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Diss Factsheets

Ecotoxicological information

Sediment toxicity

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Administrative data

sediment toxicity: short-term
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
This study was not in accordance with standard test but it was well described with enough details. However, the test results did not give a normal dose response curve. As potassic extracts is a multiconstituent substance, its toxicity to sediment organisms can be estimated based on the toxicity of each of its main constituent. In this study, the substance tested, sodium sulfate, is one of the main consituents of potassic extracts and therefore is used in the analogue approach. The analogue approach justification is described in the field "Any other information on results incl. tables"

Data source

Reference Type:
Salinity tolerances of selected macroinvertebrates of the Sabie River Kruger National Park, South Africa
Bibliographic source:
Arch. Environ. Contam. Toxicol., 32: 32-41

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
This test was an acute semi-static test on Tricorythus sp. with an exposure period of 96 h in river water.
The effect parameter observed was mortality which was defined and observed as immobility of the test animal.
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
Sodium sulphate
EC Number:
EC Name:
Sodium sulphate
Cas Number:
Molecular formula:
disodium sulfate
Details on test material:
- Name of test material: Sodium sulphate (Na2SO4)
- Substance type: industrial grade
- Physical state: no data
- Analytical purity: no data
- Impurities (identity and concentrations): no data
- Purity test date: no data
- Lot/batch No.: no data
- Expiration date of the lot/batch: no data
- Stability under test conditions: no data
- Storage condition of test material: no data
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
The following data are taken from the SIDS dossier of Sodium Sulfate (CAS N°: 7757-82-6), published on UNEP (OECD, 2005)
- Melting point: 884°C
- Boiling point: Decomposition occurs above 884°C
- Vapour pressure: No data, expected to be extremely low
- Water solubility: 161 g/L at 20°C
- Henry's law constant: No data
- log Pow: -3
- pKa: no data
- Stability in water: no data
- Stability in light: no data
- pH dependence on stability: no data

In aquatic environments, the soluble portion of the substance completely dissociates into the sulfate ion (SO42-) and the sodium cation (Na+) at neutral pH.

Sampling and analysis

Analytical monitoring:
Details on sampling:
No data

Test substrate


Test organisms

Test organisms (species):
other: Tricorythus sp.
Details on test organisms:
- Common name: no data
- Strain/clone: no data
- Justification for species other than prescribed by test guideline: Tricorythus sp. Was an indigenous invertebrates form a riffle area of the Sabie River
- Source: Sabie river, Kruger national park, South Africa
- Details on collection: no data
- Age of parental stock (mean and range, SD): no data
- Breeding conditions: no data
- Handling of egg masses and larvae: no data
- Age of animals at beginning of exposure: no data
- Feeding during test: no

- Acclimation period: 36 h
- Acclimation conditions (same as test or not): yes
- Type and amount of food: animals were unfed
- Health during acclimation (any mortality observed): Acclimation mortalities ranged between 4 and 8%. All dead animals were removed and numbers were equilzed between the raceways, before addition of salt solution

Study design

Study type:
laboratory study
Test type:
Water media type:
Type of sediment:
not specified
Limit test:
Exposure duration
96 h
Exposure phase:
total exposure duration

Test conditions

Approx 69.4 mg/L
Test temperature:
Monitored daily in each raceway
6.93 – 7.20
Reading daily in each raceway with a Checkmate CCA475627
Dissolved oxygen:
65.0 – 105.0% saturation
Measured daily in each raceway with a Hanna HI 193 meter
Not concerned
< 2.1 mg/L
Monitored spectrophotometrically every second day using a Merck spectroquant 1158 photometer:
Analyzed by the indophenols blue method
Nominal and measured concentrations:
Nominal concentrations : 0, 0.20, 0.66, 1.46 and 4.40 g/L
Details on test conditions:
- Test container (material, size): 12.5 L Perspex experimental stream system (raceway)
- Sediment volume: no data
- Weight of wet sediment with and without pore water: no data
- Overlying water volume: no data
- Depth of sediment and overlying water: no data
- Aeration: no
- Replacement of evaporated test water, if any: no data
- Substrate: Four kaolinite stones were placed to serve as a substrate with screens which serve particularly for emerging animals.

