Population-level effects of chemical pollutants are evaluated in terms of decrements of mean extinction time of populations. Analytical solutions of the mean extinction time based on the diffusion approximation were applied to published chronic ecotoxicological data provided from life table experiments or population growth experiments. Assuming a fairly large population (a million) with environmental fluctuation of an observed magnitude, chemical exposure with a concentration of 10% of LC50 is expected to cause, on average, an extinction risk of 16% reduction in the mean extinction time, which is equivalent to that induced by a 1.2% reduction of the population size (or habitat area). Although the ecological risk assessment based on mean extinction time has many limitations, it may present a possibility for interpreting the ecological risk of chemical pollutants in the context of population vulnerability.
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