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Long-term toxicity to aquatic invertebrates

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Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
The read-across justification is provided in Section 13.
Reason / purpose:
read-across source
Dose descriptor:
IC50
Effect conc.:
>= 35.9 - <= 43.5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
CaF2
Basis for effect:
growth
Remarks on result:
other: Ceriodaphnia dubia - duration of study: until 60% of control organisms produced 3rd brood
Dose descriptor:
LC50
Effect conc.:
>= 85.86 - <= 172.33 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
CaF2
Basis for effect:
mortality
Remarks on result:
other: Ceriodaphnia dubia - duration of study: until 60% of control organisms produced 3rd brood
Details on results:
Chloride acts as a major toxicity modifying factor for fluoride to some species, but not to others, suggesting there may be differing uptake pathways.
Results with reference substance (positive control):
The toxicity tests met the criteria for acceptable control performance.

Analytical results fluoride:

Measurement of fluoride were in good agreement with target concentrations: (101 +/- 9%) of target. Fluoride levels measured at test termination were 96 +/- 10% of the concentration at test start.

Validity criteria fulfilled:
yes
Conclusions:
The toxicity of fluoride to C. dubia was tested. The LC50 values ranged from 41.8 to 83.9 mg F/L, the IC50 for growth ranged from 17.5 to 22.1 mg F/L.
Using the molecular weight info, these LC50 and IC50 values can be translated to LC50 from 85.86-172.33 mg/L CaF2 and IC50 from 35.9-43.5 mg/L CaF2
Executive summary:

In this study the toxicity of fluoride to C. dubiawas investigated together with the impact of water quality variables on the toxicity of fluoride. For this reason water hardness and chloride content of the water were modified.

In the chronic toxicity test following IC50 and LC50 levels were derived as17.5 to 21.2 mg/L F and 41.8 to 83.9 mg/L F. The IC50 for growth ranged from 17.5 to 22.1 mg F/L.

As fluoride is the driving element in toxicity, read-across to CaF2 can be made. Converting the LC50 values to CaF2 (using the molecular weight info), the LC50 values ranged from to LC50 from 85.86-172.33 mg/L CaF2 and IC50 from 35.9-43.5 mg/L CaF2.

Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Recent review
Justification for type of information:
A read-across justification is provided in section 13.
Reason / purpose:
read-across source
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
7.6 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
28.96 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
reproduction
Remarks on result:
other: Close to water solubility of CaF2
Details on results:
In both long-term tests with daphnids the NOEC is based on effects on reproduction. The arithmetric mean of both tests gives a value of 8.9 mg F-/L for the NOEC. Using the molecular weight information, this corresponds to a NOEC of 18.3 mg CaF2/L.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
No reported statistics and error estimates.

The NOEC values for long-term toxicity to daphnids were 3.7 and 14.1 mg F-/L after 21 d of exposure, based on effects on reproduction, but exposure concentrations were analytically confirmed only in the study that gave the higher endpoint. The arithmetric mean of both endpoints is a NOEC of 8.9 mg F-/L.

Using the molecular weight information, this corresponds to a NOEC of 18.3 mg CaF2/L.

Validity criteria fulfilled:
not specified
Conclusions:
The 21-day NOEC for D. magna exposed to sodium fluoride ranged between 3.7 and 14.1 mg F-/L. The arithmetic mean value of the 2 studies was 8.9 mg F-/L. Using the molecular weight information, this corresponds to a NOEC of 18.3 mg CaF2/L. .
Executive summary:

The EU RAR summarises the findings of two long-term toxicity studies with D. magna exposed to sodium fluoride. The two studies provide reproductive NOEC values of 3.7 and 14.1 mg F-/L and the arithmetic mean NOEC is 8.9 mg F-/L. Using the molecular weight information, this corresponds to a NOEC of 18.3 mg CaF2/L.

Description of key information

No studies are available for calcium fluoride. Available studies on NaF were used as read-across source.

The chosen key value was the lowest reported NOECs among all the evaluated studies reported in EU RAR 2001 on a 21d study on Daphnia magna. Observed NOEC was 3.7 mg/L F-, which convertes in 7.6 mg/L CaF2.

No information was available on marine water invertebrates.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
7.6 mg/L

Additional information

A weight of evidence approach has been used to evaluate the long-term toxicity to invertebrates. A number of studies have been performed with the water-soluble salt, sodium fluoride and so toxicity of CaF2 was assessed using a read-across method for analogue substance. Effective concentrations were recalculated taking in account the different molecular weight of the source and target substance.

The EU RAR summarizes the effects of two reproductive studies of sodium fluoride onDaphnia magna. The two studies report NOEC values of 3.7 and 14.1 mg/L F-, which convert to 7.6 and 28.96 mg/L CaF2, respectively.

Pearcy et al. (2015) investigated the effect of chloride and water hardness on the fluoride toxicity. The study shows a decrease in toxicity of fluoride with increasing chloride content; hence chloride is a major modifying factor. This study confirms that toxicity results should be considered together with information on the water quality.