Project Co-Led with Professor J. Andrew Harris

In this project, over the years 2023-2026, we collected survey data on awareness of air pollution measurements and health impacts across 8 countries and 2 cities. We found high levels of variation in both public awareness of AQI, the most common tool used to communicate air pollution levels, and knowledge about the health impacts of air pollution, both across and within countries. We also document that the extent of exposure to air pollution does not predict levels of awareness, and awareness is low among some of the most highly affected populations.

Learn more about how we conducted the air quality awareness surveys

We conduct original surveys with over 30,000 respondents in 10 countries. In eight of these countries (the United States of America, Mexico, Morocco, the United Kingdom, Germany, Poland, South Africa and India), we conducted online surveys that were designed to be representative of the national population. However, due to unequal access and use of the internet, these web-based samples are, on average, more urban, more educated, and, in most countries, younger than the general population. So, our estimates about air quality awareness are likely to be under-estimates.

In addition, we conducted in-person surveys in two cities, Kampala, Uganda, and Nairobi, Kenya, that were designed to be representative of the populations of these two cities.

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Prioritisation of Air Pollution is Generally Low

Despite air pollution being a leading risk factor for death, second only to
high blood pressure, and contributing to more deaths than war, HIV/AIDS, road accidents, and malaria combined (Fuller et al., 2022), people in most countries generally do not believe it is the most important environmental concern facing their countries and communities today.

To identify how important the public thinks air pollution is compared to other environmental issues, we compile the data from 3 public opinion surveys: the Arab Barometer Wave VII survey (2023-2024), the Afrobarometer Round 9 survey (2023), and the International Social Survey Program (2020). These surveys asked respondents to identify the biggest environmental challenge facing their country or community and enabled us to investigate the attitudes of more than 100,000 people across 71 countries.

In the figure below, we group countries by the burden of disease associated with air pollution, as measured by the rate of disability adjusted life years (DALYs), then plot the percentage of them in each country that indicated that air pollution is the biggest environmental challenge.

Understand DALYs better

A disability-adjusted life year, or DALY, measures the total amount of healthy life lost because of illness, disability, or early death. One DALY is equal to one year of full health lost. It combines years lost when people die earlier than expected with years lived in less than full health (World Health Organisation, 2021).

For example, in practical terms, a DALY rate of 1,000 per 100,000 people means that, across a population of 100,000, the equivalent of 1,000 years of healthy life was lost during the period measured. Averaged across the whole population, this is about 3.7 days of healthy life lost per person, although some people will feel the effects on their health more than others.

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_{Air Pollution as the Biggest Environmental Challenge by DALY Rate (per 100,000). N = 107,548. 95% Confidence Intervals shown. Panels group countries by DALY rate per 100,000 attributable to air pollution (IHME GBD 2023). Dashed lines show the mean country−level prioritisation rate within each DALY−rate category. Grey bars highlight countries included in the main study sample.}

The plots show that the burden of disease from air pollution is not shared equally. Countries with low DALY rates due to air pollution are all high-income countries. Meanwhile, while there is a mixture of income levels in the moderate category, those with high and very high DALY rates are almost entirely low- and middle-income countries.

These figures show that there were only three countries – China, Taiwan, and Thailand – in
which more than a quarter of respondents stated that air pollution was the biggest environmental challenge, indicating generally low levels of prioritisation across countries.

As can be expected, air pollution is the least prioritised in countries with low DALYs. However, those countries facing very high DALY rates – all in Africa, with the exception of India – have substantially lower prioritisation on average than countries in either the moderate or high categories.

Access to Air Quality Data Is Low and Unequal

Low access to data about air quality in their communities could be one of the factors explaining the lack of concern among the public despite the high risks air pollution poses to human health. While some countries – mostly countries in the Global North, such as the US, Iceland, and other European countries – have good air quality monitoring coverage, which allows governments and their publics to track changing air pollution levels, the absolute majority of the world does not. As seen in the map below, most countries have fewer than 10 reference-grade/official monitors, able to record accurate air quality data, per million people (OpenAQ, 2026).

