Mediating effect of respiratory symptoms on the relationships between residential distance and QOL in physical health (a), social relationships (b), and environment (c) domains. Adjusted for gender, age, marital status, education level, annual personal income, risk perception, duration of residence, smoking, drinking, occupational exposure, outdoor activities, and consumption of local food; *p鈥�<鈥�0.05, **p鈥�<鈥�0.01, ***p鈥�&濒迟;鈥�0.001