Environment/Climate Change
Mediated impacts of China’s clean heating policy on blood pressure by indoor air pollution and indoor temperature Talia Sternbach* Talia Sternbach Xiaoying Li Xiang Zhang Ellison Carter Brian Robinson Chris Barrington-Leigh Wenlu Yuan Collin Brehmer Kaibing Xue Kennedy Hirst Shu Tao Yuanxun Zhang Guofeng Shen Jill Baumgartner Sam Harper
The Clean Heating Policy (CHP) was implemented in 2016 to transition millions of homes in northern China from coal- to electric-based heating and improve air quality. Household heating interventions may improve health, including blood pressure (BP), through improved indoor temperature and reduced air pollution (PM2.5), but can also drive behavioral, environmental, and health-related changes that may affect the assumed health benefits. Understanding the mechanisms of these interventions is thus important to maximize health benefits. We leveraged the natural experiment created by the CHP’s staggered rollout across villages in rural Beijing and applied causal mediation analysis to understand how much of the CHP’s impact on BP may be mediated through temperature and PM2.5.
We enrolled 1,438 participants >40y from 50 villages not yet treated with the CHP in winter 2018-19. In the next 3 winters, 20 villages were treated. We visited homes each winter to measure BP, administer questionnaires, and place indoor temperature and PM2.5 sensors. Mediators were the indoor temperature measured in the 5-min before BP in all homes and the winter average indoor PM2.5 measured in 25% of homes. We estimated the CHP’s total effect on BP using a difference-in-differences design, then controlled for each mediator separately, and both together, in additional models to estimate the controlled direct effects (CDE).
The CHP reduced systolic BP by 1.4 mmHg (95%CI: -3.3, 0.5) and diastolic BP by 1.6 mmHg (95%CI: -2.9, -0.3). Holding indoor temperature and PM2.5 at their baseline means (14˚C and 71 µg/m3, respectively), the CDEs for systolic and diastolic BP in the multiple mediation analysis were 0.3 mmHg (95%CI: -1.9, 2.5) and -0.6 mmHg (95%CI: -2.1, 0.9), respectively. Our analysis shows that CHP-driven improvements to indoor temperature and PM2.5 contributed to modest reductions in BP. These results provide insight into how the CHP affected BP and may inform future clean heating policies.