Relative risk and dalys assessment of indoor air pollutants in residential buildings - taking Dalian as an example

Indoor air pollution poses significant health risks, yet the differential health impacts of specific pollutants remain insufficiently quantified. Therefore, this study examined the associations between exposure to five indoor air pollutants (PM2.5, PM10, SO2, NO2, CO) and disease-specific outpatient visits in Dalian, China, aiming to elucidate both the direct and indirect health effects of indoor air pollution. First, continuous indoor air monitoring was conducted for one year in 20 representative residential units, and corresponding medical records were collected simultaneously. Next, generalized additive models combined with distributed lag nonlinear models were constructed to quantify the associations between pollutants and diseases, with adjustments for long-term trends, holiday effects, and intraweek variability. Finally, the analysis explored trends in the relative risk (RR) and disease burden of specific health outcomes as pollutant concentrations varied, while also considering the extent to which lag effects influence health outcomes. The results quantify the disease risk and burden in terms of RR and disability adjusted life years (DALYs). Among the studied pollutants, CO exhibits the strongest association with ischemic heart disease risk. At a CO concentration of 4 mg/m3, the RR reaches 1.13 (95%CI: 1.12–1.13), resulting in a disease burden of 42.08 (95%CI: 40.35–43.78) DALYs/(year·100,000). SO2 and NO2 exert the most pronounced effects on acute asthma exacerbations, with peak RRs of 1.14 (95%CI: 1.12–1.15, at 80 µg/m3) and 1.17 (95%CI: 1.16–1.18, at 0.25 mg/m3), respectively; the corresponding disease burdens are 140.76 (95%CI: 124.37-153.67) and 173.81 (95%CI: 165.60-180.03) DALYs/(year·100,000). PM10 and PM2.5 exhibit lower RRs for specific diseases, with RR values not exceeding 1.04 within the studied concentration ranges (0–200 µg/m3 for PM10 and 0–160 µg/m3 for PM2.5). However, PM10 imposes a substantial disease burden on diabetes, with a maximum value reaching approximately 800 DALYs/(year·100,000). All target pollutants show a significant positive correlation with the RRs and disease burden of corresponding disease outcomes, and lag effects also increase disease risk.