Visual Determination of Potential Dermal and Inhalation Exposure

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Research Article pubs.acs.org/journal/ascecg

Visual Determination of Potential Dermal and Inhalation Exposure Using Allura Red As an Environmentally Friendly Pesticide Surrogate Lidong Cao, Chong Cao, Ying Wang, Xiuhuan Li, Zhaolu Zhou, Fengmin Li, Xiaojing Yan, and Qiliang Huang* Laboratory of Quality and Safety Risk Assessment for Agro-Products on Biohazards, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 Yuanmingyuan West Road, Haidian District, Beijing 100193, P. R. China S Supporting Information *

ABSTRACT: Quantifying dermal and inhalation exposure to pesticides is a critical component of the decision-making procedure for risk evaluation. For traditional determination of pesticide exposure, a large amount of organic solvent is inevitably used to extract pesticides from the sampling medium. This paper presents an environmentally benign method for determining potential dermal and inhalation exposure using water-soluble Allura Red as a pesticide surrogate. Only water is used to extract the Allura Red from the sampling medium. More importantly, the operator can attain an immediate visual impression of the exposure patterns. This visual contaminant dispersion can be helpful for the development of measures to improve operational safety through pesticide management. For validation of the method, comparative exposure analyses were carried out with representative lipophilic and hydrophilic pesticides (chlorpyrifos and nitenpyram) under similar application conditions. The results indicate that Allura Red had similar exposure distributions to those of the pesticides. The total exposure measured using Allura Red is higher but of roughly the same order of magnitude as the values obtained with the pesticides. Combined with the calculated margin of exposure, this environmentally friendly method could provide a very useful reference for exposure risk assessment in various pesticide use scenarios. KEYWORDS: Pesticide exposure, Allura Red, Surrogate, Water extraction, Visualization of exposure patterns, Whole-body dosimetry

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INTRODUCTION

Risk assessment of pesticides is the cornerstone of pesticide management and includes four steps: hazard identification, dose−response assessment, exposure assessment, and risk characterization.1 Exposure determination is an important step in the decision-making procedure for risk assessment. Therefore, reliable exposure assessment methodologies are crucial. Exposure routes mainly consist of respiratory and dermal exposure. Respiratory exposure assessments greatly emphasize accurate measurements of pesticide concentrations in a worker’s breathing zone. The dermal route is usually the main exposure pathway during manipulation of the pesticide, and it is thought to contribute the greatest proportion of systemic exposure.4 In the absence of actual data on respiratory and dermal absorption, most research in this field has focused on characterizing potential inhalation and dermal exposure (PIE and PDE) using passive dosimetry, which measures the amount of pesticide that comes into contact with the skin, clothing, and breathing zone of the worker. The most frequently reported PDE sampling methods are surrogate

Pesticides play important roles in sustainable agriculture and good public health. However, there is a general misunderstanding of the differences between the toxicity of a pesticide and the actual risk, which has heightened public anxiety over their use.1 The hazard presented by a pesticide depends on its inherent toxicity and the level of human exposure under defined conditions. Therefore, the importance of reliable risk assessment of human exposure to pesticides has been growing worldwide.2 Operator exposure during pesticide manipulation is a major concern in agricultural practice. Developed countries such as those in the European Union and North America have been at the forefront of assessing exposure for pesticide handlers. These countries do not allow pesticides to be registered unless there are adequate data or model predictions to show that the operator exposure levels would be below an acceptable level in normal use.3 In many developing countries, however, no occupational exposure data are required to obtain a commercial license for a pesticide. Nevertheless, exposure risk evaluation has been attracting considerable attention, and relevant research is being done in many such countries. © 2017 American Chemical Society

Received: December 14, 2016 Revised: March 5, 2017 Published: March 20, 2017 3882

