Spatial scales in the assessment of risks of contaminants to
higher organisms, with comparison to human health
procedures
Nico van den Brink1, Uwe Schlink2, Tom Hoogland1, Hans Baveco1
1
Alterra, Wageningen UR
2
UFZ
Effects of scales on the results of spatially explicit assessments of risks of contaminants to
higher organisms may be significant. Generally, application of smaller scales (finer support),
results in the conservation of spatial variability in the modelling outcome. Top-predators
accumulate the contaminants mostly through food web uptake, and aggregate this over a
certain space. This spatial aggregation results in a decrease in the variability between
individuals, hence the contaminant level in predators may generally be less variable than in
prey items. However, this can be counteracted by specific feeding habits of the species of
concern, which can result in specific food uptake, and therefore uptake of contaminants in a
spatially non-random way. Inter-individual variation in feeding habits then results in a
relatively higher variability of the contaminants levels in predators and possibly even in a
change in the average uptake levels and associated risks.
Comparison with methods applied in human health assessment illustrates that the methods
developed in the two different disciplines focus on different types of data, and different
types of aggregation levels. Nevertheless, it will be illustrated that generally the effects of
scales on the results of risk assessments were similar for the two disciplines.