**1. Introduction**

While spraying crops, handlers are inevitably exposed to pesticides. Pesticide-handlers are directly exposed to pesticide clouds, allowing pesticides to readily enter the body through the skin and respiratory tract, which may result in acute poisoning and other chronic health issues [1–3]. Therefore, it is necessary to evaluate occupational exposure to pesticides to reduce the degree of exposure and protect handlers [4,5].

Women and the elderly, the main labor force in rural China, are not well educated and have a low level of security awareness [6]. Exposure to pesticides is one of the most serious occupational risks faced by them. Therefore, it is imperative to carry out exposure assessments for pesticides according to the fundamental realities of China.

In recent years, China has gradually paid attention to the occupational exposure assessment of pesticides. Now our exposure assessment is based on the methods used in developed countries in the West. The methods used by different people converge and there are certain differences. Dermal exposure is a key component of pesticide risk assessment and whole-body dosimetry is more accurate in estimating dermal exposure [7,8]. Yang et al. [9] and Gao et al. [10] used the whole-body sampling method to study the exposure of farmers using the 16-type knapsack manual sprayer to

spray chlorpyrifos in cornfields. Cao et al. [11] and Chen [12] studied the exposure of farmers to imidacloprid, chlorpyrifos, and lambda-cyhalothrin in wheat fields using whole-body dosimetry.

In 2018, orchards covered 11,875 thousand hectares in China, and fruit output reached 226.88 million tons [13]. The fruits covering the largest area were apples, citrus, and pears and the output of these fruits accounted for 37.6% of the total fruit production in the country [13]. Therefore, it is necessary to assess the exposure risk of operators to pesticides during treatment in apple orchards under defined-use scenarios.

In 1981, Franklin et al. [14] used air monitoring and patch techniques to estimate exposure, proposing an exposure measurement method for orchard application scenarios. Moon and Kim studied the pesticide exposure assessment of the application of fenvalerate and methomyl in apple orchards in Korea [15]. Thouvenin selected insecticide foliar application to a vineyard as the exposure scenario [16]. However, relevant reports on the occupational exposure to pesticides in orchards have not been studied in China.

In developed countries in Europe or North America, the application of pesticide chemicals is very specialized, serialized, and standardized. Depending on the application, each scene has a dedicated application machine [17]. China's pesticide application equipment models are aging, and the market share of manual sprayers reaches 80% [18]. Stretcher-type sprayers are mainly used for fruit-tree applications. This type of sprayer originated in the 1950s and 1960s and was developed to prevent serious injury from rice borers. The structure of the stretcher-type power sprayer consists of five parts—the frame, the power machine, the liquid pump, the water absorption part, and the spray part [19]. The diameter of the droplet is about 400–600 microns [20]. It has a long range and a wide spray coverage and is easy to use, but the pesticide utilization rate is only about 15% [20].

The pesticide SYP-9625 is a broad-spectrum acrylonitrile acaricide that is quick-acting and long-lasting [21]. As a newly-developed acaricide, no studies have been published on exposure risk assessment. The purpose of this work was to study the exposure data of occupational handlers using stretcher-type power sprayers for fruit tree application scenarios.

#### **2. Materials and Methods**

#### *2.1. Reagents and Materials*

Analytical standard SYP-9625 (CAS No., 1253429-01-4) (98% purity) was purchased from Shenyang Sinochem Agrochemicals R&D Co., Ltd. (Shenyang, China). The Structure of SYP-9625 is in Figure S1. The commercial SYP-9625 formulation used in the field trial was 30% suspension concentrate. Acetone and acetonitrile used for the extraction were of analytical grade; the acetonitrile used for the preparation of standard solutions was of high-performance liquid chromatography grade (Sigma-Aldrich, Steinheim, Germany). Lidded glass jars of 500 mL, 1000 mL, and 2500 mL sizes were used to extract samples. Cotton clothing was obtained from the Evolu Flagship Store (Hangzhou, China).

## *2.2. Field Trial*

Operators were local farmers; they were also volunteers. They were experienced in the application of pesticides and in good health. They had agreed to the experimental procedures and co-operated in this study. Each operator was provided with a full explanation of the study and its requirement, and any potential risks. They could withdraw from the study at any time, and for any reason. A signed, informed consent form was obtained from each operator prior to his/her participation in the study.

The exposure study was conducted in Changping district, Beijing, China. At noon in summer, the temperature is too high to spray pesticide, and it can also cause phytotoxicity to plants. Farmers generally use pesticides in the morning or evening. So our experiments were conducted from 6:30 to 10:00 on 7 June 2017. The temperature was 17.5 to 37 ◦C, sunny with a relative humidity of 27–87%, and no wind. The experiment included four male handlers (1a, 1b, 2a, 2b, 3a, 3b, 4) with a total of seven exposures. The handlers were approximately 50 years old, with height and weight of 165–175 cm and 60–70 kg, respectively. The apple trees were in the fruiting stage, and their average height was 3 m. The rows were separated by 2.5–3.8 m, with 1.5–2.5 m between trees in the same row.

