Farraj Aimen K, Walsh Leon, Haykal-Coates Najwa, Malik Fatiha, McGee John, Winsett Darrell, Duvall Rachelle, Kovalcik Kasey, Cascio Wayne E, Higuchi Mark, Hazari Mehdi S
Environmental Public Health Division, US EPA, 109 TW Alexander Drive, Research Triangle Park, Durham, NC, 27711, USA.
Human Exposure and Atmospheric Sciences Division, US EPA, 109 TW Alexander Drive, Research Triangle Park, Durham, NC, 27711, USA.
Part Fibre Toxicol. 2015 May 6;12:12. doi: 10.1186/s12989-015-0087-3.
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.
环境颗粒物（PM）的物理化学特性的季节性差异改变与气态污染物相互作用的可能性尚未得到充分研究。本研究的目的是比较2011年夏季和2012年冬季在北卡罗来纳州达勒姆市同时暴露于浓缩环境颗粒物（CAPs）和臭氧（O3）的清醒高血压大鼠的心脏反应，并根据颗粒物质量和化学组成分析反应情况。
2011年夏季和2012年冬季，大鼠通过全身吸入暴露4小时，分别暴露于单独的细颗粒物CAPs（目标浓度：150μg/m3）、单独的O3（0.2ppm）、CAPs加O3或过滤空气。分析植入生物传感器的遥测心电图（ECG）数据，以获取心率（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另一组中测量诱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PM的元素组成以及有机碳和元素碳组分。使用化学质量平衡模型从元素分析中推断颗粒物来源。
CAPs组成的季节性差异在颗粒物质量浓度（夏季，171μg/m3；冬季，85μg/m3）、粒径（夏季，324nm；冬季，125nm）、有机碳与元素碳比率（夏季，16.6；冬季，9.7）和硫酸盐水平（夏季，49.1μg/m3；冬季，16.8μg/m3）方面最为明显。冬季PM中金属的富集导致夏季和冬季的金属暴露浓度相当。源解析分析表明，与夏季暴露相比，冬季暴露期间人为源和海盐源有所富集，尽管海盐源仅占总PM质量的4%。夏季和冬季暴露期间，CAPs和O3单一污染物均对心血管有影响，有证据表明共同暴露有独特影响以及自主神经张力的相关变化。
这些发现为季节对PM质量、粒径、组成、来源以及暴露引起的心血管反应有显著影响提供了证据。尽管生物学反应存在不一致性，但尽管PM物理化学组成存在差异，两个季节中一些心血管反应仅在共同暴露组中明显。这些发现表明，仅单一的环境PM指标不足以预测与其他空气污染物相互作用对健康的潜在影响。
