Perchloric acid

Toxicity to soil macroorganisms except arthropods

Description of key information

By analogy with sodium perchlorate, the toxicity of percloric acid on earthworm was observed in sand with an acute 14d LC50 of 2550 µg/g. At the lowest tested concentration, sub-chronic effects on cocoons production were observed and therefore it was not possible to define a NOEC value. 

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

2 550 mg/kg soil dw

Additional information

No data on perchloric acid is available for this endpoint. However, one reliable key study is available for sodium perchlorate (Landrum et al., 2006), which is used in a read-across approach (ammonium perchlorate was also used in this study but only for the filter paper test which is not retained as relevant as discussed below). The justification of the read-across approach is provided in the endpoint study summary "Aquatic toxicity". The results are expressed in perchlorate moiety in order to be applicable for the derivation of the PNEC of perchloric acid.

In this study, 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. AIl 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.

In conclusion, acute tests conducted in sand with sodium perchlorate showed better dose-response relationships than the filter paper contact tests and utilized the maximum number of replicates tested. Therefore, the acute LC50 value and the sub-chronic NOEC value from these experiments should be considered: 14d-LC50 at 2550 µg/g (perchlorate anion) and 21d-NOEC < 0.1 µg/g (perchlorate anion). Although the NOEC value determined from the reproductive toxicity data represent more environmentally relevant concentrations, it was determined that the perchlorate concentrations that affected the survival and reproductive success of E. fetida are likely to occur only under extreme conditions.