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Toxicity to terrestrial arthropods

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Description of key information

The LD50 value of LD50 ≤1.67 g cryolite/m2 from a field application study with blueberry flea beetle larvae is considered as the critical acute effect value for the assessment of oral exposure in terrestrial organisms.

Key value for chemical safety assessment

Additional information

For cryolite exposure via soil (uptake from soil matrix), no data are available. However, it should be noted, that due to the dissolution behaviour, it can be expected, that when cryolite is mixed to soil matrix and gets in contact with pore water, it is dissolved to different aluminum and fluoride species and no exposure to dissolved cryolite occurs in soil.

Based on the information of U.S. EPA (1996), cryolite is applied in dust and in suspended form where much of cryolite can expected to remain in particulate form. Ingestion of cryolite is expected to be the relevant route of exposure. The substance is considered to act predominantly as stomach poison while it releases fluoride ions (U.S. EPA, 1996). Fluoride ions in turn form complexes with metal containing enzymes in stomach (Corbett et al., 1974). The available two studies on the target organisms beet armyworm (Spondoptera exigua; Yee and Toscano, 1998) and tobacco caterpillar (Spodoptera litura; Prasad et al., 2000) provide evidence on that ingestion as route of exposure and particulate form as form of exposure in combination cause increased response to increased dose.

Two other studies with honeybee (Apis mellifera; Atkins and Kellum, 1986) and blueberry flea beetle larvae (Altica sylvia;Forsythe and Collins, 1994) could be used in a tentative manner for PNEC derivation related to exposure similar to insecticidal application. The honeybee brood LD50 of 224.5 g Cryolite/m2 is related to the application rate as well as the results with the blueberry flea beetle larvae (LD50 ≤1.67 g Cryolite/m2). Target species blueberry flea beetle (short term field test) seemed to be more sensitive than honeybee brood. Despite of the uncertainty regarding to whether a proper dose-response resulted in the test with blueberry flea beetle larvae, the lower application rate of 1.67 g/m2 from this study is considered as the critical acute effect value.