Calcium fluoride

Endpoint summary

Description of key information

They key study for the bioaccumulation endpoint is a 28 -days bio-accumulation study on the read-across source substance sodium fluoride (NaF) conducted according to OECD 305, a flow-through fish test. Cyprinus carpio was exposed to 5 and 0.5 mg NaF/L. The bioconcentration factors measured at steady state are ≤ 0.66 L/kg when exposed to 5 mg NaF/L and < 6.4 L/kg when exposed to 0.5 mg NaF/L.

Conversion of the BCF value to reflect the difference in molecular weight between sodium fluoride and calcium difluoride is not relevant, as the bioaccumulated species is fluoride, not calcium difluoride.

A number of additional bioaccumulation studies are mentioned in RIVM's Integrated criteria document on fluorides. Even though the original study reports are not available today, the information in the review report is considered relevant and adequate to serve as supporting information. The BCF values reported for fluoride in the publication range from <1 to 7.5 in aquatic plants and from 50 to 150 in fish and crustacea.

Overall, the available data indicate that fluoride has low BCF values, and is considered not bioaccumulative in accordance with the REACH criteria.

Additional information

A correlation between fluoride levels in earthworms and elevated soil fluoride levels from polluted sites has been demonstrated, however levels were due to the soil content of the worm gut. Elevated fluoride content in woodlice collected from the vicinity of an Al-reduction plant has been demonstrated (Janssen et al, 1989). Sloof et al (1989) note that uptake of fluoride into plants from soil is low as a consequence of the low bioavailability of fluoride in the soil and that atmospheric uptake is generally the most important route of exposure. A relatively high rate of fluoride uptake is noted for grass species, and the consumption of fluoride containing plants may lead to elevated fluoride levels in animals and humans. Sloof et al (1989) conclude that the limited data indicate that fluoride biomagnification in the aquatic environment is of little significance. Fluoride accumulates in aquatic organisms predominantly in the exoskeleton of crustacea and in the skeleton of fish; no accumulation was reported for edible tissues.

In the terrestrial environment, fluoride accumulates in the skeleton of vertebrates and invertebrates. The EU RAR for hydrogen fluoride (2001) notes that the lowest fluoride levels are found in herbivores, with higher levels in omnivores and highest levels in predators, scavengers and pollinators; the findings indicate a moderate degree of biomagnification. Vertebrate species store most of the fluoride in the bones and (to a lesser extent) the teeth; elevated levels of fluoride in the bones and teeth have been shown in animals from polluted areas.