In vitro pesticide degradation in turfgrass soil incubated under open and sealed conditions

Evaluation of temperature corrections for pesticide half-lives in tropical and temperate soils

Temperature is a key factor that influences pesticide degradation. Extrapolating degradation half-lives (DT50) measured at a given temperature to different temperatures remains challenging, especially for tropical conditions with high temperatures. In this study, the use of the standard Arrhenius equation for correcting temperature effects on pesticide degradation in soils was evaluated and its performance was compared with that of alternative Arrhenius-based equations. To do so, a database of 509 DT50 values measured between 5 and 35 °C for 32 pesticides on tropical and temperate soils was compiled for the first time through an extensive literature search. The temperature correction models were fitted to the database using linear mixed regression approaches that included soil type and compound effects. No difference in the temperature dependence of DT50 between tropical and temperate soils was detected, regardless of the model. A comparison of the prediction performances of the models showed that constant activation energy (E_a) cannot be considered valid for the whole range of temperatures. The classical Arrhenius equation with an E_a of 65.4 kJ.mol^-1, as recommended by the European Food Safety Authority (EFSA), was shown to be valid for correcting the DT50 only for temperatures ranging from 5 to 20 °C. However, for temperatures greater than 20 °C, which are common in tropical environments, the median E_a was significantly lower at 10.3 kJ.mol^-1. These findings suggest the need to adapt the standard temperature correction of the European pesticide risk assessment temperature procedure when it is applied in tropical settings.

Contamination of honey by the herbicide asulam and its antibacterial active metabolite sulfanilamide

A number of antibacterial drugs (antibiotics) like sulfonamides, tetracyclines and streptomycin are used for the treatment of bacterial diseases in beehives. Yet, the finding of sulfanilamide residues in some 15 Swiss honeys out of some 350 samples could not be explained by such apicultural practice. Bees occasionally collect nectar from meadows treated with the herbicide asulam. Such honey is not only contaminated by asulam, but also by its degradation product sulfanilamide. This is the first report that the use of a herbicide causes the appearance of residues of an antibacterial active metabolite belonging to the category of sulfonamide drugs in food. The relevance of this finding lies in the fact that the use of the herbicide asulam might cause unacceptable residue levels of sulfanilamide in a product fbr human consumption.