Haneen Khreis

Summary: Background: Ambient air pollution is a leading global health risk and disproportionately affects populations of Low- and Middle-Income Countries (LMICs). In 2021, WHO revised its Air Quality Guidelines (AQG), lowering recommended annual limits for Particulate Matter 2.5 (PM _2.5 ) and Nitrogen Dioxide (NO ₂ ). We estimated the potential health and economic impacts of achieving WHO Interim Target 3 (IT3) and AQG concentrations across LMICs. Methods: We conducted a health impact assessment across 136 LMICs to quantify one-year changes in all-cause and cause-specific mortality (chronic obstructive pulmonary disease [COPD], ischaemic heart disease [IHD], and stroke) and disease incidence (COPD, dementia, IHD, and stroke) under WHO IT3 and AQG counterfactual scenarios for PM _2.5 and NO ₂ . Concentration-response functions were applied at 1km x 1km resolution. Economic welfare impacts of mortality risk reductions were estimated using country-adjusted values of a statistical life (VSL, Int$ PPP-adjusted 2021). Direct medical and productivity-related costs associated with incident cases were estimated using a cost-of-illness (COI) framework. Uncertainty intervals (UI) reflect uncertainty in concentration-response functions. Results: Attainment of WHO IT3 and AQG concentrations for PM _2.5 was associated with an estimated 16.04% reduction (6.58million, UI: 6.10-7.07million) and 22.97% reduction (9.43million, UI: 8.75-10.11million) in annual deaths, respectively. Corresponding VSL-based estimates of deaths averted were Int$5.5 trillion (7.0% of aggregate LMIC GDP) and Int$8.4 trillion (10.6% of GDP), respectively. For NO ₂ , IT3 and AQG scenarios were associated with estimated reductions of approximately 1.06% (approximately 435,000 deaths, UI: 388,000-483,000) and 2.79% (435,000 deaths; UI: 388,000-483,000), yielding gains of Int$0.6 trillion (0.7% of GDP) and Int$1.5 trillion (1.9% of GDP). Disease-specific mortality reductions were most prominent for IHD and stroke in Asia and Africa. Under the PM _2.5 AQG scenario, an estimated 2.82million (1.67-2.97) COPD, 1.10million (0.83-1.37) dementia, 7.3million (6.41-8.19) IHD, and 2.3million (2.19-2.41) stroke cases could be delayed or averted in one year. Associated reductions in direct medical and productivity-related costs were greatest for IHD, COPD, and stroke. NO ₂ -related morbidity reductions were smaller across all outcomes. All estimates represent one-year changes in risk relative to counterfactual exposure and may reflect delayed rather than permanently avoided events. Discussion: Achieving both WHO IT3 and AQG values in LMICs could yield substantial reductions in premature mortality and disease incidence, particularly for cardiovascular and respiratory conditions, alongside large, monetised welfare gains from reduced mortality risk. These findings underscore the considerable societal value of air quality improvements and support accelerated action toward meeting WHO guideline levels in regions bearing the highest pollution burden.

Background: Parkinson’s disease (PD), multiple sclerosis (MS) and motor neurone disease (MND) are progressive and debilitating diseases that are increasing in prevalence globally. Some primary studies show an increased risk from long-term outdoor air pollution exposure, while others contradict this association. Methods: As per Khreis et al. ¹ protocol, a systematic review and meta-analysis was undertaken to assess the associations of long-term ( > 1 year) outdoor air pollution exposure with PD, MS and MND incidence. We searched eight databases for publications up to October 2023. Primary case-control, cohort, cross-sectional or ecological studies investigating the association of long-term air pollution and adult (>18 years old) PD, MS, or MND incidence were included. Meta-analyses were carried out using random-effects models with assessment of heterogeneity and meta-bias. PROSPERO (CRD42023417961). Results: Of 31 papers included, 22 and 3 were meta-analysed for PD and MS outcomes, respectively. Most studies were from North America (14) followed by Europe (8), and Asia (6). For every 5 μg/m ³ increase of Particulate Matter 2.5 (PM _2.5 ) concentration, there was a higher PD risk (1.06; 95%CI: 1.00-1.12), but this was not true for all study settings (Prediction Interval: 0.95-1.19). This risk was largest in Asia (1.16, 95%CI:0.96-1.41). There was no evidence that PM _2.5 or nitrogen dioxide (NO ₂ ) were associated with increased risk of MS. Conclusion: This systematic review reports an increased risk of PD from long-term PM _2.5 exposure. The neurodegenerative diseases investigated here are rare and therefore alternatives to insufficiently powered cohort studies are needed to strengthen the evidence on risk.

The Integrated Transport and Health Impact Modelling Tool for Global Cities (ITHIM-Global) was developed as an open-source tool to assess the impacts of transport mode shifts on public health and the environment in low- and middle-income countries (LMICs) where the need for such assessment is urgent and rising. The model simulates the impacts on all-cause and cause-specific mortality and years of life lost outcomes through a multi-pathway framework, specifically including physical activity, air pollution exposure, and road traffic fatalities. In addition, the model estimates changes in carbon dioxide emissions resulting from these mode shifts. ITHIM-Global employs a quasi-microsimulation approach that enables individualized exposure estimates by age, sex, and activity levels and utilises up- to-date exposure and dose-response functions that account for the non-linear relationship between physical activity levels and health. To demonstrate its functionality, document its strengths and weaknesses, and aid users, the model was applied to Bogota, Colombia, using three hypothetical scenarios, each shifting 5% of trips to one of bus, car, or cycling. Results indicate that increasing public or active transport modes enhances public health, primarily driven by gains in physical activity and to a lesser extent by reductions in traffic-related emissions. Conversely, a shift to car usage worsens health outcomes due to decreased physical activity and increased pollution exposure. ITHIM-Global serves as a flexible, detailed Health Impact Assessment (HIA) tool adaptable to urban areas across LMICs and this article delves into underlying assumptions and their influence to advance generalisable lessons on risk assessment and model development. The modular structure of ITHIM-Global, its covering of individual and population-level analyses, and extensive documentation provide an accessible, evidence-based approach for city planners and practitioners to optimize transport policies that support public health and mitigate environmental harm. Highlights We describe the Integrated Transport and Health Impact Modelling Tool for Global cities (ITHIM- Global), designed for low- and middle-income country (LMIC) cities. We apply ITHIM-Global to Bogotá, simulating impacts from three mode shift scenarios with a 5- percentage point increase in car, cycling, and bus shares. We simulate the impacts on physical activity, air pollution, road traffic fatalities, and attributable mortalities and years of life lost. We describe in detail the model’s elements to aid future uptake, development, and extension to other cities. We discuss strengths, weaknesses, and underlying assumptions to advance generalisable lessons on risk assessment and model development.