Iron orthophosphate

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

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:

other: Scientifically sound study published in a peer-reviewed journal and conducted in accordance with an appropriate guideline (OECD 207).

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

Principles of method if other than guideline:

Study tested both iron phosphate and a commonly used molluscicide; iron phosphate with EDTA.

GLP compliance:

not specified

Remarks:

peer-reviewed publication

Analytical monitoring:

yes

Vehicle:

yes

Details on preparation and application of test substrate:

Treatments were: over the range of concentrations 0 (control), 0.1, 1.0, 10.0, 100.0, 1000.0, and 10,000.0 mg of chemical / kg d.w. soil.

The treatments tested were:
1) Control – no chemicals
2) Metaldehyde
3) Iron phosphate (Fe(PO4)3)
4) EDDS
5) EDTA
6) 100% Fe(PO4)3 + 3% EDDS*
7) 100% Fe(PO4)3 + 3% EDTA*
*These are the amounts of chelating agents needed to obtain complete chelation of the iron phosphate. Metaldehyde, and iron phosphate were applied, mixed with 10 g finely ground quartz sand, and EDDS and EDTA were both applied in deionized water solution. The control and EDDS and EDTA treatments also received 10 g finely ground quartz sand. There were four replicates of each treatment.

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: earthworm
- Source: no data
- Weight at test initiation: approx 1 mg

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

48 h

Test temperature:

20°C

pH:

6.0 ± 0.5

Moisture:

35% dry weight moisture content

Details on test conditions:

TEST SYSTEM
- Test container (material, size): glass jars
- Amount of soil or substrate: 750 g
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 4
- No. of replicates per control: 4


SOURCE AND PROPERTIES OF SUBSTRATE (if soil):
10% finely ground sphagnum peat (pH 5.5–6.0).
20% kaolinite clay (containing >30% kaolinite).
70% industrial quartz sand (dominant fine sand with more than 50% of particle size of 0.05–2.0 mm).
1% calcium carbonate (CaCO3 – pulverized to bring the pH of mixture to 6.0 ± 0.5).

Nominal and measured concentrations:

0, 0.1, 1.0, 10.0, 100.0, 1000.0, 10.000.0 mg of chemical / kg dry weight soil

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 10 000 mg/kg soil dw

Nominal / measured:

nominal

Basis for effect:

mortality

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

78.16 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

other: iron phosphate + 3% EDTA

Basis for effect:

mortality

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

82.98 mg/kg soil dw

Nominal / measured:

not specified

Conc. based on:

other: iron phosphate + 3% EDDS

Basis for effect:

mortality

Validity criteria fulfilled:

yes

Conclusions:

Iron phosphate alone had no significant effects on the earthworms at any of the concentrations tested. However, combinations of iron phosphate with both EDTA and EDDS had significant effects on the earthworm numbers.
This study demonstrates the low bioavailability of iron phosphate (ferric orthophosphate); when combine with a chelating agent the bioavailability is increased and the toxic effects to earthworms of iron ingestion are noted. ferric orthophosphate itself is not considered to be toxic to earthworms.

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Description of key information

LC50 (48 h) > 10 000 mg/kg (Eisenia fetida, OECD 207)

Additional information

One publication evaluating the short-term toxicity of iron (III) phosphate to earthworms is available. The study by Edwards et al. (2009) was conducted according to the OECD guideline 207. In the study Eisenia fetida was exposed to pure iron phosphate and iron phosphate with a chelating or solubilizing agent (ethyldiaminetetraceticacid (EDTA) and ethylenediaminesuccinicacid (EDDS)) to concentrations up to 10 000 mg/kg. No toxicity was observed in the treatments with only iron phosphate revealing that no short-term toxicity by the substance is expected towards soil macroorganisms.