Phosphonic acid, calcium salt (2:1)

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

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 calcium dihydrogenphosphite (Ca(H2PO3)2, CAS 13780-04-6), 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 calcium dihydrogenphosphate and potassium phosphonate upon dissolution in aqueous media. Both phosphite salts are highly soluble (>200 g/L) and are only present in their dissociated form in solution, i.e. the calcium 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 (Ca2+ 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 calcium and potassium. Moreover, calcium 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:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 135 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Remarks:

dihydrogenphosphite anion

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 135 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Remarks:

dihydrogenphosphite anion

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 168 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 168 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

mobility

Validity criteria fulfilled:

yes

Conclusions:

NOEC and EC50 > 168 mg Ca(H2PO3)2 /LResults indicate that KH2PO3/K2HPO3 did not induce short-term toxicity to Dapnia magna up to 200 mg/L. Values were corrected for Ca(H2PO3)2 based on the assumption that the phosphite anion is the active ingredient reposonsible for the effects, resulting in predicted NOEC and EC50 values of >168 mg/L.

Executive summary:

The acute toxicity of Potassium phosphonate (KH₂PO₃/K₂HPO₃) to Daphnia magna was determined in a 48‑hour full static test according to the OECD Guideline for Testing of Chemicals, No. 202 (2004) and to Council Regulation EC 440/2008 (C.2).

For this purpose, juvenile daphnids (< 24 hours old at initiation of the test) were exposed to an aqueous test medium containing the test item at five different concentrations, namely 8.5, 18.8, 41.3, 90.9 and 200.0 mg/L of Potassium phosphonate.

The exposed organisms were checked for immobilization 24 and 48 hours after test initiation.

At the end of test period, in the negative control 0 % of immobilization was observed and no daphnid showed signs of disease or stress (e.g. to be trapped on the test water surface). These values comply with the validity criterion of the test, that provide a maximum immobilization or a maximum number of daphnids showing desease or stress signs of 10 % in the negative control medium at the end of the test.

No effect was observed until 200 mg/L. Values were corrected for Ca(H2PO3)2 based on the assumption that the phosphite anion is the active ingredient reposonsible for the effects, resulting in predicted NOEC and EC50 values of >168 mg/L.

Description of key information

EC50 and NOEC > 168 mg Ca(H2PO3)2 /L

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

168 mg/L

Additional information

The acute toxicity of Potassium phosphonate (KH₂PO₃/K₂HPO₃) to Daphnia magna was determined in a 48‑hour full static test according to the OECD Guideline for Testing of Chemicals, No. 202 (2004) and to Council Regulation EC 440/2008 (C.2).

For this purpose, juvenile daphnids (< 24 hours old at initiation of the test) were exposed to an aqueous test medium containing the test item at five different concentrations, namely 8.5, 18.8, 41.3, 90.9 and 200.0 mg/L of Potassium phosphonate.

The exposed organisms were checked for immobilization 24 and 48 hours after test initiation.

At the end of test period, in the negative control 0 % of immobilization was observed and no daphnid showed signs of disease or stress (e.g. to be trapped on the test water surface). These values comply with the validity criterion of the test, that provide a maximum immobilization or a maximum number of daphnids showing desease or stress signs of 10 % in the negative control medium at the end of the test.

No effect was observed until 200 mg potassium phosphonate /L. Values were recalculated for Ca(H2PO3)2 based on the assumption that the phosphite anion is the active ingredient reposonsible for the effects, resulting in predicted LC0 and LC50 values of >168 mg Ca(H2PO3)2 /L.