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Air pollution and patients with implanted cardiac defibrillators : an epidemiological analysis and assessment of exposure Rich, Kira


This research extends previous investigations of adverse cardiovascular effects of particulate air pollutants to patients with implanted cardiac defibrillators (ICDs). Case crossover analyses were conducted for the February 14 to December 31, 2001 study period using data from ICDs worn by 34 Vancouver residents. Pollutant concentrations for days when ICD-detected arrhythmias were observed were compared to control day (± 7 days from ICD event days) concentrations. Although in general results were statistically non-significant, consistent trends suggested weak associations between summertime combustion-source primary air pollutants and cardiac arrhythmia. Odds ratios (OR) were higher in summer (7 of 9 >1) than in winter (1 of 9 >1) and ORs were highest for lag 0. For local combustion-source pollutants elemental and organic carbon, carbon monoxide and sulfur dioxide, ORs were above 1 at all lags (0-3 days) in summer. For summer and winter periods combined, results failed to indicate consistent associations between air pollution and ICD-detected arrhythmia. In the second component of the thesis, 19 patients with ICDs were monitored for exposure between May 15-August 31, 2001. For each subject, personal exposures to PM₂․₅ (particulate matter <2.5μm in aerodynamic diameter) mass concentration, filter optical absorbance (a surrogate for elemental carbon, a marker of traffic-related particles), and sulfate (a marker for regional ambient source particulate matter) were measured for 7 randomly selected 24-hour periods (≥8 days apart). Supplementary exposure-related activity data was collected using time activity diaries. Ambient measurements of PM₂․₅, sulfate and absorbance were made at a single ambient monitoring location. Relationships between personal exposures and ambient concentrations were assessed to evaluate use of ambient measurements for exposure assessment. Median ambient and personal PM₂․₅ concentrations were 6.4ug/m³ and 13.5ug/m³, respectively, while median absorbance values were 10.8x10⁻⁵m⁻¹ and 7.2x10⁻⁵m⁻¹. Median ambient and personal sulfate concentrations were 1.2ug/ m³ and 1.15ug/ m³. Median correlations (r) for individual personal versus ambient regressions for PM₂․₅, absorbance, and sulfate were 0.37, 0.50, and 0.85, respectively. The higher values for absorbance and sulfate are consistent with these components being associated with local and regional outdoor sources, respectively, whereas the lower correlation for PM₂․₅ reflects the impact of indoor sources on exposure.

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