Reaction mass of Limestone and calcium fluoride and calcium sulfate

Bioaccumulation: aquatic / sediment

Description of key information

When dissolved in water, the reaction mass of calcium fluoride, calcium sulfate and calcium carbonate will dissociate into Ca²⁺,CO₃^2-, SO₄^2- and F^-. Ca²⁺,CO₃^2-, SO₄^2- ions are essential to all living organisms (flora and fauna) and their intracellular and extra-cellular concentrations are actively regulated by homeostasis and therefore no bioaccumulation is expected for these ions. For F^- ions there is not such a homeostasis mechanism. Studies have been conducted to assess the bioaccumulation potential of NaF. In the key study by the Japanese Ministry of environment, conducted according to OECD 305, bioconcentration factors have been measured at steady state: ≤ 0.66 L/kg when exposed to 5 mg NaF/kg and < 6.4 L/kg when exposed to 0.5 mg NaF/L. Also in a report by RIVM BCF values for fluoride have been reported in the range of < 1 to 7.5 in aquatic plants and 50 - 150 in fish and crustacea. Overall the available data indicate that fluoride has low BCF values. Fluoride is hence considered not bioaccumulative in accordance with the REACH PBT criteria.

Additional information

Reaction mass of calcium fluoride, calcium sulfate and calcium carbonate is an inorganic substance that will dissociate when dissolved into water.

Its main constituent (CaF2) has a low water solubility. Calcium fluoride will dissociate to some extent (as determined by the limit of solubility) in the aqueous environment and dissociate to form calcium and fluoride ions, both of which are environmentally ubiquitous. The uptake of calcium is regulated actively by organisms (homeostasis). For F^- ions there is not such a homeostasis mechanism. Studies have been conducted to assess the bioaccumulation potential of NaF. In the key study by the Japanese Ministry of environment, conducted according to OECD 305, bioconcentration factors have been measured at steady state: ≤ 0.66 L/kg when exposed to 5 mg NaF/kg and < 6.4 L/kg when exposed to 0.5 mg NaF/L. Also in a report by RIVM BCF values for fluoride have been reported in the range of < 1 to 7.5 in aquatic plants and 50 - 150 in fish and crustacea. Overall the available data indicate that fluoride has loc BCF values. Fluoride is hence considered not bioaccumulative in accordance with the REACH PBT criteria.

The second constituent, calcium sulfate, dissociates into the calcium Ca2+ and sulfate SO42- ions at environmental pH. These are essential to all living organisms (flora and fauna) and their intracellular and extra-cellular concentrations are actively regulated (homeostasis). Aquatic or sediment bioaccumulation is therefore not expected.

The third constituent is calcium carbonate, an inorganic ionic solid, for which an octanol/water partition coefficient cannot be reliably determined. Calcium carbonate dissociates into the calcium Ca²⁺and carbonate CO₃^2-ions at environmental pH. These are essential to all living organisms (flora and fauna) and their intracellular and extra-cellular concentrations are actively regulated (homeostasis). Bioaccumulation is therefore not expected. Recent research has shown that calcium carbonate is naturally produced as an excretory product by marine teleosts. These fish continuously drink seawater to avoid dehydration. This exposes them to an excess of ingested calcium, which they precipitate into calcium carbonate crystals in the gut. The fish then excrete these unwanted chalky solids, sometimes called 'gut rocks', in a process that is separate from digestion and production of faeces. Other Phylla also produce calcium carbonate in significant quantities: Mollusc shells and certain algae coccoliths (Coccolithophores) are primarily composed of calcium carbonate.