Coarse Particulate Matter (P[M.Sub.2.5-10]) Affects Heart Rate Variability, Blood Lipids, and Circulating Eosinophils in Adults with Asthma
Yeatts, Karin, Svendsen, Erik, Creason, John, Alexis, Neil, Herbst, Margaret, Scott, James, Kupper, Lawrence, Williams, Ronald, Neas, Lucas, Cascio, Wayne, Devlin, Robert B., Peden, David B., Environmental Health Perspectives
INTRODUCTION: We investigated whether markers of airway and systemic inflammation, as well as heart rate variability (HRV) in asthmatics, change in response to fluctuations in ambient particulate matter (PM) in the coarse [PM with aerodynamic diameter 2.5-10 [micro]m (P[M.sub.2.5-10])] and fine (P[M.sub.2.5]) size range.
METHODS: Twelve adult asthmatics, living within a 30-mile radius of an atmospheric monitoring site in Chapel Hill, North Carolina, were followed over a 12-week period. Daily P[M.sub.2.5-10] and P[M.sub.2.5] concentrations were measured separately for each 24-hr period. Each subject had nine clinic visits, at which spirometric measures and peripheral blood samples for analysis of lipids, inflammatory cells, and coagulation-associated proteins were obtained. We also assessed HRV [SDNN24HR (standard deviation of all normal-to-normal intervals in a 24-hr recording), ASDNN5 (mean of the standard deviation in all 5-min segments of a 24-hr recording)] with four consecutive 24-hr ambulatory electrocardiogram measurements. Linear mixed models with a spatial covariance matrix structure and a 1-day lag were used to assess potential associations between PM levels and cardiopulmonary end points.
RESULTS: For a 1-[micro]g/[m.sup.3] increase in coarse PM, SDNN24HR, and ASDNN5 decreased 3.36% (p = 0.02), and 0.77%, (p = 0.05) respectively. With a 1-[micro]g/[m.sup.3] increase in coarse PM, circulating eosinophils increased 0.16% (p = 0.01), triglycerides increased 4.8% (p = 0.02), and very low-density lipoprotein increased 1.15% (p = 0.01). No significant associations were found with fine PM, and none with lung function.
CONCLUSION: These data suggest that small temporal increases in ambient coarse PM are sufficient to affect important cardiopulmonary and lipid parameters in adults with asthma. Coarse PM may have underappreciated health effects in susceptible populations.
KEY WORDS: asthma, coarse PM, heart rate variability, inflammatory markers, lipids, systemic inflammation. Environ Health Perspect 115:709-714 (2007). doi:10.1289/ehp.9499 available via http://dx.doi.org/ [Online 18 January 2007]
In a recent review article of the health effects of coarse airborne particles on health, Brunekreef and Forsberg (2005) call for special consideration in studying and regulating coarse particulate matter [PM with aerodynamic diameter 2.5-10 [micro]m (P[M.sub.2.5-10])] separately from fine particulate matter (P[M.sub.2.5]). Epidemiologic evidence indicates that coarse PM had as strong a short-term effect (or stronger) as fine PM on asthma, chronic obstructive pulmonary disease (COPD), cardiac, and respiratory hospital admissions (Brunekreef and Forsberg 2005; Burnett et al. 1997, 1999; Chen et al. 2004; Sheppard et al. 1999). There is a growing body of work examining the mechanisms of effect of fine PM on heart rate variability (HRV) and systemic inflammation in susceptible populations such as the elderly, individuals with COPD, and individuals with recent myocardial infarction, hypertension, diabetes, or ischemic heart disease (Chuang et al. 2005; Liao et al. 1999; O'Neill et al. 2005; Park et al. 2005; Sullivan et al. 2005; Wheeler et al. 2006). However, few if any studies have examined potential mechanisms of effect of coarse PM to explain the epidemiologic associations between increased mortality/morbidity and exposure to ambient coarse PM.
Coarse PM can be distinguished from other particulate sizes by the content of bioactive microbial products. Becker et al. have reported that coarse PM activates macrophages and monocytes in vitro in a toll-like receptor (TLR)2- and TLR4-dependent fashion, with a significant fraction of this biologic activity being ascribed to endotoxin (Becker et al. 2002; Soukup and Becker 2001). Alexis et al. (2006) recently showed that in healthy individuals, endotoxin on inhaled coarse PM elicits innate immune responses in vivo on airway macrophages. …