Epidemiological studies frequently use black carbon (BC) as a proxy for traffic-related air pollution (TRAP). However, wildfire smoke (WFS) represents an important source of BC not often considered when using BC as a proxy for TRAP. Here, we examined the potential for WFS to bias TRAP exposure assessments based on BC measurements. Weekly integrated BC samples were collected across the Denver, CO region from May to November 2018. We collected 609 filters during our sampling campaigns, 35% of which were WFS-impacted. For each filter we calculated an average BC concentration. We assessed three GIS-based indicators of TRAP for each sampling location: annual average daily traffic within a 300 m buffer, the minimum distance to a highway, and the sum of the lengths of roadways within 300 m. Median BC concentrations were 9% higher for WFS-impacted filters (median = 1.14 μg/m³, IQR = 0.23 μg/m³) than nonimpacted filters (median = 1.04 μg/m³, IQR = 0.48 μg/m³). During WFS events, BC concentrations were elevated and expected spatial gradients in BC were reduced. We conducted a simulation study to estimate TRAP exposure misclassification as the result of regional WFS. Our results suggest that linear health effect estimates were biased away from the null when WFS was present. Thus, exposure assessments relying on BC as a proxy for TRAP may be biased by wildfire events. Alternative metrics that account for the influence of “brown” carbon associated with biomass burning may better isolate the effects of traffic emissions from those of other black carbon sources.

中文翻译：

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评估野火对使用黑碳作为环境流行病学研究中交通暴露指标的影响


流行病学研究经常使用黑碳（BC）作为交通相关空气污染（TRAP）的代表。然而，野火烟雾 (WFS) 是 BC 的一个重要来源，在使用 BC 作为 TRAP 的代理时，通常不考虑该来源。在这里，我们研究了 WFS 根据 BC 测量结果对 TRAP 暴露评估产生偏差的可能性。 2018 年 5 月至 11 月，每周在科罗拉多州丹佛地区收集综合 BC 样本。我们在采样活动中收集了 609 个过滤器，其中 35% 受到 WFS 影响。对于每个过滤器，我们计算了平均 BC 浓度。我们评估了每个采样点的基于 GIS 的 TRAP 三个指标：300 m 缓冲区内的年平均日交通量、距高速公路的最短距离以及 300 m 内道路长度的总和。受 WFS 影响的过滤器的 BC 浓度中值（中值 = 1.14 μg/m ³ ，IQR = 0.23 μg/m ³ ）比未受影响的过滤器（中值 = 1.04 μg/m ³ ，IQR = 0.48 μg/m ³ ）高 9%。在 WFS 事件期间，BC 浓度升高，BC 的预期空间梯度降低。我们进行了一项模拟研究，以估计区域 WFS 导致的 TRAP 暴露错误分类。我们的结果表明，当 WFS 存在时，线性健康效应估计值会偏离零值。因此，依赖 BC 作为 TRAP 代理的暴露评估可能会因野火事件而产生偏差。考虑与生物质燃烧相关的“棕”碳影响的替代指标可以更好地将交通排放的影响与其他黑碳来源的影响分开。