DOI: 10.1021/acssuschemeng.6b03050 ACS Sustainable Chem. Eng. 2017, 5, 3882−3889

Research Article

ACS Sustainable Chemistry & Engineering skin techniques, which include patch methods5−10 and wholebody dosimetry.3,4,11−20 Recently, we reported the PDE and PIE of farmers in China to the insecticides imidacloprid and lambda-cyhalothrin using whole-body dosimetry.21,22 There are many surrogates for pesticide exposure assessment. In whole-body dosimetry, pesticide handlers are dressed in garments such as cotton or polyester coveralls that cover the entire body and are used as a sampling medium. The wholebody garments stand in for the skin in this case. For inhalation exposure to be determined, breathing is commonly simulated using a portable air-sampling pump and sampling media such as membrane filters, sorbent tubes, polyurethane foam, and charcoal. For any sampling method, pesticide extraction procedures are necessary. These procedures use many different organic solvents to extract pesticide from the sampling medium, such as methanol,10 hexane,4,15,17 acetone,3,12,18,20 and toluene.9 The large-scale use and waste disposal of organic solvent not only impacts the environment but also adversely affects laboratory personnel. These issues could be addressed if one suitable chemical compound could be used as a pesticide surrogate for exposure assessment. Because most commercial pesticides are organic compounds, the ideal surrogate would also be an organic compound that is water-soluble, safe, moderately economical, easy to measure, and preferably colorful for visual inspection of the exposure patterns. Fluorescent tracers (mostly fluorescent whitening agents) have been used to assess dermal exposure.23 However, this approach requires special video-imaging equipment, and the skin of the operator is subjected to long-wavelength ultraviolet illumination in the dark. Uranine,16 dye tracer Sunset Yellow,24 and Brilliant Blue3 have also been used as pesticide surrogates for dermal exposure assessment. However, no comparison study has examined pesticides and a surrogate in similar scenarios to show whether the surrogate is suitable for exposure assessment. In the present work, we investigated Allura Red ((2-hydroxy1-(2-methoxy, 5-methyl, 4-sulphonatophenylazo)-naphthalene6-sulfonate)disodium salt) to determine its applicability as a pesticide surrogate. Allura Red is one of the most widely used synthetic water-soluble diazo colorants, and it shows very low acute toxicity in different species of animals according to the Joint FAO/WHO Expert Committee on Food Additives as well as the European Union’s Scientific Committee for Food.25 We conducted a comparative exposure analysis between Allura Red and representative lipophilic and hydrophilic pesticides chlorpyrifos and nitenpyram using the whole-body dosimetry method in a greenhouse. Only water was used for both the preparation of the spray mixture of dye and its extraction from the sampling medium. More interestingly, the operator can attain an immediate visual impression of the exposure patterns, which would be very useful for inferring the cause of contamination and suggesting protection measures (Figure 1).

