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240 R.K. Rosenbaum et al.
non-cancer, each cover a multitude of different diseases, so this is a simplification
reflecting the fact that it is very difficult to predict the many underlying human
toxicity endpoints from the animal dose-response curves from laboratory experi-
ments with test animals which are normally the basis of the effect factor.
The severity factor represents adversely affected life years per disease case
(DALY/case), distinguishing between differences in the severity of disabilities
caused by diseases in terms of affected life years, e.g. discriminating between a
lethal cancer and a reversible skin irritation. It is quantified by the statistically
determined, population-based years of life lost (YLL) and years of life disabled
(YLD) due to a disease.
10.12.3 Emissions and Main Sources
The relevant emissions and main sources are identical to those of the ecotoxicity
impact category and discussed in Sect. 10.11.
10.12.4 Existing Characterisation Models
Again here, Sect. 10.11 contains a discussion on existing characterisation models,
which largely applies also to the human toxicity impact category.
In USEtox, the units of the two human toxicity midpoint indicators for
non-cancer and cancer are Comparative Toxic Unit for humans CTU h [disease
cases]. They can be added up to a single human health indicator, but then the
interpretation needs to consider that this intrinsically assumes equal weighting
between cancer and non-cancer effects (which includes equal weighting between
e.g. a reversible skin rash and non-reversible death). Human health endpoint
indicators in USEtox are given in the Comparative Damage Unit for human health
CDU h [DALY]. In accordance with the purpose of endpoint modelling, this indi-
cator better represents the distinction of the severity of different effects.
When interpreting human toxicity indicators from existing methods, it is
important to be aware that these only provide indicators for global population ex-
posure to outdoor and indoor emissions, while human toxicity for occupational
exposure of workers or direct exposure related to product use for consumers are not
yet covered by USEtox and the other characterisation models, despite their very high
relevance. Products of special interest in this context are cosmetics, plant protection
products, textiles, pharmaceuticals and many others, that may in particular contain
substances having toxic properties and have the potential to cause mutagenic,
neurotoxic or endocrine disrupting effects. This is the subject of ongoing research
and will be included in LCIA methods once the models are mature and operational.
For further details see Chap. 40 and Hauschild and Huijbregts (2015).