Hexafluorosilicic acid

Toxicity to terrestrial plants

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

see read across justification

Reason / purpose for cross-reference:

read-across source

Remarks on result:

other: see detailed description of results below

Details on results:

Data clearly indicate that L. plants grown in soil supplemented with various levels of Sodium Fluoride (NaF) exhibited a marked reduction in growth parameters i.e. seedling germination percentage, length of root, length of shoot, plant height, number of leaves, size of leaf, number of flower per plant, fruit-set percentage and seed-set percentage as compared to control plants. Also, the reduction in above growth parameters increased with the increase in the level of NaF in soil. In addition to this, the plants grown in soil supplemented with 400 mg NaF/kg soil showed maximum reduction in their growth parameters as compared to control plants.

A dose response realtionship is present for all test concentrations and the 50 mg NaF/kg concentration is typically adversely affected. Unfortunately, Singh et al have not calculated the NOEC. Based on the mean and SD, clear effects were seen at 100 mg NaF/kg. If the results of the 50 mg/kg treatement are differnt to the control can not be judged based on the provided data. However, typically the ranges of the mean +/-SD of the control and the 50 mg/kg NaF overlap (except for fruit set and seed set which are not typical endpoints of the guidelines for plant toxicity). Therefore the concentration of 50 mg NaF/kg was considered to be the concentration which can be used as NOEC.

Applying the conversion factor from NaF to hexafluorosilicic acid, the NOEC of 50 mg NaF/kg correscorresponds to 28.5 mg hexafluorsilicic acid/kg.

Executive summary:

Data clearly indicate that plants grown in soil supplemented with various levels of Sodium Fluoride (NaF) exhibited a marked reduction in growth parameters i.e. seedling germination percentage, length of root, length of shoot, plant height, number of leaves, size of leaf, number of flower per plant, fruit-set percentage and seed-set percentage as compared to control plants. Also, the reduction in above growth parameters increased with the increase in the level of NaF in soil. In addition to this, the plants grown in soil supplemented with 400 mg NaF/kg soil showed maximum reduction in their growth parameters as compared to control plants.

A dose response realtionship is present for all test concentrations and the 50 mg NaF/kg concentration is typically adversely affected. Unfortunately, Singh et al have not calculated the NOEC. Based on the mean and SD, clear effects were seen at 100 mg NaF/kg. If the results of the 50 mg/kg treatement are different to the control can not be judged based on the provided data. However, typically the ranges of the mean +/-SD of the control and the 50 mg/kg NaF overlap (except for fruit set and seed set which are not typical endpoints of the guidelines for plant toxicity). Therefore the concentration of 50 mg NaF/kg was considered to be the concentration which can be used as NOEC.

Applying the conversion factor from NaF to hexafluorosilicic acid, the NOEC of 50 mg NaF/kg correscorresponds to 28.5 mg hexafluorsilicic acid/kg.

Reference 2

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

see read across justification

Reason / purpose for cross-reference:

read-across source

Species:

Allium cepa

Duration:

90 d

Dose descriptor:

NOEC

Effect conc.:

200 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

NaF

Basis for effect:

growth

Remarks:

biomass of root, shoot and bulb

Details on results:

Visible symptom of F toxicity was noticed in Allium cepa L. from the added dose of 400 mg NaF /kg soil onwards. The toxicity symptoms were in terms of tip burning and even plant death. There was no significant decrease in shoot, root and bulb biomass in soil treated with low NaF concentrations (up to 200 mg NaF/kg soil). A decrease of 20%, 59% and 70% biomass was observed at 400, 600 and 800 mg NaF/kg in roots, shoots and bulbs, respectively. This suggested that the plant is unable to tolerate addition of F higher than 400 mg NaF/kg soil.
The NOEC for biomass is 200 mg NaF/kg.

Applying the conversion factor from NaF to hexafluorosilicic acid, the NOEC of 200 mg NaF/kg correscorresponds to 114 mg hexafluorsilicic acid/kg.

Executive summary:

A pot experiment was carried out under controlled condition to investigate the accumulation, uptake and toxicity effects of fluoride (F) in onion (Allium cepa L.) grown on the soil contaminated by inorganic fluoride (NaF). Six different levels of soil contamination were used by adding 0, 100, 200, 400, 600 and 800 mg NaFkg(-1) to the soil. The F concentration in shoot, bulb and root varied between 16.3 and 109.1mg Fkg(-1), 15.8 and 54.3mg Fkg(-1) and 18.6 and 151.6 mg Fkg(-1), respectively. The visible symptoms of F toxicity in terms of tip burning and death of the plant was noticed in highly contaminated soils (>400mg NaFkg(-1) soil).

The NOEC for biomass is 200 mg NaF/kg.

Applying the conversion factor from NaF to hexafluorosilicic acid, the NOEC of 200 mg NaF/kg correscorresponds to 114 mg hexafluorsilicic acid/kg

Description of key information

Two long-term studies are available. The lowest NOEC of 50 mg NaF/kg correscorresponds to 28.5 mg hexafluorsilicic acid/kg.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for terrestrial plants:

28.5 mg/kg soil dw

Additional information

Data clearly indicate that plants grown in soil supplemented with various levels of Sodium Fluoride (NaF) exhibited a marked reduction in growth parameters i.e. seedling germination percentage, length of root, length of shoot, plant height, number of leaves, size of leaf, number of flower per plant, fruit-set percentage and seed-set percentage as compared to control plants. Also, the reduction in above growth parameters increased with the increase in the level of NaF in soil. In addition to this, the plants grown in soil supplemented with 400 mg NaF/kg soil showed maximum reduction in their growth parameters as compared to control plants.

A dose response realtionship is present for all test concentrations and the 50 mg NaF/kg concentration is typically adversely affected. Unfortunately, Singh et al have not calculated the NOEC. Based on the mean and SD, clear effects were seen at 100 mg NaF/kg. If the results of the 50 mg/kg treatement are different to the control can not be judged based on the provided data. However, typically the ranges of the mean +/-SD of the control and the 50 mg/kg NaF overlap (except for fruit set and seed set which are not typical endpoints of the guidelines for plant toxicity). Therefore the concentration of 50 mg NaF/kg was considered to be the concentration which can be used as NOEC.

Applying the conversion factor from NaF to hexafluorosilicic acid, the NOEC of 50 mg NaF/kg correscorresponds to 28.5 mg hexafluorsilicic acid/kg.