Indoor pollution includes household fuel smoke, particulate matter, formaldehyde, volatile organic compounds, radon, carbon monoxide and secondhand smoke. The available statistics range from global household-energy estimates to measured concentrations in homes in South Korea and China, so geography, period and definition matter when comparing them.
Key Indoor Pollution Statistics
These figures summarize the broadest measures of indoor pollution exposure, health burden and household risk:
- In 2021, about 2.1 billion people worldwide used polluting fuels or technologies for cooking.
- At current rates, 78% of the global population is forecast to have clean cooking access in 2030.
- At current rates, nearly 1.8 billion people could lack clean-cooking solutions in 2030 worldwide.
- In 2021, 14% of urban residents and 49% of the global rural population relied on polluting cooking fuels or technologies.
- In 2022, 923 million people in sub-Saharan Africa lacked access to clean cooking.
- In 2021, household air pollution was estimated to cause 2.9 million premature deaths worldwide.
- In 2021, more than 309,000 children younger than 5 died from household-air-pollution-attributable causes worldwide.
- In 2021, household air pollution accounted for about 95 million disability-adjusted life years worldwide.
- In 2021, household air pollution accounted for 44% of pneumonia deaths among children under 5 worldwide.
- In 2021, 23% of adult COPD deaths in low- and middle-income countries were attributed to household air pollution.
- From July 2020 to August 2021, sampled South Korean households had a geometric-mean indoor PM2.5 concentration of 13.1 µg/m³.
- From July 2020 to August 2021, sampled South Korean households had a geometric-mean indoor formaldehyde concentration of 20.5 µg/m³.
- From July 2020 to August 2021, sampled South Korean households had a geometric-mean total-VOC concentration of 93 µg/m³.
- In evidence published from 1998 to 2018, estimated household PM2.5 in China was 132.2 ± 117.7 µg/m³.
- In U.S. homes, EPA recommends fixing radon at or above 4 pCi/L, about 150 Bq/m³.
- EPA estimates about 21,000 U.S. lung-cancer deaths each year are related to radon, with an uncertainty range of 8,000–45,000.
- In 2019, CPSC estimated 250 non-fire consumer-product-related carbon-monoxide deaths in the United States.
Contents
- Key Indoor Pollution Statistics
- Global Indoor Pollution Exposure and Clean-Cooking Trends
- Indoor Air Pollution Deaths, Disease and Healthy-Life Loss
- Indoor Pollution Sources and Pollutant Evidence
- Residential Indoor Pollution Measurements
- Indoor Radon Statistics and Lung-Cancer Risk
- Indoor Carbon-Monoxide and Secondhand-Smoke Data
Global Indoor Pollution Exposure and Clean-Cooking Trends
The World Health Organization’s household-air-pollution figures primarily measure exposure from polluting fuels and technologies used for cooking. They are therefore narrower than all indoor pollution, which also includes chemicals, radon, carbon monoxide and tobacco smoke.
- About 2.1 billion people worldwide used open fires or inefficient stoves with polluting fuels and technologies for cooking in the 2021/2025 fact-sheet estimate.
- Only 78% of the global population is expected to have access to clean cooking by 2030 at current rates, leaving a forecast nearly 1.8 billion people without clean-cooking solutions.
- In 2021, polluting cooking fuels and technologies were used by 14% of urban residents, compared with 49% of the global rural population.
- In 2022, 923 million people in sub-Saharan Africa lacked access to clean cooking.
- More than 750 million people worldwide lacked access to electricity in the latest cited estimate, increasing reliance on exposure-related lighting sources such as kerosene lamps.
WHO also reports that indoor smoke in poorly ventilated dwellings can reach fine-particle levels 100 times higher than acceptable levels. This describes a possible high-exposure condition, not a global average or a measurement for every home. World Health Organization, “Household air pollution”
Indoor Air Pollution Deaths, Disease and Healthy-Life Loss
For health outcomes, the WHO estimates household air pollution’s attributable burden rather than counting individual indoor-pollution incidents. The modeled 2021 burden was 2.9 million premature deaths and about 95 million disability-adjusted life years, while a separate 2019 measure estimated 86 million healthy life-years lost.
| Outcome or disease | Household-air-pollution estimate | Population and period |
|---|---|---|
| Premature deaths | 2.9 million | Worldwide, 2021 |
| Deaths among children under 5 | More than 309,000 | Worldwide, 2021 |
| Disability-adjusted life years | About 95 million | Worldwide, 2021 |
| Healthy life-years lost | 86 million | Worldwide, 2019 |
The cause-of-death distribution within the 2021 modeled estimate included 32% ischaemic heart disease, 23% stroke, 21% lower-respiratory infections, 19% COPD and 6% lung cancer. These percentages describe shares of household-air-pollution-attributable deaths, not shares of all deaths from each disease.
- Household air pollution was attributed to about 12% of all ischaemic-heart-disease deaths worldwide in 2021.
- It was attributed to about 12% of all stroke deaths worldwide in 2021.
- Household air pollution was responsible for 44% of pneumonia deaths among children under 5 and 22% of adult pneumonia deaths in 2021 worldwide.
- Exposure accounted for 23% of adult COPD deaths in low- and middle-income countries in 2021.
- Household fuel-combustion carcinogens were attributed to about 11% of adult lung-cancer deaths worldwide in 2021.
WHO’s undated summary also says almost half of lower-respiratory-infection deaths among children under 5 were caused by inhaling soot particulate matter from household air pollution. The combined household-and-ambient air-pollution estimate of 6.7 million premature deaths annually must not be treated as an indoor-only figure. World Health Organization, “Household air pollution”
Indoor Pollution Sources and Pollutant Evidence
Indoor pollution statistics cover different pollutants and source pathways. A systematic review of residential evidence screened 2,982 titles, assessed 226 full-text articles, and included 141 eligible studies from 29 countries for literature published from 2000 through 2017.
