Phosphonic acid, magnesium salt (2:1)

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:

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

Adequacy of study:

key study

Justification for type of information:

In the assessment of magnesium dihydrogenphosphite (Mg(H2PO3)2, CAS 13598-61-3), a read-across approach is followed based on the information available for potassium phosphonate (KH2PO3/K2HPO3 EC 915-179-9). This read-across strategy is based on the hypothesis that the phosphite anion is the driver for the ecotoxicological and toxicological effects of both salts.The read-across hypothesis is justified by the immediate dissociation of magnesium dihydrogenphosphate and potassium phosphonate upon dissolution in aqueous media. Both phosphite salts are highly soluble (>800 g/L) and are only present in their dissociated form in solution, i.e. the magnesium or potassium cation and the phosphite anion. The transformation of the salts into the ions is rapid and complete in relevant environmental and physiological media and therefore no systemic exposure to the salts as such occurs. Exposure to the non-common cations (Mg2+ and K+) does not influence the prediction of the (eco)-toxicity because both elements are abundantly present in natural environments and emissions from these salts do not significantly increase the exposure concentration for magnesium and potassium. Moreover, magnesium and potassium are major essential element for living organisms.Further information is included as attachment in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Duration:

14 d

Dose descriptor:

LC0

Effect conc.:

ca. 674 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Remarks:

dihydrogenphosphite anion

Basis for effect:

mortality

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

> 674 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Remarks:

dihydrogenphosphite anion

Basis for effect:

mortality

Key result

Duration:

14 d

Dose descriptor:

EC0

Effect conc.:

ca. 776 mg/kg soil dw

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

mortality

Key result

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

> 776 mg/kg soil dw

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

mortality

Validity criteria fulfilled:

yes

Conclusions:

Results indicate that Mg(H2PO3)2 did not induce an acute effect on earthwom mortality up to 776 mg/kg dw.

Executive summary:

The acute toxicity of Potassium phosphonate (KH₂PO₃/K₂HPO₃) to the earthworm Eisenia fetida was determined in a 14‑days artificial soil study according to the OECD Guideline for Testing of Chemicals No. 207 (1984).

For this purpose, adult earthworms were exposed under defined conditions to artificial soil containing the test item at five concentrations in a geometric series, namely 9.5, 30.5, 97.7, 312.5, 1000.0 mg/kg (dry weight) as Potassium phosphonate.

Moreover an artificial soil without test item was also tested as negative control.

The exposed organisms were checked for mortality 7 and 14 days after test initiation.

In the control 0 % mortality was observed after 7 days and after 14 days. This value complies with the validity criterion of the test, that provides a maximum mortality of 10 % in the negative control at the end of the test.

The obtained experimental results allowed to determine mortality endpoint; moreover the sublethal effect, body weight change, was assessed. No effects were observed up to the largest concentrations tested (1000 mg potassium phosphonate /kg dw). Values were recalculated for Mg(H2PO3)2 based on the assumption that the phosphite anion is the active ingredient reposonsible for the effects, resulting in a predicted LC50 value of >776 mg Mg(H2PO3)2 /kg dw.

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

776 mg/kg soil dw

Additional information

The acute toxicity of Potassium phosphonate (KH₂PO₃/K₂HPO₃) to the earthwormEisenia fetidawas determined in a 14‑days artificial soil study according to the OECD Guideline for Testing of Chemicals No. 207 (1984).

For this purpose, adult earthworms were exposed under defined conditions to artificial soil containing the test item at five concentrations in a geometric series, namely 9.5, 30.5, 97.7, 312.5, 1000.0 mg/kg (dry weight) as Potassium phosphonate.

Moreover an artificial soil without test item was also tested as negative control.

The exposed organisms were checked for mortality 7 and 14 days after test initiation.

In the control 0 % mortality was observed after 7 days and after 14 days. This value complies with the validity criterion of the test, that provides a maximum mortality of 10 % in the negative control at the end of the test.

The obtained experimental results allowed to determine mortality endpoint; moreover the sublethal effect, body weight change, was assessed. No effects were observed up to the largest concentrations tested (1000 mg potassium phosphonate /kg dw). Values were recalculated for Mg(H2PO3)2 based on the assumption that the phosphite anion is the active ingredient reposonsible for the effects, resulting in a predicted LC50 value of >776 mg Mg(H2PO3)2 /kg dw.