Air Pollution

Factsheet: Household air pollution

Key Facts

Around 2.1 billion people worldwide (around a quarter of the global population) cook using open fires or inefficient stoves fuelled by kerosene, biomass (wood, animal dung and crop waste) and coal, which generates harmful household air pollution.
At current rates, only 78% of the global population is expected to have access to clean cooking by 2030. This shortfall would leave nearly 1.8 billion people still without clean cooking solutions.
Household air pollution was responsible for an estimated 2.9 million deaths per year in 2021, including over 309 000 deaths of children under the age of 5.
Around 95 million disability-adjusted life years (DALYs) were attributable to household air pollution exposure in 2021.
The combined effects of ambient air pollution and household air pollution are associated with 6.7 million premature deaths annually.
Household air pollution exposure leads to noncommunicable diseases including stroke, ischaemic heart disease, chronic obstructive pulmonary disease (COPD) and lung cancer.
Women and children, typically responsible for household chores such as cooking collecting firewood, bear the greatest health burden from the use of polluting fuels and technologies in homes.
It is essential to expand use of clean fuels and technologies to reduce household air pollution and protect health. These include solar, electricity, biogas, liquefied petroleum gas (LPG), natural gas, alcohol fuels, as well as biomass stoves that meet the emission targets in the WHO Guidelines.

Factsheet: Ambient (outdoor) air quality

Key facts

Air pollution is a major environmental risk to health. By reducing air pollution levels, countries can reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma.
The lower the levels of air pollution, the better the cardiovascular and respiratory health of the population will be, both long- and short-term.
The "WHO Air quality guidelines" provide an assessment of health effects of air pollution and thresholds for health-harmful pollution levels.
In 2014, 92% of the world population was living in places where the WHO air quality guidelines levels were not met.
Ambient (outdoor air pollution) in both cities and rural areas was estimated to cause 3 million premature deaths worldwide in 2012.
Some 88% of those premature deaths occurred in low- and middle-income countries, and the greatest number in the WHO Western Pacific and South-East Asia regions.
Policies and investments supporting cleaner transport, energy-efficient housing, power generation, industry and better municipal waste management would reduce key sources of urban outdoor air pollution.
Reducing outdoor emissions from household coal and biomass energy systems, agricultural waste incineration, forest fires and certain agro-forestry activities (e.g. charcoal production) would reduce key rural and peri-urban air pollution sources in developing regions.
Reducing outdoor air pollution also reduces emissions of CO₂ and short-lived climate pollutants such as black carbon particles and methane, thus contributing to the near- and long-term mitigation of climate change.
In addition to outdoor air pollution, indoor smoke is a serious health risk for some 3 billion people who cook and heat their homes with biomass fuels and coal.

Air pollution is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere. Household combustion devices, motor vehicles, industrial facilities and forest fires are common sources of air pollution. Pollutants of major public health concern include particulate matter, carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide. Outdoor and indoor air pollution cause respiratory and other diseases, which can be fatal.

There is no Disease Outbreak data at this time

Protection of the human environment

Key facts

Worldwide, around 2.1 billion people still cook using solid fuels (such as wood, crop waste, charcoal, coal and dung) and kerosene in open fires and inefficient stoves. Most of these people are poor and live in low- and middle-income countries. There is a large discrepancy in access to cleaner cooking alternatives between urban and rural areas: in 2021, only 14% of people in urban areas relied on polluting fuels and technologies, compared with 49% of the global rural population.

Household air pollution is generated by the use of inefficient and polluting fuels and technologies in and around the home that contains a range of health-damaging pollutants, including small particles that penetrate deep into the lungs and enter the bloodstream. In poorly ventilated dwellings, indoor smoke can have levels of fine particles 100 times higher than acceptable. Exposure is particularly high among women and children, who spend the most time near the domestic hearth. Reliance on polluting fuels and technologies also require significant time for cooking on an inefficient device, and gathering and preparing fuel.

Guidance

In light of the widespread use of polluting fuels and stoves for cooking, WHO issued a set of normative guidance, the Guidelines for indoor air quality: household fuel combustion, which offer practical evidence-based guidance on what fuels and technologies used in the home can be considered clean, including recommendations discouraging use of kerosene and recommending against use of unprocessed coal; specifying the performance of fuels and technologies (in the form of emission rate targets) needed to protect health; and emphasizing the importance of addressing all household energy uses, particularly cooking, space heating and lighting to ensure benefits for health and the environment. WHO defines fuels and technologies that are clean for health at the point of use as solar, electricity, biogas, liquefied petroleum gas (LPG), natural gas, alcohol fuels, as well as biomass stoves that meet the emission targets in the WHO Guidelines.

Without strong policy action, 1.8 billion people are estimated to still lack access to clean fuels and technologies in 2030. There is a particularly critical need for action in sub-Saharan Africa, where population growth has outpaced access to clean cooking, and 923 million people lacked access in 2022. Strategies to increase the adoption of clean household energy include policies that provide financial support to purchase cleaner technologies and fuels, improved ventilation or housing design, and communication campaigns to encourage clean energy use.