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Figure 1. Schematic diagram of potential pesticide exposure assessment using Allura Red as a pesticide surrogate. used for extraction. Cotton gloves (100% cotton, 200 g/m2) were purchased from Beijing Kuailu Knitting Co., Ltd. (Beijing, China). An OVS tube with XAD-2 sorbent, and a tube holder was obtained from SKC Inc. (Eighty Four, PA, USA). Instrumentation. All liquid chromatographic analyses for Allura Red and nitenpyram were performed on an Agilent 1200 Series HPLC (Agilent Technologies, Santa Clara, CA, USA) with an autosampler, ultraviolet detector, and Eclipse Plus C18 reversed-phase column (5 μm × 4.6 mm × 150 mm). Gas chromatographic analysis for chlorpyrifos was performed on an Agilent 7890A with an autosampler, flame photometric detector (FPD), DB-17 column (1 μm × 530 μm × 30 m), and a split/splitless injector operated in splitless mode. The personal air sampler was an AirChek 2000 from SKC Inc. (Eighty Four, PA, USA). A knapsack electric sprayer was purchased from Chaoda Instrument Co., Ltd. (CD-16B, Taizhou, China). A weather meter was purchased from AZ Instrument Corp. (Taichung, Taiwan). Standard laboratory glassware and equipment such as rotary evaporator and overhead shaker were used in the extraction procedure. Chromatographic Conditions. The optimized HPLC operating conditions for Allura Red determination were a methanol−water mobile phase containing 0.5% ammonium acetate (V/V, 35:65), flow rate of 1.0 mL/min, injection volume of 5 μL, and detection wavelength of 245 nm. For nitenpyram detection, the optimized conditions were the same as those for Allura Red except for the mobile phase (V/V, 30:70) and detection wavelength (270 nm). The optimized GC-FPD operating conditions for chlorpyrifos determination were an injector temperature of 220 °C, detector temperature of 250 °C, initial oven temperature of 150 °C for 1 min followed by heating at 20 °C min−1 to 250 °C and holding for 3 min, and injection volume of 1 μL. The detector gases were hydrogen at 70 mL min−1, makeup air at 100 mL min−1, and nitrogen carrier gas at 50 mL min−1. Field Trial. Field trials were conducted in a greenhouse located in Langfang City of Hebei Province, China. The climatic conditions were recorded using a weather meter, which indicated temperatures of 26− 29 °C, relative humidity of 60−68%, and wind velocities of 0−0.1 km/ h. The crop selected for the exposure studies was maize at two growth stages with approximate heights of 50−60 and 110−120 cm. For the applicability of Allura Red as a pesticide surrogate to be demonstrated, two sets of experiments were designed. In the first, Allura Red was sprayed like a pesticide, and its exposure was determined. In the second set, actual pesticide was sprayed, and the pesticide exposure was determined. For consistency to be maintained, all the field trials were conducted by the same operator with an established spraying technique. The dye exposures were compared with those of the lipophilic and hydrophilic pesticides to assess the surrogate performance. Each spraying application was performed in triplicate. When the Allura Red was applied for the field experiment, OP-10 surfactant was added to retain the physical properties of the formulation, which was necessary because pure dye solutions in water could not easily be applied to hairy or waxy leaf surfaces. The spray liquid was prepared by dispersing 23.5 g of 80% Allura Red and 10 g of surfactant in 10 L of water in a hydraulic knapsack electric sprayer with a single cone nozzle that operates at a typical pressure of 300 kPa. The operator started spraying according to his normal

EXPERIMENTAL SECTION

Materials. Allura Red (80% purity) was purchased from Beijing Oriental Care Trading Ltd. Analytical standards of chlorpyifos and nitenpyram (98% purity) were provided by the National Pesticide Quality Supervision and Testing Center (Beijing) and used for calibration. Typical formulations of 40% chlorpyifos emulsifiable concentrate (EC) (lab-made) and 20% nitenpyram aqueous solution (Lianyungang Liben Agro-chemical Co., Ltd.) were used for field trials. Chromatographic-purity acetone was obtained from Fisher Scientific (Pittsburgh, USA), and analytical-grade acetone purchased from Sinopharm Chemical Reagent Beijing Co., Ltd. (Beijing, China) was 3883