More Data Does Not Always Mean More Concern

However, the relationship between air quality data availability and its prioritisation as an issue is not as straightforward as it might seem. For example, air quality coverage across the continent of Africa is incredibly low: most countries, except for South Africa, have fewer than 0.5 official monitors per million people. Yet, despite the almost-universally low coverage, how much individuals prioritise air pollution varies quite drastically: Uganda and Sudan have almost identical air quality monitoring capacity, but air pollution was named as the top environmental concern by only about 5% of surveyed people in Uganda, compared with nearly 25% in Sudan.

The Gap: Understanding Air Quality Data

We suspected that the accessibility of air quality data was an even greater issue than its availability – if the public has never heard of AQI, it will be difficult for them to know the degree to which they are exposed to pollution at any given time, as well as what the health risks of a given level of exposure are. One part of our surveys thus investigated people’s familiarity with the Air Quality Index (AQI), which is a tool commonly used to express the concentrations of harmful pollutants in the air.

Learn more about what the AQI is

The Air Quality Index, or AQI, is a tool that turns complex air pollution measurements into a simple scale showing how safe or unsafe the air is to breathe. It usually combines information on major pollutants such as fine particles, ozone, carbon monoxide, nitrogen dioxide, and sulfur dioxide, then reports the risk to human health based on the pollutant that poses the highest risk at that moment. AQI values usually range from 0 to 500: lower numbers mean cleaner air, while higher numbers mean more pollution and greater health risk. For example, 0–50 is considered “Good,” while anything above 300 is considered “Hazardous.” In this way, AQI helps people quickly understand air quality and decide whether they should limit outdoor activity, especially if they are more sensitive to pollution (IQAir, 2026).

_{US AQI level categories and how they relate to different PM2.5 particle concentrations, as well as health recommendations. IQAir, 2026. Different countries, such as China or India, use different PM2.5 thresholds to determine each AQI level (IQAir, 2026).}

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So, we asked respondents, “Have you ever heard or read about the Air Quality Index?” The
answer options were “Yes”, “No”, and “Don’t know”, and the percentage of surveyed people who answered “Yes” in each country is shown in the plot below.

We found that large percentages of the respondents in all countries in our sample have never heard of AQI. As shown in the plot above, the country with the highest levels of reported awareness is India (81%), followed by Mexico (72%). The samples with the lowest levels of awareness are the African cities of Kampala and Nairobi (4% and 8%, respectively).

These samples differ from the rest in that they are single cities instead of national samples.
However, if anything, these areas are likely to have higher levels of awareness than the rest
of the population in their respective countries, since the population in the capital has, on
average, higher levels of education and other measures of socio-economic status that we
expect to be correlated with knowledge.

Exposure to Pollution Does Not Predict Awareness

We might also suspect that countries or individuals who encounter more air pollution encounter tools such as the Air Quality Index more often and thus are more familiar with them. However, we find that, in general, countries with higher levels of air pollution do not necessarily exhibit higher levels of awareness.

Learn more about how we estimate PM2.5 exposure

Given the unequal monitoring of air pollution around the world, we use satellite-derived data to approximate the ambient PM2.5 exposure our survey respondents experienced in the most recent year for which data is available.

We use 2023 V6 CNNPM25 (V6.GL.02.04), a georeferenced, satellite-derived
dataset that combines aerosol optical depth (AOD) observations from multiple NASA satellite instruments with an atmospheric chemistry model and calibrates the resulting estimates to ground-based air quality monitors (van Donkelaar et al. 2024; accessed through Washington University in St. Louis).

For Kampala and Nairobi, we assigned PM₂.₅ exposure using the dataset’s grid cell containing each respondent’s location, because the survey locations were relatively precise and pollution levels can change considerably over short distances. In the other countries, respondent locations were often more clustered or less precise, so we used the average PM₂.₅ level within a 1 km radius instead, reducing the risk of treating a single recorded point as more geographically precise than it really was. We then calculated the mean PM2.5 exposure for each survey location using these estimates.

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For example, the United States and Germany have similar levels of exposure, but AQI awareness is more than 20 percentage points higher in the former. Similarly, Mexico and Morocco experience similar levels of exposure, but AQI awareness in Mexico is over 30
percentage points higher than in Morocco.

