5.5 Impact Assessment (Phase 3)
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used to convert material or energy flows into midpoint or endpoint impacts. While
these are very helpful to use, CFs can differ significantly from one another in
how they characterize the flows, the impact models they use, and how they might
optionally normalize, group, or weight different impacts.
In selecting impact categories, indicators, and methods to use for an LCA, it
is helpful to critically compare and consider available impact assessment methods
using the following basic criteria:
• Completeness: Are all conceivable effects on health and the environment taken
into account by the method?
• Practicality: How easy, time-efficient, and cost-efficient is the method? Is any
aggregation of the individual impacts reproducible?
• Scientific content: Is the latest science in terms of effects and mechanisms of
action considered? Are the local and temporal effects as well as the different
routes of exposure appropriately taken into account? Finally, is there a clearly
defined relationship between the various effects and potential damage?
• Transparency: Does the method evaluate the impacts in a traceable way?
The Life Cycle Initiative led by the United Nations Environment Programme
(UNEP) and the Society of Environmental Toxicology and Chemistry (SETAC) has
also published guidance documents on the use of impact assessment indicators in
LCIA (UNEP, 2016, 2019a).
Another relevant tool within impact assessment and used in this chapter is the
USEtox model (Rosenbaum et al., 2008; Hauschild et al., 2008). Developed with
the support of the UNEP-SETAC Life Cycle Initiative (UNEP, 2020), USEtox is
an environmental model that estimates the fate, exposure, and effects of chemicals
to characterize their human health and ecotoxicological impacts. It is the result of
an effort to gain scientific consensus and harmonize the multiple characterization
models for chemicals that existed in the past. Currently, it is being implemented
both on its own and within various LCA impact assessment methods.
Some of the other impact assessment methods that are widely used today
include LC-IMPACT (Verones et al., 2019), IMPACT World+ (Bulle et al., 2019),
Ecological Scarcity (Frischknecht and Büsser Knöpfel, 2013), and TRACI (Bare,
2011).
5.5.2 Step 2: Classification
In the classification step, the flows from the life cycle inventory are assigned to the
chosen midpoint impact categories. Some common, chemically related midpoint
impact categories include:
• Climate change
• Trophospheric ozone creation
• Freshwater eutrophication
83
used to convert material or energy flows into midpoint or endpoint impacts. While
these are very helpful to use, CFs can differ significantly from one another in
how they characterize the flows, the impact models they use, and how they might
optionally normalize, group, or weight different impacts.
In selecting impact categories, indicators, and methods to use for an LCA, it
is helpful to critically compare and consider available impact assessment methods
using the following basic criteria:
• Completeness: Are all conceivable effects on health and the environment taken
into account by the method?
• Practicality: How easy, time-efficient, and cost-efficient is the method? Is any
aggregation of the individual impacts reproducible?
• Scientific content: Is the latest science in terms of effects and mechanisms of
action considered? Are the local and temporal effects as well as the different
routes of exposure appropriately taken into account? Finally, is there a clearly
defined relationship between the various effects and potential damage?
• Transparency: Does the method evaluate the impacts in a traceable way?
The Life Cycle Initiative led by the United Nations Environment Programme
(UNEP) and the Society of Environmental Toxicology and Chemistry (SETAC) has
also published guidance documents on the use of impact assessment indicators in
LCIA (UNEP, 2016, 2019a).
Another relevant tool within impact assessment and used in this chapter is the
USEtox model (Rosenbaum et al., 2008; Hauschild et al., 2008). Developed with
the support of the UNEP-SETAC Life Cycle Initiative (UNEP, 2020), USEtox is
an environmental model that estimates the fate, exposure, and effects of chemicals
to characterize their human health and ecotoxicological impacts. It is the result of
an effort to gain scientific consensus and harmonize the multiple characterization
models for chemicals that existed in the past. Currently, it is being implemented
both on its own and within various LCA impact assessment methods.
Some of the other impact assessment methods that are widely used today
include LC-IMPACT (Verones et al., 2019), IMPACT World+ (Bulle et al., 2019),
Ecological Scarcity (Frischknecht and Büsser Knöpfel, 2013), and TRACI (Bare,
2011).
5.5.2 Step 2: Classification
In the classification step, the flows from the life cycle inventory are assigned to the
chosen midpoint impact categories. Some common, chemically related midpoint
impact categories include:
• Climate change
• Trophospheric ozone creation
• Freshwater eutrophication