Open research questions in Air Quality and Health Impacts

What the literature leaves open

• 407 Rozelin Aydın, Emine Su Turan, Esra Turhan / Volume:12 ∙ Issue:2 ∙ July 2026 The empirical scope is limited to air quality monitoring measurements and data completeness metrics.

  Integrated Assessment of Air Pollution Sources, Public Health Impacts, and Data Gaps in Adana Province: Evidence-Based Policy Interventions · 2026 · DOI

• Future research should focus on long-term agricultural impact quantification, comprehensive health impact assessment of exposed populations, seasonal variation analysis of emission patterns, and development of real-time emission control systems that respond dynamically to meteorological conditions.

  Modeling the dispersion of quarry particulate matter in Sakarya, Türkiye using AERMOD: impacts on agriculture and the environment · 2026 · DOI

• Long-term ground-based observations, size-resolved measurements, chemical characterization, and human health analyses affected by PM remain scarce in this region.

  Ambient particulate matter in Saudi Arabia (1980–2025): spatiotemporal patterns, source dynamics, and strategic research priorities · 2026 · DOI

• Abstract Volatile chemical products (VCPs) have been recognized as significant sources of reactive organic gases (ROGs) in urban environments, yet emissions from household VCPs (HVCPs, including personal care products, cleaners, and insecticides) and their air quality impacts remain poorly characterized in China.

  Household Volatile Chemical Product Emissions and Modeled Air Quality Impacts in Shanghai, China · 2026 · DOI

• Future investigations could explore alternative methodological frameworks for hourly and daily mixed-frequency data. The key limitation of this study 498 include the model constraint where the lag-response relationship for current modelling 499 500 framework may not be able to capture the hourly lag individually, further advancement can be done using alternative modelling framework. 23 In addition, one limitation is that the 501 model was tested using only a single exposure–response pair, highlighting important 502 challenges related to validation and generalizability. The MIDAS touch: Mixed data sampling regression models.

  Mixed-Frequency Regression Model for Short-Term Environmental Exposure-Response Modelling: A Simulation Study · 2026 · DOI

• Air quality monitoring infrastructure remains sparse relative to other world regions, constraining both the precision of exposure assessment and the capacity of governments to design and enforce effective mitigation policy.

  The Impact of Air Pollution on Human Health in Africa: A Critical Narrative Review · 2026 · DOI