DOI: 10.1021/acssuschemeng.6b03050 ACS Sustainable Chem. Eng. 2017, 5, 3882−3889

Research Article

ACS Sustainable Chemistry & Engineering

Figure 2. Front and back sectioning of the coveralls in nine pieces. Upper body: parts 1−5; lower body: parts 6−9. working practice. With the lance in his right-hand and in front of him, the operator sprayed one side of a row. The treatment was finished within 10 min, which was short enough to avoid overexposure or runoff of the spray mixture from the garment. For pesticide application, 40 g of 25% chlorpyrifos EC with 10 g of OP-10 was used for chlorpyrifos exposure determination, and 50 g of 20% nitenpyram aqueous solution with 10 g of OP-10 was used for nitenpyram exposure analysis. Monitoring of Potential Dermal and Inhalation Exposure. For the determination of the PDE, the protocol applied in the present study is based on the whole-body dosimetry method. Because there were no commercially available coveralls for our purpose, we designed custom-made cotton coveralls with a hood and commissioned their production at a specialized company.21 A series of different cotton materials were tested in the laboratory for their water retention performance and the recovery rate of Allura Red and pesticide. Before the spraying application, the operator was dressed with the custommade cotton coveralls and cotton gloves. After the spraying, the coveralls and gloves were taken off carefully with the help of an assistant who wore new disposable nitrile gloves to avoid cross contamination. The coveralls were then sectioned using clean scissors into nine pieces that correspond to different body parts (Figure 2). The coverall sections, gloves, and inhalation sampling tubes were packed individually in polythene bags, which were accurately labeled and stored in a freezer until extraction. For PIE to be determined, a portable battery-operated personal air sampling pump was used with an OVS sampling tube containing XAD2 sorbent (catalogue no. 226-30-16). The tube was placed in the operator’s breathing zone and connected to the pump, which was calibrated before use at a flow rate of 2 L/min. After the application, the tubes were closed with two plastic caps at either end and transported to the laboratory for extraction and analysis. Chemical Analysis. The coverall sections and gloves were extracted in closed 2 L plastic bottles using 1000 mL of water for pieces 1−3 and 6−9, 1200 mL for 4 and 5, and 200 mL for each glove. The air sampling medium was extracted with 20 mL of water in a single-necked flask. The extraction was conducted in an overhead shaker for 60 min at 200 rpm. A 1 mL fraction of each extract was filtered through a 0.22 μm pore syringe filter directly into an HPLC vial for analysis. For chlorpyrifos extraction, the coverall sections and gloves were extracted with acetone in 1 L Erlenmeyer flask, 500 mL for pieces 1−3 and 6−9, 700 mL for 4 and 5, and 150 mL for each glove. The air sampling medium was extracted similarly with 20 mL of acetone. The flasks were shaken for 60 min at 200 rpm. Each extract was evaporated to dryness and redissolved in 10 mL of acetone to prepare it for GC analysis. Validation of the Analytical Method for Allura Red. The method used for the quantitative determination of Allura Red was validated. Quality parameters such as selectivity, limit of detection

(LOD), limit of quantification (LOQ), linearity, precision, and accuracy were fully studied. For the selectivity to be tested, blank samples of cotton coverall, glove, and air sampling sorbent were extracted in water. Each extract and aqueous solution of OP-10 surfactant were subjected to HPLC analysis. There were no detectable peaks at the retention time of Allura Red, which indicates that the Allura Red chromatographic peak in each sampling medium was not attributable to more than one component. Seven calibration working solutions were prepared by dilution of a stock solution with water. The response was linear for Allura Red at concentration levels in the range of 0.01−25 mg L−1 (R2 = 0.9995). LOD and LOQ were determined as the minimum injected Allura Red concentrations that yielded signal-to-noise (S/N) ratios of 3 and 10, respectively. The LOD and LOQ for Allura Red were 0.002 and 0.005 mg L−1, respectively. For the recovery and precision of Allura Red from the different materials to be studied, clean cotton coveralls, gloves, and air sampling sorbent were spiked with known amounts of Allura Red at three concentration levels of 1, 2, and 4 mg L−1. The extraction and quantification methods used were those described for the field experiments. At the lowest concentration level, the percentages of recovery and precision (expressed as RSD% and supplied in parentheses) were 92.3% (8.2), 100.7% (6.2), and 101.7% (5.5) for the coveralls, gloves, and air sampling sorbent, respectively. For the middle concentration level, the values were 88.2% (5.7), 103.9% (5.2), and 102.4% (3.2), and those for the highest concentration level were 87.8% (3.8), 99.7% (3.3), and 101.7% (2.1), respectively. Validation of the analytical methods for chlorpyrifos and nitenpyram are presented in the Supporting Information. Calculation of Potential Dermal and Inhalation Exposure. The amounts deposited on each coverall part, glove, and air sampling tube were calculated using the concentration of Allura Red and pesticide in each extract and the final solution volume after preparation for HPLC(GC) analysis. The calibration curves of Allura Red, chlorpyrifos, and nitenpyram were used for quantitative determination of the contamination levels in the sampling medium. Exposure levels are presented as the unit exposure (UE) according to USEPA,26 which is defined as the mass of active ingredient (ai) exposure per unit mass of active ingredient handled (mg kg−1 of ai).

