Risk management of chemicals and contaminated land – from planning to verification - Environmental Deterioration and Contamination: Problems and their Management - page 263

environment, both the increase and the decrease of the risk may be slower or faster.
The risk originating from slow emission of contaminants can be eliminated by a
healthy and active environment after an adaptation period. The soil microflora is
able to degrade groundwater contaminants, the ecosystem of a wetland can clean
up contaminated runoff, etc. Depending on the ratio of the contaminant input to
the biodegrading capacity of the microflora, the balance of output risk may be at
an acceptable level.

- Continuous emission without natural attenuation results in a steadily growing risk.

Even if the load is low, the risk may increase and reach extremely high values such
as in the case of acid mine and acid rock drainage or buried hazardous wastes,
e.g., chlorinated hydrocarbons.

- High initial risk due to inherited organic contamination at abandoned sites may

be spontaneously reduced if natural attenuation is present.

- Very slow, almost invisible emission may be accumulated in the environment and

cause continuously increasing risk, and reach sooner or later an unacceptable
level of risk. Bioaccumulation and biomagnifications may enhance these silently
growing risks significantly. Slow transformations and unexpected transports of
contaminants in the environment may lead to a suddenly arising adverse effect,
also called a chemical time bomb.

Generic and site-specific risks of the same contaminant may be significantly differ-
ent, depending on the differences in environmental properties and land use specialties
between the generic, i.e., national or European “default environment'' and a certain
locality, e.g., the wetlands in the Danube Delta, the Norwegian tundra or the sodified
areas in the Hungarian Great Plain. Further differences are discussed in Section 5.3 in
this Chapter. The spatial scope of ERA can be local, regional or global as discussed in
Section 5.4.
Quantitative ERA methodology and the included transport and fate models are
versatile tools, and which can be used for the calculation of the scale of risk in any
point or at any time between the sources and the receptors. Inversely, it can also be
used for calculating the permissible maximum concentration in any spatial and time
point assuming acceptable risk for the receptors or other compliance points.
Based on this concept, quantitative ERA can be used for the creation of environ-
mental quality criteria (EQCs) or screening concentrations applying a generic ERA
model. Quality criteria for generic (natural, residential, agricultural, commercial and
industrial) land uses may lead to a nation-wide, region-wide and world-wide appli-
cable threshold value, depending on the aim of the regulators. The threshold may be
applied for authorization, prohibition, ban or intervention. Risk values and EQCs
incorporate uncertainties, which may increase with the extension of the scope of the
management. Establishment of generic and site-specific quality criteria for air, waters,
soils, sediments or wastes is increasingly “risk-based'' in present-day environmen-
tal management and regulation, compared with traditional experience- and expert
judgment-based EQCs. Quantitative ERA can be the solid basis of decision making in
the course of ERM. Decision makers take into account other information, too, such
as economic, socio-economic, or ethical arguments in making their decisions.
The impacted receptors in the environment may be humans and/or ecosystems,
individual species or communities, food chains and food webs. Risk posed by multiple