Calcium dihydroxide precipitated with carbon dioxide during sugar juice purification

Toxicity to terrestrial plants

Description of key information

No studies on SFL are available.
The key study was conducted on an analogous substance and assessed the acute toxicity of calcium carbonate (nano) to three species of plant (soybean, tomato and oat) in a GLP study performed in accordance with OECD Guideline 208. The 21 day EC50 was >1000 mg/kg dw soil and the NOEC was 1000 mg/kg dw soil.
The result from this study demonstrates that calcium carbonate is not acutely toxic to plants at the concentration tested and can be read across to SFL.

Additional information

Acute Toxicity:

Rationale for read across:

SFL is primarily composed of inorganic substances. The major constituent is calcium carbonate, along with silicon dioxide and a small amount of other inorganic salts (including calcium salts) and the remainder is composed of organic plant material. None of the components of SFL carry a classification for physical chemical properties or the environment and therefore SFL is not classified as hazardous to the environment. Since the major component of SFL is calcium carbonate, it can therefore be assumed that the properties of SFL will be governed by those of calcium carbonate. It is therefore considered appropriate for this data to be used for read-across purposes and any further testing would be scientifically unjustified.

The key study for short term toxicity to plants [Goodband (2010b)] 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 soiland the NOEC was 1000 mg/kg dw soil. Since this study can be read across to SFL, it is expected that SFL would also not be acutely toxic to plants.

 

Long Term Toxicity:

SFL is primarily composed of inorganic substances (the major constituent is calcium carbonate, along with silicon dioxide and a small amount of other inorganic salts) and the remainder is composed of organic plant material. SFL is not classified as harmful or toxic to the environment. The inorganic portion of SFL and the organic plant material are composed of substances which are naturally occurring in the environment. Hence, plants are constantly exposed to the components of SFL without suffering from any adverse or detrimental effects. Furthermore, SFL is applied to soil as a fertiliser for the purpose of improving the condition of the soil by guaranteeing an adequate supply of calcium to plants.

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.

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 (2010b)]. No toxic effects were observed at the concentration tested. As a result, calcium carbonate is considered not toxic to plants. This result is considered to be relevant to SFL based on the fact that SFL is primarily composed of calcium carbonate and other calcium salts and hence the properties of SFL are governed by those of calcium carbonate. It can therefore be assumed that SFL is not acutely toxic to plants and hence long term testing is considered to be unnecessary.

Given the extensive and continued use of SFL as a constituent of fertiliser and the natural occurrence of its components in the environment, it is considered that SFL 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 scientifically unjustified.