Effects of perchlorate on earthworm (Eisenia fetida) survival and reproductive success

The effects of perchlorate on earthworm, Eisenia fetida, survival and reproductive success were evaluated using three types of tests: dermal contact (filter paper), sand, and artificial soil. All studies utilized a range of perchlorate concentrations in order to simulate levels that are likely to occur in the environment under different scenarios (typical soil levels vs. spill levels). The OECD filter paper contact test involved exposing earthworms to the test compound on moist filter paper for 14 days to evaluate earthworm survival under a worst-case dermal exposure scenario. A similar test involved exposing the earthworms to perchlorate-contaminated sand, where earthworm survival decreased as concentration of perchlorate increased, with no worms surviving 14 days at the highest treatment concentrations (> 2000 μg/g). However, the perchlorate concentrations that affected the survival of E. fetida are likely to occur only under extreme conditions (e.g. spills). The effect of perchlorate on the reproductive success (cocoon production) of E. fetida over a 4-week test period in artificial soil and a 3-week test period in sand was also examined. Production of cocoons was observed in soil containing up to 100 μg/g perchlorate, with no production in the uppermost treatment groups (1000 μg/g). Cocoon production was highest in the control group, although overall cocoon production appeared to be low. In contrast to the acute toxicity tests, perchlorate did affect earthworm reproduction at environmentally relevant soil concentrations. In addition, preliminary data suggest that cocoons produced under perchlorate contamination did not hatch as well as cocoons produced in control soil despite incubation of both sets of cocoons in clean soil or sand.