The potential for seasonal differences in the physicochemical characteristics of ambient particulate matter (PM) to modify interactive effects with gaseous pollutants has not been thoroughly examined. The purpose of this study was to compare cardiac responses in conscious hypertensive rats co-exposed to concentrated ambient particulates (CAPs) and ozone (O3) in Durham, NC during the summer and winter, and to analyze responses based on particle mass and chemistry. Rats were exposed once for 4 hrs by whole-body inhalation to fine CAPs alone (target concentration: 150 μg/m3), O3 (0.2 ppm) alone, CAPs plus O3, or filtered air during summer 2011 and winter 2012. Telemetered electrocardiographic (ECG) data from implanted biosensors were analyzed for heart rate (HR), ECG parameters, heart rate variability (HRV), and spontaneous arrhythmia. The sensitivity to triggering of arrhythmia was measured in a separate cohort one day after exposure using intravenously administered aconitine. PM elemental composition and organic and elemental carbon fractions were analyzed by high-resolution inductively coupled plasma–mass spectrometry and thermo-optical pyrolytic vaporization, respectively. Particulate sources were inferred from elemental analysis using a chemical mass balance model. Seasonal differences in CAPs composition were most evident in particle mass concentrations (summer, 171 μg/m3; winter, 85 μg/m3), size (summer, 324 nm; winter, 125 nm), organic:elemental carbon ratios (summer, 16.6; winter, 9.7), and sulfate levels (summer, 49.1 μg/m3; winter, 16.8 μg/m3). Enrichment of metals in winter PM resulted in equivalent summer and winter metal exposure concentrations. Source apportionment analysis showed enrichment for anthropogenic and marine salt sources during winter exposures compared to summer exposures, although only 4% of the total PM mass was attributed to marine salt sources. Single pollutant cardiovascular effects with CAPs and O3 were present during both summer and winter exposures, with evidence for unique effects of co-exposures and associated changes in autonomic tone. These findings provide evidence for a pronounced effect of season on PM mass, size, composition, and contributing sources, and exposure-induced cardiovascular responses. Although there was inconsistency in biological responses, some cardiovascular responses were evident only in the co-exposure group during both seasons despite variability in PM physicochemical composition. These findings suggest that a single ambient PM metric alone is not sufficient to predict potential for interactive health effects with other air pollutants.

中文翻译：

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季节性环境颗粒物和臭氧共同暴露对大鼠的心脏影响。

尚未彻底研究环境颗粒物（PM）的理化特性季节性差异可能改变与气态污染物的相互作用的可能性。这项研究的目的是比较夏季和冬季在北卡罗来纳州达勒姆市集中暴露于浓缩的环境颗粒（CAPs）和臭氧（O3）的清醒性高血压大鼠的心脏反应，并根据颗粒质量和化学成分分析反应。在2011年夏季和2012年冬季，通过全身吸入将大鼠暴露于单独的细小CAP（目标浓度：150μg/ m3），单独的O3（0.2 ppm），单独的CAPs和O3或过滤空气中，暴露4小时。分析了来自植入式生物传感器的ECG数据的心率（HR），ECG参数，心率变异性（HRV）和自发性心律失常。在暴露后一天，使用静脉注射乌头碱在单独的队列中测量对引发心律失常的敏感性。分别通过高分辨率电感耦合等离子体质谱法和热光热解汽化法分析了PM的元素组成以及有机和元素碳组分。使用化学质量平衡模型从元素分析中推断出微粒来源。CAPs组成的季节性差异在颗粒物质量浓度（夏季为171μg/ m3；冬季为85μg/ m3），尺寸（夏季为324 nm；冬季为125 nm），有机碳和元素碳比（夏季为16.6）中最为明显。 ；冬季为9.7）和硫酸盐含量（夏季为49.1μg/ m3；冬季为16.8μg/ m3）。冬季PM中金属的富集导致夏季和冬季金属暴露浓度相当。来源分配分析显示，与夏季相比，冬季暴露期间人为和海洋盐源的富集，尽管总PM质量中只有4％归因于海洋盐源。在夏季和冬季暴露期间，均存在使用CAPs和O3引起的单一污染物对心血管的影响，这证明了共同暴露和自律性变化的独特影响。这些发现为季节对PM的质量，大小，组成和贡献来源以及暴露引起的心血管反应的显着影响提供了证据。尽管生物学反应不一致，但尽管PM理化成分存在差异，但在两个季节中仅在共同暴露组中才出现一些心血管反应。