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Ecotoxicological information

Toxicity to soil microorganisms

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Reference
Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Recent review of published work on fluoride ions.
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
no guideline followed
Principles of method if other than guideline:
The EU RAR summarises the results of a number of relevant studies
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not relevant
Analytical monitoring:
not specified
Details on sampling:
No details of sampling given in review.
Vehicle:
no
Details on preparation and application of test substrate:
No details on preparation and application of test substance given in the review.
Test organisms (inoculum):
soil
Total exposure duration:
63 d
Test temperature:
Not stated
Moisture:
Not stated.
Details on test conditions:
No further details given in review
Nominal and measured concentrations:
not stated
Reference substance (positive control):
no
Duration:
24 d
Dose descriptor:
NOEC
Effect conc.:
3 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Dehydrogenase inhibition
Remarks on result:
other: sodium fluoride
Duration:
63 d
Dose descriptor:
NOEC
Effect conc.:
340 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: NH4-minerilisation
Remarks on result:
other: potassium fluoride
Duration:
63 d
Dose descriptor:
NOEC
Effect conc.:
106 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: NO3-mineralisation
Remarks on result:
other: potassium fluoride
Duration:
63 d
Dose descriptor:
NOEC
Effect conc.:
1 060 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: P-mineralisation
Remarks on result:
other: potassium fluoride
Details on results:
The NOEC values detailed in the report range from 106 to 3000 mg/kg. The 63 day experiments were carried out in a micro-ecosystem containing poplar litter (30% o.m) and the isopod Porcellio scaber Latr. Nitrification was found to be the most sensitive in the micro-ecosystem test.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Not applicable

The NOEC values detailed in the report range from 106 to 3000 mg/kg. The 63 d 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 in the micro-ecosystem test.

Validity criteria fulfilled:
not applicable
Conclusions:
The NOEC values detailed in the report range from 106 to 3000 mg/kg. The 63 d experiments were carried out in a micro-ecosystem containing poplar litter (30% o.m) and the isopod Porcellio scaber Latr. Nitrification was found to be the most sensitive in the micro-ecosystem test.
Executive summary:

The EU RAR reports NOEC values from 106 to 3000 mg/kg. 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.

Description of key information

Calcium fluoride is the main constituent of the substance, so its worst case value was chosen for the registered dossier. The 2 others constituents of the substance, calcium sulfate and calcium carbonate, are ubiquitous in the environment and essential to living organims. No studies are available for CaSO4 but no hazards are expected. No toxicity of calcium carbonate has been showed ina GLP-study performed in accordance OECD 216 (NOEC=1000 mg/kg).

No studies are available for calcium fluoride, but the EU RAR (2001) reports NOEC values from 106 to 3000 mg/kg fluoride (equivalent to 218 -6116.5 mg/kg for CaF2).

As calcium fluoride is present at 47.5% in the reaction mass of calcium fluoride, calcium sulfate and calcium carbonate, the NOEC used for the registered substance is equal to 456.8 -12876.84mg/kg dw. Based on these NOEC values, the registered substance was found to have no effect on soil microorganisms.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
456.8 mg/kg soil dw

Additional information

The substance is a reaction mass of calcium fluoride and calcium sulfate and calcium carbonate. No studies on microorganisms toxicity are available on the substance itself, nor on the main constituent (calcium fluoride). The EU RAR reports NOEC values from 106 to 3000 mg/kg fluoride (equivalent to 218 -6166.5 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.

Regarding calcium sulfate, calcium and sulfate ions are ubiquitous in the environment. Calcium is an important constituent of most soils and the minerals found in soil are mostly compounds of calcium with other substances. Furthermore, calcium sulfate, as Gypsum, is used as an inorganic fertiliser to improve soil quality. Important applications include:

• for the reclamation of sodic soils through ion exchange (calcium replacing sodium)

• to reduce run-off water and its resulting erosion in dry agricultural areas as an ameliorant for acidic subsoils and soils in forestry

• to improve Ca- and S-nutritional elements in agriculture (rape and cereals)

• Gypsum is also useful as an additive for soils with high levels of sodium

Sulfur-reducing bacteria comprise several groups of bacteria that use sulfate as an oxidizing agent. Calcium sulfate is not toxic to these forms of bacteria and since it is used to enhance the quality of soil, it is expected that calcium sulfate would not be toxic to soil microorganisms.

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 soil microorganisms.

Regarding calcium calcium carbonate, the nano form was tested because this form was anticipated to represent the worst case as it is likely to be more soluble than the bulk form due to the smaller particle size and hence greater surface area. However, the results are directly applicable to the bulk form of calcium carbonate. The key study (Clarke, 2010) was performed to OECD Guideline 216 and in accordance with GLP and was therefore assigned a reliability of 1.The study assessed the effect of calcium carbonate (nano) on the nitrogen transformation activity of soil microorganisms at a nominal concentration of 1000 mg/kg. No adverse effects on the nitrogen transformation rate were exhibited at the concentration tested. Hence, the 28 day EC50 for calcium carbonate (nano) was found to be >1000 mg/kg soil dwand the NOEC was 1000mg/kg soil dw. Calcium carbonate is therefore not toxic to soil microorganisms.

Using a weight of evidence approach for the 3 constituents of the substance, calcium fluoride is the main constituent and showed a low toxicity with a NOEC of 218 mg/kg dw. The 2 others constituents of the substance, calcium sulfate and calcium carbonate, are ubiquitous in the environment and essential to living organims without any hazards.

As calcium fluoride is present at 47.5% in the reaction mass of calcium fluoride, calcium sulfate and calcium carbonate, the NOEC used for the registered substance is equal to 458.9 mg/kg dw. Based on this NOEC value, the registered substance was found to have no effect on soil microorganisms.