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Air pollution in Henan province is serious and is significantly impacted by pollution transmission and interactions with surrounding areas. The emission sources in 18 cities in Henan province were labeled and applied to the WRF-CMAQ traceability model for simulation in January, April, July, and October of 2017. The pollutant distribution results showed that due to the combined influence of emissions and meteorology, the concentrations of PM 2.5 , NO 2 , and SO 2 in Henan province were the highest in winter and the lowest in summer. The seasonal variation in O 3 -8h concentration was the highest in summer, followed by spring, and the lowest in winter. There was a large difference in pollutant concentrations between different seasons. The average concentrations of PM 2.5 , NO 2 , and SO 2 in winter in Henan province were 4.17, 4.12, and 6.24 times those in summer, respectively, whereas the concentration of O 3 -8h in summer was 2.24 times that in winter. Since PM 2.5 , NO 2 , and SO 2 are closely related to primary emissions and have a certain homology, the distributions of high values of these three pollutants were higher in the north and lower in the south, and the seasonal trends were more consistent. The seasonal distribution of O 3 -8h varied widely, with high O 3 -8h values mainly distributed in the northeastern region of Henan province in summer, when meteorological conditions contributed to O 3 production; in winter, spring, and autumn, high O 3 -8h values were mainly distributed in the southern part of Henan province due to the suppression of meteorological conditions and NO x consumption. The results of the study on the transport of pollutants showed that extra-provincial transport and natural sources contributed the most to the concentrations of PM 2.5 , O 3 -8h, NO 2 , and SO 2 in winter, with 36.20%-72.32%, 77.96%-96.08%, 49.45%-78.80%, and 59.05%-88.85%, respectively. When considering only local emissions and intra-provincial transmission, the contributions of emissions to local concentrations of the four pollutants in summer were the highest in all cities of Henan province. The contributions of intra-provincial transmission to PM 2.5 and O 3 -8h in spring were the largest, with 25.63%-74.69% and 30.21%-80.01%, respectively, and the contributions of intra-provincial transmission to NO 2 and SO 2 in winter were larger, with 26.02%-76.96% and 20.30%-82.34%. The transmission paths of PM 2.5 , NO 2 , and SO 2 were more similar in Henan province, with more transmission from north to south in winter, from west to east and southwest to northeast in spring, from southwest to northeast in summer, and from north to south in autumn; however, the transmission of PM 2.5 was more complicated. The O 3 -8h transport path was more different from the others, especially in autumn when pollutants were mostly transported from north to south, but the O 3 -8h transport path from southwest to northeast was obvious.

The aims of the study were to present the prevalence of dental service utilization among adults (age between 18 and 65) in Chinese megacities and to examine the associations of health insurance and city of residence with dental visits. This study was a cross-sectional analysis of the 2019 New Era and Living Conditions in Megacities Survey data with a sample of 4835 participants aged 18-65 from 10 different megacities in China. The data including gross domestic product (GDP) per capita of each megacity obtained from the National Bureau of Statistics of China as a city-level characteristic. After adjusting sampling weights, approximately 24.28% of the participants had at least one dental visit per year. Findings from multilevel mixed-effects linear models showed that participants residing in megacities with higher GDP per capita (β = 0.07, p < 0.001) who had Urban Employee Basic Medical Insurance (β = 0.25, p < 0.001) or Urban Resident Basic Medical Insurance (β = 0.19, p < 0.01) had more frequent dental visits after adjusting demographic characteristics, socioeconomic status, health status, health behavior and attitude, and oral health indicators. Margins post-estimation model results demonstrated disparities in the predicted probability of having never visited a dentist by types of health insurance and city of residence. In conclusion, the prevalence of dental visits in China was found to be low. This study highlights socioeconomic inequalities in dental service utilization. There is a great need to develop more dental care programs and services and expand health insurance to cover dental care in China.