Air pollution: one of the world’s greatest public health threats

The health impacts of air pollution
Keswani, A., Akselrod, H., & Anenberg, S. C. (2022). Health and clinical impacts of air pollution and linkages with climate change. NEJM Evidence, 1(7), EVIDra2200068.

“Air pollution is one of the world’s greatest public health threats, reducing global life expectancy more than smoking, alcohol or childhood malnutrition. Recent studies estimate that fine particulate matter called PM2.5—pumped out by cars, factories, woodstoves and wildfires—causes nearly nine million premature deaths annually.” [Greenspan, J. (2023). Air Pollution Is Really Dangerous, Even More New Evidence Shows: Dirty air has been linked to poor health outcomes, ranging from suicidality to low birth weight. Scientific American]

Featured articles:

*Keswani, A., Akselrod, H., & Anenberg, S. C. (2022). Health and clinical impacts of air pollution and linkages with climate change. NEJM Evidence, 1(7), EVIDra2200068. [PDF] [Cited by]

“… review the linkages between climate change and air pollution and suggest strategies that clinicians may use to mitigate the adverse health impacts of air pollution.

In 2021, the World Health Organization declared climate change to be ‘the single biggest health threat facing humanity.’ Fossil fuel combustion, the major source of climate-warming greenhouse gases, also produces harmful air pollution, now considered to be among the leading risk factors contributing to premature mortalityEvery organ system, including the kidneys, lungs, heart, and brain, may be affected by air pollution and climate change.”

*Molitor, D., Mullins, J. T., & White, C. (2023). Air pollution and suicide in rural and urban America: Evidence from wildfire smoke. Proceedings of the National Academy of Sciences of the United States of America, 120(38), 1. [PDF] [Cited by]

“Air pollution poses well-established risks to physical health, but little is known about its effects on mental health. We study the relationship between wildfire smoke exposure and suicide risk in the United States in 2007 to 2019 using data on all deaths by suicide and satellite-based measures of wildfire smoke and ambient fine particulate matter (PM2.5) concentrations. We identify the causal effects of wildfire smoke pollution on suicide by relating year-over-year fluctuations in county-level monthly smoke exposure to fluctuations in suicide rates and compare the effects across local areas and demographic groups that differ considerably in their baseline suicide risk. In rural counties, an additional day of smoke increases monthly mean PM2.5 by 0.41 μg/m3 and suicide deaths by 0.11 per million residents, such that a 1-μg/m3 (13%) increase in monthly wildfire-derived fine particulate matter leads to 0.27 additional suicide deaths per million residents (a 2.0% increase). These effects are concentrated among demographic groups with both high baseline suicide risk and high exposure to outdoor air: men, working-age adults, non-Hispanic Whites, and adults with no college education. By contrast, we find no evidence that smoke pollution increases suicide risk among any urban demographic group. This study provides large-scale evidence that air pollution elevates the risk of suicide, disproportionately so among rural populations.”

*Vohra, K., Vodonos, A., Schwartz, J., Marais, E. A., Sulprizio, M. P., & Mickley, L. J. (2021). Global mortality from outdoor fine particle pollution generated by fossil fuel combustion: Results from GEOS-Chem. Environmental Research, 195, 110754. [Cited by]