• 45 (24 h mean) 15 (24 h mean) 9 (8 h mean) - 25 (24 h mean) 40 (24 h mean) 100 (8 h mean) - - Mean (± SD) 40 ± 17 22 ± 9 0.46 ± 0.05 21 ± 4 41 ± 4 3 ± 0.5 48 ± 16 23 ± 3 47 ± 14 were evaluated. Mice exposed to filtered air (FA) showed preserved pulmonary architecture without evidence of inflammation. Bronchioles and alveolar structures were intact, with well-organized alveolar septa composed of type I and II pneumocytes. In contrast, PM2.5-exposed inflammation, animals exhibited marked pulmonary characterized by perivascular and peribronchial leuko- cyte infiltration, alveolar septal thickening, and epithelial hyperplasia. BAL analysis confirmed these findings, dem- onstrating a significant increase in lymphocyte proportion in the PM2.5 group compared with FA controls (p < 0.05), whereas neutrophil proportions did not differ significantly between groups (Fig. 1). PM2.5-induced maxillae and tongue inflammation independently of experimental periods (30 or 60 days) Regardless of exposure duration (30 or 60 days), histologi- cal alterations were consistently observed across PM2.5- exposed groups. In filtered air (FA)-exposed animals, both tongue and periodontal tissues exhibited preserved histoar- chitecture, including well-defined filiform papillae, intact keratinized stratified epithelium, and organized lamina propria. Gingival and palatal mucosa showed normal mor- phology, with intact periodontal ligament and alveolar bone structure. In contrast, PM2.5 exposure induced marked epithelial and connective tissue alterations in both tissues, including hyperkeratosis, acanthosis, and epithelial disor- ganization, accompanied by lamina propria thickening and focal mononuclear inflammatory infiltrates. Additionally, PM2.5 exposure increased mast cell presence and degranu- lation in periodontal and lingual tissues (Figs. 2 and 3). PM2.5 exposure increased pro-inflammatory cytokine levels at both 30 and 60 days PM2.5 exposure induced a significant increase in pro- inflammatory cytokine levels in both periodontal and tongue tissues. IL-6, TNF-α, CXCL1, and CXCL2 were significantly elevated in PM2.5-exposed animals compared with controls, independently of exposure duration (30 or 60 days) (p < 0.05; Figs. 2 and 3). Effects of PM2.5 exposure on oxidative stress markers PM2.5 exposure induced a significant oxidative imbalance in both evaluated tissues. Activities of antioxidant enzymes (SOD, CAT, and GPx) were significantly reduced in peri- odontal and tongue tissues (p < 0.05 or p < 0.01, depending on marker), whereas levels of TBARS (MDA equivalents) 1 3Air Quality, Atmosphere & Health (2026) 19:122 Page 7 of 15 122 Fig. 1 Photomicrographs of lung tissue and bronchoalveolar lavage analysis. (A) Representative photomicrographs of lung parenchyma (H&E staining) of mice exposed to polluted air (CAP) or filtered air (FA) for 30 or 60 days (20x and 40x magnification). (B) Results are expressed as mean values ± standard deviation, indicating the percent- age of macrophages, neutrophils, and lymphocytes. Note: *p < 0.05 when compared to filtered air (FA) groups were significantly increased (p < 0.05), indicating enhanced lipid peroxidation (Fig. 4). Effect of PM2.5 on LPS-induced periodontal inflammation In FA-exposed animals, LPS administration induced classi- cal features of periodontal inflammation, including epithe- lial disruption, inflammatory cell infiltration, and alveolar bone resorption. Control animals (FA + vehicle), subjected to identical handling and injection procedures but receiv- ing sterile saline instead of LPS, exhibited minimal inflam- matory changes, preserved gingival morphology, and no significant alveolar bone loss, confirming that periodontal breakdown in LPS-treated groups was attributable to LPS- specific inflammatory stimulation rather than procedural stress. In contrast, prior PM2.5 exposure significantly exac- erbated LPS-induced periodontal damage. Histological analysis revealed increased inflammatory cell infiltration, particularly lymphocytes, as well as enhanced osteoclast activity in resorption lacunae. Micro-CT analysis confirmed greater alveolar bone loss in the PM2.5 + LPS group, evi- denced by a significant reduction in BV/TV compared with LPS + FA controls (p < 0.05). This exacerbated response was associated with increased TNF-α, CXCL1, and CXCL2 lev- els, reduced antioxidant enzyme activity (SOD, CAT, GPx), and increased lipid peroxidation (TBARS) in periodontal tissues (Fig. 5).

  PM2.5 exposure induces oral tissue alterations and exacerbates experimental periodontitis via oxidative stress and mast cell activation · 2026 · DOI

• This study has certain limitations. First, as an observational epi- demiological cohort, this study cannot establish causality. Despite the application of rigorous restricted cubic spline (RCS) models and tem- poral decomposition analysis, we cannot directly confirm the micro- causal mechanisms underlying the 8.5 μg/m3 concentration inflection point, and any proposed biological pathways discussed herein remain purely speculative. Future research must integrate toxicology or multi- omics technologies to further investigate the potential pathways through which long-term, low-dose SO2 exposure affects the airway immune microenvironment. Second, the validity of our air pollution exposure measurement warrants careful consideration. Our assessment relies on residential geospatial data at a 1 km resolution. While this provides robust ambi- ent estimates, it cannot perfectly represent true individual-level inha- lation doses, as it inherently does not account for children’s specific mobility patterns, the significant proportion of time spent indoors, or complex micro-environmental variations. This gap introduces an inevitable risk of exposure misclassification bias. However, in spatial epidemiology, such misclassification is generally non-differential and typically biases the observed associations toward the null. This sug- gests that the true long-term associations between SO2 and persistent asthma risk could potentially be even more pronounced than our models indicate. Furthermore, due to this macro-environmental mea- surement limitation, the observed 8.5 μg/m3 inflection point should not be interpreted as a precise individual biological threshold, but rather as an ambient public health reference level. The lack of individ- ual-level monitoring via GPS trajectories or wearable sensors also means our earlier discussion regarding particulate-induced avoidance behaviors is presented strictly as a hypothesis. Third, our study may not have fully accounted for uncontrolled confounders, such as indoor air quality, maternal smoking, in-utero tobacco exposure, and the baseline phenotypic heterogeneity since children with established asthma were not excluded. Finally, this study cohort is predominantly concentrated in southwestern China. The specific geographical and climatic characteristics, as well as the emission structure of this region, may affect the generalizability of the findings. Future external validation of this reference concentration is required in cohorts with broader geographical and climatic heterogeneity.

