| Metabolic Syndrome and Inflammatory Responses to Long-Term Particulate Air Pollutants Jiu-Chiuan Chen1,2 and Joel Schwartz2,3 1Department of Epidemiology, University of North Carolina School of Public Health, Chapel Hill, North Carolina, USA; 2Department of Environmental Health, and 3Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA Abstract
Background: Human data linking inflammation with long-term particulate matter (PM) exposure are still lacking. Emerging evidence suggests that people with metabolic syndrome (MS) may be a more susceptible population. Objectives: Our goal was to examine potential inflammatory responses associated with long-term PM exposure and MS-dependent susceptibility. Methods: We conducted secondary analyses of white blood cell (WBC) count and MS data from The Third National Health and Nutrition Examination Survey and PM10 (PM with aerodynamic diameter < 10 µm) data from the U.S. Environmental Protection Agency Aerometric Information Retrieval System. Estimated 1-year PM10 exposures were aggregated at the centroid of each residential census-block group, using distance-weighted averages from all monitors in the residing and adjoining counties. We restricted our analyses to adults (20–89 years of age) with normal WBC (4,000–11,000  106/L) , no existing cardiovascular disease, complete PM10 and MS data, and living in current residences > 1 year (n = 2,978 ; age 48.5 ± 17.8 years) . Mixed-effects models were constructed to account for autocorrelation and potential confounders. Results: After adjustment for demographics, socioeconomic factors, lifestyles, residential characteristics, and MS, we observed a statistically significant association between WBC count and estimated local PM10 levels (p = 0.035) . Participants from the least polluted areas (1-year PM10 < 1st quartile cutoff: 27.8 µg/m3) had lower WBC counts than the others (difference = 145 106/L ; 95% confidence interval, 10–281) . We also noted a graded association between PM10 and WBC across subpopulations with increasing MS components, with 91 106/L difference in WBC for those with no MS versus 214, 338, and 461 106/L for those with 3, 4, and 5 metabolic abnormalities (trend-test p = 0.15) . Conclusions: Our study revealed a positive association between long-term PM exposure and hematological markers of inflammation and supported the hypothesized MS-dependent susceptibility. Key words: air pollution, environmental health, metabolic syndrome, particles, risk factors, susceptibility, white blood cells. Environ Health Perspect 116:612–617 (2008) . doi:10.1289/ehp.10565 available via http://dx.doi.org/ [Online 25 February 2008]
Address correspondence to J-C. Chen, Department of Epidemiology, University of North Carolina School of Public Health, 2104G, McGavran-Greenberg, CB# 7435, Chapel Hill, NC 27599 USA. Telephone: (919) 962-2756. Fax: (919) 966-2089. E-mail: jcchen@unc.edu This study is supported by U.S. Environmental Protection Agency grants R827353 and R832416 and National Institute of Environmental Health Sciences grant E-S0002. The authors declare they have no competing financial interests. Received 15 June 2007 ; accepted 25 February 2008.
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