Department of Environmental and Occupational Health Sciences, University of Washington School of Public Health, Seattle, WA, USA.
College of Agricultural, Human, and Natural Resource Sciences, Area Extension Education, Washington State University, Prosser, WA, USA.
Ann Work Expo Health. 2018 Nov 12;62(9):1134-1146. doi: 10.1093/annweh/wxy082.
Pesticide spray drift represents an important cause of crop damage and farmworker illness, especially among orchard workers. We drew upon exposure characteristics from known human illness cases to design a series of six spray trials that measured drift from a conventional axial fan airblast sprayer operating in a modern orchard work environment. Polyester line drift samples (n = 270; 45 per trial) were suspended on 15 vertical masts downwind of foliar applications of zinc, molybdenum, and copper micronutrient tracers. Samples were analyzed using inductively coupled plasma mass spectrometry and resulting masses were normalized by sprayer tank mix concentration to create tracer-based drift volume levels. Mixed-effects modeling described these levels in the context of spatial variability and buffers designed to protect workers from drift exposure. Field-based measurements showed evidence of drift up to 52 m downwind, which is approximately 1.7 times greater than the 30 m (100 ft) 'Application Exclusion Zone' defined for airblast sprayers by the United States Environmental Protection Agency Worker Protection Standard. When stratified by near (5 m), mid (26 m), and far (52 m) distances, geometric means and standard deviations for drift levels were 257 (1.8), 52 (2.0), and 20 (2.3) µl, respectively. Fixed effect model coefficients showed that higher wind speed [0.53; 95% confidence interval (CI): 0.35, 0.70] and sampling height (0.16; 95% CI: 0.11, 0.20) were positively associated with drift; increasing downwind distance (-0.05; 95% CI: -0.06, -0.04) was negatively associated with drift. Random effects showed large within-location variability, but relatively few systematic changes for individual locations across spray trials after accounting for wind speed, height, and distance. Our study findings demonstrate that buffers may offer drift exposure protection to orchard workers from airblast spraying. Variables such as orchard architecture, sampling height, and wind speed should be included in the evaluation and mitigation of risks from drift exposure. Data from our study may prove useful for estimating potential exposure and validating orchard-based bystander exposure models.
农药喷雾飘移是作物损害和农场工人患病的一个重要原因，尤其是在果园工人中。我们借鉴了已知人类疾病病例的暴露特征，设计了一系列六项喷雾试验，以测量在现代果园工作环境中使用常规轴流风机空气射流喷雾器作业时的飘移情况。聚酯线飘移样本（n=270；每个试验 45 个）悬挂在叶片喷施锌、钼和铜微量元素示踪剂下风侧的 15 个垂直桅杆上。使用电感耦合等离子体质谱法对样本进行分析，将所得质量除以喷雾器罐混浓度，以创建基于示踪剂的飘移体积水平。混合效应模型根据空间变异性和旨在保护工人免受飘移暴露的缓冲区描述了这些水平。基于现场的测量结果表明，飘移距离可达下风侧 52 米，这大约是美国环境保护署（EPA）《工人保护标准》为空气射流喷雾器定义的 30 米（100 英尺）“应用排除区”的 1.7 倍。按近（5 米）、中（26 米）和远（52 米）距离分层时，飘移水平的几何平均值和标准差分别为 257（1.8）、52（2.0）和 20（2.3）µl。固定效应模型系数表明，更高的风速[0.53；95%置信区间（CI）：0.35，0.70]和采样高度（0.16；95%CI：0.11，0.20）与飘移呈正相关；随着下风距离的增加（-0.05；95%CI：-0.06，-0.04）与飘移呈负相关。随机效应显示，在考虑风速、高度和距离后，每个喷雾试验的个体位置的飘移变化相对较少，但位置内的变异性较大。我们的研究结果表明，缓冲区可能为果园工人提供空气射流喷雾的飘移暴露保护。在评估和减轻飘移暴露风险时，应包括果园结构、采样高度和风速等变量。我们研究的数据可能有助于估计潜在的暴露情况，并验证基于果园的旁观者暴露模型。