  Environmental safety thresholds for children with asthma symptoms: a prospective study of multitemporal air pollution exposure and longitudinal trajectories · 2026 · DOI

• The relatively small sample size is an important limitation of the present study as it reduces the ability to detect subtle physiological effects or to generalize the findings to broader populations. The lower valid/total ratios observed for some participants and exposure scenarios are another limitation of the present study.

  A chamber study of respiratory and autonomic responses to hydrotreated vegetable oil exhaust using ECG-derived respiration · 2026 · DOI

• This review paper provided insight into the substantial part of microplastics in conjugation with particulate matter on the development and progression of pulmonary cancer. Microplastic contamination in interior environments clearly poses a concerning risk to human health, particularly in relation to lung cancer, according to this detailed review of recent research and evidence. There exist numerous sources of microplastics, ranging from everyday necessities to outdoor pollution and various indoor activities. These microplastics are highly susceptible to becoming airborne and contaminating enclosed spaces, where they can remain suspended in the air. Inhalation of these airborne microplastics leads to their accumulation in the pulmonary system, resulting in persistent exposure and associated health risks. Research has demonstrated that various forms of microplastics when potentially integrated with PM can induce oxidative stress, cellular damage, and inflammation in lung cells upon exposure. These cellular responses can set off a series of cascading processes linked to the initiation and progression of lung cancer, including DNA damage, genomic instability, and alterations in gene expression. The mechanisms underlying the carcinogenic effects of microplastics as well as PM on lung cells have been extensively studied using model organisms and in vitro experiments, shedding light on the intricate pathways through which microplastics contribute to lung carcinogenesis. Even though these studies suggest the development of pulmonary carcinogenesis attributable to microplastic exposure, long-term epidemiological studies in human populations are required to provide definitive proof on lung cancer development. This review signifies the imperative need for precise risk assessment of diverse microplastics from identified and unidentified sources, their complex interactions with other carcinogens, precise transport mechanisms inside the human body, and standardized methodology for microplastic detection. These measures should account for variations in airborne microplastic dispersion influenced by climatic conditions, resulting in a comprehensive understanding of their pulmonary carcinogenic risks. It is essential to acknowledge the complexity of indoor microplastics and how they interact with other environmental elements. The distribution and transportation of microplastics are influenced by fluctuations in climatic conditions, modulating their toxicological profiles.

  Unraveling the Impact of Microplastics and Particulate Matter on Lung Cancer: A Climate Perspective on Air Pollution and Public Health · 2026 · DOI

• Given that patients with VHD carry a substantial risk of cardio- vascular mortality and impose a considerable socioeconomic burden, the determinants of their prognosis remain to be fully 6 Hu X, et al.

  Ambient fine particulate matter exposure and prognosis in patients with valvular heart disease · 2026 · DOI

• Moreover, future research is needed to incorporate compo- nent- and mixture-specific exposure-response relationships in South and Southeast Asia to allow a more comprehensive evaluation of synergistic health effects and further refine the conclusions. 5 exposure remains an important limitation and highlights a priority for future epi- demiological research in South and Southeast Asia.

  Air quality and health benefits achievable by mitigating Indian coal-fired power plant SO2 emissions · 2026 · DOI

• In addition, no standardized method exists for assessing communities close to urban industrial clusters that encircle industrial development regions in the EIA and social impact assessment (SIA) evaluations.

  Framework for Evaluating and Mitigating Industrial Air Pollution in India: Systematic Review of Concepts and Unmet Needs · 2024 · DOI

• ABSTRACT Outdoor air pollution can affect physical labor productivity and mental health, but it remains to be studied how indoor air quality (IAQ) exposure affects working‐age populations' subjective well‐being and physical health.

