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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
07/03/1990-09/03/1990
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
See read-across justification report under Section 13 ‘Assessment Reports’.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
In accordance with REACH Annex XI, Section 1.5, of Regulation (EC) No. 1907/2006 (REACH) the standard testing regime may be adapted in cases where a grouping or read-across approach has been applied.

The similarities may be based on:
(1) a common functional group
(2) the common precursors and/or the likelihood of common breakdown products via physical or biological processes, which result in structurally similar chemicals; or
(3) a constant pattern in the changing of the potency of the properties across the category

(1) The source and target substances are both inorganic salts of a monovalent cation from Group 1A of the periodic table, sodium or potassium, and pyrophosphoric/orthophosphoric acid. Thus, they all share the Na+ or K+ cation and the P2O74-/PO43- anion as common functional groups.
(2) All members of the group will ultimately dissociate into the common breakdown products of the Na+ or K+ cations and the P2O74-/PO43- anion.
(3) Potassium and Sodium cations are essential micronutrients that are ubiquitous in the environment. As such, their uptake is tightly regulated and is therefore not considered to pose a risk for ecotoxicity. The pyrophosphate anion is unstable in aqueous solutions with the degree of instability varying according to pH. In distilled water pyrophosphates will hydrolyse slowly via abiotic mechanisms to inorganic phosphate. In natural waters a number of different processes can occur; abiotic hydrolysis, biotic degradation (as a result of the action of phosphatases which cleave pyrophosphate into orthophosphate subunits) and assimilation by organisms in the water all resulting in an ultimate breakdown product of orthophosphate. It is therefore deemed scientifically justified to avoid any further vertebrate testing and use the data from a study conducted on an orthophosphate (with either a potassium or sodium cation) for hazard assessment purposes.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See read-across justification report under Section 13 ‘Assessment Reports’.

3. ANALOGUE APPROACH JUSTIFICATION
See read-across justification report under Section 13 ‘Assessment Reports’.

4. DATA MATRIX
See read-across justification report under Section 13 ‘Assessment Reports’.
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
EPA OTS 797.1300 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids)
Deviations:
yes
Remarks:
One concentration and a no-treatment control were tested in triplicate. a control exposure to determine the effects of pH on test organisms was not conducted. Ph and dissolved oxygen concentration were not measured at 24 hr.
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
not specified
Details on sampling:
- Concentrations: samples were collected from the control treatment groups at 0 and 48 hrs.
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances):
- Controls: vehicle
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): filtered (milli-Q filter) deionized, well water
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia magna (water flea)
- Source: Stock cultures maintained at ESE.
- Age at study initiation (mean and range, SD): <24hr
- Feeding during test - no

Test type:
static
Water media type:
freshwater
Total exposure duration:
48 h
Post exposure observation period:
No
Hardness:
188 mg/L as CaCO3 at 0h
Test temperature:
20 ± 2°C
pH:
Control test:7.7-8.2 (measured at 0 and 48hr)
Test substance: 8.0-8.3 (measured at 0 and 48hr)
Dissolved oxygen:
Control test: 8.0-9.7 mg/L (measured at 0 and 48hr)
Test substance: 8.0-9.6 mg/L (measured at 0 and 48hr)
Salinity:
Not applicable
Nominal and measured concentrations:
Control:
nominal concentration: 0 mg/L

Test:
nominal concentration: 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: cylindical, glass, exposure chambers ( 100 mm diameter X 50 mm height)
- Type: closed
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 3
- No. of vessels per vehicle control (replicates): 3



TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Milli-Q water. Pumped from a deep well and passed through activated charcoal, cation, anion and mixed beds and then through the Milli-Q system prior to use. Sanple collected on 8 March 1990.
-pH: 7
- Total organic carbon: 1.3 mg/L
- Metals:
arsenic: <2.3 µg/L
aluminium: <27.5 µg/L
cadmium: <0.5 µg/L
calcium: 0.3 mg/L
chromium: <7.1 µg/L
cobalt: <16.4 µg/L
copper: <3.6 µg/L
iron: 23.3 µg/L
lead: < 1.4 µg/L
mercury:<0.2 µg/L
magnesium: 0.5 µg/L
nickel: <26.0 µg/L
selenium: <1.8 µg/L
silver: <6.8 µg/L
sodium: 3.0 µg/L
zinc: 8.3 µg/L
- Pesticides:
Pesitcides-Organochlorine & PCB's: <0.006 µg/L
Organophosphate: <0.088 µg/L

