{ "abstract": "Childhood pneumonia is a major public health issue in Mongolia and other low- and middle-income countries (LMIC). Identifying modifiable environmental risk factors and vulnerable populations is essential for developing effective prevention strategies. We investigated whether short-term exposure to ambient air pollutants was associated with daily outpatient visits for pneumonia among children under 5 years of age in Ulaanbaatar, Mongolia, and assessed whether age and sex modified these associations. We conducted a time-series analysis from 2014 to 2019 using daily outpatient visits for pneumonia among children under 5 years of age and daily concentrations of particulate matter with an aerodynamic diameter ≤2.5 μm (PM2.5), particulate matter with an aerodynamic diameter ≤1 μm (PM1), particulate matter with an aerodynamic diameter ≤10 μm (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3)in Ulaanbaatar. Associations between ambient air pollutants and daily pneumonia outpatient visits were estimated using generalized additive models (GAMs) with a quasi-Poisson distribution. The models estimated relative risks (RRs) per interquartile range (IQR) increase in pollutant concentrations while adjusting for long-term trends, seasonality, temperature, humidity, day of the week (DOW), holidays, and raw coal ban policy. We examined pollutant effects across different lag periods, assessed effect modification by age and sex, and evaluated the robustness of associations using multi-pollutant models. A total of 48,488 outpatient visits for pneumonia were recorded. At lag day 2, each IQR increase in pollutant concentration was associated with an increased risk of outpatient visits: PM2.5 [RR =1.057; 95% confidence interval (CI): 1.015-1.100], PM1 (1.065; 1.025-1.106), SO2 (1.136; 1.023-1.261), and NO2 (1.383; 1.108-1.726). PM10 and O3 showed positive but non-significant associations. We observed effects based on age and sex where infants under 1 year old demonstrated significant effect on pneumonia outpatient visits at lag day 0 for NO2 (RR =1.565; 95% CI: 1.161-2.110) and PM1 (RR =1.098; 95% CI: 1.046-1.152) and male exhibited a greater effect size for PM2.5, PM1 and NO2. In multi-pollutant models, PM2.5 and NO2 remained positively associated with pneumonia outpatient visits after adjustment for co-pollutants, whereas the associations for PM1 were attenuated. Short-term exposure to ambient air pollution, particularly NO2, PM1, SO2 and PM2.5, was associated with increased risk of daily outpatient visits for clinically diagnosed pneumonia among children under 5 years of age in Ulaanbaatar. The consistency of PM2.5 and NO2 associations in multi-pollutant models suggests that these pollutants may represent important independent contributors to childhood pneumonia risk. Boys and infants appeared to be more susceptible, highlighting vulnerable populations that may benefit from targeted air pollution mitigation strategies.", "abstract_shown": true, "affiliations": [ "School of Public Health, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.", "Nicholas School of the Environment, Duke University, Durham, NC, USA.", "Department of Medicine, Division of Infectious Diseases, University of Texas Medical Branch, Galveston, TX, USA.", "Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.", "School of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, Duke University, Durham, NC, USA.", "Global Health Institute, Duke University, Durham, NC, USA." ], "article_type": "research article", "arxiv": null, "author_total": 9, "authors": [ { "affs": [ 0 ], "name": "Oyu Tsogtbayar", "orcid": "0000-0003-3836-1787" }, { "affs": [ 0 ], "name": "Batzorig Bayartsogt", "orcid": "0000-0001-7697-394X" }, { "affs": [ 1 ], "name": "Yihui Ge", "orcid": "0000-0002-8115-5949" }, { "affs": [ 0 ], "name": "Ser-Od Khuyagaa", "orcid": "0000-0002-8778-317X" }, { "affs": [ 2 ], "name": "Gregory C Gray", "orcid": "0000-0002-4628-5908" }, { "affs": [ 3 ], "name": "Damdindorj Boldbaatar", "orcid": "0000-0002-0925-9823" }, { "affs": [ 4 ], "name": "Robert M Tighe", "orcid": "0000-0002-3465-9861" }, { "affs": [ 1, 5 ], "name": "Junfeng Jim Zhang", "orcid": "0000-0003-3759-6672" }, { "affs": [ 0 ], "name": "Davaalkham Dambadarjaa", "orcid": "0000-0001-6999-9367" } ], "bibtex": "https://research.draconitic.com/paper/bx7nnvx3h01w1.bib", "cited_by": 0, "doi": "10.21037/jtd-2026-1940", "fulltext_url": "https://europepmc.org/articles/PMC13740698", "id": "bx7nnvx3h01w1", "issns": [ "2072-1439", "2077-6624" ], "landing_url": "https://europepmc.org/article/MED/42996647", "language": "eng", "licence": "CC-BY-NC-ND", "licence_label": "CC BY-NC-ND", "licence_source": "article", "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/", "metadata_licence": null, "native_subjects": [ [ "openalex", "2307|Air Quality and Health Impacts" ] ], "openalex": "W7223555729", "pdf_url": "https://europepmc.org/articles/PMC13740698?pdf=render", "pmcid": "PMC13740698", "pmid": "42996647", "published": "2026-10-19", "publisher": null, "ris": "https://research.draconitic.com/paper/bx7nnvx3h01w1.ris", "sources": [ { "first_seen": "2026-11-09T15:20:41Z", "native_id": "MED:42996647", "source": "europepmc", "url": "https://europepmc.org/article/MED/42996647" } ], "subjects": [ { "field": "medicine", "origin": "openalex:2307|Air Quality and Health Impacts", "subfield": "pharmacology-toxicology" } ], "title": "Associations between air pollution and pediatric pneumonia incidence in Ulaanbaatar, Mongolia: age and sex susceptibility.", "title_text": "Associations between air pollution and pediatric pneumonia incidence in Ulaanbaatar, Mongolia: age and sex susceptibility.", "type": "peer-reviewed", "updated_at": "2026-11-09T15:20:41Z", "url": "https://research.draconitic.com/paper/bx7nnvx3h01w1", "venue": "Journal of thoracic disease", "versions": [] }