Background: There is limited evidence on whether particulate matter (PM) can augment the progression of atherosclerosis; furthermore, the specific attributes of PM responsible for health effects are unclear. We developed models to predict exposure to PM <10 μm (PM10) and also to predict a measure of oxidative potential (the capacity of particles to induce oxidative damage). Our objectives were (1) to estimate the association between PM10 and carotid intima-media thickness, a measure of subclinical atherosclerosis, and (2) to compare this association with that of PM10 weighted by its oxidative potential (PM10*OP).
Methods: Analysis was based on 2348 participants of the Whitehall II cohort of British civil servants who had intima-media thickness measured between 2003 and 2005 and lived in Greater London. Weekly PM10 and PM10*OP were predicted at each participant's residence. Primary exposure metrics were defined as PM10 and PM10*OP averaged over the year before scan. We estimated associations between exposure metrics and intima-media thickness using generalized linear regression models.
Results: An interquartile range increase (5.2 μgm−3) in PM10 was associated with a 5.0% (95% confidence interval = 1.9% to 8.3%) increase in intima-media thickness after covariate adjustment. The association for an interquartile range change in PM10*OP (1.5 m−3) was weaker: 1.2% (0.2% to 2.2%).
Conclusions: These findings support a relationship between PM exposure and atherosclerosis. PM weighted by this particular measure of oxidative potential was not more predictive of the extent of atherosclerosis than PM mass concentration.
From the aDepartment of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine London, United Kingdom; bMRC-HPA Centre for Environment and Health, King's College, London, United Kingdom; cDepartment of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA.
Supported by the Policy Research Programme in the UK Department of Health as part of the Health Effects of Outdoor and Indoor Air Pollution initiative. The views expressed are not necessarily those of the Department. C.T. was funded by the UK Economic and Social Research Council (RES-064-27-0026). The authors reported no other financial interests related to this research.
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Correspondence: Cathryn Tonne, Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, 15-17 Tavistock Place, London WC1H 9SH, United Kingdom. E-mail: email@example.com.
Received July 15, 2011
Accepted December 13, 2011