a Occupational and Environmental Medicine, Department of Public Health and Clinical Medicine , Umeå University , Umeå, Sweden.
b Department of Applied Physics and Electronics , Umeå University , Umeå, Sweden.
J Occup Environ Hyg. 2018 Nov;15(11):767-772. doi: 10.1080/15459624.2018.1508875.
The University of North Carolina passive aerosol sampler (UNC sampler) could be an alternative when measuring occupational dust exposure, but the time required for microscopic imaging of the sampler needs to be reduced to make it more attractive. The aims of this study were to (1) characterize the effect on precision when reducing imaging, in order to shorten analysis time and (2) assess if the position of the images makes a difference. Eighty-eight samplers were deployed in different locations of an open pit mine. Sixty images were captured for each UNC sampler, covering 51% of its collection surface, using scanning electron microscopy. Bootstrapped samples were generated with different image combinations, to assess the within-sampler coefficient of variation (CV) for different numbers of images. In addition, the particle concentration relative to the distance from the center of the sampler was studied. Reducing the number of images collected from the UNC sampler led to up to 8.3% CV for 10 images when calculating respirable fraction. As the overall CV has previously been assessed to 36%, the additional contribution becomes minimal, increasing the overall CV to 37%. The mean concentrations of the images were modestly related to distance from the center of the sampler. The CV changed from 8.26% to 8.13% for 10 images when applying rules for the image collection based on distance. Thus, the benefit of these rules on the precision is small and the images can therefore be chosen at random. In conclusion, reducing the number of images analyzed from 60 to 10, corresponding to a reduction of the imaged sampling area from 51% to 8.5%, results in a negligible loss in precision for respirable fraction dust measurements in occupational environments.
北卡罗来纳大学被动气溶胶采样器（UNC 采样器）在测量职业性粉尘暴露时可能是一种替代方法，但需要缩短对采样器进行微观成像的时间，使其更具吸引力。本研究的目的是：(1) 描述减少成像对精度的影响，以缩短分析时间；(2) 评估图像的位置是否有差异。将 88 个采样器部署在露天矿的不同位置。使用扫描电子显微镜对每个 UNC 采样器拍摄 60 张图像，覆盖其收集表面的 51%。使用bootstrap 生成不同的图像组合，评估不同数量的图像的采样器内变异系数（CV）。此外，还研究了颗粒浓度与采样器中心距离的关系。从 UNC 采样器采集的图像数量减少，导致计算呼吸性粉尘时 10 张图像的 CV 高达 8.3%。由于之前已经评估了总 CV 为 36%，因此额外的贡献变得微不足道，将总 CV 增加到 37%。图像的平均浓度与采样器中心距离有一定的关系。基于距离的图像采集规则应用于 10 张图像时，CV 从 8.26%变为 8.13%。因此，这些规则对精度的影响很小，因此可以随机选择图像。总之，将分析的图像数量从 60 张减少到 10 张，相当于将成像采样面积从 51%减少到 8.5%，对职业环境中呼吸性粉尘测量的呼吸性粉尘部分的精度几乎没有损失。
