This study aims to investigate cardiopulmonary effects of chemical constituents and sources of indoor fine particulate matter (PM_2.5). Forty-three stable patients with chronic obstructive pulmonary disease (COPD) were recruited from November 2015 to May 2016 in Beijing, China. Daily indoor and outdoor PM_2.5 were collected for five consecutive days simultaneously. Twenty-four elements were measured and principal component analysis was used for source appointment. Pulmonary function and blood pressure (BP) were also measured at daily visit. Linear mixed-effect models were used to estimate the effect of each constituent and source. Bayesian kernel machine regression (BKMR) models were used to estimate the overall effect of all measured constituents. This study found that during the heating season, most constituents of indoor PM_2.5 were significantly associated with elevated BP of COPD patients, while few associations were observed with pulmonary function. Most associations were not significant during the non-heating season. Similar results were observed in joint effect analyses. Further, combustion sources throughout the study period and road dust sources during the heating season were significantly associated with increased BP. Therefore, our study highlights the importance of controlling combustion and road dust sources to protect cardiovascular health from indoor PM_2.5, especially during the heating season.

indoor particulate matter, chemical constituents, source, chronic obstructive pulmonary disease, cardiopulmonary function