*2.8. Statistical Analysis*

Results were expressed as mean±SD and statistical significance was determined by one-way analysis of variance (ANOVA) followed by the least significant di fference (LSD) using the statistical software SPSS (SPSS 19.0; SPSS Inc., Chicago, IL, USA). The level of statistical significance was established at *p* < 0.05.

#### **3. Results and Discussion**

#### *3.1. Validation of the Analytical Method*

Recovery experiments were carried out at three di fferent fortification levels in nine replicates and the relative recovery rates were calculated via the matrix-matched calibration curves. Acetone was chosen as the extraction solvent for cotton wool, gauze, and XAD-2. In this study, SYP-9625 detected in di fferent materials had a high recovery rate, and a method of detection and analysis of SYP-9625 concentrations in di fferent matrices was established. Acceptable recoveries were obtained in the ranges of 91.02–102.35% from cotton wool, 97.34–103.45% from gauze, 95.33–107.26% from outer gloves, 93.28.9–97.65% from XAD-2, and 103.25–110.37% from 0.01% Aerosol OT. The recovery and precision of SYP-9625 (expressed as relative standard deviation) are shown in Table 1, RSDs were less than 10% in all samples, demonstrating the excellent repeatability of the process. Therefore, a combination of UPLC-MS detection, and the utilized extraction method could serve as a conventional detection method for SYP-9625 in all of the above matrices.


**Table 1.** SYP-9625 recovery from field-fortified samples.

Since this orchard is far away from our laboratory, we needed to clarify whether the pesticides on the various exposed substrates would be lost during transportation The recovery rate of the sample added to the on-site recovery test was approximately 91.5%. This proves that the loss of pesticides during storage and transportation is below 10%. The OECD(Organization for Economic Co-operation and Development) pointed out that the samples were su fficiently stable within 30% decline of the recovery rate [24].

#### *3.2. Dermal and Inhalation Exposure during Application*

In this study, we measured pesticide exposure by dermal and inhalation routes using standard systemic dosimetry and air sampling methods. In the practical application of pesticides, farmers wear clothes with at least one layer of clothing. Actual dermal exposure (ADE) is the amount of pesticide that passes through the clothes and is exposed to the skin. The handlers wear two layers of clothing during application and the inner layer of clothing is used to simulate the skin. Potential dermal exposure (PDE) during application is the sum of dosimeter readings for the inner and outer layers. The pesticide test results for the inner clothing, hand wash, and face/neck wipes were calculated as actual dermal exposure (ADE) [23]. The inhalation exposure was calculated as the amount of active compound adsorbed by the XAD-2 sorbent tube on the air sampler throughout the application period. The pesticide exposure in this study was measured by PDE. Table 2 lists the pesticide unit exposures of the two layers of clothing inside and outside the applicator. According to the literature, the occupational exposure of pesticides in the field is quite di fferent for di fferent pesticide application personnel, and the di fference is related to the operating habits and proficiency [10]. Therefore, the final experimental results are based on average.


**Table 2.** Unit exposures at various parts of the body (mg/kg a.i. handled).

A, inner-layer garment; b, outer-layer garment; 1, front torso (above the waist); 2, rear torso (above the waist); 3, right and left upper arms (shoulder to elbow); 4, right and left forearms (elbow to cuff); 5, right and left thighs (waist to knee); 6, right and left lower shins (knee to cuff); 7, cap; 8, left glove; 9, right glove; 10, mask; 11, face wipe; 12, neck wipe; 13, hand washes; 14, XAD-2.

#### 3.2.1. Dermal Unit Exposure during Application

The total PDE of handlers was 350 mg·kg−1. These data is close to the exposure assessment data for the fruit tree application scenario reported by Zhao et al. [25] and lower than the exposure data for the knapsack sprayer in cornfields and peanut fields reported by Gao et al. [10] and Chen et al. [12], but higher than the exposure data using pesticide speed sprayer application in an apple orchard [26]. As shown in Table 3, according to the UE of each garment, the highest contaminated sections were hands and shins, accounting for an average of 59% and 19% of total dermal exposure, respectively.

