[nitrilotris(methylene)]trisphosphonic acid, potassium salt

Short-term toxicity to aquatic invertebrates

Description of key information

There are no data for the test substance. A 48 h EC50 value of 297 mg/L has however been determined for the effects of ATMP acid on the immobility of the freshwater flea Daphnia magna. This value is equivalent to a concentration of 485 mg/L for ATMP-xK (CAS 27794-93-0, where x = 5).
A 48 h LC50 value of 94 mg/L has similarly been determined for the effects of ATMP acid on mortality of the marine invertebrate Acartia tonsa. This value is equivalent to a concentration of 155 for ATMP-xK (CAS 27794-93-0, where x = 5).

Additional information

Freshwater

Reliable data on the short term toxicity of ATMP-xK salts, 27794-93-0, to freshwater invertebrates are not available. However, a reliable 48 h EC50 value of 297 mg active acid/L has been determined for the effects of ATMP acid (CAS 6419-19-8) on the immobility of the freshwater flea Daphnia magna.

The results of tests conducted on ATMP and its salts are directly comparable, because 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, ATMP will be ionised typically four or five times, and will form stable complexes with metal ions.

Here, the value of 297 mg equivalent active acid/L may be directly read-across. It is convenient to convert the result into units of mg ATMP-xK salt/L at relevant conditions of pH by considering the ionisation state of ATMP 6419-19-8 at the 297 mg/L concentration.

The pH of the test medium at concentration 297 mg/L was between 2 and 8, average 5. At this pH ATMP is ionised 4 times (pKa₅= pH 5.56), hence the calculation aims to determine the concentration of ATMP-xK (where x = 4) which would be equivalent to 297 mg active acid/L. In the calculation we also remove the number of hydrogen atoms substituted by the sodium salt from the MW of ATMP, in this case 4.

The 96 h LC50 for ATMP 6419-19-8 is 297 mg/L, which is equivalent to a 96 h LC50 value of 297 * 1.51 = 485 mg/L ATMP-xK (CAS 27794-93-0, where x = 4)[using MW(ATMP-4Na)/MW(ATMP) = (299.05+((39.098-1.008)*4) /299.05 = 1.51]

 

Marine

Reliable data on the short term toxicity of ATMP-xK salts, 27794-93-0, to marine invertebrates are not available. However, a reliable 48 h LC50 value of 94 mg active acid/L has been determined for the effects of ATMP-xNa (CAS 20592-85-2) on the immobility of the marine invertebrate Acartia tonsa.

The results of tests conducted on ATMP and its salts are directly comparable, because 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, ATMP will be ionised typically four or five times, and will form stable complexes with metal ions.

Here, the value of 94 mg equivalent active acid/L may be directly read-across. It is convenient to convert the result into units of mg ATMP-xK salt/L at relevant conditions of pH by considering the ionisation state of ATMP-xNa at the 94 mg/L concentration.

The pH of the test medium at concentration 94 mg/L was not reported, so a typical value of pH 7 is selected. At this pH ATMP is ionised 5 times (pKa₅= pH 6.66), hence the calculation aims to determine the concentration of ATMP-xK (where x = 5) which would be equivalent to 94 mg active acid/L. In the calculation we also remove the number of hydrogen atoms substituted by the sodium salt from the MW of ATMP, in this case 5.

The 48 h LC50 value of 94 mg active acid/L is equivalent to a 48 h LC50 value of 297 * 1.64 = 155 mg/L ATMP-xK (CAS 27794-93-0, where x = 5)[using MW(ATMP-5K)/MW(ATMP) = (299.05+((39.098-1.008)*5) /299.05 = 1.64]