reaction mass of Calcium chloride and Sodium chloride

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

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

Adequacy of study:

weight of evidence

Study period:

2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted following OECD guideline, but report does not mention whether GLP was followed and sufficient data is available for interpretation of results.

Justification for type of information:

See attached file

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

other: The effect on the number of fronds at different times (24, 48, 72 and 96h) was determined based on IC50 according to APHA (1995).

Principles of method if other than guideline:

Guideline followed

GLP compliance:

not specified

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Analytical monitoring:

no

Details on sampling:

Not applicable

Vehicle:

no

Details on test solutions:

In this study NaCl was used as the reference substance.

Test organisms (species):

Lemna minor

Details on test organisms:

TEST ORGANISM
- Common name: Duckweed, Lemna minor
- Source (laboratory, culture collection): Lemna minor, obtained in São Paulo, Brazil from rivers and submitted in cultures for reproduction in laboratories.
- Method of cultivation: Duckweed plants were grown in a continuously aerated 5-L aquarium at 20°C (APHA, 1995). A continuous photoperiod was provided by “warm white” fluorescent lights at an intensity of 5,000 lux, so as to avoid an increase in temperature. All the cultures and experiments were carried out under non-axenic conditions, in a variation of Hoagland’s nutrient medium, according to APHA (1992) and Lewis (1995).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

None

Hardness:

No data

Test temperature:

20 Deg.C

pH:

No data

Dissolved oxygen:

No data

Salinity:

No data

Nominal and measured concentrations:

0, 2000, 4000, 6000, 7000 and 8000 mg/L (0, 2, 4, 6, 7 and 8g/L)

Details on test conditions:

TEST SYSTEM
- Incubation chamber used: no
- Test vessel: small glass jars.
- Material, size, headspace, fill volume: 20 ml
- No. of colonies per vessel: 1
- No. of fronds per colony: 4
- No. of vessels per control (replicates): 4


GROWTH MEDIUM
- All the cultures and experiments were carried out under non-axenic conditions, in a variation of Hoagland’s nutrient medium, according to APHA (1992) and Lewis (1995).


OTHER TEST CONDITIONS
- Light intensity and quality: A continuous photoperiod was provided by “warm white” fluorescent lights at an intensity of 5,000 lux.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of frond number: manual counting

Reference substance (positive control):

yes

Remarks:

NaCl

Duration:

96 h

Dose descriptor:

IC50

Effect conc.:

6 870 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

frond number

Details on results:

The tests showed that with as little as 6.00g.L–1 NaCl, there was substantial inhibition of growth, especially with exposure times of 72 and 96h, with greater effect at the latter time. After 96 h, the number of fronds in the control was 87, reduced to less than a third with 8g.L–1 NaCl (25 fronds). At the lowest concentrations (1, 2 and 4g.L–1), growth inhibition was the same over time. Frond number decreased with increasing concentrations of NaCl, especially after 48h exposure. This was also demonstrated statistically using the equation y = 96e-0.0827x with r² = 0.88.

Results with reference substance (positive control):

In this study NaCl was used as the reference substance.

Reported statistics and error estimates:

After 24h, mortality rates were determined using the linear and exponential models. All data were first subjected to a Shapiro-Wilk test for normality and to Levene’s test for homogeneity, prior to evaluation by analysis of variance. The data were transformed into Log (x + 1) values. The level of significance was set at a = 0.01. All statistical analyses were performed using the SAS commercial software packages.

Refer attachment 1- Effect of NaCl for different exposure times.

Validity criteria fulfilled:

not applicable

Conclusions:

Effect of NaCl on the number of fronds at different times (24, 48, 72 and 96h) showed differences in their replication at 96h. The sensitivity of Lemna to sodium chloride, the reference substance, at concentrations of 0, 2000, 4000, 6000, 7000 and 8000 mg/L (0, 2, 4, 6, 7 and 8g/L), was determined for comparison and resulted in an IC50 of 6870 mg/l (6.87g/L)

Executive summary:

In the present study NaCl was used as the reference substance.

Lemna minor, obtained in São Paulo, Brazil from rivers and submitted in cultures for reproduction in laboratories, was chosen for the toxicity tests.Duckweed plants were grown in a continuously aerated 5-L aquarium at 20°C (APHA, 1995). A continuous photoperiod was provided by “warm white” fluorescent lights at an intensity of 5,000 lux, so as to avoid an increase in temperature. All the cultures and experiments were carried out under non-axenic conditions, in a variation of Hoagland’s nutrient medium, according to APHA (1992) and Lewis (1995).

The effect of NaCl on Lemna was determined based on frond replication and pigment content according to OECD 2002. The effect of NaCl on the number of fronds at different times (24, 48, 72 and 96h) was determined based on IC50 according to APHA (1995).

Effect of NaCl on the number of fronds at different times (24, 48, 72 and 96h) showed differences in their replication at 96h. The sensitivity of Lemna to sodium chloride, the reference substance, at concentrations of 0, 2000, 4000, 6000, 7000 and 8000 mg/L (0, 2, 4, 6, 7 and 8g/L), was determined for comparison and resulted in an IC50 of 6870 mg/l (6.87g/L)

Description of key information

No experimental data are available to assess the short-term toxicity of the reaction mass of calcium chloride and sodium chloride to aquatic plants other than algae. No information is available for calcium chloride but reliable information is available for sodium chloride.

There is no information supporting the fact that calcium chloride should be more toxic than sodium chloride to aquatic plants other than algae. Accordingly, the sodium chloride IC50 determined on Lemna minor (i.e. 6870 mg/L) is considered to appropriately reflect the toxicity of the reaction mass of calcium chloride and sodium chloride.

Key value for chemical safety assessment

EC50 for freshwater plants:

6 870 mg/L

Additional information

No experimental data are available to assess the toxicity of the reaction mass of calcium chloride and sodium chloride to aquatic plants other than alge. Nevertheless, reliable information is available for sodium chloride (NaCl).

The effect of NaCl on Lemna minor was studied based on OECD TG 221 based on frond numbers at various times (24, 48, 72, 96 hr). Concentrations ranging from 2 to 8 g/L were tested. Based on this key study, the IC50 of sodium chloride after 96 hr exposure was determined to be 6870 mg/L.

Both sodium chloride and calcium chloride are expected to exhibit a toxic effect to aquatic plants due to their impact on osmotic pressure. There is no information supporting the fact that calcium chloride should be more toxic than sodium chloride to aquatic plants other than algae. This is supported by the fact that numerous experimental data found similar LC/EC50 values for other kinds of aquatic organisms (including fishes, aquatic invertebrates and aquatic algae and cyanobacteria).

Accordingly, the sodium chloride IC50 determined on Lemna minor is considered to appropriately reflect the toxicity of the reaction mass of calcium chloride and sodium chloride.