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RESULTS AND DISCUSSION Potential Dermal and Inhalation Exposure of Allura Red and Chlorpyrifos. For the PDE and PIE of Allura Red and the representative lipophilic pesticide chlorpyrifos (1.4 mg/ L soluble in water) to be compared, all the spraying applications were carried out by the same operator in similar scenarios. The coveralls were cut into nine pieces, along with the gloves and air sampling medium to obtain the distribution 3884

DOI: 10.1021/acssuschemeng.6b03050 ACS Sustainable Chem. Eng. 2017, 5, 3882−3889

Research Article

ACS Sustainable Chemistry & Engineering

Table 1. Potential Dermal and Inhalation Exposure for Applications (n = 3) of Allura Red and Chlorpyrifos on Maize (110−120 cm) under Similar Conditions operator exposure (mg/kg) Allura Red

chlorpyrifos

body region

mean

SD

proportion

mean

SD

proportion

head chest back left arm right arm left glove right glove left thigh right thigh left leg right leg upper body lower body gloves inhalation total exposure

3.74 71.47 9.37 186.66 282.75 89.94 164.95 722.88 745.91 528.69 378.06 553.99 2375.55 254.90 0.07 3184.51

1.35 4.22 5.99 38.09 69.54 14.23 28.85 73.75 128.70 115.96 52.74 108.54 185.72 42.71 0.06 302.19

0.12 2.24 0.29 5.86 8.88 2.82 5.18 22.70 23.42 16.60 11.87 17.40 74.60 8.00 0.02 100

2.67 7.86 15.78 60.19 90.51 38.52 87.00 110.08 219.35 48.64 46.78 177.00 424.85 125.52 1.52 728.89

1.31 10.31 17.41 2.95 1.43 11.25 11.33 21.00 45.27 11.29 14.37 16.61 79.24 2.49 1.65 92.40

0.37 1.08 2.16 8.26 12.42 5.29 11.94 15.10 30.09 6.67 6.42 24.28 58.29 17.22 0.21 100.00

exposure to the right- than the left-hand. The exposures measured on the right-hand for Allura Red and chlorpyrifos application were 5.2 and 11.9% of the total exposure, whereas those for the left-hand were 2.8 and 5.3%, respectively. This phenomenon resulted from the operator holding the spray lance with the right-hand such that any leaks from the lance, trigger handle, or hose could contribute to right-hand exposure. The total hand exposure of chlorpyrifos (17.2%) was higher than that of Allura Red (8.0%), which generally reflects the common occurrence of dominant hand contamination due to accidental splashing or leakage of the spray tank solution. Therefore, regular inspection and maintenance of the equipment and careful spray are necessary to avoid unexpected exposure. The PIE contributed little to the total exposure. The very low contribution could be ascribed to the low spray droplet concentration in the breathing zone of the operator due to the low application pressure and climatic conditions without wind in the greenhouse. These results are in accordance with the opinion of Machado-Neto, who mentioned that ≥99% of the total exposure occurs through the dermal route.27 Although the Allura Red and chlorpyrifos had similar exposure patterns, another important concern is the amount of contaminant deposited on the sampling media, which is essential data for risk assessment. As shown in Table 1, the total PDE and PIE values (n = 3) for Allura Red and chlorpyrifos were 3185 and 729 mg kg−1 of ai, respectively. Allura Red is deposited on the body of the operator approximately four times more than that of chlorpyrifos. The higher exposure level could be attributed to the high water solubility and uniform distribution in the spray mixture. It is well-known that pesticide exposure depends on the application scenario. Thus, we also compared the exposure of Allura Red and chlorpyrifos for 50−60 cm maize. The total PDE and PIE of Allura Red (846 mg kg−1 of ai) are approximately two times higher than those of chlorpyrifos (371 mg kg−1 of ai), and the exposure pattern was also similar (Table 2 and Figure 4). The legs had the highest exposure, corresponding to 84.7 and 78.7% of the total measured exposures of Allura Red and chlorpyrifos, respectively. This can

of the contamination over the whole body. The spray was applied to maize with an approximate height of 110−120 cm. The PDE and PIE levels of Allura Red and chlorpyrifos to the operator are presented in Table 1. The exposure distribution for each part of the body is generally similar between Allura Red and chlorpyrifos application, as indicated by Figure 3. The

