Variability of Pesticide Dissipation Half-Lives in Plants

Information on dissipation kinetics of pesticides in food crops and other plants is a key aspect in current risk and impact assessment practice. This is because human exposure to pesticides is predominantly caused by residues in agricultural crops grown for human and animal consumption. However, modeling dissipation of pesticides in plants is highly uncertain and therefore strongly relies on experimental data. Unfortunately, available information on pesticide dissipation in plants from experimental studies only covers a small fraction of possible combinations of substances authorized for use on food and fodder crops. Additionally, aspects and processes influencing dissipation kinetics are still not fully understood. Therefore, we systematically reviewed 811 scientific literature sources providing 4513 dissipation half-lives of 346 pesticides measured in 183 plant species. We focused on the variability across substances, plant species and harvested plant components and finally discuss different substance, plant and environmental aspects influencing pesticide dissipation. Measured half-lives in harvested plant materials range from around 1 hour for pyrethrins in leaves of tomato and pepper fruit to 918 days for pyriproxyfen in pepper fruits under cold storage conditions. Ninety-five percent of all half-lives fall within the range between 0.6 and 29 days. Our results emphasize that future experiments are required to analyze pesticide–plant species combinations that have so far not been covered and that are relevant for human exposure. In addition, prediction models would help to assess all possible pesticide–plant species combinations in the context of comparative studies. The combination of both would finally reduce uncertainty and improve assumptions in current risk and impact assessment practice

Chronic hazard index (<i>CHI</i>) for each metal and metalloid at the three study sites.

<p>Chronic hazard index (<i>CHI</i>) for each metal and metalloid at the three study sites.</p

Average daily intake of heavy metals and metalloids by adults and children and the respective hazard quotients.

<p>Average daily intake of heavy metals and metalloids by adults and children and the respective hazard quotients.</p

Conceptual illustration of the fate pathways of mining-related emissions of heavy metals and metalloids in the environment potentially leading to exposures for human and ecological receptors.

<p>Conceptual illustration of the fate pathways of mining-related emissions of heavy metals and metalloids in the environment potentially leading to exposures for human and ecological receptors.</p

Heavy metal and metalloid contamination factors and ecological risk factors at the three tailings sites.

<p>Heavy metal and metalloid contamination factors and ecological risk factors at the three tailings sites.</p

Toxicological parameters for heavy metals and metalloids used in health risk assessment.

<p>Toxicological parameters for heavy metals and metalloids used in health risk assessment.</p

Health risk parameters and values used.

<p>Health risk parameters and values used.</p

Concentrations of heavy metals and metalloids in samples of tailings contaminated soils.

<p>Concentrations of heavy metals and metalloids in samples of tailings contaminated soils.</p

Mean relative abundance of minerals identified in samples.

<p>Mean relative abundance of minerals identified in samples.</p

Distribution of pathways contributing to potential human exposure following an assumed emission of different heavy metals and metalloids of 1 kg per day to natural soil.

<p>Distribution of pathways contributing to potential human exposure following an assumed emission of different heavy metals and metalloids of 1 kg per day to natural soil.</p