Air pollution (ambient and household), results from various emission sources like industrial activities, polluting fuel use in households, traffic (i.e., vehicles, trucks, etc.) and others, which constitutes a complex mixture of pollutants in the air that are harmful to health.

Of all these pollutants, fine particulate matter seems to have the greatest impact on human health. In high-income countries, urban outdoor air pollution ranks in the top ten risk factors to health and is the first environmental risk factor. While, in low-and middle-income countries women and children bear the greatest health impacts from the use of polluting fuels and technologies in households.

Quantifying the health burdens due to air pollution exposures (ambient, household and/or joint of both) is necessary to guide decision making and reinforce the need for improving air quality to actively promote health.

Burden of disease attributed to air pollution (per 100 000 population, age-standardized) is defined as the number of deaths (or DALYs) attributed to air pollution per 100 000 population, adjusted for differences in age distribution across population group by applying the observed age-specific rates for each population to a standard population.

The disease burden attributed to air pollution is expressed in terms of deaths and disability adjusted life years (DALYs) as: mean raw figures and age-standardized rates and its 95% confidence intervals.

Epidemiological evidence has shown that the exposure to air pollution is associated several diseases, those with the strongest evidence are considered in these estimates, i.e.:

1. Lower respiratory infections in general population;
2. Strokes in adults (25 years and over);
3. Ischaemic heart diseases in adults (25 years and over);
4. Chronic obstructive pulmonary diseases in adults (25 years and over); and
5. Lung cancers in adults (25 years and over).

Deaths and DALYs are calculated through comparative risk assessment methods that estimate the reduction in disease that would occur if exposures were reduced to an alternative baseline level that has a minimum risk, assuming all other conditions remain unchanged. The age-standardized rates adjust for differences in population age distribution by applying the observed age-specific rates for each population to a standard population. These rates can therefore be used to compare the health burdens between countries without being affected by the differences in age distribution from country to country.

Burden of disease; air pollution; deaths; disability adjusted life years, household air pollution; ambient air pollution; health impact assessment; comparative risk assessment.

Estimates for the three risk factors (i.e., ambient air pollution, household air pollution and joint of both) are available by country / group (i.e., global, SDG regions, WHO regions and World Bank income levels), year, sex, 5-yr age groups and disease cause.

Estimates using comparative risk assessment methods.

Impact

Brut number of deaths and DALYs are calculated through comparative risk assessment methods that estimate the reduction in disease that would occur if exposures were reduced to an alternative baseline level bearing a minimum risk, while other conditions remain unchanged. This burden of disease is calculated by cause by first combining information on the increased (or relative) risk of a disease resulting from air pollution exposure, with information on how widespread this exposure is in the population (i.e., the annual mean PM2.5 concentration to which the population is exposed). This allows to calculate the 'population attributable fraction' (PAF), which is the fraction of a given disease observed in the population that can be attributed to the exposure. Applying this fraction to the background disease burden occurred in the population (e.g. Ischaemic heart disease expressed in terms of deaths or DALYs), gives the total number of deaths or DALYs that can be attributed to air pollution.
Based on those brut numbers, the age-standardized rates adjust for differences in population age distribution by applying the observed age-specific rates for each population to a standard population. These rates can therefore be used to compare the health burdens between countries without being affected by the differences in age distribution from country to country.

Estimates at global and regional groups (i.e., SDG regions, WHO regions and WB income levels) are available by grouping and summarizing the disaggregated estimates for the countries contained in each group and considering the population sizes for the rates.

Per 100 000 population

Every 2-4 years

The joint disease burden figures from ambient and household air pollution may not be equal to the sum of their independent impacts since household air pollution is emitted into the ambient environment and therefore contributes to ambient air pollution exposure and related burden of disease, therefore it’s necessary to apply a specific method to minimize the risk of double counting the health impacts.

Main references:

• WHO. Sustainable Development Goal Indicator 3.9.1: mortality attributed to air pollution. Geneva, World Health Organization, 2024.
• Brauer M, Amann M, Burnett RT, Cohen A, Dentener F, Ezzati M, et al. Exposure assessment for estimation of the global burden of disease attributable to outdoor air pollution. Environ Sci Technol. 2012;46(2):652-60. doi: 10.1021/es2025752.
• Burnett RT, Pope A, Ezzati M, Olives C, Lim SS, Mehta S, et al. An intgrated risk function for estimating the global burden of disease attributable to ambient fine particulate matter exposure. Environ Health Perspect. 2014. doi: 10.1289/ehp.1307049.
• Lim SS, Vos T, Flaxman AD, Danaei G, Shibuya K, Adair-Rohani H, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. The Lancet. 2012;380(9859):2224-60. doi: 10.1016/S0140-6736(12)61766-8.

sdg_airpollution@who.int

Dr Sophie Gumy

The availability of updated and accurate estimates relies on:

• State of the art of epidemiological evidence on air pollution and health effects
• Availability of background health disease burdens by country from WHO Global Health Estimates (GHE)
• Methods to globally estimate ambient air pollution exposures and availability of measurements of ground-level pollutants
• WHO global household energy model updates