COD: 6.0 mg/L

filterable solids: 13.0 mg/L

OTHER TEST CONDITIONS
- Photoperiod: 16-hours light and 8-hours dark.
- Light intensity: no data


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Test organisms were observed daily for immobilisation (upon prodding) and any behavioural changes , and paralysed organisms removed.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not applicable
- Justification for using less concentrations than requested by guideline: Results of range-finding study.
- Range finding study
- Test concentrations: up to 100 mg/L
- Results used to determine the conditions for the definitive study: In a range-finding test, mortalities occured down to 0.1 mg test substance/L of exposure water. However it was believed that mortalities occured due to the possible contamination of exposure chambers. Thererfore, in the definitive test, the test substance was used to provide nominal exposure concentrations of 0 mg/L (dilution water control) and 100 mg/L
Reference substance (positive control):
yes
Remarks:
sodium doceyl sulfate
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
based on test material purity of 100%
Basis for effect:
mobility
Remarks:
immobilisation
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
based on test material purity of 100%
Basis for effect:
mobility
Remarks:
immobilisation
Details on results:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: A precipitate was noted in two treatment exposures at 48 hr.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Statistical analysis (t-test) of data indicated there was no significant (alpha + 0.05) difference between the number of daphnids immobilised in control and treatment exposures.

 

Table 1: Immobility of water fleas (D. magna) exposed to tetrapotassium pyrophosphate in a 48-hr static , acute toxicity test.

 

Nominal concentration of tetrapotassium pyrophosphatea

(mg/L)

Cumulative number of immobilised organisms and

Percent mortality (parenthic value)

24 hr

48 hr

0 (control)

0(0)

0(0)

100

0(0)

2(7)

 

a Cacluated based on 100% puroty of the test substance. Source: ESE 1990.

Validity criteria fulfilled:
yes
Conclusions:
The test substance, tetrapotassium pyrophosphate, was not acutely toxic to the water flea, Daphnia magna, at a nominal concentration of 100 mg/L.

Read-across is justified on the basis detailed in rationale for reliability above. This study is therefore considered to be of sufficient adequacy and reliability to be used as a key study and no further testing is justified.

Description of key information

One key study exists on the analogous substance tetrapotassium pyrophosphate. Read-across is justified on the basis of the rationale detailed below. This study is considered to be adequate for the purpose of classification and labelling in accordance with Regulation (EC) No. 1272/2008 (EU CLP) and as such no further testing is required.
The additional data, from the literature, supports this conclusion.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
100 mg/L

Additional information

Rationale for read across:

Study is conducted to GLP and in compliance with agreed protocols, with no deviations from standard test guideline. Reliability has been changed to reflect the fact that this study is conducted on an analogue substance.

 

In accordance with Annex XI, section 1.5 of Regulation (EC) No 1907/2006 (REACH) a read across approach may be used when substances have similarities based on the likelihood of common breakdown products via physical and biological processes, which result in structurally similar chemicals.

 

Sodium and potassium pyrophosphates are ionic in nature and therefore dissociate readily into cations and anions in water the toxicity of the both the cation and the anion must be addressed. Potassium and Sodium cations are essential micronutrients that are ubiquitous in the environment. As such, their uptake is tightly regulated and is therefore not considered to pose a risk for ecotoxicity. The pyrophosphate anion is unstable in aqueous solutions with the degree of instability varying according to pH. In distilled water pyrophosphates will hydrolyse slowly via abiotic mechanisms to inorganic phosphate. In natural waters a number of different processes can occur; abiotic hydrolysis, biotic degradation (as a result of the action of phosphatases which cleave pyrophosphate into orthophosphate subunits) and assimilation by organisms in the water all resulting in an ultimate breakdown product of orthophosphate.

 

It is therefore considered appropriate; due to the physicochemical nature of the substance tested and its identity, for this data to be used for read-across purposes for the following substances:

 

 - disodium dihydrogenpyrophosphate

 - trisodium hydrogen diphosphate

 - tetrasodium pyrophosphate

 

Any further testing would not be scientifically justified as all substances would ultimately dissociate to their anionic and cationic forms in natural waters and these ions (Na+, K+and PO43-(from P2O74-) are all ubiquitous and are not considered to pose a risk of ecotoxicity.