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Long-term toxicity to fish

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No data on long-term toxicity of ATMP-xK (CAS 27794-93-0, where x = 5), to fish are available. A 60-day NOEC of 40 mg/L has however been determined for the effects of the substance on growth of Salmo gairdneri (now known as Onychorhynchus mykiss) based on the results of a test with ATMP acid (CAS 6419-19-8).

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No data on long term toxicity of ATMP xK salts, 27794-93-0, to fish are available. However, a reliable ELS study deriving a 60 day NOEC value of 23 mg/L (as active acid) has been determined for the effects of ATMP acid (CAS 6419-19-8) on growth of O. mykiss fry.

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 23 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 23 mg/L on day 60 was between 7.3 and 8. At this pH ATMP is ionised 5 times (pKa5= pH 6.6, pKa6= pH 12), hence the calculation is to determine the concentration of ATMP-xK (where x = 5) which would be equivalent to 23 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 60 d NOEC for ATMP 6419-19-8 is 23 mg/L, which is equivalent to a 60 d NOEC value of 23 * 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]