enough (e.g., where the biodegradation rate constant k b < 10 −3 s −1 ):
• A shift into exhaust air for volatile substances (log K H > −5) 2
• A shift into waste (biomass) for substances with low polarity (log K ow > 3) 3
Environmental exposure assessment involves using models on two different
scales:
• Local: Calculation of the local predicted environmental concentrations (PEC local )
using emission rates and considering immediate dilution. This includes emissions
from point sources (e.g., from a single factory) and from population-related
sources (e.g., from municipal wastewater treatment plants).
• Regional or continental: Calculation of predicted environmental concentrations
for a specific region (PEC regional ) or an even larger area (PEC continental ) using
emission rates and information about the distribution and transformation of the
substance in the environment. This includes emissions from area-related sources
(e.g., from large farming operations) or from many point sources that are lumped
together.
6.4.2.1 Local Exposure (Point and Diffuse Emission Sources)
Exposure assessment on a local scale focuses on the immediate entry of emissions
into the environment and intends to determine the local exposure levels (PEC local ).
To estimate local exposures, several models exist with different degrees of
accuracy to describe the entry, dilution, and fate of chemicals released into water,
air, and soil (van Leeuwen and Vermeire, 2007). Regardless of the exact choice of
the model, the following approach can generally be used to estimate the PEC local :
1. Determine the upper and lower bounds of the emission flows and the annual
amount of product used.
2. Analyze the potential emission sources and the maximum emission; this analysis
should result in describing the quantity, concentration, and dynamics of the
emission.
3. Estimate the removal of the substance by means of environmental technology
(e.g., wastewater treatment plant (WWTP), exhaust air purification plant, etc.).
4. Identify the exposed environmental compartments.
5. Estimate the amount of substance entering each environmental compartment.
2 K H : Henry’s law constant [Pa m 3 mol −1 ].
3 K ow : octanol-water partition coefficient [−]