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.