Centre for Human Exposure Science, Institute of Occupational medicine, Research Avenue North, Edinburgh EH14 4AP, UK.
School of Physics, National University of Ireland, Univeristy Road, Galway H91TK33, Ireland.
Ann Work Expo Health. 2017 Apr 1;61(3):344-355. doi: 10.1093/annweh/wxw023.
Agricultural workers tend to have high exposures to organic dusts which may induce or exacerbate respiratory disorders. Studies investigating the effect of work tasks and farm characteristics on organic dust exposures among farm workers suggest that handling of animal feed is an important exposure determinant; however, the effect of the animal feeding system has not been explored in any detail.
To measure the exposure of Irish dairy farmers to inhalable dust, endotoxin, and total volatile organic compounds (TVOCs) during parlour work and to explore whether levels of exposure to these agents depend on the applied feeding system in the farms.
Thirty-eight personal exposure measurements were collected from farmers across seven dairy farms. The farms used manual, loft, or semi-automated feeding systems. Information on worker tasks and farm characteristics was collected during the surveys. Associations between exposure concentrations and feeding systems, worker tasks, and other farm characteristics were explored in linear mixed-effect regression models with farmer identity treated as a random effect.
Exposure concentrations were variable and had a geometric mean (GM; geometric standard deviation) of 1.5 mg m-3 (1.8) for inhalable dust and 128 EU m-3 (2.5) for endotoxin. More than 50% of the exposure measurements for endotoxin, and organic dust exceeded recommended health-based occupational exposure limits. Endotoxin levels were somewhat lower in farms using semi-automatic feeding systems when compared to those using manual feeding systems but in multivariate regression analysis associations were not statistically significant (β = -0.54, P = 0.4). Performance of activities related to handling and spreading of hay or straw was the strongest determinant for both inhalable dust and endotoxin exposure (β = 0.78, P ≤ 0.001; β = 0.72, P = 0.02, respectively). The level of dust exposure increased also as a consequence of a lower outdoor temperature, and higher ratio of distributed feed per cow (P = 0.01). Stationary measurements of TVOC and CO2 concentrations inside the dairy parlours had a GM of 180 ppb (1.9) and 589 ppb (1.3), respectively. The use of cow teat disinfectants and building ventilation were both strong predictors of TVOC concentrations within parlours.
Dairy farm workers can be exposed to high and variable levels of inhalable dust and endotoxin and may be at risk of respiratory disease. Results from this study suggest that exposure control strategies for organic dusts and TVOCs exposures should consider building ventilation and work tasks such as spreading of bedding material, using spray disinfectants and animal feeding. Until effective permanent engineering controls are established farm workers should be encouraged to wear respiratory protective equipment during these tasks.
农业工人往往会接触到大量的有机粉尘，这可能会导致或加重他们的呼吸道疾病。研究表明，工作任务和农场特征会影响农场工人接触有机粉尘的情况，其中处理动物饲料是一个重要的暴露决定因素；然而，动物饲养系统的影响还没有被详细研究过。
测量爱尔兰奶牛场工人在牛舍工作期间对可吸入粉尘、内毒素和总挥发性有机化合物（TVOC）的暴露水平，并探讨这些因素的暴露水平是否取决于农场应用的饲养系统。
从七个奶牛场的 38 名农民身上采集了 38 次个人暴露测量值。这些农场使用手动、阁楼或半自动喂养系统。在调查期间收集了有关工人任务和农场特征的信息。使用线性混合效应回归模型，将农民身份视为随机效应，探讨暴露浓度与喂养系统、工人任务和其他农场特征之间的关系。
暴露浓度变化较大，可吸入粉尘的几何平均值（GM；几何标准差）为 1.5 mg m-3（1.8），内毒素为 128 EU m-3（2.5）。超过 50%的内毒素和有机粉尘暴露测量值超过了基于健康的职业接触限值。与使用手动喂养系统的农场相比，使用半自动喂养系统的农场内毒素水平略低，但在多变量回归分析中，关联没有统计学意义（β=-0.54，P=0.4）。与处理和散布干草或稻草有关的活动是可吸入粉尘和内毒素暴露的最强决定因素（β=0.78，P≤0.001；β=0.72，P=0.02）。由于室外温度较低和每头牛分配的饲料比例较高，粉尘暴露水平也会增加（P=0.01）。牛舍内 TVOC 和 CO2 浓度的固定测量值分别为 180 ppb（1.9）和 589 ppb（1.3）。奶牛乳房消毒和建筑通风的使用都是牛舍内 TVOC 浓度的强烈预测因素。
奶牛场工人可能会接触到高浓度且变化较大的可吸入粉尘和内毒素，可能有患呼吸道疾病的风险。本研究结果表明，有机粉尘和 TVOC 暴露的暴露控制策略应考虑建筑通风和工作任务，如散布床上用品、使用喷雾消毒剂和动物喂养。在建立有效的永久性工程控制措施之前，应鼓励农场工人在这些任务中佩戴呼吸防护设备。
