IAQ relationship to human health

From Indoor Air Quality Wiki
Revision as of 14:12, 16 September 2026 by Ular.palmiste (talk | contribs)

Air stands as a fundamental life-building element, and the quality of indoor air in settings like homes, schools, public structures, healthcare facilities, and private residences plays a pivotal role in people's well-being and overall health.[1] Modern populations in developed nations spend up to 90% of their time indoors, with roughly 70% of that time spent inside domestic home environments.[2][3] Globally, household air pollution caused an estimated loss of 86 million healthy life years (DALYs) in 2019, with the heaviest burden borne by women and children in low- and middle-income nations.[4] An estimated 3.2 million premature deaths annually are attributed to household air pollution resulting from incomplete fuel combustion and indoor pollutants, including over 237,000 deaths of children under five years of age.[4]

In the European Union, ambient and indoor air pollution represents the foremost environmental health concern, causing approximately 400,000 premature deaths each year.[5][6] Impaired indoor air quality (IAQ) is responsible for the annual loss of an estimated 2 million disability-adjusted life years across the EU.[5][7] Poor indoor air quality is directly linked to a broad spectrum of acute and chronic disorders, including asthma, chronic obstructive pulmonary disease (COPD), cardiovascular disease, stroke, cognitive decline, and lung cancer.[8][9][2]

How indoor air pollution affects people

The concept of exposure

Both short-term and long-term exposure to indoor air pollution can give rise to severe health complications:

  • Short-term exposure triggers immediate physiological reactions, including sensory irritation of the eyes, nose, and throat, as well as headaches, dizziness, nausea, and acute fatigue.[10] While often transient, acute exposures can provoke life-threatening bronchoconstriction in individuals with pre-existing respiratory conditions like asthma.[1][2]
  • Long-term exposure occurs through sustained or repeated inhalation of particulate matter, chemical compounds, and bioaerosols over months or years.[11] Chronic inhalation leads to persistent airway inflammation, systemic oxidative stress, impaired cellular immune responses, reduced oxygen delivery, DNA damage, and epigenetic modifications.[2][12] Over time, these pathological alterations culminate in chronic respiratory ailments, cardiovascular degeneration, and malignant neoplasms.[11][13]

Susceptibility to indoor air pollution

Indoor air pollution affects occupants heterogeneously. Susceptibility depends on pollutant toxicity, concentration, exposure duration, and individual biological and social factors.[10][2] Specific population groups exhibit significantly elevated vulnerability:

Women

In many domestic settings, women experience disproportionately high exposure to combustion by-products generated during cooking and domestic heating.[4] Household air pollution exposure during pregnancy is associated with adverse maternal outcomes and abnormal fetal lung development.[14] Prenatal exposure to particulate matter and toxic gases significantly elevates the risk of low birth weight, intrauterine growth retardation, preterm delivery, and infant pneumonia during the first year of life.[4][2]

Children

Infographic on children's exposure to air pollution [15]

Children represent an exceptionally vulnerable group due to unique anatomical and behavioural factors:

  • Children breathe faster than adults and inhale significantly higher air volumes relative to their body weight.[15][16]
  • Their respiratory, immune, and central nervous systems are still actively developing, making cellular tissues highly susceptible to toxic injury and disruption.[15]
  • Children spend substantial time near floor level, where pollutant concentrations, resuspended dust, and semi-volatile compounds accumulate.[13]

Studies demonstrate pronounced vulnerability to environmental tobacco smoke, traffic-derived particulate matter, nitrogen dioxide, and indoor allergens.[10][17] Research from the EDIAQI project underscores clear dose-response relationships: for every 10 µg/m³ increase in indoor coarse particulate matter (PM2.5-PM10), children experience a 6% increase in symptom days involving wheezing, coughing, or chest tightness.[2] Similarly, each 10 µg/m³ increase in indoor fine particles (PM2.5) is linked to a 7% increase in days with severe wheezing and a 4% increase in days requiring rescue medication use.[2] Globally, nearly half of all fatal lower respiratory infections in children under five are caused by inhaling particulate matter from household pollution.[4]