Each year, 2.9 million people die prematurely from illnesses attributable to the household air pollution caused by the incomplete combustion of solid fuels and kerosene used for cooking. Furthermore, 95 million disability-adjusted life years (DALYs) were attributable to household air pollution exposure in 2021. Particulate matter and other pollutants in household air pollution inflame the airways and lungs, impair immune response and reduce the oxygen-carrying capacity of the blood.

Among these 2.9 million deaths from household air pollution exposure:

32% are from ischaemic heart disease: 12% of all deaths due to ischaemic heart disease, accounting for over a million premature deaths annually, can be attributed to exposure to household air pollution;
23% are from stroke: approximately 12% of all deaths due to stroke can be attributed to the daily exposure to household air pollution arising from using solid fuels and kerosene at home;
21% are due to lower respiratory infection: exposure to household air pollution almost doubles the risk for childhood LRI and is responsible for 44% of all pneumonia deaths in children less than 5 years old. Household air pollution is a risk for acute lower respiratory infections in adults and contributes to 22% of all adult deaths due to pneumonia;
19% are from chronic obstructive pulmonary disease (COPD): 23% of all deaths from chronic obstructive pulmonary disease (COPD) in adults in low- and middle-income countries are due to exposure to household air pollution; and
6% are from lung cancer: approximately 11% of lung cancer deaths in adults are attributable to exposure to carcinogens from household air pollution caused by using kerosene or solid fuels like wood, charcoal or coal for household energy needs.

Household air pollution accounted for the loss of an estimated 86 million healthy life years in 2019, with the largest burden falling on women living in low- and middle-income countries.

Almost half of all deaths due to lower respiratory infection among children under 5 years of age are caused by inhaling particulate matter (soot) from household air pollution.

There is also evidence of links between household air pollution and low birth weight, tuberculosis, cataract, nasopharyngeal and laryngeal cancers.

WHO provides technical support and capacity building to countries and regions to evaluate and scale-up health-promoting household fuels and technologies. To address household air pollution and its negative impact on health, WHO:

develops guidelines for indoor air quality and household fuel combustion, to provide health-based recommendations on the types of fuels and technologies that protect health, and effective strategies for the dissemination and adoption of cleaner household fuels and technologies;
builds capacity at the country and regional level through direct consultations and workshops on household energy and health;
maintains the global household energy database to monitor progress in the transition to cleaner fuels and stove combinations in households, reporting as the custodian agency for reporting on SDG indicator 7.1.2, the proportion of the population with primary reliance on clean fuels and technologies. WHO also supports assessments of burden of disease from household air pollution resulted from the use of polluting fuel and technologies;
develops and updates tools and resources such as the Clean Household Energy Solutions Toolkit (CHEST) to help countries identify stakeholders working on household energy and public health to design, implement and monitor policies addressing household energy for better health;
supports governments to estimate costs and health benefits of implementing household energy interventions;
convenes the global Health and Energy Platform of Action (HEPA), which strengthens cooperation between the health and energy sectors to ensure universal access to clean and sustainable energy for households and health-care facilities in order to protect health;
works with countries, researchers and other partners to harmonize methods of planning and evaluation across settings for consistent and rigorous household energy and health assessments;
leads efforts with countries and surveying agencies to enhance, harmonize and pilot questions for national censuses and surveys, including assessing the health risks of using polluting household energy, as well as differentiated gender impacts from household energy practices; and
develops guidance and resources for integrating clean household energy into global health and climate change initiatives as well as decision-support tools.

Background

Outdoor air pollution is a major environmental health problem affecting everyone in developed and developing countries alike.

WHO estimates that in 2012, some 72% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and strokes, while 14% of deaths were due to chronic obstructive pulmonary disease or acute lower respiratory infections, and 14% of deaths were due to lung cancer.

Some deaths may be attributed to more than one risk factor at the same time. For example, both smoking and ambient air pollution affect lung cancer. Some lung cancer deaths could have been averted by improving ambient air quality, or by reducing tobacco smoking.

A 2013 assessment by WHO’s International Agency for Research on Cancer (IARC) concluded that outdoor air pollution is carcinogenic to humans, with the particulate matter component of air pollution most closely associated with increased cancer incidence, especially cancer of the lung. An association also has been observed between outdoor air pollution and increase in cancer of the urinary tract/bladder.

Ambient (outdoor air pollution) in both cities and rural areas was estimated to cause 3 million premature deaths worldwide per year in 2012; this mortality is due to exposure to small particulate matter of 10 microns or less in diameter (PM₁₀), which cause cardiovascular and respiratory disease, and cancers.

