Residues of veterinary pharmaceuticals enter the environment via application of manure onto agricultural land, where particularly antibiotics can cause phytotoxicity. Terrestrial plant tests according to OECD test guideline 208 are part of the environmental risk assessment of veterinary pharmaceuticals. However, this standard approach might not be appropriate for veterinary medicinal products forming non-extractable residues or transformation products in manure and manure-amended soil. To assess such products, a new test design including a more realistic exposure scenario via manure application is needed.
To this aim, an extended plant test was developed in the present study and tested with the veterinary antibiotics florfenicol and tylosin tartrate. With each substance, plant tests with four different types of application were conducted: a standard test according to OECD 208 and three tests with application of the antibiotic via spiked cattle and pig manure: either without storage, or incubated aerobically or anaerobically (in both cases both for different time periods).
The application of the test substances via freshly spiked and aerobically incubated manure had no significant influence on the test results. However, application with anaerobically incubated manure significantly reduced phytotoxity increasing the EC10 value by a factor up to 64 for tylosin tartrate and up to 540 for florfenicol. When using cattle manure, a stronger reduction of phytotoxicity was observed than with pig manure.
In the extended plant test, seedling emergence and growth were comparable to the standard OECD 208 test and reliable effect concentrations could be established. The test design thus proved suitable for inclusion into the plant test strategy for veterinary medicinal products.
This work was partly funded by the German Environment Agency (FKZ 3711 63 424).
For additional information, see full article in Environmental Sciences Europe:
Richter, E., Berkner, S., Ebert, I., Förster, B., Graf, N., Herrchen, M., Kühnen, U, Römbke, J., Simon, M. (2016). Results of extended plant tests using more realistic exposure scenarios for improving environmental risk assessment of veterinary pharmaceuticals. Environmental Sciences Europe 28:22.
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