Elderly

Older adults experience heightened vulnerability to indoor air pollution due to age-related physiological decline, including reduced mucociliary clearance, diminished renal and hepatic chemical clearance capacities, and pre-existing cardiovascular or pulmonary diseases.[10] Chronic exposure to fine particulate matter and combustion gases Chemistry impairs myocardial function, accelerates vascular stiffness, worsens chronic obstructive pulmonary disease, and accelerates cognitive impairment.[18][5]

Individuals with pre-existing conditions

Individuals diagnosed with chronic respiratory conditions (such as asthma, chronic bronchitis, and COPD) and cardiovascular disorders have compromised physiological reserves.[19] In patients with asthma, exposure to low levels of nitrogen dioxide (NO2) from gas cookers, volatile organic compounds (VOCs), or formaldehyde prompts bronchial hyperreactivity and airway remodeling.[1][20] Furthermore, particulate matter exposure induces systemic vascular inflammation and plaque instability, dramatically increasing the acute risk of myocardial infarction and stroke in cardiac patients.[21][22]

Socioeconomically disadvantaged households

Socioeconomic status strongly modulates indoor environmental risks across Europe.[23][24] Low-income households frequently experience fuel poverty and reside in substandard housing characterized by inadequate insulation, structural dampness, and visible mold growth.[5] These residences often lack effective mechanical ventilation, rely on inefficient solid fuel or gas space heaters, and are located closer to high-traffic motorways and industrial installations.[5][13] The convergence of elevated environmental exposures and limited healthcare access creates severe health inequities across the European building stock.[23]

Health effects of indoor air pollution

Air pollution produces health consequences spanning multiple physiological systems:

  1. Sensory impacts
  2. Cognitive impacts
  3. Acute and allergic respiratory effects
  4. Chronic systemic and cardiovascular effects
  5. Carcinogenic effects
  6. Premature mortality

The full scope of health outcomes associated with complex indoor pollutant mixtures remains active ground for scientific investigation, as interactive cocktail effects and sub-micron particle dynamics are continually uncovered.[2][25]

Sensory impacts

Sensory impacts involve direct stimulation of trigeminal and olfactory nerve endings in the mucous membranes of the eyes, nose, and upper airways.[26] Common manifestations include burning or itching sensations in the eyes, nasal congestion, sinus irritation, throat dryness, hoarseness, and unpleasant odor annoyance.[10] These symptoms are primary drivers of Sick Building Syndrome (SBS), frequently resulting from insufficient outdoor air ventilation, elevated total volatile organic compounds (TVOC), and formaldehyde outgassing from construction materials and adhesives.[27][3]

Cognitive impacts

Elevated indoor air pollutants can directly impair central nervous system function, executive processing, and academic performance:

  • Elevated carbon dioxide (CO2), serving as a proxy for inadequate ventilation and occupant bioeffluents, correlates with drowsiness, diminished concentration, and reduced decision-making speed in school classrooms and offices.[28][29]
  • Exposure to nitric oxide (NO), nitrogen dioxide (NO2), and fine particulate matter is associated with measurable reductions in verbal abilities, attention span, and executive functioning.[10][28]
  • In older populations, long-term exposure to traffic-related particulate matter that infiltrates indoor microenvironments accelerates cognitive decline and increases the risk of neurodegenerative conditions such as Alzheimer's disease.[18][5]

Acute and allergic respiratory effects

Short-term exposures induce acute illnesses and exacerbate chronic allergic diseases:

  • Asthma exacerbation: Indoor particulate matter (PM2.5 and PM10), nitrogen dioxide from unvented gas appliances, and second-hand tobacco smoke directly aggravate asthma symptoms, increasing emergency department admissions.[20][30] Second-hand tobacco smoke aggravates asthma by shifting the balance of regulatory T cells (Treg) and T helper 17 (Th17) cells towards a Th17 profile, characteristic of severe, corticosteroid-resistant asthma.[2]
  • Moisture and Biological Agents: Indoor dampness and mould proliferation increase the risk of respiratory infections, allergic rhinitis, and wheezing by approximately 30% to 50%.[31] Pervasive perennial allergens, such as house dust mite antigens (Der p 1 and Der f 1), trigger high allergenicity, sensitization, and chronic mucosal inflammation.[2][32]
  • Carbon Monoxide (CO) Poisoning: Malfunctioning combustion heating systems can cause acute carbon monoxide toxicity, impairing oxygen transport via carboxyhemoglobin formation and leading to tissue hypoxia, neurological damage, or fatal poisoning.[1]