People living in low- and middle-income countries disproportionately experience the burden of outdoor air pollution with 87% (of the 3 million premature deaths) occurring in low- and middle-income countries, and the greatest burden in the WHO Western Pacific and South-East Asia regions. The latest burden estimates reflect the very significant role air pollution plays in cardiovascular illness and premature deaths – much more so than was previously understood by scientists.

Most sources of outdoor air pollution are well beyond the control of individuals and demand action by cities, as well as national and international policymakers in sector like transport, energy waste management, buildings and agriculture.

There are many examples of successful policies in transport, urban planning, power generation and industry that reduce air pollution:

for industry: clean technologies that reduce industrial smokestack emissions; improved management of urban and agricultural waste, including capture of methane gas emitted from waste sites as an alternative to incineration (for use as biogas);
for transport: shifting to clean modes of power generation; prioritizing rapid urban transit, walking and cycling networks in cities as well as rail interurban freight and passenger travel; shifting to cleaner heavy duty diesel vehicles and low-emissions vehicles and fuels, including fuels with reduced sulfur content;
for urban planning: improving the energy efficiency of buildings and making cities more compact, and thus energy efficient;
for power generation: increased use of low-emissions fuels and renewable combustion-free power sources (like solar, wind or hydropower); co-generation of heat and power; and distributed energy generation (e.g. mini-grids and rooftop solar power generation);
for municipal and agricultural waste management: strategies for waste reduction, waste separation, recycling and reuse or waste reprocessing; as well as improved methods of biological waste management such as anaerobic waste digestion to produce biogas, are feasible, low cost alternatives to the open incineration of solid waste. Where incineration is unavoidable, then combustion technologies with strict emission controls are critical.

In addition to outdoor air pollution, indoor smoke is a serious health risk for some 3 billion people who cook and heat their homes with biomass fuels and coal. Some 4.3 million premature deaths were attributable to household air pollution in 2012. Almost all of that burden was in low-middle-income countries as well.

The 2005 "WHO Air quality guidelines" offer global guidance on thresholds and limits for key air pollutants that pose health risks. The Guidelines indicate that by reducing particulate matter (PM₁₀) pollution from 70 to 20 micrograms per cubic metre (μg/m), we can cut air pollution-related deaths by around 15%.

The Guidelines apply worldwide and are based on expert evaluation of current scientific evidence for:

particulate matter (PM)
ozone (O₃)
nitrogen dioxide (NO₂) and
sulfur dioxide (SO₂), in all WHO regions.

Particulate matter

Definition and principal sources

PM affects more people than any other pollutant. The major components of PM are sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water. It consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. The most health-damaging particles are those with a diameter of 10 microns or less, (≤ PM₁₀), which can penetrate and lodge deep inside the lungs. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer.

Air quality measurements are typically reported in terms of daily or annual mean concentrations of PM₁₀ particles per cubic meter of air volume (m³). Routine air quality measurements typically describe such PM concentrations in terms of micrograms per cubic meter (μg/m³). When sufficiently sensitive measurement tools are available, concentrations of fine particles (PM_2.5 or smaller), are also reported.

PM_2.5
10 μg/m³ annual mean
25 μg/m³ 24-hour mean

PM₁₀
20 μg/m³ annual mean
50 μg/m³ 24-hour mean

In addition to guideline values, the Air Quality Guidelines provide interim targets for concentrations of PM₁₀ and PM_2.5 aimed at promoting a gradual shift from high to lower concentrations.

If these interim targets were to be achieved, significant reductions in risks for acute and chronic health effects from air pollution can be expected. Progress towards the guideline values, however, should be the ultimate objective.

The effects of PM on health occur at levels of exposure currently being experienced by many people both in urban and rural areas and in developed and developing countries – although exposures in many fast-developing cities today are often far higher than in developed cities of comparable size.

"WHO Air Quality Guidelines" estimate that reducing annual average particulate matter (PM₁₀) concentrations from levels of 70 μg/m³, common in many developing cities, to the WHO guideline level of 20 μg/m³, could reduce air pollution-related deaths by around 15%. However, even in the European Union, where PM concentrations in many cities do comply with Guideline levels, it is estimated that average life expectancy is 8.6 months lower than it would otherwise be, due to PM exposures from human sources.

In developing countries, indoor exposure to pollutants from the household combustion of solid fuels on open fires or traditional stoves increases the risk of acute lower respiratory infections and associated mortality among young children; indoor air pollution from solid fuel use is also a major risk factor for cardiovascular disease, chronic obstructive pulmonary disease and lung cancer among adults.

There are serious risks to health not only from exposure to PM, but also from exposure to ozone (O₃), nitrogen dioxide (NO₂) and sulfur dioxide (SO₂). As with PM, concentrations are often highest largely in the urban areas of low- and middle-income countries. Ozone is a major factor in asthma morbidity and mortality, while nitrogen dioxide and sulfur dioxide also can play a role in asthma, bronchial symptoms, lung inflammation and reduced lung function.