**Table 3.** Distribution of dermal exposure during application (mg/kg a.i. handled).


All data are presented as mean±standard error (n = 7). Different lessters(a, b) in each row indicate significant difference at *p* ≤ 0.05 (least significant difference).

We found that the exposure of hands, which refers to the sum of the exposure of the left and right gloves plus that of the handwashing solution, was considerably greater than other body parts. This is different from the results of Zhao et al. [15,24]. While Li et al. [27] showed that when spraying high places with a spray gun, the most contaminated sections were hands. This could be attributed to the different types of application equipment used. In our experiments, the applicator needed two hands to hold the sprayer in order to work properly, and the hands were the only body part in direct contact with the applicator. High pressure can cause pesticide liquid overflow in the connection between the hose and spray lance onto the hand. Further, most of the pesticide liquid sprayed from the nozzle, but liquid flow along the spray lance to the hand was possible. In addition, any problems that occurred during the application process needed to be addressed using both hands, such as pulling a hose for pesticide delivery, and handling the leakage of pesticide [28,29]. The high exposure level of shins may be due to a large number of pesticides deposited on the ground weeds during the application of pesticides into the base of apple trees [30,31]. In addition, handlers needed to walk through the weeds in order to facilitate the application of pesticides [25]. These results are similar to those obtained by Noh et al. [32], who reported when spraying onto lower crops (about 80–100 cm high), workers are exposed while moving.

However, when handlers are wearing long pants and pure cotton gloves, hand exposure decreased by 76%, shin exposure decreased more than 99%, and the ADE was reduced by 85.43% to 51.1 mg·kg−1. This shows that clothing plays a very good role in protecting against pesticides, especially for those who regularly apply pesticides. This is consistent with the conclusions of Ren et al. [33] and An et al. [34]. Hands were still exposed significantly, so the protection of the hands during the application of pesticides should be given extra attention. In order to further reduce the contamination of the hands, we recommend that handlers wear impermeable gloves such as chemical-resistant gloves. The exposure of the left and right hand is approximately the same (Table 4), because during the application process, the handlers need to change the way in which the spray gun is held based on the direction in which they are walking, and the height of the fruit tree, in order to facilitate spraying.



All data are presented as mean ±standard error (n = 7). Letter (a) in each column indicate significant a difference at *p* ≤ 0.05 (least significant difference).

In the orchard application scenario, a handler stands under the tree to apply the pesticide to the oblique crown above the tree. The liquid droplets collide with the leaves and bounce to fall under the force of gravity [35]. The pesticide drifts to the head and body of the handler. During our experiment, the handler's head was protected by a cotton baseball cap. The exposure to the head was not significant, at only 8.75 mg·kg−1, which may be related to the small overall head area. As can be seen from Table 3, the wearing of a cap reduced the skin exposure of the head to 1.31 mg·kg−1, and the protection rate was about 85%. However this protection rate was relatively low compared with other body parts. Since the brain is an essential organ that controls many human organs, the head should be better protected. Therefore, we recommend wearing a wide-brimmed sun visor with cotton or waterproof material during the actual application of pesticides. This can increase the coverage of the head and neck to prevent the pesticide liquid from scattering on the head. At the same time, it can also protect the skin from sunlight and reduce the damage of ultraviolet rays to the skin. In fact, farmers usually wear straw hats when they work. This kind of hat can prevent pesticides from falling on the face and neck. This protective measure can be considered in future experiments.

#### 3.2.2. Inhalation Exposure during Application

Inhalation exposure occurred when airborne pesticide vapors or droplets appeared in working areas owing to the application of pesticides.

In this application scenario, the inhalation unit exposure was 0.72 mg·kg−1, which was only 0.13% of the total skin exposure. The data were slightly higher than the orchard pesticide application scenario reported in Korea (0.7 × 10−<sup>3</sup> mg) [25]. This may be because our fruit trees are denser, the workers are close to the fruit trees during the application process, and the whole process of application is under the cloud of pesticides, therefore more pesticides are inhaled.

Stretcher-type electric sprayers are widely used in orchards. Therefore, more experimental data on citrus, grape, pear, and other fruits are needed to ge<sup>t</sup> diverse results, also a larger sample size would be good for representative results.