PM2.5 and PM10 were the most-studied pollutant measures in that review. Smoking was identified as a major indoor PM2.5 source, but the review’s synthesis spans heterogeneous studies and does not provide one pooled effect size in the cited extract.
The evidence base also illustrates why indoor pollution cannot be reduced to one household product or one pollutant. Household combustion, smoking, outdoor infiltration, cooking, building materials, renovation and fragranced products can be relevant in different studies, while the measured outcome may be a particle concentration, a gas concentration or an attributable health estimate. Systematic review, “Indoor Exposure to Selected Air Pollutants in the Home Environment”
Residential Indoor Pollution Measurements
Measured residential data show the difference between a national household sample and a literature synthesis. A nationally representative South Korean study measured indoor air quality in 1,182 households from July 2020 to August 2021.
| Measurement | South Korean residential result | Definition and period |
|---|---|---|
| Indoor PM2.5 | 13.1 µg/m³ | Geometric mean, July 2020–August 2021 |
| Indoor formaldehyde | 20.5 µg/m³ | Geometric mean, same study period |
| Indoor total VOC | 93 µg/m³ | Geometric mean; aggregate TVOC measure |
In the Korean observational analysis, indoor PM2.5 was associated with outdoor PM2.5, indoor CO2, season, indoor smoking, house size, gas cooking and air-cleaner use. Formaldehyde was associated with indoor CO2, season, house size, residential period and air-cleaner use; TVOC was associated with indoor CO2, residence floor, house size, residence time, recent renovation and diffuser use.
Ventilation-related factors were positively correlated with indoor PM2.5 and negatively correlated with indoor formaldehyde and TVOC. These are associations from an observational study, not controlled intervention effects. Peer-reviewed study, “Characteristics and exposure determinants of PM2.5, formaldehyde, and total volatile organic compounds in residential indoor air in Korea”
China evidence comes from a household-weighted literature synthesis of studies published from 1998 through 2018, rather than one contemporaneous national survey:
- Overall estimated household PM2.5 was 132.2 ± 117.7 µg/m³.
- Estimated rural household PM2.5 was 164.3 ± 104.5 µg/m³.
- Estimated urban household PM2.5 was 123.9 ± 122.3 µg/m³.
- Kitchen household-PM2.5 levels were highest among the kitchen, bedroom and living-room sampling locations.
- The highest province-level inhaled household-PM2.5 dose among school-age children differed by up to 5.9 µg/(kg·day).
The Korean values are geometric means from sampled households, and the China values are synthesis estimates; neither is a global indoor-air average. Peer-reviewed study, “Characterization and exposure assessment of household fine particulate matter pollution in China”
Indoor Radon Statistics and Lung-Cancer Risk
Radon is an indoor pollutant measured in both U.S. homes and outdoor air. EPA reports an average indoor concentration of 1.3 pCi/L, or 50 Bq/m³, compared with an average outdoor concentration of 0.4 pCi/L, or 15 Bq/m³.
| EPA radon level or estimate | Value | Interpretation |
|---|---|---|
| Fix a home at or above | 4 pCi/L, about 150 Bq/m³ | Recommended action level |
| Consider mitigation between | 2–4 pCi/L, 75–150 Bq/m³ | Advisory range |
| Average indoor U.S. home | 1.3 pCi/L, 50 Bq/m³ | National average |
| Average outdoor air | 0.4 pCi/L, 15 Bq/m³ | Outdoor comparison |
EPA states that the action level is not a safe/unsafe biological cutoff and that there is no known safe exposure level. Its figures should be used as decision points, not as a prediction of an individual home’s concentration. U.S. Environmental Protection Agency, “What is EPA’s Action Level for Radon and What Does it Mean?”
EPA estimates about 21,000 U.S. lung-cancer deaths each year are related to radon, with an uncertainty range of 8,000–45,000, and about 2,900 annual radon-related lung-cancer deaths among never-smokers. These are model-based estimates, not observed cohort counts.
| Lifetime smoking status and radon exposure | Estimated lung-cancer cases per 1,000 people |
|---|---|
| Smokers at 20 pCi/L | About 260 |
| Smokers at 4 pCi/L | About 62 |
| Never-smokers at 20 pCi/L | About 36 |
| Never-smokers at 4 pCi/L | About 7 |
The table is EPA’s lifetime-risk model and uses the 4 pCi/L action level as one comparison point. U.S. Environmental Protection Agency, “Health Risk of Radon”
Indoor Carbon-Monoxide and Secondhand-Smoke Data
Carbon monoxide statistics often cover a defined subset of incidents rather than every poisoning death. The U.S. Consumer Product Safety Commission estimated 250 consumer-product-related non-fire CO deaths in 2019, excluding fire-related incidents and products outside CPSC jurisdiction.
Portable generators were associated with an estimated 765 non-fire CO deaths from 2009 through 2019. They accounted for 40% of CO deaths related to consumer products under CPSC jurisdiction during that period, so the denominator is not all carbon-monoxide fatalities. U.S. Consumer Product Safety Commission, “New CPSC Report Shows Upward Trend in Carbon Monoxide (CO) Fatalities”
Secondhand smoke is another residential exposure pathway, distinct from household-fuel pollution. CDC guidance states that smoke can persist in the home and that fans, filtration and ventilation do not eliminate exposure; the supplied source provides prevention guidance rather than a quantified population estimate. Centers for Disease Control and Prevention, “Preventing Exposure to Secondhand Smoke in the Home”