For pesticide application, the spray solution was prepared by mixing 300 L of water with 100 mL 30% suspension concentrate. Each handler followed their normal pace to spray pesticide across one acre. The application was carried out simultaneously by four stretcher-type electric sprayers. The machinery was provided by the farmers who planted the fruit trees and had been in use for 1 to 4 years. New, old, or different sprayers may have caused different exposures. The sprayer in Figure 1 is a relatively-new stretcher-type electric sprayer. Four farmers had more than ten years of experience in spraying pesticides. They randomly-selected instruments and used them to complete seven application experiments. In the process of application, the handlers sprayed according to their usual spraying habit in order to obtain real exposure. Their spray habits had been formed through long-term work. These farmers' spraying techniques were considered representative of typical spraying behaviors.

**Figure 1.** Stretcher-type power sprayer.

#### *2.3. Potential Dermal and Inhalation Exposure Monitoring*

#### 2.3.1. Potential Dermal Exposure Monitoring

Dermal exposure was determined using a whole-body dosimetry method, including the two sets of clothing, inside and outside hat, masks, and inside and outside gloves. The basic requirements were as follows: (1) inner clothing—using a cotton content greater than 70%, white, thin, long-sleeved shirt and trousers, round neck, cuffs, neckline tightened; (2) outer clothing—generally with cotton content greater than 70%, white, thick, long-sleeved shirt and trousers, round neck, cuffs, neckline tightened; (3) inside hat—with eight layers of white gauze (20 × 40 cm); (4) outside hat—single-layer, cotton white hat with brim; (5) masks—medical gauze masks; (6) inner gloves—white thin glove with a cotton content greater than 70%; and (7) outer gloves—white thick-lined gloves with cotton content greater than 70%. For accurate quantitative calculations, the handlers wore two layers of clothing during application, and the inner layer of clothing was used to simulate the skin.

#### 2.3.2. Potential Inhalation Exposure Monitoring

Inhalation exposure was measured using a personal air monitor equipped with a portable battery-operated sampling pump and a solid sorbent tube (ORBO 609 Amberlite® XAD-2 400/200 mg). XAD-2 resin was used for capturing the pesticides in the air (each handler's breathing zone). Personal air sampling pumps with XAD-2 filter tubes were used to monitor inhalation exposure. Inhalation UE was calculated with the formula:

UE(mg·kg−1of a.i.handled) = exposure dose(mg)<sup>×</sup>application time(min)×air change rate(<sup>L</sup> min−<sup>1</sup>) flow rate(<sup>L</sup> min−<sup>1</sup> )<sup>×</sup>sampling time(min)×kg of a.i. handled

An air change rate of 29 L·min−<sup>1</sup> and an air sampler's pumping rate of 2 L·min−<sup>1</sup> was assumed [22]. The application and sampling time was assumed to be equal because the orchard size was small and there was no need for rest periods during applications.

## *2.4. Handler Sampling*

After the end of the application, the air sampling pump was turned o ff and the XAD-2 tubes were collected for cryopreservation and transportation. Sampling time was defined as the time from the start to the end of spraying. The protective clothing was divided into six parts as depicted in Figure 2, labeled, and transported in the dark to be stored under freezing conditions.

**Figure 2.** Garment sectioning for whole-body analysis.

Some body parts were cleaned and the resultant wash was collected, as follows: the assistant wore clean disposable gloves and thoroughly wiped the worker's face/neck with moist medical gauze. Approximately 4 mL of 0.01% Aerosol OT(Sodium dioctyl sulfosuccinate) was evenly distributed over the gauze. The steps above were repeated. Each gauze was then collected and labeled. The handlers immersed both hands in 400 mL of 0.01% Aerosol OT solution and scrubbed carefully for at least 30 s. The hands were then rinsed with about 100 mL of solution, which was consistent with the above. This 500 mL sample was collected and labeled [23].

To evaluate the stability of SYP-9625 during storage and transportation, an on-site addition recovery test was carried out in the area near the application site. A certain concentration of pesticide standard solution was prepared, the pesticide solution was spread evenly on a complete part of the clothes (such as thighs), and the volume recorded. Then the clothes were put in a sealed bag and transported under the same conditions as the experimental samples. Each material had a di fferent amount of additive, and two repetitions were taken: (1) underwear (size: 30 cm × 30 cm) 10× and 100× LOQ (limit of quantitation); (2) outer coat (size: 30 cm × 30 cm) 100× and 1000× LOQ; (3) handwashing solution (solution volume: 50 mL) 10× and 100× LOQ; (4) facial and neck wipes 20× and 200× LOQ; (5) inner gloves 10× and 100× LOQ; (6) outer gloves 100× and 1000× LOQ; and (7) air filter samples 10× and 100× LOQ.

The LOQ of each component and matrix reflected the minimum amount of data that could be quantified.

The samples from the on-site additional recovery test had the same environmental conditions as the samples from the application and used the same transport and storage conditions.
