Environmental Engineering Reference
In-Depth Information
Quantitative ERA is necessary for the final decision making on the ERM and
environmental risk reduction (ERR) activity, or for the selection of the ERM options
and ERR alternatives.
4.2 Generic and site-specific quantitative ERA
Generic ERA for legislative purposes, based on the hazard of the chemical substance,
product or waste is usually evaluated in the context of a generic environment, for
example, a country, a watershed or a larger region such as Europe. Evidently, this kind
of ERA involves high uncertainties due to statistical errors, spatial diversification and
environmental heterogeneities.
Site-specific risk measures the hazard in the context of a concrete locality, or
region considering environmental characteristics, land uses and typical receptors
within the land in question. Site-specific management needs a risk value for decision
making based on the specific environmental characteristics, land uses and receptors.
When the impacted environment is extended, its specific characterization will be lim-
ited. While a local or a watershed-scale environment can be mapped in detail or
characterized by numerical models, a large region or the globe needs more generic
approximation.
In practice, a mixture of generic and site-specific information is often used in
the tiered ERA procedure applying generic information in the site-specific assess-
ment's first tier. PEC (predicted environmental concentration) may be calculated using
generic environmental characteristics if site-specific assessment or historical data are
not available. However, they should be step-wise replaced with site-specific informa-
tion, otherwise the pessimistic approach is not satisfied (generic characteristics may be
higher or lower than the site-specific ones) and negative cases may be excluded without
being properly justified. Other usual generic elements of the site-specific ERAs are the
PNEC values (predicted no effect concentration, i.e., predicted concentration which
does not affect the ecosystem adversely) and the DNEL values (derived no-effect level
for humans) or TDI (tolerable daily intake by humans). When characterizing risk,
predicted environmental concentration (PEC) is compared to PNEC (in the case of an
ecosystem) and D, the dose taken in by humans (or ADI, the average daily intake) to
DNEL (for humans). The dose, taken in by humans is determined from PEC by known
intake parameters. The amount of air of one breath and the number of breaths gives
the daily air intake. Multiplying the inhaled air volume by the predicted contaminant
concentration in air (PEC air ) gives the contaminant intake. The concentration of the
contaminant in water and the daily water consumption give the daily intake by water.
RCR, the risk characterizing ratio, is PEC/PNEC for the ecosystem, and D/DNEL or
ADI/TDI for humans.
Generic risk tools concentrate on the assessment of the chemical substance, its
physico-chemical characterization, and environmental fate and behavior. The environ-
ment is characterized with national or regional default values, given that the precise
location of the target environment is not known. Data from databases and the results of
mathematical, chemical and biological models is preferred for the purposes of generic
ERA. In site-specific cases, the characteristics of the site and the relevant land uses
should be considered. For example: the threshold concentration in fish should be lower
Search WWH ::




Custom Search