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Ecotoxicological information

Toxicity to soil macroorganisms except arthropods

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Description of key information

Toxicity to soil macroorganisms except arthropods:
Di-isodecyl phthalate ester (DIDP) did not effect earthworm (Eisenia fetida) survival in soil, based on 14-day limit studies at very high concentrations, 7,664 mg/kg natural soil (dw) and 8,435 mg/kg artifical soil (dw). An analog to DIDP, di-isononyl phthalate ester (DINP, CAS #68515-48-0) did not effect earthworm (Eisenia fetida) reproduction, based on a 56-day limit study in an artificial soil at a high measured concentration of 982.4 mg/kg soil (dw).

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:
7 664 mg/kg soil dw
Long-term EC10, LC10 or NOEC for soil macroorganisms:
982.4 mg/kg soil dw

Additional information

The toxicity of di-isodecyl phthalate ester (DIDP) as measured by mortality to the earthworm (Eisenia fetida) was evaluated in a 14-day study using natural and artificial soils. The toxicity of di-isononyl phthalate ester (DINP), an analog to DIDP, as measured by reproduction to the earthworm (Eisenia fetida) was evaluated in a 56 day study using an artificial soil. No significant mortality was observed in natural and artificial soils dosed with DIDP after 14 days at a nominal loading rate of 10,000 mg/kg soil (dw), which measured 7,664 mg/kg natural soil (dw) and 8,435 mg/kg artificial soil (dw) (concentrations are from analyses of soils at test initiation). DINP did not effect earthworm (Eisenia fetida) reproduction, based on a 56-day limit study in artificial soil at a high measured concentration of 982.4 mg/kg soil (dw). Because DINP and DIDP are structurally similar and exhibit the same biological activity, these data support the conclusion that DIDP would also not effect earthworm reproduction.

DINP is appropriate to use as an analog to DIDP on the principle that substances of similar structure have similar properties. The two substances are structurally similar; each is a diester containing two alkyl chains differing in length by one carbon, C9 for DINP and C10 for DIDP. The similarities in physical structure result in similar physico-chemical properties as well. DINP and DIDP have similar water solubilities (0.61 and 0.17 ug/L), and partition coefficients (both 8.8), and demonstrate similar results in ready biodegradibility tests and environmental toxicity tests. Given that both substances would be expected to act similarly, and do act similarly it is reasonable to use DINP as an analog for DIDP.