The Indoor Microbiome and Immune Development

Research within EDIAQI utilizing birth cohorts (such as COPSAC and ATOPICA) demonstrates that indoor dust serves as the primary reservoir for indoor microbial communities.[25][33] The diversity and composition of microbial taxa in domestic dust profoundly shape the infant immune system:

  • High microbial diversity in early-life environments (e.g., farming households and homes with multiple siblings or pets) exerts a protective effect against childhood asthma and atopy.[2][33]
  • Fungal richness in infant bedding dust at 6 months of age is associated with a significantly lower risk of developing asthma and allergic rhinitis by age 6.[34][2]
  • Environmental urbanicity scores show that a rural-imprinted bed dust microbiome provides protection against allergic airway sensitization compared to urbanized microbial environments.[34]

Chronic Systemic and Cardiovascular Effects

Prolonged exposure to indoor air pollutants is a major driver of systemic and vascular disease:

  • Cardiovascular Outcomes: Globally, 32% of premature deaths from household air pollution result from ischaemic heart disease, and 23% stem from stroke.[4] Fine particulate matter (PM2.5) and ultrafine particles enter pulmonary alveoli and cross into the bloodstream, triggering vascular endothelial inflammation, oxidative stress, and platelet activation.[4][2]
  • Ozone and Blood Pressure: Even at concentrations below current WHO air quality guidelines, short-term exposure to indoor and outdoor ozone induces platelet activation, increases arterial blood pressure, and elevates arterial clotting markers in healthy adults.[9][35]
  • Metabolic Disorders: Longitudinal cohort analyses demonstrate that chronic exposure to combustion-derived fine particles and nitrogen oxides disrupts metabolic pathways, elevating systemic biomarkers associated with type 2 diabetes mellitus and metabolic syndrome.[36][5]

Carcinogenic Effects

Multiple indoor air pollutants are classified as Group 1 known human carcinogens by the International Agency for Research on Cancer (IARC):[37]

  • Radon (222Rn): A naturally occurring radioactive gas seeping from soil and bedrock into basements and ground floors. Radon solid decay progeny deposit deep in the tracheobronchial tree, causing alpha radiation damage to cellular DNA. Radon is the second leading cause of lung cancer after tobacco smoking in Europe, prompting EU Council Directive 2013/59/EURATOM to establish a national reference level not exceeding 300 Bq/m³.[38][39]
  • Polycyclic Aromatic Hydrocarbons (PAHs): Emitted by incomplete combustion during cooking, heating, candle use, and ambient infiltration. High molecular weight PAHs (such as benzo[a]pyrene, BaP) bind predominantly to fine and ultrafine particles (PM1 and PM2.5), carrying high mutagenic and carcinogenic potency.[40][13] EDIAQI source apportionment and incremental lifetime cancer risk (ILCR) assessments confirm that although domestic exposure levels typically fall below regulatory danger thresholds, long-term exposure to particle-bound BaP equivalents in poorly ventilated or biomass-heated spaces presents notable carcinogenic risks.[40][13]
  • Volatile Organics and Building Materials: Formaldehyde (Group 1 carcinogen) and benzene emit continuously from particle boards, varnishes, furnishings, and tobacco smoke, elevating long-term risks of nasopharyngeal cancer and leukemia.[1][13] Legacy materials including asbestos and creosote-treated wood represent persistent indoor carcinogenic reservoirs.[1][13]

Emerging Pollutants

Research within EDIAQI focuses on emerging indoor air pollutants whose physical and toxicological dimensions remain under-regulated:

  • PM1 and Ultrafine Particles (UFPs, <100 nm): Emitted during domestic cooking, candle burning, and heating, UFPs possess an exceptionally high surface-area-to-mass ratio.[41][40] They bypass mucosal clearance, reach deep alveolar sacs, and translocate directly across the air-blood barrier into the vascular system and secondary organs.[41][2]
  • Black Carbon (BC): A combustion-derived graphitic particle fraction carrying toxic chemical condensates directly into deep lung tissue, amplifying localized oxidative stress and vascular toxicity.[2][42]
  • Indoor Microplastics: Synthetic textile fibers, furniture erosion, and polymer dust create airborne microplastic exposure (<5 mm). Inhaled microplastics lodge in lung tissue and can release endocrine disruptors, plasticizers, and persistent organic compounds directly to epithelial cells.[43][25]

