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Short-term toxicity to fish

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Description of key information

96 h LC50 270 mg active acid/L (r-a) Salmo gairdneri (new name: Oncorhynchus mykiss)
96 h LC50 8080 mg active acid/L (r-a) Cyprinodon variegatus

Key value for chemical safety assessment

Additional information

Freshwater

Data on short term toxicity of DTPMP-xNa salts, CAS 22042-96-2, on short term toxicity to freshwater fish are available, however since the data is related to active acid content and it is possible to freely read-across from DTPMP acid (CAS 15827-60-8) to the sodium salt and the lowest EC50 is represented by data on the acid, this has been read-across.

A reliable 96 h LC50 value of 216 mg/L has been determined for the effects of DTPMP on the mortality of the freshwater fish Salmo gairdneri (new name: Oncorhynchus mykiss).

The results of tests conducted on DTPMP and its salts are directly comparable, because the substance will fully dissociate in solution and the ionisation state will depend only on the pH of the test medium. The counterion is not considered to contribute to effects in fish. At environmentally-relevant pH values, DTPMP will be ionised typically 6-8 times, and will form stable complexes with metal ions.

Here, the value of 216 mg equivalent active acid/L may be directly read-across. It is convenient to convert the result into units of mg DTPMP-xNa salt/L at relevant conditions of pH by considering the ionisation state of DTPMP (CAS 15827-60-8)at the 216 mg/L concentration.

The pH range of the test medium is thought to be around 7. At this pH DTPMP is ionised 7 times (pKa7= pH 7.23), hence the calculation is to determine the concentration of HEDP-xNa (where x = 7) which would be equivalent to 216 mg active acid/L. In the calculation we also remove the number of hydrogen atoms substituted by the sodium salt from the MW of HEDP, in this case 7.

The 96 h LC50 for DTPMP acid is 216 mg/L, which is equivalent to a 96 h LC50 value of 216 * 1.26 = 270 mg/L DTPMP-xNa

[using MW(DTPMP-7Na)/MW(DTPMP) = 573.2+((21.982-1.008)*7) / 573.2= 1.26

 

Marine

No data on short term toxicity of DTPM-xNa salts, CAS 22042-96-2, to marine fish are available. However, a reliable 96 h LC50 value of 6435 mg active acid/l has been determined for the effects of DTPMP acid (CAS 15827-60-8) towards the mortality of the marine fish Cyprinodon variegatus.

The results of tests conducted on DTPMP and its salts are directly comparable, because the substance will fully dissociate in solution and the ionisation state will depend only on the pH of the test medium. The counterion is not considered to contribute to effects in fish. At environmentally-relevant pH values, DTPMP will be ionised typically 6-8 times, and will form stable complexes with metal ions.

Here, the value of 6435 mg equivalent active acid/L may be directly read-across. It is convenient to convert the result into units of mg DTPMP-xNa salt/L at relevant conditions of pH by considering the ionisation state of DTPMP (CAS 15827-60-8) at the 6435 mg/L concentration.

The pH range of the test medium is thought to be around 7. At this pH DTPMP is ionised 7 times (pKa7= pH 7.23), hence the calculation is to determine the concentration of HEDP-xNa (where x = 7) which would be equivalent to 216 mg active acid/L. In the calculation we also remove the number of hydrogen atoms substituted by the sodium salt from the MW of HEDP, in this case 7.

The 96 h LC50 for DTPMP acid is 6435 mg/L, which is equivalent to a 96 h LC50 value of 6435 * 1.26 = 8080 mg/L DTPMP-xNa

[using MW(DTPMP-7Na)/MW(DTPMP) = 573.2+((21.982-1.008)*7) / 573.2= 1.26