Cardiopulmonary Toxicity Induced by Ambient Particulate Matter (BI City Concentrated Ambient Particle Study)

Alterations in heart rate variability (HRV) have been reported in rodents exposed to concentrated ambient particles (CAPs) from different regions of the United States. The goal of this study was to compare alterations in cardiac function induced by CAPs in two distinct regional atmospheres. AirCARE 1, a mobile laboratory with an EPA/Harvard fine particle (particulate matter <2.5 {micro}m; PM{sub 2.5}) concentrator was located in urban Detroit, MI, where the PM mixture is heavily influenced by motor vehicles, and in Steubenville, OH, where PM is derived primarily from long-range transport and transformation of power plant emissions, as well as from local industrial operations. Each city was studied during both winter and summer months, for a total of four sampling periods. Spontaneously hypertensive rats instrumented for electrocardiogram (ECG) telemetry were exposed to CAPs 8 h/day for 13 consecutive days during each sampling period. Heart rate (HR), and indices of HRV (standard deviation of the average normal-to-normal intervals [SDNN]; square root of the mean squared difference of successive normal-to-normal intervals [rMSSD]), were calculated for 30-minute intervals during exposures. A large suite of PM components, including nitrate, sulfate, elemental and organic carbon, and trace elements, were monitored in CAPs and ambient air. In addition,more » a unique sampler, the Semi-Continuous Elements in Air Sampler (SEAS) was employed to obtain every-30-minute measurements of trace elements. Positive matrix factorization (PMF) methods were applied to estimate source contributions to PM{sub 2.5}. Mixed modeling techniques were employed to determine associations between pollutants/CAPs components and HR and HRV metrics. Mean CAPs concentrations in Detroit were 518 and 357 {micro}g/m{sup 3} (summer and winter, respectively) and 487 and 252 {micro}g/m{sup 3} in Steubenville. In Detroit, significant reductions in SDNN were observed in the summer in association with cement/lime, iron/steel, and gasoline/diesel factors, while associations with the sludge incineration factor and components were less consistent. In winter, increases in HR were associated with a refinery factor and its components. CAPs-associated HR decreases in winter were linked to sludge incineration, cement/lime, and coal/secondary factors and the majority of their associated components. Specific relationships for increased rMSSD in winter were difficult to determine due to lack of consistency between factors and associated constituents. In Steubenville, we observed significant changes in HR (both increases and decreases), SDNN, and rMSSD in the summer, but not in the winter. We examined associations between individual source factors/PM components and HRV metrics segregated by predominant wind direction (NE or SW). Changes in HR (both increases and decreases) were linked with metal processing, waste incineration, and iron/steel factors along with most of their associated elemental constituents. Reductions in SDNN were associated with metal processing, waste incineration, and mobile source factors and the majority of elements loading onto these factors. There were no consistent associations between changes in rMSSD and source factors/components. Despite the large number of coal-fired power plants in the region, and therefore the large contribution of secondary sulfate to overall PM mass, we did not observe any associations with the coal/secondary factor or with the majority of its associated components. There were several inconsistencies in our results which make definitive conclusions difficult. For example, we observed opposing signs of effect estimates with some components depending on season, and with others depending on wind direction. In addition, our extensive dataset clearly would be subject to issues of multiple comparisons, and the 'true' significant results are unknown. Overall, however, our results suggest that acute changes in cardiac function were most strongly associated with local industrial sources. Results for coal-fired power plant-derived PM were inconsistent and largely nonsignificant, whereas traffic and metal-related industries appeared to have stronger impacts. Importantly, our findings highlight the value of combining both factor analytical and component-specific analyses when interpreting results; relying on only one approach may not provide a complete picture of exposure-health relationships. « less