CFD Investigation of Particle Inhalability in Low Windspeeds

描述(由申请人提供)：计算流体动力学(CFD)建模技术可用于检查污染物的传输和估计个人接触。这项工作建议使用CFD来研究低速环境中的颗粒吸入，这是典型的职业环境。这项工作的长期目标是为制定可吸入颗粒物采样器的国际性能标准提供指导，这些采样器在室内使用时几乎没有空气流动。现有的标准是从更大风速的实验中发展出来的，这可能高估了工人在室内环境中吸入的颗粒物的数量。CFD方法允许模拟均匀的颗粒浓度场，使我们能够避免与大颗粒的均匀悬浮相关的实验困难。初步研究已经开发、验证和验证了单个类人形状的计算机表示，以使用标准k-epsilon湍流模型研究迎风方向的粒子吸入。这项研究将：(1)检查吸入效率估计对面部特征尺寸、湍流方程和反弹参数的敏感性，以量化吸入效率估计中的不确定性；(2)调查迎风以外的方向上的颗粒吸入，以了解方位和速度参数对人形颗粒吸入的影响；(3)提出用于制定可吸入颗粒采样器标准的低速吸入效率曲线。这项工作支持了NORA优先研究领域的暴露评估方法。目前令人担忧的是，使用现有的高速IPM标准收集的职业暴露样本收集颗粒物的效率高于工人可以吸入的颗粒物。如果是这样的话，基于大规模暴露的估计将高估个人的真实暴露。一旦将健康影响研究应用于这些暴露估计，风险估计将基于高估的暴露。这将导致风险评估实际上低估了接触工人的风险。这项研究将确定评估工作场所暴露于大颗粒的抽样标准是否需要调整，以改善暴露和风险估计。

DESCRIPTION (provided by applicant): Computational fluid dynamics (CFD) modeling techniques can be used to examine contaminant transport and to estimate personal exposure. This work proposes to use CFD to investigate particle aspiration in low velocity environments, typical of the occupational environment. The long-term objective of this work is to provide guidance to the development of an international performance criterion for inhalable particle samplers when used indoors with little air movement. The existing criterion was developed from experiments in larger windspeeds, which may overestimate the amount of particles that are inhaled by a worker in an indoor setting. CFD methods allow the simulation of uniform particle concentration fields, allowing us to avoid the experimental difficulties associated with uniform suspension of large particles. Initial research has developed, validated, and verified a computer representation of a single humanoid form to investigate particle aspiration using the standard k-epsilon turbulence model in the facing-the-wind orientation. This research will: (1) examine the sensitivity of aspiration efficiency estimates to facial feature dimensions, turbulence equations, and bounce parameters to quantify uncertainty in aspiration efficiency estimates; (2) investigate particle aspiration at orientations other than facing-the-wind to understand the influences of orientation and velocity parameters on particle aspiration for a humaniod form; (3) to propose a low velocity aspiration efficiency curve for use in the development of an inhalable particle sampler criterion. This work supports the Exposure Assessment Methods NORA priority research area. There is current concern that occupational exposure samples collected using the existing high-velocity IPM criterion collects particles at efficiencies greater than what can be inhaled by workers. If so, mass-based exposure estimates will overestimate the true exposures of individuals. Once health effects studies are applied to these exposure estimates, risk estimates will be based on overestimated exposures. This will result in risk assessments that actually underestimate the risk of exposure to workers. This research will identify whether the sampling criterion to assess exposures to large particles in workplaces requires adjustment to improve exposure and risk estimates.