Stephanie Chan

Project title: Residential Exposure to Air Pollution and Blood Pressure: A Cross-sectional Assessment of the NIEHS Sister Study

Degree: MPH | Program: Environmental and Occupational Health (EOH) | Project type: Thesis/Dissertation
Completed in: 2011 | Faculty advisor: Joel D. Kaufman


Long- and short-term air pollution exposures, especially to fine particulate matter (with aerodynamic diameter less than 2.5 microns, or PM2.5), have been associated with cardiovascular morbidity and mortality. There is evidence that short-term exposures to PM2.5 (i.e. daily increases in exposure) are associated with an increase in arterial blood pressure, and there is interest in the effects of long-term exposures (i.e. increased annual average exposures) on blood pressure. Increased arterial blood pressure is a risk factor for cardiovascular disease including myocardial infarction and stroke, and observing associations with blood pressure may help to explain the cardiovascular effects of air pollution. This study is a cross-sectional assessment of the relationships between long-term residential traffic-related air pollution exposure and blood pressure in The Sister Study cohort.

The National Institute of Environmental Health Sciences' Sister Study is a nationwide cohort investigating environmental and genetic risk factors for breast cancer. The study sample included 50,884 women, all with sisters with breast cancer, between the ages of 35 and 74 at baseline examination (2003 to 2009). Geographic information systems were used to assess residential proximity to major roadways, satellite-based nitrogen dioxide (NO2) concentrations, and PM2.5 concentrations for each participant. Linear regression was used to model blood pressure, and relative risk regression was used to model the presence of hypertension.

There was no association between blood pressure and residence near a major roadway after adjusting for age, race/ethnicity, household income, education, marital status, alcohol use, employment status, perceived stress, blood mass index, waist/hip ration, smoking status, diabetes, high cholesterol, neighborhood socioeconomic status, and urbanicity. Similarly, there was no association between blood pressure and an interquartile range increase in NO2 concentrations, after adjusting for potential confounders. However, a 10 μg/m3 increase in PM2.5 (RR=1.08, 95%CI: 1.01 to 1.15)

PM2.5 concentrations were associated with small increases in systolic and diastolic blood pressure, increased risk of having high blood pressure readings in the prehypertensive and hypertensive range, and increased risk of a prior hypertension diagnosis. The findings reported by this study contribute to a growing body of literature on the effects of long-term air pollution and blood pressure.