Individual-Level Concentrations of Fine Particulate Matter Chemical Components and Subclinical Atherosclerosis: A Cross-Sectional Analysis Based on 2 Advanced Exposure Prediction Models in the Multi-Ethnic Study of Atherosclerosis

Abstract

Long-term exposure to outdoor particulate matter with an aerodynamic diameter less than or equal to 2.5 µm (PM2.5) has been associated with cardiovascular morbidity and mortality. The chemical composition of PM2.5 that may be most responsible for producing these associations has not been identified. We assessed cross-sectional associations between long-term concentrations of PM2.5 and 4 of its chemical components (sulfur, silicon, elemental carbon, and organic carbon (OC)) and subclinical atherosclerosis, measured as carotid intima-media thickness (CIMT) and coronary artery calcium, between 2000 and 2002 among 5,488 Multi-Ethnic Study of Atherosclerosis participants residing in 6 US metropolitan areas. Long-term concentrations of PM2.5 components at participants' homes were predicted using both city-specific spatiotemporal models and a national spatial model. The estimated differences in CIMT associated with interquartile-range increases in sulfur, silicon, and OC predictions from the spatiotemporal model were 0.022 mm (95% confidence interval (CI): 0.014, 0.031), 0.006 mm (95% CI: 0.000, 0.012), and 0.026 mm (95% CI: 0.019, 0.034), respectively. Findings were generally similar using the national spatial model predictions but were often sensitive to adjustment for city. We did not find strong evidence of associations with coronary artery calcium. Long-term concentrations of sulfur and OC, and possibly silicon, were associated with CIMT using 2 distinct exposure prediction modeling approaches.

The importance of the exposure metric in air pollution epidemiology studies: When does it matter, and why?

“…Findings in Sun et al were generally consistent across the three approaches, and were not highly sensitive to the approach (Sun et al 2013). Kim et al showed that findings from the two models were similar, but were often sensitive to adjustment for city (Kim et al 2014). Across the two studies, findings were consistent for some PM 2.5 components (though still with differences in magnitude and precision), and different for others.…”

Particulate Matter and Subclinical Atherosclerosis: Associations between Different Particle Sizes and Sources with Carotid Intima-Media Thickness in the SAPALDIA Study

“…However, given that LUR model performance was lower for the crustal source than for the vehicular one, these results could also be related to an increased measurement error of the crustal source. To our knowledge, the effect of specific PM 2.5 components and sources on CIMT has only been investigated in the MESA study (Kim et al 2014). The analysis was focused on elemental carbon and organic carbon as markers of combustion sources, silicon as marker of crustal dust, and sulfur as indicator of sulfate (secondary aerosol).…”

“…However, findings were not consistent (Bauer et al 2010; Diez Roux et al 2008; Kim et al 2014; Künzli et al 2005; Perez et al 2015; Rivera et al 2013; Su et al 2015; Wilker et al 2013). Four longitudinal studies published to date, all of them conducted in North America, also yielded inconsistent results.…”

“…The association between specific PM 2.5 components and subclinical atherosclerosis has only been investigated in the Multi-Ethnic Study of Atherosclerosis (MESA) study (Kim et al 2014). To our knowledge, no epidemiological study has assessed the association of subclinical atherosclerosis with ultrafine particles (UFP), despite their stronger atherogenic effect in animal studies when compared to larger size fractions (Araujo et al 2008).…”

Advances in Understanding Air Pollution and CVD

“…MESA Air biostatistics researchers have also published on methods for selecting and combining data from multiple sources, 68 exposure estimation, 69, 70 choice of exposure prediction models, 6, 71-73 and reduced-rank spatio-temporal modeling.…”