Cellular Toxicological Mechanisms

The EDIAQI project investigates the biological mechanisms of action (MoA) connecting indoor exposures to clinical endpoints using human biomonitoring, in vitro (2D and 3D cell models), and in vivo models in accordance with 3R principles (Replace, Reduce, Refine):[25][2]

  • Primary DNA Damage: Assessed via the alkaline comet assay, measuring single-strand and double-strand DNA breaks in human alveolar epithelial cells (A549), hepatic spheroids (HepG2), and peripheral blood lymphocytes (PBLs).[25]
  • Genomic Instability: Evaluated via the cytokinesis-block micronucleus (CBMN) assay in peripheral blood lymphocytes and non-invasive exfoliated buccal cells of children, detecting chromosomal breakage, whole chromosome loss, nucleoplasmic bridges, and nuclear buds.[44][25]
  • Histone Phosphorylation (γ-H2AX): Utilizing automated microscopy to identify DNA double-strand break response markers in cellular matrices exposed to complex chemical mixtures.[45][25]
  • Epigenetic Reprogramming: Investigating genome-wide DNA methylation changes that alter immune regulatory gene expression in young children exposed to indoor pollutants.[2][25]

Mortality

At its most extreme, indoor air pollution leads to premature mortality. According to the World Health Organization, of the 3.2 million annual global deaths attributable to household air pollution:

  • 32% result from ischaemic heart disease.[4]
  • 23% result from stroke.[4]
  • 21% result from acute lower respiratory infections.[4]
  • 19% result from chronic obstructive pulmonary disease.[4]
  • 6% result from tracheal, bronchus, and lung cancer.[4]

