Observational Study of Pollutant Dynamics and Health Risks in Indoor Air Quality across Building Types

IJEP 46(11): 1084-1090 : Vol. 46 Issue 11 (November 2026)

Full Text

H. Ramamohan*, B. Govindarajulu, G. Gowrisankara Rao and B. Umesh

Aditya Institute of Technology and Management, Department of Civil Engineering, Tekkali – 532 201, Andhra Pradesh, India

Abstract

Many initiatives have been undertaken to address the harmful effects of increased indoor air pollutants on public health. This is due to efforts to make homes airtight to improve energy efficiency, which have created buildings with low ventilation rates, resulting in the buildup of indoor air pollutants to harmful levels. This study presents a comparative analysis of indoor air quality (IAQ) across four building typologies (schools, hospitals, offices and residences) using observational measurements of CO, CO2, PM2.5, PM10, formaldehyde and indoor temperature. The study derived a composite indoor health index (IHI) as a normalized sum of pollutant exceedances relative to World Health Organization (WHO) guidelines and applied random forest regression with leave-one-out cross-validation to identify predictors of health risk. Results show pervasive exceedances of WHO limits, as classrooms had mean CO2 »1932 ppm, hospitals recorded PM2.5 »342.5 mg/m³, offices exhibited elevated CO (»34.6 ppm) and residences showed very high formaldehyde (»16.4 ppm). The random forest model (LOOCV R² »0.99) identified PM2.5 and CO2 as dominant contributors to the IHI. This cross-building, multipollutant analysis highlights building-specific pollutant signatures and emphasizes the need for targeted mitigation strategies, including ventilation upgrades, source control and continuous monitoring, to protect occupant health. Hence, the present study offers thorough information on the various air pollutants in a crucial indoor setting, which will further aid researchers in the field to identify and mitigate them more precisely.

