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Toxicity to terrestrial plants

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Description of key information

The substance is a reaction mass of calcium fluoride and calcium sulfate and calcium carbonate. No studies on plant toxicity are available on the substance itself, nor on the main constituent (calcium fluoride) nor on calcium sulfate : calcium fluoride is used in fertiliser preparations for application to various plant species, Calcium sulfate is ubiquitous in the environment. Toxicity to terrestrial plants is therefore likely to be low.

One GLP-study (OECD 208) is available on calcium carbonate (nano form) :

EC50 (21 days) >1000 mg/kg dw soil

NOEC= 1000 mg/kg dw soil

The result from this study demonstrates that calcium carbonate is not acutely toxic to plants at the concentration tested.

No toxicity of the reaction mass of calcium fluoride and calcium sulfate and calcium carbonate is expected on terrestrial plants.

Key value for chemical safety assessment

Additional information

The substance is a reaction mass of calcium fluoride and calcium sulfate and calcium carbonate. No studies on plant toxicity are available on the substance itself, nor on the main constituent (calcium fluoride) nor on calcium sulfate : calcium fluoride is used in fertiliser preparations for application to various plant species, so toxicity to terrestrial plants is therefore likely to be low.

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

The various reports quoted by JRC suggest that the effect of gypsum on plants is extremely variable depending on the plant, soil type and location. However, the overall results indicate that apart from special crops (e.g. certain fruit trees) the gypsum concentration in soils should be limited to 15 %.

Investigations by Sanderson (2004), on behalf of Agriculture & Agri-Food Canada, on the use of gypsum as an organic amendment in lowbush blueberry production, indicated that gypsum application, with or without fertiliser application, was an effective method to increase nutrient uptake in the lowbush blueberry. Gypsum significantly influenced nutrient uptake and general plant health more than any other fertiliser application evaluated in this region.

Sulfur (as sulfate) is a major plant nutrient, and is essential for crop growth.

 

 

Calcium is an important constituent of most soils and the minerals found in soil are mostly compounds of calcium with other substances. Soil calcium is necessary for proper plant functions and helps in producing healthy fruits and flowers. Some of the functions that require soil calcium include enzyme activity for the absorption of other nutrients, proper cell formation and division, increased metabolic activities, starch breakdown and nitrate uptake. Without soil calcium plants tend to lose their colour, have a short life and produce little or no fruit. Many fertilisers available today make use of calcium and calcium-rich salts to neutralise soils and make them less acidic. Calcium has strong relationships with other substances found in the soil like magnesium, potassium and sodium. Together these nutrients make the soil so rich that almost all kinds of plants can be grown with it. Soil calcium is mainly important for lowering the pH level and the associated acidity. It is often recommended to include up to 40 – 50% of calcium in any fertilizer to account for its deficiency in the soil. The resulting plants will have stronger roots and better growth rate than a calcium deficient soil. In addition to this, calcium also helps in regulating the flow of water and air in the soil for proper absorption by the plant cells. Calcium is known as an essential nutrient for higher plants and one of the basic inorganic elements of algae. Calcium plays crucial roles in strengthening cell walls and plant tissues, reducing the toxicity of soluble organic acids, elongating roots, and so on. The calcium content of plants varies between 0.1 and > 0.5% of the dry weight depending on the growing conditions, plant species, and plant organ. In well-balanced growing nutrient solutions with controlled pH, maximal growth rates were obtained at calcium supply levels of 2.5-100 uM. Also, calcium can be supplied at higher concentrations and might reach more than 10% of the dry weight without symptoms of serious inhibition of plant growth, at least in calcicole plant species. 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 plants at the concentrations released to soil. Therefore, the performance of a short-term toxicity test to plants is not scientifically justified.

Regarding 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 for short term toxicity to plants (Goodband, 2010) was performed to OECD Guideline 208 and in accordance with GLP and was therefore assigned a reliability of 1. The study assessed the acute toxicity of calcium carbonate (nano) to three species of plant (soybean, tomato and oat) in a limit test. No toxic effects on either growth or seedling emergence were noted at the concentration tested. Hence, the 21 day EC50 for calcium carbonate (nano) was found to be >1000 mg/kg dw soil and the NOEC was 1000 mg/kg dw soil.

Calcium carbonate and calcium and carbonate ions are ubiquitous in the environment and are found naturally in soil, water and sediment. As mentioned above, calcium is an important constituent of most soils and the minerals found in soil are mostly compounds of calcium with other substances. Furthermore, calcium carbonate is used as an inorganic fertiliser to improve soil quality, both pH and structure and guarantees an adequate supply of calcium to plants. Furthermore, a seedling emergence and growth test was performed according to OECD 208 using a concentration of calcium carbonate (nano) of 1000 mg/kg dw soil (Goodband, 2010). No toxic effects were observed at the concentration tested. As a result, calcium carbonate is considered not toxic to plants and hence long term testing is considered to be unnecessary. Given the extensive and continued use of calcium carbonate as a constituent of fertiliser and its natural occurrence in the environment, it is considered that calcium carbonate would not have a detrimental effect on plants at the concentrations released to soil. Therefore, the performance of long term toxicity tests on plants is not scientifically justified.

Using a weight of evidence approach for the 3 constituents of the substance, no toxicity of the reaction mass of calcium fluoride and calcium sulfate and calcium carbonate is expected on terrestrial plants.

 

References:

Sanderson K (2004), Gypsum as an Organic Amendment in Lowbush Blueberry Production, Agriculture & Agri-food Canada, Report 2004F-05E

Nachtergaele F, FAO, Rome – Italy, Criterion 6.3 “Soil gypsum content” cited in Common bio-physical criteria to define natural constraints for agriculture in Europe, JRC Scientific and Technical Reports, Draft report EUR XXXXX EN.