Abstract
Plant protection spray treatments may expose non-target organisms to pesticides. In the pesticide registration procedure, the honey bee represents one of the non-target model species for which the risk posed by pesticides must be assessed on the basis of the hazard quotient (HQ). The HQ is defined as the ratio between environmental exposure and toxicity. For the honey bee, the HQ calculation is not consistent because it corresponds to the ratio between the pesticide field rate (in mass of pesticide/ha) and LD50 (in mass of pesticide/bee). Thus, in contrast to all other species, the HQ can only be interpreted empirically because it corresponds to a number of bees/ha. This type of HQ calculation is due to the difficulty in transforming pesticide field rates into doses to which bees are exposed. In this study, we used a pragmatic approach to determine the apparent exposure surface area of honey bees submitted to pesticide treatments by spraying with a Potter-type tower. The doses received by the bees were quantified by very efficient chemical analyses, which enabled us to determine an apparent surface area of 1.05 cm2/bee. The apparent surface area was used to calculate the exposure levels of bees submitted to pesticide sprays and then to revisit the HQ ratios with a calculation mode similar to that used for all other living species. X-tomography was used to assess the physical surface area of a bee, which was 3.27 cm2/bee, and showed that the apparent exposure surface was not overestimated. The control experiments showed that the toxicity induced by doses calculated with the exposure surface area was similar to that induced by treatments according to the European testing procedure. This new approach to measure risk is more accurate and could become a tool to aid the decision-making process in the risk assessment of pesticides.
Highlights
Human activity generates many environmental disruptions and myriads of anthropogenic chemical substances [1]
This exposure level enabled assessing the exposure surface area of a honey bee that could be used in the assessment of the risk posed by plant protection products as recommended by the European Food Safety Agency (EFSA) [11]
The first involves the determination of the apparent surface area by projection from photographs, which results in a surface area of approximately 0.5 cm2/bee [23]
Summary
Human activity generates many environmental disruptions and myriads of anthropogenic chemical substances [1]. In human risk assessment a more modern approach involves the determination of benchmark doses (BMD) or concentrations, which correspond to the levels of exposure at which a given effect is observed, determined by modeling the entire dose-effect relationship [5,6]. These toxicological values can be lowered by uncertainty or safety factors such as those used to take into account intraspecific variability and extrapolation from model species, which correspond to interspecific variability. When the exposure level is higher than the toxicological value, the situation is at risk for the considered biological organism, which results in HQ or TER values higher or lower than 1, respectively
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