Keywords

Indoor air quality, PM2.5, CO2, Health risk index, Ventilation, Formaldehyde

References

  1. WHO. 2021. WHO global air quality guidelines: Particulate matter (PM2.5and PM10), ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide. World Health Organization, Geneva.
  2. Allen, J. G., MacNaughton, P., Satish, U., Santanam, S., Vallarino, J. and Spengler, J.D. 2016. Associations of cognitive function scores with carbon dioxide, ventilation and volatile organic compound exposures in office workers. Env. Health Perspectives. 124(6): 805–812. DOI: 10.1289/ehp.1510 037.
  3. Young, A.S., Parikh, S., Dedesko, S., Bliss, M., Xu, J., Zanobetti, A., Miller, S.L. and Allen, J.G. 2024. Home indoor air quality and cognitive function over one year for people working remotely during Covid-19. Building Env., 257: 111551. DOI: 10.1016/j.buildenv.2024.111551.
  4. Burge, P.S. 1992. The sick building syndrome: Where are we in 1992? Indoor Env., 1(4): 199–203. DOI: 10.1159/000463443.
  5. Burge, P.S. 2004. Sick building syndrome. Occupational Env. Medicine. 61(2): 185–190. DOI: 10. 113 6/oem.2003.008813.
  6. Crump, K.S. and Farrar, D.B. 1989. Statistical analysis of data on airborne asbestos levels collected in an EPA survey of public buildings. Regulatory Toxicol. Pharmacol., 10(1): 51–62. DOI: 10.1016/0273-2300(89)90009-7.
  7. Mølhave, L. 2003. Organic compounds as indicators of air pollution. Indoor Air. 13(Suppl. 6): 12–19. DOI: 10.1034/j.1600-0668.13.s.6.2.x.
  8. Patrick, D.L., Burke, L.B., Gwaltney, C.J., Leidy, N.K., Martin, M.L., Molsen, E. and Ring, L. 2011. Content validity—Establishing and reporting the evidence in newly developed patient-reported outcomes (PRO) instruments for medical product evaluation: ISPOR PRO Good Research Practices Task Force report: Part 1—Eliciting concepts for a new PRO instrument. Value Health. 14(8): 967–977. DOI: 10. 1016/j.jval.2011.06.014.
  9. Nie, T., Zhang, G., Sun, Y., Wang, W., Wang, T. and Duan, H. 2025. Effects of indoor air quality on human physiological impact: A review. Build., 15(8): 1296. DOI: 10.3390/buildings15081 296.
  10. Branco, P.T., Silva, V. and Mendes, A. 2024. A review of relevant parameters for assessing indoor air quality in schools. Build. Env., 239: 110497.
  11. Honan, D., Gallagher, J., Garvey, J. and Littlewood, J. 2024. Indoor air quality in naturally ventilated primary schools: A systematic review of the assessment and impacts of CO2levels. Build., 14(12): 4003. DOI: 10.3390/buildings14124003.
  12. Llanos-Jiménez, J., Suárez, R., Alonso, A. and Sendra, J. J. 2024. Objective and subjective indoor air quality and thermal comfort indices: Characterization of mediterranean climate archetypal schools after the Covid-19 pandemic. Indoor Air. 2024: 2456666. DOI: 10.1155/ 2024/2456666.
  13. Santana, E.G.F., Suzuki, E.H., Prado, R.T.A. and Kurokawa, F.A. 2024. Thermal comfort and indoor air quality in hospitals in the subtropics: Analysis of operating rooms and waiting rooms conditions. Indoor Built Env., 33(5). DOI: 10.1177/1420326X2 31224654.
  14. Garcia, A., Saez, Y., Harris, I., Huang, X. and Collado, E. 2025. Advancements in air quality monitoring: A systematic review of IoT-based air quality monitoring and AI technologies. Artificial Intelligence Review. 58(9): 275. DOI: 10.1007/s10462-025-11277-9.
  15. Dai, X., Shang, W., Liu, J., Xue, M. and Wang, C. 2023. Achieving better indoor air quality with IoT systems for future buildings: Opportunities and challenges. Sci. Total Env., 895: 164858. DOI: 10.1016/j.scito-tenv.2023.164858.
  16. Amaripadath, D., Rahif, R., Velickovic, M. and Attia, S. 2023. A systematic review on role of humidity as an indoor thermal comfort parameter in humid climates. J. Build. Eng., 68: 106039. DOI: 10.101 6/j.jobe.2023.106039.
  17. Norbäck, D., Wieslander, G., Zhang, X. and Zhao, Z. 2011. Respiratory symptoms, perceived air quality and physiological signs in elementary school pupils in relation to displacement and mixing ventilation system: An intervention study. Indoor Air. 21(5): 427–437. DOI: 10.1111/j.1600-0668.2011. 00717.x.
  18. Smedje, G., Mattsson, M. and Walinder, R. 2011. Comparing mixing and displacement ventilation in classrooms: pupils’ perception and health. Indoor Air. 21(6): 454–461. DOI: 10.1111/j.1600-0668. 2011.00725.x.
  19. Yu, C.W. and Crump, D. 2011. Standards for evaluating indoor air. Indoor Built Env., 20(4): 389–392. DOI: 10.1177/1420326X11417330.
  20. Wallace, L.A. 1991. Comparison of risks from outdoor and indoor exposure to toxic chemicals. Env. Health Perspectives. 95: 7–13. DOI: 10.1289/ehp.9 1957.
  21. Chauhan, A.J. and Johnston, S.L. 2003. Air pollution and infection in respiratory illness. British Medical Bulletin. 68(1): 95–112. DOI: 10.1093/bmb/ldg022.
  22. Deng, Z., Chen, W. and Liu, S. 2024. Impact of indoor air quality and multi-domain factors on occupant productivity and well-being: A review. J. Build. Eng., 78: 104908. DOI: 10.1016/j. jobe.2024.104 908.
  23. Baeza-Romero, M.T., Ávila-López, A. and García-García, A. 2022. A review of critical residential building parameters and indoor air quality. Sci. Total Env., 801: 149884. DOI: 10.1016/j. scitotenv.2021.149884.
  24. Williams, A., Davies, B. and Parker, L. 2024. Indoor air quality perceptions and attitudes towards health risk: A mixed-methods study. Int. J. Env. Res. Public Health. 21(5): 3002.
  25. Altmann, A., Tolosi, L., Sander, O. and Lengauer, T. 2010. Permutation importance: a corrected feature importance measure. Bioinformatics. 26(10): 1340–1347. DOI: 10.1093/bioinformatics/ btq134.
  26. ASHRAE. 2019. ANSI/ASHRAE standard 62.1-2019: Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, Georgia, USA.
  27. Salthammer, T., Zhang, Y. and Mo, J. 2021. Assessing human exposure to SVOCs in materials, products and indoor air: A critical review. Indoor Air. 31(5): 1192–1214. DOI: 10.1111/ina. 12800.
  28. Satish, U., Mendell, M.J., Shekhar, K., Hotchi, T., Sullivan, D., Streufert, S. and Fisk, W.J. 2012. Is CO an indoor pollutant? Direct effects of low-to-moderate CO concentrations on human decision-making performance. Env. Health Perspectives. 120(12): 1671–1677. DOI: 10.1289/ ehp.11047 89.
  29. Zhang, Y., Mo, J. and Weschler, C.J. 2022. Reducing health risks from indoor exposures in hospitals: Insights from particulate matter and ventilation studies. Indoor Air. 32(3): e12990. DOI: 10.1111/ina. 12990.
  30. Salthammer, T., Mentese, S. and Marutzky, R. 2010. Formaldehyde in the indoor environment. Chem. Reviews. 110(4): 2536–2572. DOI: 10.10 21/cr800399g.
  31. Chojer, H., Branco, P.T.B.S., Martins, F.G., Alvim-Ferraz, M.C.M. and Sousa, S.I.V. 2024. Source identification and mitigation of indoor air pollution using monitoring data – Current trends. Env. Tech. Innovation. 30: 103534. DOI: 10.1016/j.eti.2024. 103 534.
  32. Amin, M., Bachtiar, V.S., Hanami, Z.A. and Hustim, M. 2025. Characterization of particulate matter in indoor air from cooking activities in rural Indonesian households. Atmos., 16(10): 1124. DOI: 10.3 390/atmos16101124.