Learn the difference between AQI categories and annual PM2.5 targets

The figure above uses WHO annual PM₂.₅ targets, which are yet another tool for interpreting PM₂.₅ exposure. AQI categories describe short-term air quality, while WHO annual PM₂.₅ targets describe long-term exposure. AQI bands are designed to communicate current or recent pollution levels and the associated health concern. WHO annual targets instead compare the average PM₂.₅ concentration over a full year with long-term health benchmarks. The 2021 WHO Air Quality Guidelines recommend an annual mean concentration of 5 µg/m³ or lower, with interim targets at 10, 15, 25, and 35 µg/m³ to help places with higher pollution progressively move toward the guideline. Because the figure uses annual average PM₂.₅ exposure, the WHO annual guideline and interim targets are the more appropriate benchmarks.

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The United States, the United Kingdom, and Germany all have similar levels of exposure on average, but levels of awareness about AQI vary from 31 percent in Germany to 52 percent in the United States. India appears to be the only case with both high exposure and awareness.

With the exception of India, respondents who were exposed to more PM2.5 than the median respondent in each of our country samples were not more aware of AQI than respondents experiencing less pollution.

Lack of Awareness About the Non-Respiratory Threat

The low prioritisation of air pollution could be explained by a lack of understanding of just how severe its effects on human health are. We asked respondents: “To the best of your
knowledge, which of the following are possible health consequences from prolonged exposure to air pollution?” followed by a list of health issues, of which they could select multiple.

From this, we create two binary variables, one indicating whether a respondent identified at least one respiratory effect of air pollution (pneumonia or lung cancer), and whether they
identified at least one non-respiratory effect (stroke, heart disease, or Alzheimer’s disease).

We find that most respondents – over 70 percent in all countries – identify at least one respiratory health effect of air pollution, significantly fewer are aware that air polution also impacts the heart and brain

This is important, because although air pollution is associated in the public mind with respiratory illness, some of the greatest risk to human health is actually due to its effect on the heart. Cardiovascular diseases account for nearly 60 percent of all deaths due to ambient air pollution, followed by chronic obstructive pulmonary disease (16 percent), and with lung cancer trailing at just 6 percent. Air pollution has serious effects on the brain as well, and estimated to be responsible for about one quarter of all deaths due to dementia (Health Effects Institute 2025).

Who Is Likely to be More Aware?

To identify who is actually likely to be more aware of the AQI as well as the health effects of air pollution, we collected a set of respondent-level characteristics, presented in the coefficient plots below. We show two kinds of outcomes: health effects knowledge (respiratory and non-respiratory effects) and AQI awareness (basic awareness
and the index showing whether respondents who claimed to have heard of AQI could answer questions about it).

The predictors of health knowledge are often systematically different for respiratory and non-respiratory effects. Education, age, and being a female are positively correlated with identifying at least one respiratory impact, while living in an urban area and being male are positively associated with knowledge of non-respiratory health effects. Those with above-median PM2.5 exposure are also more likely to know at least one non-respiratory effect. This is the only outcome for which exposure seems to matter.

_{Predictors of health effects knowledge, AQI awareness and AQI knowledge. Health−Effects Knowledge: N = 35,680. Self−reported AQI Awareness: N = 35,643; AQI Definition Knowledge: N = 11,960. 95% CIs shown. Models include country fixed effects; outcomes are standardized (mean 0, SD 1). Nairobi is excluded from AQI Definition Knowledge because the question used a different scale. PM2.5 is coded above vs. at/below each survey location’s sample median (reference = at/below). Reference categories: men, rural, below complete secondary, age 34 and below, unemployed/other.}

AQI awareness and definitional knowledge are positively correlated with age and education. Interestingly, basic awareness is positively correlated with living in an urban area, being employed, and being male, but the definitional knowledge (conditional on having heard of AQI) is positively correlated with the opposite of all those factors. This may suggest either over-claiming awareness is more common among some demographic groups, or that these groups are more likely to casually encounter the term.

_{Characteristics associated with AQI awareness by surveyed location.}