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Long-term toxicity to aquatic invertebrates

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Description of key information

(28 d) NOEC ≥ 40 mg/L with Daphnia magna

Key value for chemical safety assessment

Additional information

No data on long term toxicity of ATMP xK salts (CAS 27794-93-0) to invertebrates are available. However, a study is available for the parent acid ATMP (CAS 6419-19-8). A 28 day NOEC value of ≥ 25 mg/L (as active acid) has been determined for the effects of ATMP acid (CAS 6419-19-8) on adult survival and reproduction of D. 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 25 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 23 mg/L concentration.

The pH of the test medium at concentration 25 mg/L on day 28 was ca. 7. At this pH ATMP is ionised 5 times (pKa5= pH 6.6), hence the calculation is to determine the concentration of ATMP-xK (where x = 5) which would be equivalent to 25 mg active acid/L. In the calculation we also remove the number of hydrogen atoms substituted by the potassium salt from the MW of ATMP, in this case 5.

The 28 d NOEC for ATMP 6419-19-8 is 25 mg/L, which is equivalent to a 28 d NOEC value of 25 * 1.64 = 40 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]