Yet others feel that this attitude does not address concerns about the possible additive and synergistic effects of multiple trace contaminants. They feel it relies too heavily upon traditional approaches instead of ones that might deal better with the actual risk. Risk assessment is at best an imprecise science. It combines information on the level of exposure to a substance, as well as its toxicity, to characterize what is likely to happen to humans or other animals that may be exposed. Confusion often arises from the scientific uncertainties associated with this assessment.
People tend to take risks when they are self-imposed or well known, but resist involuntary risk.
For example, models have been developed to simulate the movement and fate of pesticides in the subsoil and predict concentrations over time and depth. Although these tools are useful, results can seldom be used to say for certain whether real problems exist, unless they are validated using actual data. However, they can be useful for estimating trends over time making regional comparisons spotlighting areas where further investigation is needed meeting the ever-growing requirements under international agreements to report on Canada's environmental performance.