Figure 3. Potential dermal and inhalation exposure for applications (n = 3) of Allura Red and chlorpyrifos on maize (110−120 cm) under similar conditions.

lower part of the body (the thighs and lower legs) was the most exposed, representing 74.6 and 58.3% of the total measured exposures during the application of Allura Red and chlorpyrifos, respectively. This could be attributed to the maize height (110−120 cm) and density or the operator’s movements as he walked forward into the spray cloud and made frequent contact with the recently sprayed dense foliage and stalks. On the upper body, the most contaminated area of the operator was the arms, corresponding to approximately 14.7 and 20.7% of the total exposure to Allura Red and chlorpyrifos, respectively. Similar lateral exposure distributions also occurred between Allura Red and chlorpyrifos. There was greater 3885

DOI: 10.1021/acssuschemeng.6b03050 ACS Sustainable Chem. Eng. 2017, 5, 3882−3889

Research Article

ACS Sustainable Chemistry & Engineering

Table 2. Potential Dermal and Inhalation Exposure for Applications (n = 3) of Allura Red and Chlorpyrifos on Maize (50−60 cm) under Similar Conditions operator exposure (mg/kg) Allura Red

chlorpyrifos

body region

mean

SD

proportion

mean

SD

proportion

head chest back left arm right arm left glove right glove left thigh right thigh left leg right leg upper body lower body gloves inhalation total exposure

1.30 6.44 14.20 1.35 2.53 2.92 11.95 30.95 58.00 343.01 373.43 25.82 805.39 14.87 0.07 846.15

0.20 4.73 7.10 0.39 1.62 1.38 5.83 12.39 17.66 79.77 91.12 11.87 187.46 6.89 0.03 195.04

0.15 0.76 1.68 0.16 0.30 0.34 1.41 3.66 6.85 40.54 44.13 3.05 95.18 1.76 0.01 100.00

0.48 0.87 5.52 0.82 2.38 3.28 8.05 23.80 33.50 122.08 169.76 10.09 349.14 11.33 0.06 370.62

0.10 0.87 4.19 0.30 0.53 1.24 4.21 10.31 13.68 35.06 39.49 5.30 95.11 5.41 0.08 104.85

0.13 0.24 1.49 0.22 0.64 0.88 2.17 6.42 9.04 32.94 45.80 2.72 94.20 3.06 0.02 100.00

Potential Dermal and Inhalation Exposure of Allura Red and Nitenpyram. For the possibility of Allura Red to be further verified as a pesticide surrogate for exposure assessment, the representative hydrophilic pesticide nitenpyram (590 g/L soluble in water) was also compared with Allura Red. The PDE and PIE results for 110−120 cm maize are presented in Table 3. Because both Allura Red and nitenpyram have high solubility in water, the exposure distributions for each body part are quite similar, as shown in Figure 5. Because the same crop was used, the amount of spray solution reaching the lower part of the body was still much higher than that deposited on the upper body part, accounting for 77.5 and 80.2% of the total exposure to the Allura Red and nitenpyram, respectively. On the upper body, the arms were the most exposed with 12.8 and 6.8% of the total exposure to Allura Red and nitenpyram. The lateralization of hand exposure occurred in this case as well with the right-hand more exposed than the lefthand. However, the back exposure of nitenpyram was higher than that of Allura Red, which could be due to spray tank leakage as a consequence of incorrect assembly or inspection of the equipment before use. The total PDE and PIE values (n = 3) for Allura Red and nitenpyram were 3006 and 2310 mg kg−1 of ai. Thus, Allura Red exposure is similar to that of nitenpyram. Exposure Risk Assessment Using Allura Red as Pesticide Surrogate. Although there were a limited number of repetitions, it is obvious that the Allura Red exposure patterns were similar to those of the actual pesticides. Moreover, the experimental results indicate that the total PDE of Allura Red is higher but of roughly the same order of magnitude as the values measured with pesticides. The exposure level of Allura Red was approximately 2−4 times higher than that of lipophilic chlorpyrifos. For representative hydrophilic pesticide, the Allura Red exposure is basically the same as that of nitenpyram. These results demonstrate that Allura Red can serve as a pesticide surrogate for exposure determination and does not underestimate the health risk. Thus, the dermal and inhalation exposure (DE and IE, expressed as mg/day) of each pesticide were calculated based on the measured PDE and PIE of the surrogate and the real

