Effects of particulate air pollution on blood pressure in a highly exposed population in Beijing, China: A repeated-measure study

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 _2.5and Elemental Carbon (EC, a tracer of traffic particles) measured using portable monitors during work hours; and ambient PM ₁₀averaged 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 _2.5was 94.6 g/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 g/m ³ increase in 8-day ambient PM ₁₀was 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 _2.5and EC during work hours were not associated with increased BP. Conclusions: Our results indicate delayed effects of ambient PM ₁₀on 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.