In the European region alone, exposure to particulate matter in indoor settings shortens the life expectancy of each citizen by nearly one full year on average.[2][5] Integrating source control, advanced air filtration, and continuous sensor-based ventilation monitoring represents an urgent public health priority to protect vulnerable populations throughout Europe.[25][2]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19
  3. ↑ 3.0 3.1
    Halios, C. H., Landeg-Cox, C., Lowther, S. D., Middleton, A., Marczylo, T., & Dimitroulopoulou, S. (2022). Chemicals in European residences–Part I: A review of emissions, concentrations and health effects of volatile organic compounds (VOCs). Science of the Total Environment, 839, 156201.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11
    World Health Organization. (2023, September 26). Household air pollution and health (Fact sheet).
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7
  6. ↑
  7. ↑
    Asikainen, A., Carrer, P., Kephalopoulos, S., de Oliveira Fernandes, E., Wargocki, P., & Hänninen, O. (2016). Reducing burden of disease from residential indoor air exposures in Europe (HEALTHVENT project). Environmental Health, 15(S1), 61-72.
  8. ↑
    European Commission. EU clean air policy.
  9. ↑ 9.0 9.1
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5
    Scientific Committee on Health and Environmental Risks (SCHER). (2008). Opinion on risk assessment on indoor air quality. European Commission, Directorate-General for Health and Consumer Protection, Brussels.
  11. ↑ 11.0 11.1
    González-Caballero, M. C., et al. (2023). Pollution, Indoor Air. In Reference Module in Biomedical Sciences. Elsevier.
  12. ↑
  13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 13.6
  14. ↑
    Šrám, R. J., et al. (2005). Ambient air pollution and pregnancy outcomes: a review of the literature. Environmental Health Perspectives, 113(4), 375-382.
  15. ↑ 15.0 15.1 15.2
    European Environment Agency. (2023). Air pollution and children's health. (Briefing no. 07/2023)
  16. ↑
    Bennett, W. D., & Zeman, K. L. (1998). Deposition of fine particles in children spontaneously breathing at rest. Inhalation Toxicology, 10(9), 831-842.
  17. ↑
  18. ↑ 18.0 18.1
    Ranft, U., et al. (2009). Long-term exposure to traffic-related particulate matter impairs cognitive function in the elderly. Environmental Research, 109(8), 1004-1011.
  19. ↑
    Cincinelli, A., & Martellini, T. (2017). Indoor air quality and health. International Journal of Environmental Research and Public Health, 14(11), 1286.
  20. ↑ 20.0 20.1
    Tiotiu, A. I., et al. (2020). Impact of air pollution on asthma outcomes. International Journal of Environmental Research and Public Health, 17(17), 6212.
  21. ↑
  22. ↑
  23. ↑ 23.0 23.1
    Laurent, É. (2022). Air (ine) quality in the European Union. Current Environmental Health Reports, 9(2), 123-129.
  24. ↑
    WHO Regional Office for Europe. (2019). Environmental health inequalities in Europe: Second assessment report. Copenhagen: WHO Regional Office for Europe.
  25. ↑ 25.0 25.1 25.2 25.3 25.4 25.5 25.6 25.7 25.8
  26. ↑
    Wolkoff, P. (2008). "Healthy" eye in office-like environments. Environment International, 34(8), 1204-1214.
  27. ↑
    Jafari, M. J., et al. (2015). Association of sick building syndrome with indoor air parameters. Tanaffos, 14(1), 55-62.
  28. ↑ 28.0 28.1
    Sadrizadeh, S., Yao, R., Yuan, F., Awbi, H., Bahnfleth, W., Bi, Y., ... & Li, B. (2022). Indoor air quality and health in schools: A critical review for developing the roadmap for the future school environment. Journal of Building Engineering, 57, 104908.
  29. ↑
  30. ↑
  31. ↑
  32. ↑
    Gaffin, J. M., & Phipatanakul, W. (2009). The role of indoor allergens in the development of asthma. Current Opinion in Allergy and Clinical Immunology, 9(2), 128-135.
  33. ↑ 33.0 33.1
  34. ↑ 34.0 34.1
    Lehtimäki, J., et al. (2021). Urbanized microbiota in infants, immune constitution, and later risk of atopic diseases. Journal of Allergy and Clinical Immunology, 148(1), 234-243.
  35. ↑
    Day, D. B., et al. (2017). Association of ozone exposure with cardiorespiratory pathophysiologic features in healthy adults. JAMA Internal Medicine, 177(9), 1344-1353.
  36. ↑
    Nassan, F. L., et al. (2021). Ambient PM2.5 species and ultrafine particle exposure and their differential metabolomic signatures. Environment International, 151, 106447.
  37. ↑
    International Agency for Research on Cancer (IARC). (2013). Outdoor air pollution. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 109. Lyon, France.
  38. ↑
  39. ↑
  40. ↑ 40.0 40.1 40.2
    Lovrić, M., Račić, N., Pehnec, G., Horvat, T., Lovrić Štefiček, M. J., & Jakovljević, I. (2024). Indoor Polycyclic Aromatic Hydrocarbons: Relationship to Ambient Air, Risk Estimation, and Source Apportionment Based on Household Measurements. Atmosphere, 15(12), 1525.
  41. ↑ 41.0 41.1
    Manigrasso, M., Vitali, M., Protano, C., & Avino, P. (2018). Ultrafine particles in domestic environments: Regional doses deposited in the human respiratory system. Environment International, 118, 134-145.
  42. ↑
    Zhao, Y., et al. (2020). Measurement of ultrafine particles and black carbon in indoor residential environments. Atmospheric Environment, 228, 117428.
  43. ↑
    Carreira, L., et al. (2023). Inhalation of indoor microplastics and potential respiratory health hazards. Environmental Pollution, 318, 120890.
  44. ↑
    Bonassi, S., et al. (2021). The micronucleus assay in human lymphocytes as a biomarker of genotoxic risk. Scientific Reports, 11, 16793.
  45. ↑
    Štampar, M., Tomc, J., Filipič, M., & Žegura, B. (2019). Hepatocyte spheroids as an advanced 3D in vitro model for genotoxicity testing. Archives of Toxicology, 93, 3321-3333.
Retrieved from ‘http://206.189.52.199/index.php?title=IAQ_relationship_to_human_health&oldid=1858’