Figure 4. Potential dermal and inhalation exposure for applications (n = 3) of Allura Red and chlorpyrifos on maize (50−60 cm) under similar conditions.

be attributed to the crop height (50−60 cm) and the position of the sprayer nozzle, which was closer to the lower part of the operator in this scenario. Although the application scenario changed between different maize heights, the Allura Red had a similar exposure pattern to that of chlorpyrifos. During our previous studies of wheat (70−80 cm high) field application of the insecticide imidacloprid, the lower part of the body was also the most exposed, representing 80% of the total measured exposure.21 Analogous exposure scenarios mainly including crop height and spray equipment contributing to the similar exposure pattern. A very interesting study regarding potential dermal and inhalation exposure to chlorpyrifos for building termite control in Australia was reported by Cattani.28 Three application procedures including preconstruction, postconstruction, and under-floor were systematically conducted. The potential dermal exposure distribution and level were different from those of chlorpyrifos in the present study, which clearly demonstrates that the pesticide exposure is scenario-dependent. 3886

DOI: 10.1021/acssuschemeng.6b03050 ACS Sustainable Chem. Eng. 2017, 5, 3882−3889

Research Article

ACS Sustainable Chemistry & Engineering

Table 3. Potential Dermal and Inhalation Exposure for Applications (n = 3) of Allura Red and Nitenpyram on Maize (110−120 cm) under Similar Conditions operator exposure (mg/kg) Allura Red

nitenpyram

body region

mean

SD

proportion

mean

SD

proportion

head chest back left arm right arm left glove right glove left thigh right thigh left leg right leg upper body lower body gloves inhalation total exposure

5.58 98.91 24.29 141.49 243.77 69.85 92.93 644.81 715.30 548.21 421.06 514.04 2329.37 162.78 0.02 3006.21

2.32 20.14 14.72 41.17 82.05 10.65 21.70 122.39 79.61 59.84 42.37 112.46 154.02 32.33 0.03 297.43

0.19 3.32 0.81 4.74 8.17 2.34 3.12 21.62 23.98 18.38 14.12 17.10 77.49 5.41 0.00 100.00

9.53 73.13 117.96 64.77 94.15 40.86 57.21 565.78 653.91 325.65 307.13 359.53 1852.46 98.07 0.01 2310.07

4.98 17.41 25.22 20.12 25.64 11.71 16.04 71.62 158.18 58.95 91.41 91.49 325.01 6.40 0.01 307.95

0.41 5.11 3.17 2.80 4.08 1.77 2.48 24.49 28.31 14.10 13.30 15.56 80.19 4.25 0.00 100.00

MOE inhalation = NOAELpesticide/(IEpesticide × IAFpesticide /BW) (4)

MOE total = 1/(1/MOEdermal + 1/MOE inhalation)

(5)

where NOAELpesticide is the level of a specific pesticide (mg/kg/ day) at which no adverse effects are observed and is used as an appropriate toxicological end-point, which is generally available for a defined commercial pesticide, DAFpesticide and IAFpesticide are the dermal and inhalation absorption factors for a specific pesticide, and BW is the average human body weight (generally 70 kg was adopted). Taking into account 10 times intraspecies variability and 10 times interspecies variability, the total target MOE is 100 for occupational handlers. Scenarios with MOEs greater than 100 are considered to be safe.

