Magnesium bis(dihydrogenorthophosphate)

Toxicity to soil macroorganisms except arthropods

Administrative data

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study performed in accordance with the relevant guidelines but not under the conditions of GLP. Substance is provided as supporting data only as substance is not considered to be toxic to terrestrial organisms and as such an investigation of earthworm toxicity is not required. Justification for read-across. The following substances are considered to be similar enough to facilitate read-across for aquatic toxicity. Sodium and potassium orthophosphates: Sodium dihydrogenorthophosphate Disodium hydrogenorthophosphate Trisodium orthophosphate Potassium dihydrogenorthophosphate Dipotassium hydrogenorthophosphate Tripotassium orthophosphate Potassium pentahydrogen bis(phosphate) Tripotassium trihydrogen diphosphate dihydrate. Calcium and magnesium orthophosphates: Calcium bis(dihydrogenorthophosphate) Calcium hydrogenorthophosphate Tricalcium bis(orthophosphate) Tricalcium phosphate (including bone ash and hydroxyapatite) Magnesium hydrogenorthophosphate Trimagnesium bis(orthophosphate) Magnesium bis(dihydrogenorthophosphate) All members of the group are structurally similar ionic inorganic compounds with the anion only changing by the number of hydrogen atoms to account for changes in charge due to increase in cation numbers. Progression through each group sees an increase in cation number from one to three followed by a change in cation. Cations are group 1 alkali metals sodium and potassium and group 2 alkaline earth metals calcium and magnesium. Na and K are in the +1 ionic state and Ca and Mg are in the +2 state. All cations are ubiquitous in natural waters and therefore the different cations are not considered to be of relevance for assessing the ecotoxicity of the aforementioned substances. The strategy is therefore designed to assess the toxicity of the phosphate ion (also ubiquitous and predicted to be low). All potassium and sodium orthophosphates are highly soluble and therefore represent a worst case in terms of bioavailability in natural waters. The magnesium and calcium orthophosphates are less soluble but are expected to dissociate to the ionic forms in water and therefore the toxicity results can be read across on the basis that all cations (Na+, K+, Ca2+ and Mg2+) are abundant in natural waters and are unlikely to contribute to toxicity. The aforementioned substances differ in their acid or alkaline nature when dissolved in water, with pH values ranging from ca. pH3 to pH >14. The effect of pH on the test organisms is not expected to have a significant effect in the natural environment and therefore when taking in to account the substance to be tested; it was decided to test one which results in a solution of around pH 7 and therefore any pH-related effects will be discounted.

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

Test material

Test material information

Constituent 1

Reference substance name:

potassium dihydorgenorthophosphate

IUPAC Name:

potassium dihydorgenorthophosphate

Constituent 2

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

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

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.