Association of short-term exposure to ambient carbon monoxide with hospital admissions in China

Abstract

Evidence on the acute effects of ambient carbon monoxide (CO) pollution on morbidity risk in developing countries is scarce and inconsistent. We conducted a multicity case-crossover study in 26 largest cities in China from January, 2014 to December, 2015 to examine the association between short-term exposure to CO and daily hospital admission. We fitted conditional logistic regression to obtain effect estimates of the associations. We also performed subset analyses to explore the health effects of CO at low levels. During the study period, a total of 14,569,622, 2,008,786 and 916,388 all-cause, cardiovascular and respiratory admissions were identified, respectively. A 1 mg/m3 increase in the CO concentrations corresponded to a 3.75% (95% CI, 3.63–3.87%), 4.39% (95% CI, 4.07–4.70%), and 4.44% (95% CI, 3.97–4.92%) increase in all-cause, cardiovascular, and respiratory admissions on the same day, respectively. The associations were robust to controlling for criteria co-pollutants. In subset analyses, negative effects of short-term CO exposure on hospital admission were observed at lower concentrations (<1 mg/m3), while positive effects were observed at higher concentrations (>2 mg/m3). In conclusion, current CO levels in China were significantly associated with increased daily hospital admissions.

Effects of ambient carbon monoxide on daily hospitalizations for cardiovascular disease: a time-stratified case-crossover study of 460,938 cases in Beijing, China from 2013 to 2017

“…Moreover, associations between ambient CO and cardiovascular mortality had further been confirmed in a nationwide time-series analysis in 272 cities in China [ 7 ] and in the China Air Pollution and Health Effects Study (CAPES) [ 13 ]. Our results were consistent with previous studies performed in different Chinese cities [ 7 , 13 , 14 , 35 ] that reported a significant CO exposure effect on lag 0 and lag 1 day, and a maximum CO exposure effect on lag 0–1 day. Another recent study conducted in Beijing showed similar findings compared to our results [ 36 ].…”

“…PCA is a multivariate method and has been applied in various multipollutant studies. Our current findings were consistent with those of previous studies exploring the association between CO exposure and the risk of hospital admissions for CVD after adjusting for PM 2.5 , NO 2 , SO 2 and O 3 [ 7 , 14 ].…”

“…The exposure-response relationship was approximately linear and there was no noticeable threshold effect below which CO exposure had no effects on cardiovascular hospitalizations in the current analysis, which was in accordance with other findings in previous studies [ 7 , 13 ]. However, a multicity study in the 26 largest cities in China showed a negative effect of CO exposure on total CVD admissions observed below 1 mg/m 3 CO concentrations [ 14 ], which was also observed in our study. Therefore, further studies are necessary to explore the exposure-response relationship curve between CO levels and cardiovascular admissions.…”

“…The adverse health effects of ambient CO exposure on cardiovascular mortality has been reported in multi-city analyses in China [ 7 , 13 ]. To the best of our knowledge, only one multi-city study conducted in China examined the short-term effects of ambient CO on CVD hospital admissions [ 14 ]. This study showed that a 1 mg/m 3 increase in CO concentrations was associated with a 4.4% increase in CVD hospital admissions [ 14 ].…”

“…To the best of our knowledge, only one multi-city study conducted in China examined the short-term effects of ambient CO on CVD hospital admissions [ 14 ]. This study showed that a 1 mg/m 3 increase in CO concentrations was associated with a 4.4% increase in CVD hospital admissions [ 14 ]. However, the short-term effects of ambient CO exposure on cause-specific CVD hospitalizations in China remain unknown.…”