Association between ambient particulate matter and hospital outpatient visits for chronic obstructive pulmonary disease in Lanzhou, China

Until now, a number of epidemiological studies have focused on the association between ambient particulate matter pollution and chronic obstructive pulmonary disease (COPD), especially in developed countries. There are limited evidences on the association between short-term exposure to particulate matters (PM 2.5 , PM C , and PM 10 ) and overall hospital outpatient visits for COPD at the same time in China. Thus, a time-series analysis on the short-term association between three subtypes of PM (PM 2.5 , PM C , and PM 10 ) and daily hospital outpatients for COPD in Lanzhou, China was conducted, from 2014 to 2017.An over dispersed, generalized additive model was used to analyze the associations after controlling for time trend, weather conditions, day of the week, and holidays. Stratified analyses were also performed by age and gender. The results disclosed that a 10-μg/m 3 increase in PM 2.5 concentration at a lag of 0–7 days was associated with 1.190% (95% CI 0.176~2.215%). For PM c , therewere not statistically significant effects at any lag days, but we could find the greatest effect at lag07 that a 10-μg/m 3 increase in concentration was associated with 0.014% (95% CI − 0.065~0.093%). PM 10 also exerted a high effect for COPD (0.185% increase; 95% CI − 0.046~0.417%) when 6 days of exposures (lag6), however, no significance relationship could be found. For COPD among males, positive results were observed for PM 2.5 with lags of 0–7 days, a 10-μg/m 3 increase was 1.184% (95% CI 0.095~2.284%). The effect of PM 2.5 on females was also most significant at lag07, a 10-μg/m 3 increase was 1.254% (95% CI 0.053~2.469%). For those aged