Dipotassium hydrogenorthophosphate

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

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

The source chemical and dipotassium hydrogenorthophosphate have the following similarities:

1. Both substances are inorganic salts of monovalent cations 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. 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 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’.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

GLP compliance:

no

Remarks:

no data provided in the literature

Vehicle:

no

Details on preparation and application of test substrate:

- Controls: unamended soil

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 type:

laboratory study

Substrate type:

natural soil

Limit test:

no

Total exposure duration:

28 d

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

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

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

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.

Description of key information

One key study exists. Study was performed on an analogous substance in accordance with OECD 207 and reported in the literature.

Additional information

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

In addition, potassium and phosphate ions (from the natural breakdown of potassium dihydrogenorthophosphate) are ubiquitous in the environment and are found naturally in soil, water and sediment. All are assimilated by species residing in the sediment, water or soil and are essential for maintaining a good chemical balance. Furthermore, inorganic phosphate fertilizers (containing K+, and PO4 - ions) are often added to soils to improve soil quality. Given the extensive use of inorganic phosphates as soil fertilizers and the natural occurrence of the ions in the environment it is unlikely that inorganic phosphates of this nature would have a detrimental effect on soil macroorganisms and plants and hence further toxicity studies are scientifically unjustified.