Household air pollution: Health impacts
Household air pollution is one of the leading causes of disease and premature death in the developing world.
Exposure to smoke from cooking fires causes 3.8 million premature deaths each year, mostly in low- and middle-income countries, including:
Burning fuels such as dung, wood and coal in inefficient stoves or open hearths produces a variety of health-damaging pollutants, including particulate matter (PM), methane, carbon monoxide, polyaromatic hydrocarbons (PAH) and volatile organic compounds (VOC). Burning kerosene in simple wick lamps also produces significant emissions of fine particles and other pollutants.
Particulate matter is a pollutant of special concern. Many studies have demonstrated a direct relationship between exposure to PM and negative health impacts. Smaller-diameter particles (PM2.5 or smaller) are generally more dangerous, as they can reach deep into the small airways of the body and deposit on the alveoli – the tiny sacs in the lungs where oxygen exchanges with carbon dioxide in the blood. Ultrafine particles (one micron in diameter or less) can penetrate into tissues and organs, posing an even greater risk of systemic health impacts.
Exposure to indoor air pollutants can lead to a wide range of adverse health outcomes in both children and adults, from respiratory illnesses to cancer to eye problems. Members of households that rely on polluting fuels and devices also suffer a higher risk of burns, poisonings, musculoskeletal injuries and accidents.
The health risks of household air pollution are strongly correlated with poverty. These risks are not distributed evenly across countries, or even within countries. People in sub-Saharan Africa, South and East Asia and the Western Pacific experience the highest rates of health problems from exposure to indoor pollutants. Within these regions, the burden of disease falls most heavily on rural households. And within these households, women, children and the elderly bear the brunt of the health and other impacts of household energy use.
Impacts on women and children
Women and children are at heightened risk from household air pollution exposure. In most developing countries, women and children perform the domestic tasks related to energy provision: gathering and processing fuel, tending the hearth and cooking meals. As they spend the most time in the kitchen, women and children have higher rates of exposure to particulate matter and other pollutants streaming out of stoves and open fires.
This has tragic consequences. Half of all child pneumonia deaths are caused by breathing in this smoke. Women suffer from higher risk of noncommunicable diseases related to pollution exposure, but also from chronic strain and injuries associated with fuel collection.
A recent analysis found in WHO's Burning Opportunity report reveals that girls in sub-Saharan African households that rely on polluting cooking sources spend three times as many hours each week gathering fuel and water as girls in households that mainly use cleaner stoves and fuels. Some children in households relying on polluting fuels spend about 30 hours per week gathering fuel and water. In addition to the opportunity cost of their time, the physical burdens imposed by this never-ending task has serious implications for children’s long-term health.
Household energy and poverty
Because they lack the resources to obtain cleaner fuels and devices, people in lower-income households rely mostly on fuels that they can freely gather, such as wood and dung. This lack of access to modern, cleaner energy sources puts them at much higher risk of adverse health outcomes, but also undermines their well-being in other ways.
Reliance on inefficient household fuels and devices limits the time available, especially to women, for income generation, schooling and other opportunities for economic development.
Households that rely on traditional biomass fuels often spend many hours a day on fuel collection. Similarly, households with limited or no access to a clean and reliable source of lighting (e.g. electricity) can lose opportunities for educational and income-generating activities outside of daylight hours.
Energy poverty thus locks people in a vicious cycle, sapping them of time, damaging their health, and limiting their access to better livelihoods, education and other paths out of poverty.
Household energy use is a significant source of climate-warming pollution. Emissions from the incomplete combustion of both biomass and fossil fuels in traditional stoves, inefficient heaters, open fires or wick lamps include both greenhouse gases and short-lived climate pollutants (SLCPs) such as methane, black carbon and volatile organic compounds that contribute to the formation of ozone (a powerful warming agent).
There is increasing evidence that many household energy solutions that are clean for health are also clean and beneficial for the environment and the global climate. Several measures that would reduce exposure to household air pollution would also generate significant environmental benefits. Switching to low-emission cookstoves and fuels, replacing kerosene lamps with electric lights, and using passive design principles to reduce fuel consumption for space heating (e.g. solar heating, insulation) would result in significant reductions of both carbon dioxide and SLCP emissions. Reduced demand for biomass for cooking and heating would lead to reduced deforestation rates, and increased absorption of carbon dioxide by trees.
Residential burning contributes 25 percent of global black carbon emissions. Black carbon – fine particles in soot emitted from incomplete combustion – is the second biggest contributor to climate change after carbon dioxide. It lasts only 7 to 10 days in the atmosphere, on average, but is a highly potent warming agent and extremely efficient at absorbing sunlight and radiating heat. Black carbon is a major driver of glacier retreat and thinning in mountainous regions and the Arctic, as it reduces the albedo of snow and ice (i.e. reflectance of solar radiation away from the earth's surface). It also disrupts regional climate systems such as the South Asian Monsoon.
Household air pollution also has negative impacts on agricultural production. Black carbon reduces the amount of sunlight that reaches crops, impeding photosynthesis, and methane and other precursor gases emitted by inefficient combustion contribute to the formation of ground-level ozone, which damages crops.
Energy poverty is also a significant driver of deforestation, as more than half of all wood harvested globally is used for fuel. One third of this harvesting is unsustainable, as trees and vegetation are not replanted to fully replace what’s cut, leading to a net addition of greenhouse gases to the atmosphere on the order of 2% of global emissions. This huge demand for biomass disrupts ecosystems and destroys wildlife habitat on a large scale.
Ambient air pollution impacts
Household air pollution is a major contributor the global problem of ambient (outdoor) air pollution. Cooking alone is the source of 12% of global ambient fine particulate matter (PM2.5), and causes about 500,000 of the 3.9 million premature annual global deaths from ambient air pollution.
Pollution escapes from household chimneys and openings in the building envelope, and can linger in the immediate vicinity of the home. This polluted ambient air cycles back inside the home through windows, doors and gaps in the envelope, further reducing indoor air quality.
Stove hoods, chimneys and other improved ventilation strategies thus offer limited benefits. Reducing emissions at the source by improving or obviating combustion is the best intervention for improving health outcomes. Expanding access to clean household energy sources will thus be a critical piece of solving the global ambient air pollution crisis.