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Agency (U.S. EPA) intends to control exposure to toxic substances with risk levels
–4
–7
ranging from 10 to 10 (0.00001 to 0.01%) throughout life (Masters, 1991).
Environmental Risk Assessment is a process for determining the probability for
negative effects on human health or the environment as a result of exposure to one
or more physical, chemical or biological agents. ERA requires knowledge about the
negative effects of exposure to chemical substances or materials, as well as knowl-
edge about the intensity and duration necessary for these to cause negative effects
on population and the environment. Decision-making within sound risk management
entails examining the various choices for risk reduction. The risk assessment scope
is generally local; environmental impacts are presented in the form of risk per
researched recipient because it is the case with the value for exposure to toxic
–7
–4
substances at levels entailing a risk ranging from 10 to 10 throughout life.
Environmental risk assessment will be explained in detail in Chapter 4.
1.5.4.3 Impact Pathway Analysis (IPA)

Contrary to this approach, the Impact Pathway Analysis (IPA) estimates the overall
damage, including even relatively small contributions, in locations more than 1000
km away from the source of emissions. The damage is presented in the form of
costs, but because these costs are not included in the price of the product or service
responsible for the emissions, they are known as external costs.
An example of an IPA scheme is shown in Figure 1.5. After the location and
technology producing the pollutant have been selected, Phase 1 deals with the
calculation of emissions and the plant’s demand for resources. Phase 2 concerns the
distribution of emissions to several recipients. The following phases consider the
transition processes and impact assessments, for example, a bad fruit crop or higher
incidence of asthma attacks. Once all physical impacts have been calculated, eco-
nomic assessments are applied to the impacts to estimate damages in currency
amounts (euros, dollars, yens). Impact pathway analysis is explained as a special
form of ERA at the end of Chapter 4.

Units Phases Examples
kg Emission Particles
Transportation Changes in
g/m? conentration
of pollutants
g/d Natural processes Deposition in the
respiratory system
Number of Impact Asthma
patients

Euros Damage Change in health
FIGURE 1.5 Impact pathway analysis (IPA) scheme. (Adapted from European Commission
— DGX11), ExternE – Externalities of Energy, ECSC-EC-EAEC, Brussels-Luxembourg,
1995.)

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