Analysis of the dissipation kinetics of ivermectin at different temperatures and in four different soils.
The study target was to assess the usefulness of the OECD test guideline 307 for the veterinary pharmaceutical ivermectin. Laboratory microcosm studies were conducted to investigate the aerobic and anaerobic transformation of ivermectin in soils from three locations in Europe (York, Madrid and Tåstrup) and an artificial soil. The reason to include an artificial soil in the study was to understand the exposure potential of ivermectin in a parallel eco-toxicological study with non-target organisms in this soil for a longer duration. Three kinetic models (first-order (SFO), availability-adjusted first-order (AAFO) and bi-exponential first-order (BFO)) were applied to fit the observed transformation dynamics and to derive dissipation times. Dissipation rates were highly dependent on the tested soils. Under aerobic conditions, dissipation was remarkably faster in the three natural soils tested (DT(50)=16.1-36.1d) than in the artificial soil (DT(50)>500d). Furthermore, a clear increase in DT(50) values was seen when the temperature was lowered from 20 to 6 degrees C. The results indicated that dissipation in soils with comparably strong sorption and low degrees of desorption (i.e. the York soil and to some extent the Tåstrup soil) were best described by the AAFO model. While dissipation in the Madrid soil which had a lower sorption coefficient and a higher degree of reversibility of sorption could be satisfactorily described with the SFO model. Our data further showed that no significant dissipation occurred under anaerobic conditions.
Krogh
Kristine A
KA
Copenhagen University, Faculty of Pharmaceutical Science, Department of Pharmaceutics and Analytical Chemistry, Section of Toxicology and Environmental Chemistry, Universitetsparken 2, DK-2100 Copenhagen, Denmark. kak@farma.ku.dk
Jensen
Gitte G
GG
Schneider
Manuel K
MK
Fenner
Kathrin
K
Halling-Sørensen
Bent
B
D000977:Antiparasitic Agents / Q000737:chemistry*; D001673:Biodegradation, Environmental; D007559:Ivermectin / Q000737:chemistry*; D007700:Kinetics; D012987:Soil; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry*; D013696:Temperature
D000977:Antiparasitic Agents; D012987:Soil; D012989:Soil Pollutants; D007559:Ivermectin