Reaction mass of Limestone and calcium fluoride and calcium sulfate

Endpoint summary

Description of key information

The substance is a reaction mass of calcium fluoride and calcium sulfate and calcium carbonate. The typical composition of the reaction mass is: ca. 47.5 % CaF₂, ca. 22.3 % CaSO₄ and ca. 12.1 % CaCO₃.  No studies are available on the substance itself, instead the assesment of the hazard of the substance was performed based on data available for the 3 constituents as weight of evidence approach. Data from the respective REACH registration dossiers of CaF₂, CaSO₄ and CaCO₃ has been used as a basis. 

CaSO₄ : Given the extensive and continued use of calcium sulfate as a fertiliser and for chemical treatments of soils and its natural occurrence in the environment, it is considered that calcium sulfate would not have a detrimental effect on terrestrial organisms.

CaCO₃: Also calcium carbonate is ubitiquous in the environment. No detrimental effects are expected on terrestrial organisms, which was also confirmed in the studies performed. The results of these studies demonstrate that the concentration of calcium carbonate (nano) that might cause toxicity to terrestrial species is greater than the highest concentration tested and is therefore greater than the maximum solubility of calcium carbonate in water. On this basis, calcium carbonate is not acutely toxic to terrestrial organism.

CaF_2: It is to be noted that the toxicity of CaF₂ is primarily expected from fluoride ions which will be released to the environment upon dissolution of the salt. Similarly, the toxicity of the more soluble NaF is determined by the released fluoride ions. As such the extensive dataset available for NaF has also been used to assess the toxicity of CaF₂. For more details and justification for this read-across, we refer to section 13. 

Conclusion on reaction mass:

CaSO₄, lime, is not expected to exert any toxic effect on soil organisms. This is demonstrated by its extensive use as fertiliser and soil conditioner (pH). No toxic effects have been observed in the studies with CaCO₃ upto and including the highest concentration tested (1000 mg/kg CaCO₃), confirming that also CaCO₃ does not exert toxic effects to soil organisms. Studies with calcium fluoride show that CaF₂ (or NaF) can exert some toxicity to soil organisms albeit at elevated concentrations. The lowest recorded NOEC value is 217 mg/kg dw soil CaF₂ towards soil micro-organisms. Taking into consideration that there is only 50% (ca. 47.5 %) CaF2 in the reaction mass and that the additional of Ca2+ through CaSO4 and CaCO3 would even further reduce the toxicity of CaF2 as free F- will be complexed, the NOEC for the reaction mass is 434 mg/kg dw soil. This NOEC value is used as a worst-case value for the reaction mass and calculation of the PNEC. As worst-case no correction is made to account for the composition of the reaction mass. 

Below a detailed overview of the available terrestrial toxicity data is provided on which the conclusion for the reaction mass is based.

Toxicity to soil macro-organisms

The toxicity of various fluoride compounds to Eisenia fetida was investigated over a period of 22 weeks (OECD 207) by Vogel and Ottow (1992). The rate of maturity of the earthworms was significantly reduced when sodium fluoride and potassium fluoride was used. The number of hatchlings was reduced in the presence of sodium fluoride, while the number of cocoons was reduced in the presence of a low concentration of sodium fluoride and potasium fluoride . A NOEC (22d) value of 16000 mg/kg soil dw was observed for CaF₂.

 

Also the toxicity of CaCO₃ to the earthworm Eisenia foetidahas been assessed in an OECD 207 study using an artificial soil. The acute toxicity of the test item, gave a 14 day LC50 value of >1000 mg/kg and a NOEC of 1000 mg/kg.

 

Toxicity to terrestrial arthropods

The effects of fluoride concentration were investigated on the numbers of Porcellio scaber in leaf litter. Leaf litter was collected from eight sites at various distances away from an aluminium reduction plant. Results showed that litter collected far from the plant had a lower fibre content, was more sapric and was less acid. Total acid extractable F- in the litter and upper 15 cm of soil was about 41 times as much at the closest site (700 mg/kg) as at the most distant sites (12 and 16 mg/kg). In a bioassay of litter from the study sites, woodlice (Porcellio scaber) had an abnormally high mortality in litter that contained 440 mg/kg or more of acid extractable F-. When F- was added in the form of NaF to the litter, a significant increase in mortality was observed only in treatments exceeding 800 mg/kg (Beyer et al, 1987) : a NOEC value (126d) of 800 mg/kg (equivalent to 860.2 mg/kg of CaF2) was determined. 

 

 

Toxicity to terrestrial plants

Calcium fluoride is used in fertiliser preparations for application to various plant species. Toxicity of CaF₂ applied during fertilisation is therefore not expected when applied as instructed. However, at elevated concentrations fluoride contamined soils may inhibit growth and transpiration of planted trees as demonstrated in a study by Clausen (2015) on willow trees.

The effect of CaCO₃ on terrestrial plants has also been assessed in an OECD 208. The toxicity of calcium carbonate to three species of plant (soybean, tomato and oat) has been investigated and gave a 21 day EC50 of >1000 mg/kg dw soil based on both the seedling emergence and growth. Correspondingly the NOEC was 1000 mg/kg dw soil. This study showed that there were no toxic effects to plants at the concentration tested.

 

 

Toxicity to soil micro-organisms

The EU RAR (2001) reports NOEC values from 106 to 3000 mg/kg of fluoride (equivalent to 218-6116.5 mg/kg for CaF2). The 63 day experiments were carried out in a micro-ecosystem containing poplar litter (30% o.m) and the isopod Porcellio scaber. Nitrification was found to be the most sensitive endpoint investigated in the micro-ecosystem test.

A low toxicity of the reaction mass of calcium fluoride and calcium sulfate and calcium carbonate is expected on soil organisms.

 

The effect of the calcium carbonate on the nitrogen transformation activity of soil microorganisms has been investigated over a 28-day period in an OECD 216 study. The outcome was an EC50 value of greater than 1000 mg/kg. Correspondingly the NOEC was 1000 mg/kg.