Biomedical Engineering Reference
In-Depth Information
and pollutant emissions associated with each dollar spent in this sector. Since
the expenditure of each sector on all other sectors is included, it is possible to
exhaustively describe the chain of suppliers and impacts for a given service.
The disadvantage compared with Process LCA is that IO LCA is not able to
differentiate products from the same sector (e.g., it is not able to distinguish
T-shirt A from T-shirt B if they have the same price), which is a main issue
for the manufacturing phase of nano-based materials.
11.1.2.3 Life Cycle Impact Assessment
Inventories are useful for comparing the environmental emissions of differ-
ent products, but are not sufficient to compare, for example, one product that
uses more detergent to another that generates some nanosilver emissions.
Impact assessment estimates the environmental and human health impacts
associated with these emissions so that the impacts can then be compared
between different chemicals.
Impact assessment evaluates the impact on the environment from the
emissions inventoried previously. It can be broken down into three steps
5
:
• Classification determines which emissions contribute to which envi-
ronmental impacts (greenhouse effect, human toxicity, ecotoxicity,
resource use, etc.).
• Midpoint characterization weighs the emissions for each impact
c at e gor y.
• Damage characterization aggregates impact categories into damage
categories (damage to human health, ecosystems, climate equilib-
rium, resources, and ecosystem services) corresponding to areas that
deserve protection.
An additional normalization step can be carried out to show the contribu-
tion of the studied product to the global impact, for a given impact category.
Environmental impact assessment can be completed in the interpretation
phase with a social-based weighting of impacts or damages to evaluate the
relative importance of intermediate classes of impact or damage categories.
Many different methods exist (see review by Hauschild et al.
6
). For human
toxicity and ecotoxicological impacts, impact assessment methods estimate
chemical impacts using environmental and exposure models that simulate
the fate (transport, dilution, and degradation), exposure (e.g., human intake),
and effects (e.g., dose-response and severity) of many chemicals in a con-
sistent manner such as with the United Nations Environment Programme
(UNEP)—Society of Environmental Toxicology and Chemistry (SETAC) con-
sensus toxicity model (USEtox™ model
7, 8
; Figure 11.2).
The various cause-effect models yield a list of characterization factors
expressing the impact in kilogram of a reference substance per kilogram of
