Scientific and engineering improvement of environmental risk management - Environmental Deterioration and Contamination: Problems and their Management - page 419

ecosystem, which causes uncertainties in the quantity and quality as well as mobil-
ity and bioavailability of the contaminants. Contaminants may undergo significant
changes due to interaction with the living part of the ecosystem over the long term
and the changes in the ecosystem's metagenome, species diversity, adaptation, resis-
tance, tolerance and community structure are all further sources of uncertainties.
Many of these changes are hidden from the common assessment tools and increase
uncertainty in an undefined scale and way. The borderline of contaminant trans-
port is uncertain in all three directions. Characterization and modeling subsurface
layers, subsurface water levels, flow rates and flow directions are accompa-
nied by high modeling and parameter uncertainty, and multiple measurement
errors;
- Land uses imply uncertainties due to multiple land uses, e.g., natural, recreational,
residential, agricultural land use with closely related natural or protected natural
land uses. Further uncertainties lie in multiple exposures: human exposures to
drinking water, eating food and respiring air contaminated with the same chemical
substance or with a mixture of chemicals. Unidentified land uses, highly uncertain
land uses accompanied with high time-related, spatial and individual variations
also add to the uncertainties. Information on the exposures and sensitivities of land
users and the final receptors of the hazardous contaminants are generally uncer-
tain, and there are no nation-wide or site-specific assessment data, thus default
values or estimates are used for risk assessment and risk management;
- Receptors , i.e., the ecosystem and humans are no homogeneous groups. Both
of them consist of subgroups and individuals with different exposures and sen-
sitivities. In addition to these intraspecies variations, the same individual may
have more or less sensitive periods during a day, a season or during his or her
life span;

- Exposure of the receptors is uncertain due to irregular activities and consump-

tion, seasonal variations, differences in behaviors and lifestyle during summer and
winter, weekdays and weekends, etc. Considerable effort is needed to obtain valid
information from the assessment of the exposure parameters. Lack of data is typ-
ical in this respect, so that read-across and utilization of each other's national
exposure parameters are widespread practices. This brings more uncertainty into
the system because, for example, the behavior and consumption of the United
States' population significantly differ from the European, or the Norwegian from
the Hungarian ones. Site-specific exposure of humans needs thorough surveying
because uncertain sampling, inadequate questionnaires with misleading questions,
erroneous answers and mistakes in the evaluation, improperly selected statistical
evaluation methods and the misinterpretation of the outcome may increase the
uncertainty. Compilation of a suitable questionnaire requires proper knowledge
on the risk model of the contaminated land, the identified contaminants, sources,
transport pathways, contaminated environmental compartments, the types of land
uses and users of the land, the receptors, the lifestyle and habits of residents,
employees, the ecosystem, etc.;

- Assessment by measurement on a contaminated site should be the last in a long

series of necessary steps in contaminated land management. We should stop delu-
sive “experts,'' who walk around the contaminated site with a spatula and some
plastic bags in their pockets, hunting visually “contaminated'' locations to take