Exposure to fine particulate matter (PM_2.5) has well-established systemic human health effects due in part to the chemical components associated with these exposures. Oxidative stress is a hypothesized mechanism for the health effects associated with PM_2.5 exposures. The oxidative potential of PM_2.5 has recently been suggested as a metric that is more indicative of human health effects than the routinely measured PM_2.5 concentration. The purpose of this study was to analyze and compare the oxidative potential and elemental composition of PM_2.5 collected at two locations during different seasons. PM_2.5 was collected onto PTFE-coated filters (n = 16) along two highways in central Oregon, USA in the Winter (January) and Summer (July/August). PM_2.5 was extracted from each filter via sonication in methanol. An aliquot of the extraction solution was used to measure oxidative potential using the dithiothreitol (DTT) assay. An additional aliquot underwent analysis via inductively coupled plasma—mass spectrometry (ICP-MS) to quantify elements (n = 20). Differences in PM_2.5 elemental composition were observed between locations and seasons as well as between days in the same season. Overall, concentrations were highest in the winter samples but the contribution to total PM_2.5 mass was higher for elements in the summer. Notably, the oxidative potential (nM DTT consumed/µg PM_2.5/min) differed between seasons with summer samples having nearly a two-fold increase when compared to the winter. Significant negative correlations that were observed between DTT consumption and several elements as well as with PM_2.5 mass but these findings were dependent on if the data was normalized by PM_2.5 mass. This research adds to the growing evidence and justification for investigating the oxidative potential and composition of PM_2.5 while also highlighting the seasonal variability of these factors.

中文翻译：

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PM2.5的化学成分和氧化电位的季节性变化

暴露于细颗粒物（PM _2.5）对人体健康具有公认的系统健康影响，部分原因是与这些暴露有关的化学成分。氧化应激是与PM _2.5暴露相关的健康影响的一种推测机制。最近有人提出PM _2.5的氧化电位是一种比常规测量的PM _2.5浓度更能指示人类健康影响的指标。这项研究的目的是分析和比较不同季节在两个位置收集的PM _2.5的氧化电位和元素组成。PM _2.5收集到PTFE包被的滤器（Ñ= 16）沿冬季（一月）和夏季（七月/八月）在美国俄勒冈州中部的两条高速公路上行驶。通过在甲醇中超声处理从每个过滤器中提取PM _2.5。使用二硫苏糖醇（DTT）测定法将提取液的等分试样用于测量氧化电位。通过电感耦合等离子体质谱法（ICP-MS）对另一等分试样进行分析，以定量元素（n = 20）。在地点和季节之间以及同一季节的几天之间，观察到PM _2.5元素组成的差异。总体而言，冬季样品中的浓度最高，但夏季元素对PM _2.5总质量的贡献较高。值得注意的是，氧化电位（nM DTT消耗量/ µg PM_2.5 /分钟）在不同季节之间有所不同，夏季样品与冬季相比增加了近两倍。在DTT消耗量与几种元素以及PM _2.5质量之间观察到了显着的负相关性，但这些发现取决于是否通过PM _2.5质量对数据进行了标准化。这项研究为研究PM _2.5的氧化潜力和组成增加了越来越多的证据和依据，同时强调了这些因素的季节性变化。