Background: Although childhood cancer accounts for a small percentage of total cancer cases globally, it remains a critical public health issue. Studying the incidence of childhood and adolescent cancer in Ulaanbaatar, where nearly half of Mongolia's population resides, is essential for improving diagnosis and treatment quality. Objective: To investigate the patterns and trends of new childhood and adolescent cancer cases in Ulaanbaatar from 2015 to 2024. Material and Method: A descriptive cross-sectional study was conducted. Based on statistical data from the Center for Health Development, incidence rates per 100,000 population were calculated and analyzed using STATA 14.2 software. Results: A total of 516 new cases were recorded during the study period, with an average incidence rate of 9.0 per 100,000 population. The incidence increased by 35.2%, rising from 8.8 in 2015 to 11.9 in 2022. Regarding cancer types, hematological and lymphoid malignancies dominated (50%). The highest incidence was observed in the 0–4 age group (12.5). The male-to-female ratio was 1.4, showing a male predominance. By district, the highest overall incidence rates were observed in Bayangol (10.3 per 100,000), Songinokhairkhan (9.6), and Bayanzurkh (9.4), while the lowest rates were observed in Nalaikh (4.7) and Bagakhangai (0.0). Conclusion The incidence of childhood cancer in Ulaanbaatar has shown an increasing trend over the last decade. The patterns of cancer types, age, and sex distribution are consistent with international and Asian regional trends.

Background: The capital city of Mongolia, Ulaanbaatar is not only one of the coldest capitals in the world but has also become one of the most polluted cities in recent years due to the prolonged effects of severe cold. According to the World Health Organization (WHO), the most harmful air pollutant to human health is PM2.5. These fine particulate matters can penetrate the human body through the respiratory tract, causing various changes in the body and the oral cavity. Aim: Relationship between dental caries, gingivitis and periodontal status and PM2.5 air pollutant levels among 12 years old children in different areas of Ulaanbaatar. Materials and Methods: The study population consisted of 190 children aged 12 years old, who were selected from high and low level areas with air pollutant PM2.5 in Ulaanbaatar city, Mongolia. We obtained informed consent No.24-25/10-1 of the Ethical Committee, MNUMS. The oral examination of every child was done according to WHO recommendation (2013). We determined the prevalence of dental caries and mean DMFT score, and the prevalence of gingivitis, and CAL score. Statistical analysis was done by the SPSS 29 software. Results: The prevalence and mean DMF/t score of dental caries were 96% аnd 5.37±2.75 among children living in the high level area of the PM2.5 air pollutant; and 91% and 5.39±3.95 in the low level area, respectively (p<0.01). The prevalence of gingivitis was 23.2% among all children; 25.2% among children living in the high level area of the PM2.5 air pollutant and 20.5% in the low level area. The CAL score was 1.89±0.89 mm in the high polluted area and 1.94±0.77 mm in the low polluted area (p<0.001). Conclusion The prevalence of dental caries and gingivitis and the mean DMFT and CAL score among children living in air polluted areas were higher than low polluted areas.