Disodium hydrogenorthophosphate

Toxicity to soil macroorganisms except arthropods

Administrative data

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

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. Both substances are inorganic salts of a monovalent cation from Group 1A of the periodic table, sodium or potassium, and phosphoric acid. Thus, they all share the Na+ or K+ cation and the 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 PO43- anion. 3. Sodium and potassium orthophosphates have been shown to have a similar toxicological profile and physicochemical nature and therefore this data is considered to be adequate and reliable for use in read-across. Any further testing would not be scientifically justified as all substances will dissociate to their anionic and cationic forms in natural waters and these ions (Na+, K+ and PO43-) are all ubiquitous and are not considered to pose a risk of ecotoxicity

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’.

Cross-reference

Reason / purpose for cross-reference:

read-across: supporting information

Data source

Reference

Reference Type:

publication

Title:

A comparison of the relative toxicity of bone meal and other P sources used as remedial treatments to the earthworm

Author:

Atuah L & Hodson ME

Year:

2011

Bibliographic source:

Pedobiologica - International Journal of Soil Biology

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

GLP compliance:

no

Remarks:

Study was not performed for the purpose of REACH registration.

Test material

Test material information

Constituent 1

Reference substance name:

Potassium dihydrogenorthophosphate

EC Number:

231-913-4

EC Name:

Potassium dihydrogenorthophosphate

Cas Number:

7778-77-0

Molecular formula:

H3O4P.2K

IUPAC Name:

potassium dihydrogen phosphate

Details on test material:

- Name of test material (as cited in study report): potassium hydrogen phosphate (KH2PO4)

Test substrate

Vehicle:

no

Details on preparation and application of test substrate:

- Controls: unamended soil

Test organisms

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: earthworm
- Source: Blades biological Ltd, Cowden, Edenbridge, Kent, UK
- Age at test initiation (mean and range, SD): no data
- Weight at test initiation (mean and range, SD): 340 +/- 3.7 mg

ACCLIMATION
- Acclimation period: no data

Study design

Study type:

laboratory study

Substrate type:

natural soil

Limit test:

no

Total exposure duration:

28 d

Test conditions

Test temperature:

20°C

pH:

7-7.2

Moisture:

60% water holding capacity

Details on test conditions:

TEST SYSTEM
- Test container (material, size): no data
- Amount of soil or substrate: 500 g
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 4
- No. of replicates per control: 8


SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: Jetting Loam - bought
- Soil texture (if natural soil): sieved to less than 2mm

Properties are similar to the OECD standard soil.

OTHER TEST CONDITIONS
- Photoperiod: performed in dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mortality


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8

Nominal and measured concentrations:

15,000 mg P/kg with concentrations decreasing by a factor of 1.8 downwards to 441 mg P/kg

Reference substance (positive control):

not specified

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

> 3 500 other: mg P/ kg

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality

Effect concentrations 2

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

> 3 500 other: mg P / kg

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

LC50 (14 day and 28 day values) of potassium dihydrogen phosphate was found to be > 3500 mg P / kg.