  Impacts of Indoor Air Quality on Working‐Age Populations' Subjective Well‐Being: Evidence From China Labor Dynamics Survey · 2024 · DOI

• The relationship between dispersion modeling predictions and actual microsphere deposition on urban vegetation leaves has not been validated at multiple sites with concurrent atmospheric measurement and leaf deposition analysis using SEM-EDX characterization. This limits the reliability of using vegetation-based monitoring to verify air quality dispersion models.

  SEM-EDX IDENTIFICATION AND CHARACTERIZATION OF AIRBORNE MICROSPHERES: POTENTIAL EFFECTS ON HUMAN HEALTH · 2023 · DOI

• Car engine air filters have been proposed as useful samplers for ambient airborne microspheres, but standardized protocols for quantitative extraction, preservation, and SEM-EDX analysis of collected particles from filters are absent. Comparability between car engine air filter sampling and direct atmospheric sampling methods is not established.

  SEM-EDX IDENTIFICATION AND CHARACTERIZATION OF AIRBORNE MICROSPHERES: POTENTIAL EFFECTS ON HUMAN HEALTH · 2023 · DOI

• Cell viability effects of airborne ultrafine particles are studied using electron microscopic analysis, but the specific contribution of individual microsphere chemical constituents (identified via EDX) to cytotoxicity and inflammatory responses remains unknown. Dose-response relationships between specific elemental compositions of microspheres and cellular toxicity need establishment.

  SEM-EDX IDENTIFICATION AND CHARACTERIZATION OF AIRBORNE MICROSPHERES: POTENTIAL EFFECTS ON HUMAN HEALTH · 2023 · DOI

• The seasonal variation in heavy metal concentrations within airborne PM2.5 is documented, but temporal dynamics of microsphere morphology, size distribution, and elemental composition (via SEM-EDX) across seasons in the same urban-industrial location have not been systematically characterized. Source apportionment of microspheres from diesel engines versus combustion versus mineral sources requires multi-season data.

  SEM-EDX IDENTIFICATION AND CHARACTERIZATION OF AIRBORNE MICROSPHERES: POTENTIAL EFFECTS ON HUMAN HEALTH · 2023 · DOI

• While leaf microstructures of woody species are documented as PM-capturing surfaces, there is no quantitative correlation between specific leaf traits (surface roughness, trichome density, hydrophobicity) and their efficacy in capturing microspheres of different sizes and chemical compositions using SEM-EDX analysis. This limits the application of vegetation as passive biomonitors for airborne microsphere deposition.

  SEM-EDX IDENTIFICATION AND CHARACTERIZATION OF AIRBORNE MICROSPHERES: POTENTIAL EFFECTS ON HUMAN HEALTH · 2023 · DOI

• The paper establishes that aluminum is present in airborne microspheres and has been linked to neurodegenerative diseases, but there is no direct mechanistic study comparing aluminum concentrations in airborne particulates with aluminum levels measured in human brain tissue from different exposure cohorts. Bioavailability assessment of aluminum from inhaled microspheres needs investigation.

  SEM-EDX IDENTIFICATION AND CHARACTERIZATION OF AIRBORNE MICROSPHERES: POTENTIAL EFFECTS ON HUMAN HEALTH · 2023 · DOI

• The SEM-EDX characterization of airborne microspheres lacks standardized protocols for size fractionation and elemental composition analysis across different indoor environments (primary schools, offices, industrial areas). Current studies analyze coarse particles and ultrafine particles separately, but the relationship between microsphere morphology, chemical composition, and respiratory deposition efficiency in children versus adults at different breathing heights remains uncharacterized.

  SEM-EDX IDENTIFICATION AND CHARACTERIZATION OF AIRBORNE MICROSPHERES: POTENTIAL EFFECTS ON HUMAN HEALTH · 2023 · DOI

• The limited literature and methodological challenges in this field, including heterogeneous outcome definitions, exposure assessment, and residual confounding, suggest further high-quality studies are warranted to investigate potentially causal associations between air pollution and poor mental health.

