Risk management of chemicals and contaminated land – from planning to verification - Environmental Deterioration and Contamination: Problems and their Management - page 264

Figure 9.7 Step-wise environmental risk assessment of a chemical substance: conservative, iterative,
and efficient.
contaminants, through multiple pathways for complex ecosystems and multiple human
land uses is typical in most of the site-specific cases. Site characterization using analyt-
ical instruments, numerical modeling of the source-transport-receptor pathway and
other sophisticated tools are not sufficient to estimate with high certainty the risk of
individual receptors. The solution in these cases is an ERA based on direct toxicity
testing and/or ecosystem and human health assessment.
ERA is a tiered procedure which applies a conservative estimation approach, as
formerly discussed. When starting the assessment with available historical data and
pessimistic estimations, negative cases can first be excluded. The tiered and iterative
ERA is a time- and cost-efficient solution, which makes the exclusion of negative cases
possible at a minimum cost, and allows financial resources to be used at maximum
efficiency for the highest risk cases (Figure 9.7).