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CONCLUSIONS Allura Red was selected as a pesticide surrogate for exposure assessment based on its distinctive properties, such as solubility in spray mixtures, low detection limit, quick quantification, stability, moderate cost, low toxicity, and a bright color that differentiates it from coveralls or naturally occurring substances. A whole-body dosimetry method has been proposed to determine the PDE and PIE to Allura Red using custommade cotton coveralls, an air sampling medium, and cotton gloves. An HPLC analytical method was developed and validated, including performance parameters such as the LOD and LOQ, linear range, recovery, and precision. When Allura Red was applied to simulate a pesticide, immediate visualization of the contaminant dispersion over the body was achieved, which is very useful as an educational tool for training purposes. This visual exposure determination has value in enhancing learning, stimulating discussion, and promoting safe practices. Being able to visually see the contamination can help the workers protect themselves from pesticide exposure. On the other hand, only water was used for the extraction procedure from the sampling medium, which greatly reduces the adverse effects to the environment and laboratory personnel resulting from large-scale use of organic solvent.

Figure 5. Potential dermal and inhalation exposure for applications (n = 3) of Allura Red and nitenpyram on maize (110−120 cm) under similar conditions.

amount of pesticides commonly applied during 1 day of application DEpesticide = PDEAllura Red × pesticideapplied

(1)

IEpesticide = PIEAllura Red × pesticideapplied

(2)

where PDEAllura Red and PIEAllura Red are the values (mg/kg of ai) measured for Allura Red using the proposed method, and pesticideapplied is the amount in kg of pesticide applied during 1 day of application. It is generally known that the exposure data itself cannot be used as a risk indicator because it must be related to the acceptable exposure limits. Therefore, the margin of exposure (MOE) has been proposed as a simple and useful risk indicator that relates the acceptable exposure to the quantity absorbed by the body29 MOEdermal = NOAELpesticide/(DEpesticide × DAFpesticide /BW) (3) 3887

DOI: 10.1021/acssuschemeng.6b03050 ACS Sustainable Chem. Eng. 2017, 5, 3882−3889

Research Article

ACS Sustainable Chemistry & Engineering

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Lipophilic chlorpyrifos and hydrophilic nitenpyram were compared to Allura Red under similar application conditions, and the results showed that Allura Red had similar exposure distributions to those of the pesticides. The total exposure measured using Allura Red was greater but of roughly the same order of magnitude as those of the pesticides, which demonstrates that Allura Red can be applied as a pesticide surrogate for exposure assessment. Assessment of operator exposure to a pesticide is a very complicated task that fluctuates greatly depending on the application scenarios, such as the application equipment, application rate and duration, the type of job performed by the operator, the type of pesticide formulations, the personal protective equipment, the climatic conditions, and the training and aptitude of the operator. Cumulative dermal exposures are also sometimes needed to determine when several pesticides are applied at the same time. When focusing on a specific pesticide, special extraction and analytical methods should be developed based on the particular physicochemical properties, which is tedious and cost-prohibitive. Combined with the calculated MOE values, this environmentally friendly and visual determination method of using Allura Red as a pesticide surrogate could provide a very useful reference for exposure risk assessment in various pesticide application scenarios.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.6b03050. Detailed validation of the analytical methods for chlorpyrifos and nitenpyram (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]; tel./fax: +86-10-6281-6909. ORCID

Lidong Cao: 0000-0001-7217-7102 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Key Research and Development Plan of China (2016YFD0200703) and State Key Development Program for Basic Research of China (No. 2014CB932204).

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REFERENCES

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DOI: 10.1021/acssuschemeng.6b03050 ACS Sustainable Chem. Eng. 2017, 5, 3882−3889

Research Article

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DOI: 10.1021/acssuschemeng.6b03050 ACS Sustainable Chem. Eng. 2017, 5, 3882−3889