Custodes Futurifor the advancement of humanity

Environmental factor, barrier 1 of 9

Air pollution

Air pollution is associated with millions of premature deaths and can impair thinking, and household pollution from cooking fuels kills children.

Evidence

  • Scale. According to WHO, ambient and household air pollution combined are associated with 6.7 million premature deaths a year. Ambient pollution caused about 4.2 million in 2019 and household pollution an estimated 2.9 million in 2021, including over 309,000 children under 5. These estimates come from different years, so they do not sum to the combined total.
  • Effects on thinking. Long-term air pollution exposure in China impaired verbal and math test performance, and the effect on verbal scores grew stronger with age (Zhang, Chen, and Zhang, 2018).

Why it matters: The child deaths remove potential future contributors, including possible pioneers, before any ability can develop.

Proposed and experimental methods

Methods that are proposed, under trial, approved in some places, or tried and then failed. Each shows a stage label and an evidence rating. A stage label shows how far a method has progressed, not whether it works. The stage labels are explained on the environmental factor page.

  • Low emission zones (In wide use, B). Cities charge or ban older, more polluting vehicles inside a defined zone. For car-free neighborhood design see "Chronic disease, obesity, and physical inactivity" in the biological factors. Early estimates for London's 2019 Ultra Low Emission Zone (ULEZ) differ several-fold by method: one found an average nitrogen dioxide (NO2) fall of less than 3% across London in the first weeks, with no significant effect on fine particles (PM2.5) (Ma et al., 2021), while a later causal analysis found 19.6% lower NO2 at traffic sites and 8.2% at background sites in the first three months, no detectable NO2 effect of the 2023 city-wide expansion, and no significant PM2.5 benefit (Tong et al., 2025). In a cohort of 3,414 children, lung function (FEV1) grew 10 mL per year faster in London than in comparison town Luton after the ULEZ (233 versus 223 mL per year), closing a baseline gap of 38 mL within four years (Wood et al., 2026).
  • Coal and oil power plant closures (In wide use, B). Retiring fossil fuel power plants removes a large local pollution source. After eight coal and oil plants closed in California, preterm birth among mothers living within 5 km fell from 7.0% to 5.1% relative to mothers 10 to 20 km away, in a difference-in-differences analysis of 57,005 births (Casey et al., 2018). The study covers only eight plants in one state.
  • Automated monitoring and real-time public pollution data (Approved but not scaled, B). Replacing manually reported readings with automatic monitors and publishing the data in real time. When China automated its monitoring stations, reported PM10 rose 35% immediately and stayed higher, which suggests earlier figures had been understated by local officials (Greenstone et al., 2022). After China began releasing real-time air quality data in 2013, people avoided outdoor exposure and bought more protective products, and the authors estimate the health benefits exceeded the program's costs by an order of magnitude (Barwick et al., 2024). Both studies come from one country.
  • Subsidized clean cooking gas connections (In wide use, contested, C). India's Pradhan Mantri Ujjwala Yojana (PMUY) gives poor women free liquefied petroleum gas (LPG) connections to replace wood and dung. Sales data from one district in Karnataka showed PMUY users refilled cylinders less than half as often as general rural customers (Kar et al., 2019). A national difference-in-differences study found the scheme sharply raised LPG connections but had limited effect on gas use and on women's education, employment, and health, although women gained mobility and decision-making power, and households kept using solid fuels alongside gas (Nandwani and Jain, 2026).
  • Not shown to help: Free LPG stoves and fuel for pregnant women (Large trial, B). The HAPIN trial gave 3,200 pregnant women in Guatemala, India, Peru, and Rwanda a free LPG stove and unlimited fuel for 18 months, with near-total uptake, and cut children's median fine particle exposure from 66.0 to 24.2 μg per cubic meter (McCollum et al., 2024). Birth weight did not differ (adjusted difference 19.6 g, 95% CI -10.1 to 49.2) (Clasen et al., 2022), and neither did severe pneumonia in the first year (incidence rate ratio 0.96) (McCollum et al., 2024). Exposure in the LPG group remained above the WHO annual guideline, so the trial does not show whether lower levels would help.

Sources cited on this page

  1. WHO: Burden of disease from unsafe water, sanitation and hygiene, 2019 update (2023) B Moderate
  2. Zhang, X., Chen, X., & Zhang, X. (2018). The impact of exposure to air pollution on cognitive performance. PNAS, 115(37), 9193-9197. DOI B Moderate
  3. Barwick, P. J., Li, S., Lin, L., & Zou, E. Y. (2024). From fog to smog: The value of pollution information. American Economic Review, 114(5), 1338-1381. link B Moderate
  4. Casey, J. A., Karasek, D., Ogburn, E. L., Goin, D. E., Dang, K., Braveman, P. A., et al. (2018). Retirements of coal and oil power plants in California: Association with reduced preterm birth among populations nearby. American Journal of Epidemiology, 187(8), 1586-1594. link B Moderate
  5. Clasen, T. F., Chang, H. H., Thompson, L. M., Kirby, M. A., Balakrishnan, K., Díaz-Artiga, A., et al. (2022). Liquefied petroleum gas or biomass for cooking and effects on birth weight. New England Journal of Medicine, 387(19), 1735-1746. link B Moderate
  6. Greenstone, M., He, G., Jia, R., & Liu, T. (2022). Can technology solve the principal-agent problem? Evidence from China's war on air pollution. American Economic Review: Insights, 4(1), 54-70. link B Moderate
  7. Kar, A., Pachauri, S., Bailis, R., & Zerriffi, H. (2019). Using sales data to assess cooking gas adoption and the impact of India's Ujjwala programme in rural Karnataka. Nature Energy, 4(9), 806-814. link C Limited
  8. Ma, L., Graham, D. J., & Stettler, M. E. J. (2021). Has the ultra low emission zone in London improved air quality? Environmental Research Letters, 16, 124001. link B Moderate
  9. McCollum, E. D., McCracken, J. P., Kirby, M. A., Grajeda, L. M., Hossen, S., Moulton, L. H., et al. (2024). Liquefied petroleum gas or biomass cooking and severe infant pneumonia. New England Journal of Medicine, 390(1), 32-43. link B Moderate
  10. Nandwani, B., & Jain, M. (2026). Impact of cooking fuel connection subsidies on women outcomes: Evidence from India's gender-responsive clean energy policy. Journal of Environmental Management, 418, 130979. link C Limited
  11. Tong, C., Dai, Y., Cole, M., Elliott, R. J. R., Bartington, S. E., Liu, B., et al. (2025). Further improvement in London's air quality demands more than the Ultra Low Emission Zone policy. npj Clean Air, 1(1), 29. link B Moderate
  12. Wood, H. E., Hajmohammadi, H., Dove, R. E., Scales, J., Tsocheva, I., Chavda, J., et al. (2026). Impact of the Ultra Low Emission Zone on lung function growth in children in London, UK: A prospective parallel cohort study. Lancet Public Health, 11(10), e733-e743. link B Moderate

Every source for this factor is listed on the environmental factor page.