Background:
Individuals are exposed to air pollution and ionizing radiation from natural sources through inhalation of particles. This study investigates the association between cardiac arrhythmias and short-term exposures to fine particulate matter (particulate matter ≤2.5 µm aerodynamic diameter; PM
2.5
) and particle radioactivity.
Methods:
Ventricular arrhythmic events were identified among 176 patients with dual-chamber implanted cardioverter-defibrillators in Boston, Massachusetts between September 2006 and June 2010. Patients were assigned exposures based on residential addresses. Daily PM
2.5
levels were estimated at 1-km×1-km grid cells from a previously validated prediction model. Particle gross β activity was used as a surrogate for particle radioactivity and was measured from several monitoring sites by the US Environmental Protection Agency’s monitoring network. The association of the onset of ventricular arrhythmias (VA) with 0- to 21-day moving averages of PM
2.5
and particle radioactivity (2 single-pollutant models and a 2-pollutant model) before the event was examined using time-stratified case-crossover analyses, adjusted for dew point and air temperatures.
Results:
A total of 1,050 VA were recorded among 91 patients, including 123 sustained VA among 25 of these patients. In the single-pollutant model of PM
2.5
, each interquartile range increase in daily PM
2.5
levels for a 21-day moving average was associated with 39% higher odds of a VA event (95% CI, 12%–72%). In the single-pollutant model of particle radioactivity, each interquartile range increase in particle radioactivity for a 2-day moving average was associated with 13% higher odds of a VA event (95% CI, 1%–26%). In the 2-pollutant model, for the same averaging window of 21 days, each interquartile range increase in daily PM
2.5
was associated with an 48% higher odds of a VA event (95% CI, 15%–90%), and each interquartile range increase of particle radioactivity with a 10% lower odds of a VA event (95% CI, –29% to 14%). We found that with higher levels of particle radioactivity, the effect of PM
2.5
on VAs is reduced.
Conclusions:
In this high-risk population, intermediate (21-day) PM
2.5
exposure was associated with higher odds of a VA event onset among patients with known cardiac disease and indication for implanted cardioverter-defibrillator implantation independently of particle radioactivity.
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