Effects of outdoor air pollution on hospital admissions from cardiovascular diseases in the capital city of Mongolia

Cardiovascular diseases (CVD) are one of the primary causes of morbidity worldwide, while ambient air pollution (AAP) is a major contributor to CVD. This study is the first study that aimed to compare the differences in AAP concentrations and acute effects on the risk of admissions from CVD, ischaemic heart diseases (IHD), and stroke before and after introducing the new type of coal briquette in Ulaanbaatar, Mongolia. We collected daily hospital admission records, air quality and meteorology data between January 1, 2016 and December 31, 2022. The relative risks (RRs) of cause-specific hospitalisations associated with daily concentrations of AAP were estimated by a time-stratified case-crossover analysis with conditional Poisson distributed lag models. Overall, acute exposure to the pollutants, except for O 3 , was positively associated with an increased risk of all admissions. For each interquartile range (IQR) increase in PM 2.5 , PM 10 , SO 2 , NO 2 and CO, the risk of CVD admissions increased by 0.5% (RR = 1.005; 95% CI: 0.998, 1.012) at lag0, 2.9% (RR = 1.029; 95% CI: 1.014, 1.044), 2.5% (RR = 1.025; 95% CI: 1.010, 1.040), 4.1% (RR = 1.041; 95% CI: 1.016, 1.068) and 0.3% (RR = 1.003; 95% CI: 0.995, 1.012) at lag01, respectively. Subgroup analyses showed greater risks of CVD admissions for women and people aged <65 years, in the cold season, and after the raw coal ban period. During the cold winter season, Ulaanbaatar's AAP levels remained higher than the World Health Organization's guidelines, regardless of consuming the new coal briquettes. Adopting alternative efficient methods to improve air quality and associated health outcomes is necessary. • Overall, acute exposure to the criteria air pollutants, except for O 3 , was positively associated with an increased risk of all admissions. • PM 10 , SO 2 and NO 2 pollutants consistently showed the most elevated effects on admissions from CVD and stroke. • Subgroup analyses revealed that women, those aged <65 years, during the cold season and after consuming the new types of coal briquette had a higher risk of CVD admissions.