The burning of fossil fuels – especially coal, petrol, and diesel – is a major source of airborne fine particulate matter (PM2.5), and a key contributor to the global burden of mortality and disease. Previous risk assessments have examined the health response to total PM2.5, not just PM2.5 from fossil fuel combustion, and have used a concentration-response function with limited support from the literature and data at both high and low concentrations. This assessment examines mortality associated with PM2.5 from only fossil fuel combustion, making use of a recent meta-analysis of newer studies with a wider range of exposure. We also estimated mortality due to lower respiratory infections (LRI) among children under the age of five in the Americas and Europe, regions for which we have reliable data on the relative risk of this health outcome from PM2.5 exposure. We used the chemical transport model GEOS-Chem to estimate global exposure levels to fossil-fuel related PM2.5 in 2012. Relative risks of mortality were modeled using functions that link long-term exposure to PM2.5 and mortality, incorporating nonlinearity in the concentration response. We estimate a global total of 10.2 (95% CI: −47.1 to 17.0) million premature deaths annually attributable to the fossil-fuel component of PM2.5. The greatest mortality impact is estimated over regions with substantial fossil fuel related PM2.5, notably China (3.9 million), India (2.5 million) and parts of eastern US, Europe and Southeast Asia. The estimate for China predates substantial decline in fossil fuel emissions and decreases to 2.4 million premature deaths due to 43.7% reduction in fossil fuel PM2.5 from 2012 to 2018 bringing the global total to 8.7 (95% CI: −1.8 to 14.0) million premature deaths. We also estimated excess annual deaths due to LRI in children (0–4 years old) of 876 in North America, 747 in South America, and 605 in Europe. This study demonstrates that the fossil fuel component of PM2.5 contributes a large mortality burden. The steeper concentration-response function slope at lower concentrations leads to larger estimates than previously found in Europe and North America, and the slower drop-off in slope at higher concentrations results in larger estimates in Asia. Fossil fuel combustion can be more readily controlled than other sources and precursors of PM2.5 such as dust or wildfire smoke, so this is a clear message to policymakers and stakeholders to further incentivize a shift to clean sources of energy.”

*White, A. J., Fisher, J. A., Sweeney, M. R., Freedman, N. D., Kaufman, J. D., Silverman, D. T., & Jones, R. R. (2023). Ambient fine particulate matter and breast cancer incidence in a large prospective US cohort. Journal of the National Cancer Institute. [PDF] [Cited by]

“Background: Fine particulate matter (PM2.5) has been inconsistently associated with breast cancer incidence, however, few studies have considered historic exposure when levels were higher.

Methods: Outdoor residential PM2.5 concentrations were estimated using a nationwide spatiotemporal model for women in the National Institutes of Health–AARP Diet and Health Study, a prospective cohort located in 6 states (California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania) and 2 metropolitan areas (Atlanta, GA, and Detroit, MI) and enrolled in 1995-1996 (n = 196 905). Annual average PM2.5 concentrations were estimated for a 5-year historical period 10 years prior to enrollment (1980-1984). We used Cox regression to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between a 10 µg/m3 increase in PM2.5 and breast cancer incidence overall and by estrogen receptor status and catchment area.

Results: With follow-up of participants through 2017, a total of 15 870 breast cancer cases were identified. A 10 ug/m3 increase in PM2.5 was statistically significantly associated with overall breast cancer incidence (HR = 1.08, 95% CI = 1.02 to 1.13). The association was evident for estrogen receptor–positive (HR = 1.10, 95% CI = 1.04 to 1.17) but not estrogen receptor–negative tumors (HR = 0.97, 95% CI = 0.84 to 1.13; Pheterogeneity = .3). Overall breast cancer hazard ratios were more than 1 across the catchment areas, ranging from a hazard ratio of 1.26 (95% CI = 0.96 to 1.64) for North Carolina to a hazard ratio of 1.04 (95% CI = 0.68 to 1.57) for Louisiana (Pheterogeneity = .9).

Conclusions: In this large US cohort with historical air pollutant exposure estimates, PM2.5 was associated with risk of estrogen receptor–positive breast cancer. State-specific estimates were imprecise but suggest that future work should consider region-specific associations and the potential contribution of PM2.5 chemical constituency in modifying the observed association.”

See also —

Greater air pollution and heat tied to adverse pregnancy outcomes

Air pollution can cause declines in human intelligence

How wildfire smoke can harm human health, even when the fire is hundreds of miles away – a toxicologist explains

Questions? Please let me know (engelk@grinnell.edu).