Exposure to fine particulate matter and acute effects on blood pressure: effect modification by measures of obesity and location.

BACKGROUND: Observational studies and controlled experiments have provided evidence that airborne particulate matter (PM) is capable of acutely increasing blood pressure (BP) in certain scenarios. The goal of this study was to evaluate whether and to what extent obesity and community location affect relationships between fine particulate matter (PM(2.5)) and blood pressure (BP) measures.
METHODS: Using data from a stratified random sample survey of adults conducted in 2002-3 in Detroit, Michigan, we tested body mass index (BMI) and waist circumference (WCIR) in separate models as effect modifiers of the relationship between PM(2.5) exposure and BP. We also tested interactions with community location. Models were adjusted for covariates with established pro-hypertensive effects.
RESULTS: PM(2.5) exposure was positively associated with increased pulse pressure (PP) for those categorised as obese (BMI> or =30) across lags 2 (beta 4.16, p<0.05) and 3 days (beta 2.55, p<0.05) prior to BP measure. WCIR similarly modified the effect of exposure to PM(2.5) on PP (beta 4.34, p<0.003). The observed effects were enhanced in the community with closer proximity to local emissions of PM(2.5), and for residents classified as obese (BMI> or =30) or with WCIR above high-risk cuts points.
CONCLUSIONS: This community-based study suggests that positive associations between PM(2.5) exposure and PP and systolic BP are enhanced in areas proximate to sources of PM (2.5) emissions. These patterns were observed for all residents, but were more visible and consistent among those who were obese. Research is needed to examine the mechanistic pathways by which air particles interact with obesity and location to affect BP, and inform community interventions to reduce the population burden of hypertension and related co-morbidities.