## 3 Results and Discussion
### Potential Dermal Exposure of Operators to Allura Red  
In recent years, as society continues to pay more attention to issues such as the quality and safety of agricultural products and environmental pollution, attention to pesticide risk assessment has also risen sharply. Pesticide operator exposure measurement is an important part of pesticide risk assessment. Due to the influence of planting scales and modes, many areas in China still use the backpack-type, large-volume spray method to apply pesticides. In addition, pesticide application personnel lack the necessary safety protection. Thus, operator exposure risk to pesticide is worthy of attention. It is well accepted that pesticide operator exposure is dependent on scenarios. Influential factors such as crop type [42; 43], application experience [44], climatic condition [6], and spraying equipment [45; 46] can affect the exposure level. It is obvious that the pesticide exposure of the knapsack spray operator is greater than that of the UAV pilot. Despite this, the pesticide exposure assessment of the operator during the spraying application with the UAV, especially the comparison with the conventional ground sprayer of the knapsack electric sprayer, has not been well investigated. In the present study, this comparison was performed. Due to the unique performance mentioned above, Allura Red was used as a pesticide surrogate for exposure assessment of operators. The potential dermal exposure of operators to Allure Red sprayed by knapsack electric and UAV sprayers is summarized in Table 3. For each treatment, the operator conducted similar spraying in triplicate. To eliminate the influence of the differences in spraying time, exposure levels are presented as the unit exposure (UE), namely the mass of active ingredient (ai) exposure per unit mass of active ingredient applied (mg/kg of ai). As shown in Table 3, the total UE to Allure Red of operators A and B were 2516.17 and 1387.86 mg/kg, respectively, which was greatly higher than that of the UAV operator (134.51 mg/kg), indicating the lower exposure risk for the operator manipulating the UAV. Due to individual spraying experiences and habits, operator A (female) and B (male) had obvious different exposure levels. The height of the cowpea is taller than the operators spraying with a knapsack electric sprayer. Thus, the operators would swing the lance from top to bottom, walking forward into the area being sprayed. As a consequence, both the upper part of the body (head, chest, back, and arms) and the lower part (thigh and leg) were inevitably exposed. Interestingly, the exposures of right hands (158.65 and 140.01 mg/kg) were greater than those of left hands (64.78 and 50.02 mg/kg). The lateralization of hand \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Operator Exposure (mg/kg)**} \\ \cline{2-7}
**Body Region** & **Op. A a** & **Op. A** & **Op. B a** & **OP. B** & **Op. C a** & **Op. C** \\  & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** \\ \hline Mask & 13.68 & 4.66 & 5.75 & 3.91 & 1.08 & 0.78 \\ Head & 192.42 & 16.61 & 70.11 & 33.62 & 8.95 & 3.92 \\ Chest & 358.40 & 47.37 & 141.34 & 62.66 & 14.39 & 2.91 \\ Back & 239.53 & 62.02 & 125.84 & 47.37 & 13.91 & 9.34 \\ Left arm & 326.79 & 48.85 & 135.57 & 55.26 & 10.89 & 2.80 \\ Right arm & 259.60 & 43.95 & 125.24 & 38.79 & 12.82 & 2.02 \\ Left glove & 64.78 & 17.79 & 50.02 & 13.78 & 7.49 & 0.88 \\ Right glove & 158.65 & 25.55 & 140.01 & 16.94 & 8.52 & 0.28 \\ Left thigh & 161.41 & 23.30 & 89.06 & 10.76 & 16.38 & 7.32 \\ Right thigh & 190.70 & 23.68 & 102.84 & 35.80 & 15.08 & 7.83 \\ Left leg & 292.33 & 67.25 & 166.58 & 23.30 & 13.79 & 3.67 \\ Right leg & 257.88 & 55.90 & 235.49 & 86.84 & 11.21 & 5.51 \\ Total exposure & 2516.17 & 28.18 & 1387.86 & 238.46 & 134.51 & 38.99 \\ \hline \hline \end{tabular}  
* Op. A: operator A (female), Op. B: operator B (male), Op. C: operator C. Operators A and B performed the spraying with knapsack electric sprayers, and operator C is a UAV pilot.  
\end{table}