Biomedical Engineering Reference
In-Depth Information
Emission
Fate
factor
Chemical fate
Intake
fraction iF
Air
Soil
Water
Time-integrated concentration
Human exposure
Concentration-
response
Species
exposure—intake
Dose taken in
Dose-reponse
Ecotox
effect
factor
Potentially affected
fraction of species
Human
effect
factor
Disease
incidence
Severity
Damage to
human health
Damage to
aquatic ecosystems
FIGURE 11.2
USEtox source-to-impact diagram from emission to human and ecosystem health damage.
the substance emitted. Human toxicity (a midpoint category) is expressed
as the equivalent kilogram of chloroethylene emitted to air, and the human
health endpoint damage is in units of disability-adjusted life years (DALYs),
which are the sum of the years of life lost and years of life disabled (as
defined by the World Health Organization). The advantage of endpoint
factors is that they aggregate midpoint impacts and are therefore easier to
interpret. However, more assumptions and models are necessary to link the
midpoint units to the endpoint units (e.g., the assumption that each equiva-
lent kilogram of chloroethylene corresponds to a given number of DALYs),
making them more uncertain than midpoint factors. Because none of the
impact assessment methods is recognized as a standard, a robust LCA will
use several in parallel to determine the dominant impacts in all methods.
11.1.2.4 Interpretation and Uncertainty
Interpretation is a key step in the iterative process of LCA, determining
what can be neglected and what must be examined in more depth. A factor
