Effects of indoor air purification intervention on blood pressure, blood­oxygen saturation, and heart rate variability: A double-blinded cross-over randomized controlled trial of healthy young adults.

The use of indoor air purifier (IAP) has received growing attention as a mitigation strategy for reducing indoor air pollution, but the evidence on their cardiovascular benefits is unclear. This study aims to evaluate whether the use of IAP can reduce the adverse effects of indoor particulate matter (PM) on cardiovascular health among young healthy population. A randomized, double-blind, cross-over, IAP intervention of 38 college students was conducted. The participants were assigned into two groups to receive the true and sham IAPs for 36 h in random order. Systolic and diastolic blood pressure (SBP; DBP), blood oxygen saturation (SpO2), heart rate variability (HRV) and indoor size-fractioned particulate matter (PM) were real-time monitored throughout the intervention. We found that IAP could reduce indoor PM by 41.7-50.5 %. Using IAP was significantly associated with a reduction of 2.96 mmHg (95 % CI: -5.71, -0.20) in SBP. Increased PM was significantly associated with increased SBP (e.g., 2.17 mmHg [0.53, 3.81], 1.73 mmHg [0.32, 3.14] and 1.51 mmHg [0.28, 2.75] for an IQR increment of PM1 [16.7 µg/m3], PM2.5 [20.6 µg/m3] and PM10 [37.9 µg/m3] at lag 0-2 h, respectively) and decreased SpO2 (-0.44 % [-0.57, -0.29], -0.41 % [-0.53, -0.30] and - 0.40 % [-0.51, -0.30] for PM1, PM2.5 and PM10 at lag 0-1 h, respectively), which could last for about 2 h. Using IAPs could halve indoor PM levels, even in relatively low air pollution settings. The exposure-response relationships suggested that the benefits of IAPs on BP may only be observed when indoor PM exposure is reduced to a certain level.

Association of Solid Fuel Use With Risk of Cardiovascular and All-Cause Mortality in Rural China.

Importance: When combusted indoors, solid fuels generate a large amount of pollutants such as fine particulate matter. Objective: To assess the associations of solid fuel use for cooking and heating with cardiovascular and all-cause mortality. Design, Setting, and Participants: This nationwide prospective cohort study recruited participants from 5 rural areas across China between June 2004 and July 2008; mortality follow-up was until January 1, 2014. A total of 271 217 adults without a self-reported history of physician-diagnosed cardiovascular disease at baseline were included, with a random subset (n = 10 892) participating in a resurvey after a mean interval of 2.7 years. Exposures: Self-reported primary cooking and heating fuels (solid: coal, wood, or charcoal; clean: gas, electricity, or central heating), switching of fuel type before baseline, and use of ventilated cookstoves. Main Outcomes and Measures: Death from cardiovascular and all causes, collected through established death registries. Results: Among the 271 217 participants, the mean (SD) age was 51.0 (10.2) years, and 59% (n = 158 914) were women. A total of 66% (n = 179 952) of the participants reported regular cooking (at least weekly) and 60% (n = 163 882) reported winter heating, of whom 84% (n = 150 992) and 90% (n = 147 272) used solid fuels, respectively. There were 15 468 deaths, including 5519 from cardiovascular causes, documented during a mean (SD) of 7.2 (1.4) years of follow-up. Use of solid fuels for cooking was associated with greater risk of cardiovascular mortality (absolute rate difference [ARD] per 100 000 person-years, 135 [95% CI, 77-193]; hazard ratio [HR], 1.20 [95% CI, 1.02-1.41]) and all-cause mortality (ARD, 338 [95% CI, 249-427]; HR, 1.11 [95% CI, 1.03-1.20]). Use of solid fuels for heating was also associated with greater risk of cardiovascular mortality (ARD, 175 [95% CI, 118-231]; HR, 1.29 [95% CI, 1.06-1.55]) and all-cause mortality (ARD, 392 [95% CI, 297-487]; HR, 1.14 [95% CI, 1.03-1.26]). Compared with persistent solid fuel users, participants who reported having previously switched from solid to clean fuels for cooking had a lower risk of cardiovascular mortality (ARD, 138 [95% CI, 71-205]; HR, 0.83 [95% CI, 0.69-0.99]) and all-cause mortality (ARD, 407 [95% CI, 317-497]; HR, 0.87 [95% CI, 0.79-0.95]), while for heating, the ARDs were 193 (95% CI, 128-258) and 492 (95% CI, 383-601), and the HRs were 0.57 (95% CI, 0.42-0.77) and 0.67 (95% CI, 0.57-0.79), respectively. Among solid fuel users, use of ventilated cookstoves was also associated with lower risk of cardiovascular mortality (ARD, 33 [95% CI, -9 to 75]; HR, 0.89 [95% CI, 0.80-0.99]) and all-cause mortality (ARD, 87 [95% CI, 20-153]; HR, 0.91 [95% CI, 0.85-0.96]). Conclusions and Relevance: In rural China, solid fuel use for cooking and heating was associated with higher risks of cardiovascular and all-cause mortality. These risks may be lower among those who had previously switched to clean fuels and those who used ventilation.