Acute effects of hourly particulate-matter air pollution on 24 h ambulatory blood pressure in Chinese elderly individuals: a prospective panel study

Abstract

BackgroundThe association between hourly exposure to air pollution and blood pressure, and its threshold effects, are unclear. We aimed to examine the association between hourly PM2·5 and PM10 exposure and 24 h ambulatory blood pressure among a panel of Chinese elderly individuals. MethodsWe recruited 261 subjects (mean age 66·9 years [SD 5·8]; 115 [44%] women) from Kailuan community in Tangshan City, China, during Jan 1 to Dec 31, 2013. We monitored 24 h ambulatory systolic and diastolic blood pressure for each participant. Hourly concentrations of PM2·5 and PM10 were obtained from Tangshan Environmental Monitoring Centre, and hourly temperature and dewpoint temperature from the Chinese Meteorology Sharing System. Generalised additive mixed models were used to examine the effects of hourly PM2·5 and PM10 on hourly systolic blood pressure, diastolic blood pressure, and pulse–pressure difference, controlling for potential confounders. Written consent was obtained from participants. The study was approved by The University of Queensland behaviour and social sciences ethical review committee. FindingsMean concentrations of hourly PM2·5 and PM10 were 128·3 μg/m3 (SD 113·9) and 208·1 μg/m3 (154·1), respectively. Effects of hourly PM2·5 and PM10 on 24 h ambulatory systolic or diastolic blood pressure or pulse–pressure difference were non-linear, with thresholds at 120 μg/m3 for PM2·5 and 190 μg/m3 for PM10. Increases in PM2·5 and PM10 above thresholds associated with increased systolic blood pressure, diastolic blood pressure, and pulse–pressure difference. The effects lasted for 3 h. Results were robust when controlling for hourly NO2, SO2, and O3 concentrations and hourly and dewpoint temperature. InterpretationAcute increases in ambient particulate-matter air pollution above certain concentrations increase blood pressure among Chinese elderly individuals. Avoiding exposure to high concentrations of ambient air pollution might protect elderly health. Strengths of our study are the prospective design and broad assessment of potential confounders. We used community-level air pollution rather than personal exposure data, which could underestimate the effects of air pollutants on blood pressure. FundingAustralian National Health and Medical Research Council.