Effects of the perchlorate anion on Eisenia fetida

The effects of the perchlorate anion on Eisenia fetida survival and reproductive success were evaluated using three types of tests: dermal contact, artificial soil, and sand. 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 in order to evaluate earthworm survival. A similar test involved exposing the earthworms to perchlorate-spiked sand. There was a significant difference between pre-exposure and postexposure weights in each experiment with respect to perchlorate concentration at both typical soil and spill levels. These significant differences were largely a result of significant reductions in earthworm weights post exposure in some if not all perchlorate concentrations utilized in which mortality from perchlorate exposure was high.

Earthworm survival decreased as concentration of sodium perchlorate increased, with no worms surviving 14 days at the highest treatment concentrations (> 2000 ppm). From these data, a LC50 value of 2,000 ppm for sodium perchlorate was calculated. Likewise, earthworm survival decreased as concentration of ammonium perchlorate increased, with no worms surviving 14 days at the highest treatment concentrations (> 10,000 ppm). From these data, a LCso value of 5,500 ppm for ammonium perchlorate was calculated. It was determined that perchlorate did not affect earthworm survival at environmentally relevant soil concentrations.

The effect of perchlorate on reproductive success (cocoon production) of Eisenia fetida over a 4-week test period was also examined. There was also a significant difference between pre-exposure and post-exposure weights in each experiment with respect to perchlorate concentration at both typical soil and spill levels. These significant differences were largely a result of significant reductions in earthworm weights post exposure in some if not all perchlorate concentrations utilized in which mortality from perchlorate exposure was high. In the artificial soil experiment, production of cocoons was observed in soil containing up to 100 ppm perchlorate, with no production in the uppermost treatment group (> 1000 ppm). Cocoon production was highest in the control group, although overall cocoon production was low. We estimated an EC50 for sodium perchlorate in the artificial soil of 2.5 ppm. Preliminary data also suggested that cocoons produced under perchlorate contamination did not hatch as well as cocoons produced in control soil despite incubation in clean soil or sand.

A similar test involved exposing the earthworms to perchlorate-spiked sand. Cocoon production in the last cocoon production experiment were observed up to 100 ppb perchlorate, with no production in the uppermost treatment groups (> 1 ppm). From these data, an EC50 value of 80 ppb was estimated. There was insufficient time to incubate these cocoons in untreated sand to assess cocoon viability.

In addition to the reproductive toxicity data collected, opportunistic acute toxicity data was gathered. Sodium perchlorate was determined to be lethal to all replicates above 1,000 ppm. From these data, a conservative LC50 value of 250 ppb was calculated. Although the EC50 values estimates are more plausible, perchlorate would not affect earthworm reproduction at environmentally relevant soil concentrations.