- No. of organisms per container (treatment): 25
- No. of replicates per treatment group: 3
- No. of replicates per control / vehicle control: no data
- Feeding regime: unfed

- Details on volume additions: yes, 20% of the water was replaced daily

- Type of water: fresh water
- Source of water: Sabie river water
- Location: South Africa
- Description of sampling site: no data
- Filtration: no data
- Alkalinity: no data
- Salinity: no data
- Conductivity: no data
- Particulate matter: no data
- Total organic carbon: no data
- Chemical oxygen demand: no data
- Unionized ammonia: no data
- Residual chlorine: no data
- Total organic chlorine compounds and PCBs: no data
- Total organophosphorous compounds: no data
- Total organic chlorine: no data

No data

No data

No data

Temperature and light conditions could not be strictly controlled.
Temperature : maintained between 14 and 23°C with the use of two air-conditionning units
Light: OSRAM biolux tubes provided wavelengths of light similar to sunlight
Lighting: generally maintained at a 12:12 h light:dark cycle

The test criterion was mortality which was defined and observed as immobility of the test animal.


- Spacing factor for test concentrations: 4 concentrations 0.2, 0.66, 1.46 and 4.4 g/L
- Justification for using less concentrations than requested by guideline: not concerned
- Range finding Study
- Test concentrations: 0, 0.66, 1.83, 3.65, 5.5, 7.34 g/L
- Results used to determine the conditions for the definitive study: Conductivity values/salt concentrations were selected for definitive testing on the basis of unreplicated range-finding mortality results. The highest and lowest conductivities were repeated to determine the upper and lower limits of mortality, and two other conductivities selected around the potential LC50 value.
Reference substance (positive control):
not specified

Results and discussion

Effect concentrations
96 h
Dose descriptor:
Effect conc.:
0.66 other: g/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
Details on results:
The LC50 value for sodium sulfate was experimentally observed to be at 100 mS/m, ie 0.66 g/L Na2SO4

- Concentration / response curve: no
- Cumulative immobilization: yes
- Other effects: not described
Reported statistics and error estimates:
Statistical method:
To determine the tolerance of riverine organisms to sodium sulphate, LC50 values were statistically determined using the US-EPA probit analysis programme, version 1.4.
To statistically test for significance of mortalities recorded between replicates of definitive experiments, and between mortalities at different salt concentrations, the percentage cumulative mortality data were arcsin-transformed and one-way analysis of variance tests (ANOVA) carried out a 95% confidence level.
The computer package Statgraphics, version 5.0, was employed for this analysis.

Statistical results:
The statistical analysis for cumulative mortalities recorded during sodium sulphate definitive experiments showed that at 50 mS/m no significant difference could be detected between mortalities in the control and experimental systems (f= 16.65; P< 0.00001).
At 100 mS/m, both the control and experimental mortalities were replicated, and a significant difference was evident between them (f= 6.80; P= 0.0001).
The same result was seen at 200 mS/m (f= 4.92; P= 0.0012) and at 600 mS/m (f= 6.62; P= 0.0003).
Mortalities recorded at 50 mS/m were significantly different from mortalities at all other conductivities, while there was no statistical difference between these and the results moted at 600 mS/m was significant (f= 5.77; P< 0.00001).

The data could not be analyzed using the probit program since the probit model requires a normal distribution of concentration response data

Any other information on results incl. tables

Analogue approach justification

Potassic extracts is a multiconstituent substance. As its main constituents are simple inorganic salts (i.e. potassium sulfate, sodium sulfate and calcium sulfate), in aquatic environment, the soluble portion of each constituent completely dissociates into the sulfate ion (SO42 -) and the corresponding cations: potassium (K+), sodium (Na+) and calcium (Ca2 +) at neutral pH.

The physico-chemical properties of the main constituents are similar and they are not harmful to the aquatic organisms tested (rem: calcium sulfate is less soluble than the other constituents of the potassic extracts, but its water solubility is sufficiently high to determine the absence of toxicity to aquatic organisms at concentration higher than 100 mg/L, showing absence of harmful effect to the tested organisms, as it is also showed for the other constituents).

Therefore, sodium sulfate, along with the other salts present in the potassic extracts, can be used in a read-across approach to assess the sediment toxicity of the multiconstituent substance.

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
Sodium sulfate is not hazardous to Tricorythus sp. in the exposure conditions defined in this study, with an EC50-96h of 660.00 mg/L
Executive summary:

A 96h acute toxicity test was conducted using Sabie River water and an Ephemeropteran mayfly Tricorythus sp. found in the river.

Experiment was conducted in flowing water systems known as raceways. The tolerance of the mayfly to sodium sulphate was assessed at a range of selected conductivity levels/concentrations:0, 0.20, 0.66, 1.46 and 4.40 g/L.


The LC50 value for sodium sulfate was experimentally observed to be at 100 mS/m, ie 0.66 g/L Na2SO4


No information about abnormal effects observed was reported in the study.


Based on the results of this study, Sodium sulfate does not hazardous to Tricorythus sp. in the exposure conditions defined in this study.


Results Synopsis

Test Organism: Tricorythus sp.

Test Type: semi-static

96h-LC50:  660.00 mg/L

Endpoint(s) Effected: Mortality