Effects of Particulate Air Pollution on Blood Pressure in a Highly Exposed Population in Beijing, China: A Repeated-Measure Study

Abstract

Background: Particulate Matter (PM) exposure is critical in Beijing due to high population density and rapid increase in vehicular traffic. PM effects on blood pressure (BP) have been investigated as a mechanism mediating cardiovascular risks, but results are still inconsistent. The purpose of our study is to determine the effects of ambient and personal PM exposure on BP.

Methods: Before the 2008 Olympic Games (June 15-July 27), we examined 60 truck drivers and 60 office workers on two days, 1-2 weeks apart (n = 240). We obtained standardized measures of post-work BP. Exposure assessment included personal \(PM_{2.5}\) and Elemental Carbon (EC, a tracer of traffic particles) measured using portable monitors during work hours; and ambient \(PM_{10}\) averaged over 1-8 days pre-examination. We examined associations of exposures (exposure group, personal \(PM_{2.5}/EC\), ambient \(PM_{10}\)) with BP controlling for multiple covariates.

Results: Mean personal \(PM_{2.5}\) was \(94.6 μg/m^3\) (SD = 64.9) in office workers and 126.8 (SD = 68.8) in truck drivers (p-value < 0.001). In all participants combined, a \(10 μg/m^3\) increase in 8-day ambient \(PM_{10}\) was associated with BP increments of 0.98 (95%CI 0.34; 1.61; p-value = 0.003), 0.71 (95%CI 0.18; 1.24; p-value = 0.01), and 0.81 (95%CI 0.31; 1.30; p-value = 0.002) mmHg for systolic, diastolic, and mean BP, respectively. BP was not significantly different between the two groups (p-value > 0.14). Personal \(PM_{2.5}\) and EC during work hours were not associated with increased BP.

Conclusions: Our results indicate delayed effects of ambient \(PM_{10}\) on BP. Lack of associations with exposure groups and personal \(PM_{2.5}/EC\) indicates that PM effects are related to background levels of pollution in Beijing, and not specifically to work-related exposure.