Household and Indoor Air Pollution

Household and indoor air pollution is the contamination of air within homes and enclosed spaces, dominated in much of the world by smoke from burning solid fuels such as wood, charcoal, crop residues, dung and coal for cooking and heating. It is a major environmental health risk, falling disproportionately on women and young children in low- and middle-income countries.

Definition

Household and indoor air pollution refers to harmful agents present in the air of indoor environments, arising chiefly from inefficient combustion of solid fuels and kerosene in poorly ventilated dwellings, but also from tobacco smoke, building materials and other indoor sources.

Scope

This topic covers the principal sources of indoor air contamination, the pollutants involved (especially fine particulate matter and carbon monoxide), the populations most exposed, and the respiratory and other health outcomes associated with chronic exposure. It also notes the link between household combustion and outdoor air quality. It treats indoor exposure distinctly from ambient outdoor pollution.

Key concepts

• Solid-fuel combustion (wood, charcoal, dung, crop residue, coal)
• Indoor fine particulate matter and carbon monoxide
• Cooking and heating practices
• Ventilation and dwelling characteristics
• Disproportionate exposure of women and children
• Clean cooking and fuel transition
• Contribution to ambient air pollution

Mechanisms

Incomplete combustion of solid fuels in open fires or simple stoves releases high concentrations of fine particulate matter, carbon monoxide and other products of combustion into enclosed living spaces. In poorly ventilated dwellings these accumulate to levels far exceeding outdoor guidelines, and prolonged inhalation drives airway inflammation and contributes to respiratory disease; the same emissions also escape outdoors and add to ambient particulate pollution.

Clinical relevance

Household air pollution is a recognised risk factor associated at the population level with respiratory infections in children and chronic respiratory and other conditions in adults, shaping the disease burden in communities that rely on solid fuels. This entry characterises population exposure and risk and is not guidance for individual clinical care.

Epidemiology

Billions of people, concentrated in low- and middle-income countries, rely on solid fuels, and household air pollution has been estimated in comparative risk assessments to cause millions of premature deaths each year, with the burden borne disproportionately by women, who often do the cooking, and by young children.

Evidence & guidelines

Comparative risk assessments and reviews summarised by Smith and colleagues and by Gordon and colleagues link household air pollution to respiratory and other outcomes, and modelling shows that solid-fuel cooking also raises outdoor PM2.5. The WHO global air quality guidelines (2021), together with WHO guidelines on household fuel combustion, frame recommended pollutant levels and cleaner-fuel transitions.

Key figures

• Kirk R. Smith

Seminal works

• smith-2014
• gordon-2014

Frequently asked questions

What is the main source of household air pollution worldwide?

In low- and middle-income settings the dominant source is the burning of solid fuels such as wood, charcoal, crop residues, dung and coal for cooking and heating, often in poorly ventilated homes.

Who is most exposed to household air pollution?

Women, who frequently spend long periods cooking over solid-fuel stoves, and young children who stay near them are the most heavily exposed groups.