Improving Air Quality Indices for Personalized Health Warnings from Pollution Exposure

A recent response to the World Health Organization (WHO) State of Global Air 2025 report has indicated the critical need for direct associations between air quality and cardiovascular outcomes, which the report lacks.1,2

“This was a commentary on the World Health Organization roadmap for air quality, and the driver for this was the recognition that most air quality indices that inform the public are not really linked to health outcomes,” Sanjay Rajagopalan, MD, the chief academic and scientific officer at University Hospitals Case Medical Center and a co-author of the publication, told HCPLive in an exclusive interview. “In other words, they don’t provide you with an indicator of what the air quality might do to actual health outcomes, and that’s an important inefficiency.”

Air pollution ranks as the second leading risk factor for death worldwide – in 2023, pollution exposure accounted for roughly 8 million deaths. Almost all populated areas in the world do not meet WHO air quality targets due to fine particulate matter, or particles with a diameter ≤2.5 µm, also known as PM2.5. This particle directly contributes to cardiovascular, metabolic, neurologic, and respiratory diseases.1

Although most mortality is a result of long-term PM2.5 exposure, Rajagopalan notes that a significant proportion of annual deaths is attributed to short-term exposures lasting a few days or less. To protect individuals from accidental exposure during short-term increases in air pollution, such as wildfire smoke, the US regularly releases daily values from local air-quality indices (AQIs).1

To this end, the WHO released its January 2026 report, an evaluation of AQI tools to ensure their alignment with the latest scientific evidence. In the document, the organization distinguished 2 broader categories of AQIs: conventional AQIs, which break down short-term pollutant concentrations with standardized, unitless scales, and air-quality health indices (AQHIs), which provide values indicative of health risks associated with exposures to mixtures of pollutants like PM2.5 or ozone.1,2

AQHIs calculate risk estimates via regression analyses from country-specific, short-term epidemiologic studies. In addition to collating all health risks into a single value, AQHIs work to communicate the risks associated with exposure to air pollution more accurately than standard AQIs. Cited by the WHO as a prime example, Canada’s 2008 AQHI, updated recently for increasingly prevalent wildfire smoke, could potentially drive further AQHI development for individual countries or geographic areas.1

While the WHO report provides a framework for evaluating AQIs in multiple aspects, Rajagopalan and colleagues note that the models typically rely on a one-size-fits-all risk-communication strategy, which limits their actionability on an individual basis. Disparities in health literacy, linguistic diversity, and occupational realities can skew the effectiveness of both AQIs and AQHIs on certain patient populations.1

To that end, Rajagopalan and colleagues encourage further research to enhance both the design and effectiveness of these models. Additionally, their implementation into clinical care may provide patients a more nuanced and direct interaction with the warning models, allowing them to receive direct and personalized suggestions for their individual conditions.1

“I completely refute the idea that environmental factors are non-actionable, that there are things you can’t do anything about,” Rajagopalan said. “There are things we can do as a community to bring forth these very important connections between individual health, population health, and planetary health.”

Editors’ Note: Rajagopalan reports disclosures with Bayer Healthcare and Novo Nordisk.

References

1. Brook RD, Rajagopalan S. Improving Global Air-Quality Indices — the WHO’s New Roadmap. NEJM. 2026;394(24):2390-2392. doi:10.1056/nejmp2601256

2. State of global air 2025: a report on air pollution and its role in the world’s leading causes of death. Boston: Health Effects Institute, 2025 https://www.stateofglobalair.org/resources/report/state-global-air-report-2025