  Air Pollution (Particulate Matter) Exposure and Associations with Depression, Anxiety, Bipolar, Psychosis and Suicide Risk: A Systematic Review and Meta-Analysis · 2019 · DOI

• Inconsistent findings of effect modification among previous studies may be partially explained by choice of SES stratification criteria, and the use of multiplicative models combined with differing baseline risk across SES populations.

  Assessment of neighbourhood-level socioeconomic status as a modifier of air pollution–asthma associations among children in Atlanta · 2016 · DOI

• However, adequate direct evidence to identify the shape of the mortality RR functions at the high ambient concentrations observed in many places in the world is lacking.

  An Integrated Risk Function for Estimating the Global Burden of Disease Attributable to Ambient Fine Particulate Matter Exposure · 2014 · DOI

• CONCLUSIONS: Although the type and extent of exposure assessment will necessarily depend on the goal and design of the cookstove study, without improved understanding of exposure-response relationships, the level of air pollution reduction necessary to meet the health targets of cookstove interventions will remain uncertain.

  Health and Household Air Pollution from Solid Fuel Use: The Need for Improved Exposure Assessment · 2013 · DOI

Most-cited papers in Air Quality and Health Impacts

• An Integrated Risk Function for Estimating the Global Burden of Disease Attributable to Ambient Fine Particulate Matter Exposure · Environmental Health Perspectives · 2014 · 1,649 citations
• Exposure measurement error in time-series studies of air pollution: concepts and consequences. · Environmental Health Perspectives · 2000 · 981 citations
• Potential Role of Ultrafine Particles in Associations between Airborne Particle Mass and Cardiovascular Health · Environmental Health Perspectives · 2005 · 773 citations
• Ambient Air Pollution and Atherosclerosis in Los Angeles · Environmental Health Perspectives · 2004 · 643 citations
• Spatial and Temporal Variation in PM _2.5 Chemical Composition in the United States for Health Effects Studies · Environmental Health Perspectives · 2007 · 614 citations
• Air Pollution (Particulate Matter) Exposure and Associations with Depression, Anxiety, Bipolar, Psychosis and Suicide Risk: A Systematic Review and Meta-Analysis · Environmental Health Perspectives · 2019 · 577 citations
• Ambient Air Pollution and Pregnancy Outcomes: A Review of the Literature · Environmental Health Perspectives · 2005 · 547 citations
• A Growing Role for Gender Analysis in Air Pollution Epidemiology · Environmental Health Perspectives · 2009 · 546 citations
• A Cohort Study of Traffic-Related Air Pollution Impacts on Birth Outcomes · Environmental Health Perspectives · 2008 · 508 citations
• Exposure Assessment for Atmospheric Ultrafine Particles (UFPs) and Implications in Epidemiologic Research · Environmental Health Perspectives · 2005 · 506 citations

Most recent work

• Air quality and health benefits achievable by mitigating Indian coal-fired power plant SO2 emissions · npj Clean Air · 2026
• A bibliometric review of advances in copula modelling of extreme air pollution events · Discover Environment · 2026
• Air pollution-related health impacts from domestic waste burning and associated interventions: the merits of a traditional versus machine learning scoping review methodology · Environmental Monitoring and Assessment · 2026
• Data fusion in air pollution exposure assessment: Methods, applications, and future directions · Journal of the Air & Waste Management Association · 2026
• Disparity in non-communicable disease burden attributable to ambient PM2.5 exposure among adult population subgroups in India · Journal of Exposure Science & Environmental Epidemiology · 2026
• Strong demand for clean air policies in Majority World cities · Nature Cities · 2026
• Converting categorical risk estimates into continuous effects in environmental health systematic reviews and meta-analyses. · PubMed · 2026
• Prevalence and predictors of indoor secondhand smoke (SHS) exposure among the Nigerian household population: evidence from the Demographic and Health Survey 2024 · International Journal of Health Promotion and Education · 2026
• Multi Scale Analysis of Particulate and Gaseous Pollutants in Hyderabad: Trends, Correlations, and Machine Learning Enhanced Predictive Insights · Aerosol Science and Engineering · 2026
• Spatiotemporal Trends and WHO Guideline Exceedances of PM₂.₅ in Bangladesh · Civil Engineering Beyond Limits · 2026

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