Environmental tobacco smoke (ETS) is estimated to be a significant contributor to in-vehicle human exposure to fine particulate matter of 2.5 μm or smaller (PM_2.5). A critical assessment was conducted of a mass balance model for estimating PM_2.5 concentration with smoking in a motor vehicle. Recommendations for the range of inputs to the mass-balance model are given based on literature review. Sensitivity analysis was used to determine which inputs should be prioritized for data collection. Air exchange rate (ACH) and the deposition rate have wider relative ranges of variation than other inputs, representing inter-individual variability in operations, and inter-vehicle variability in performance, respectively. Cigarette smoking and emission rates and vehicle interior volume are also key inputs. The in-vehicle ETS mass balance model was incorporated into the Stochastic Human Exposure and Dose Simulation for Particulate Matter (SHEDS-PM) model to quantify the potential magnitude and variability of in-vehicle exposures to ETS. The in-vehicle exposure also takes into account near-road incremental PM_2.5 concentration from on-road emissions. Results of probabilistic study indicate that ETS is a key contributor to the in-vehicle average and high-end exposure. Factors that mitigate in-vehicle ambient PM_2.5 exposure lead to higher in-vehicle ETS exposure, and vice versa.

据估计，环境烟草烟雾 (ETS) 是导致车内人体接触 2.5 μm 或更小的细颗粒物 (PM _2.5 ) 的一个重要因素。对用于估算机动车内吸烟情况下PM _2.5浓度的质量平衡模型进行了严格评估。根据文献综述给出了质量平衡模型输入范围的建议。敏感性分析用于确定数据收集时应优先考虑哪些输入。空气交换率（ACH）和沉积率比其他输入具有更宽的相对变化范围，分别代表操作中的个体间变异性和性能中的车辆间变异性。卷烟吸烟率和排放率以及车辆内部容积也是关键输入。车内 ETS 质量平衡模型被纳入颗粒物随机人体暴露和剂量模拟 (SHEDS-PM) 模型中，以量化车内 ETS 暴露的潜在量级和变异性。车内暴露还考虑了道路排放导致的近路 PM _2.5浓度增量。概率研究结果表明，ETS 是车内平均和高端暴露的关键贡献者。减轻车内环境 PM _2.5暴露的因素会导致车内 ETS 暴露较高，反之亦然。