The Lancet Respiratory Medicine Commission
Respiratory risks from household air pollution in low and middle income countries

https://doi.org/10.1016/S2213-2600(14)70168-7Get rights and content

Summary

A third of the world's population uses solid fuel derived from plant material (biomass) or coal for cooking, heating, or lighting. These fuels are smoky, often used in an open fire or simple stove with incomplete combustion, and result in a large amount of household air pollution when smoke is poorly vented. Air pollution is the biggest environmental cause of death worldwide, with household air pollution accounting for about 3·5–4 million deaths every year. Women and children living in severe poverty have the greatest exposures to household air pollution. In this Commission, we review evidence for the association between household air pollution and respiratory infections, respiratory tract cancers, and chronic lung diseases. Respiratory infections (comprising both upper and lower respiratory tract infections with viruses, bacteria, and mycobacteria) have all been associated with exposure to household air pollution. Respiratory tract cancers, including both nasopharyngeal cancer and lung cancer, are strongly associated with pollution from coal burning and further data are needed about other solid fuels. Chronic lung diseases, including chronic obstructive pulmonary disease and bronchiectasis in women, are associated with solid fuel use for cooking, and the damaging effects of exposure to household air pollution in early life on lung development are yet to be fully described. We also review appropriate ways to measure exposure to household air pollution, as well as study design issues and potential effective interventions to prevent these disease burdens. Measurement of household air pollution needs individual, rather than fixed in place, monitoring because exposure varies by age, gender, location, and household role. Women and children are particularly susceptible to the toxic effects of pollution and are exposed to the highest concentrations. Interventions should target these high-risk groups and be of sufficient quality to make the air clean. To make clean energy available to all people is the long-term goal, with an intermediate solution being to make available energy that is clean enough to have a health impact.

Introduction

Household air pollution (HAP) is usually measured indoors, and arises from domestic activities of cooking, heating, and lighting, particularly in low and middle income countries (LMICs). 3 billion people worldwide are exposed to toxic amounts of HAP every day because they use solid fuels, a term that includes biomass fuels (derived from plant sources) or coal for combustion resulting in the release of products of incomplete combustion such as carbon monoxide and particulate matter (PM). Furthermore, solid fuel is commonly used in homes with poor or absent chimney ventilation of smoke.

Cooking is the energy requirement that consumes most solid fuel worldwide. The sources of fuel vary considerably, with coal use being predominant in China, described in the later section on lung cancer, but wood and charcoal being more common in Africa and India. Animal dung is used among pastoralist communities, particularly those at high altitude (eg, Nepal, Afghanistan) or in savannahs where wood is rare (eg, Kenya, Ethiopia). Fuel-deprived communities often burn domestic rubbish and plant residues (eg, straw, maize husks); whereas urban communities commonly burn kerosene or charcoal. The toxic content of smoke from all of these fuels differs widely and has overlap with the known toxicity of traffic, industrial, and tobacco smoke. Lighting can also result in substantial HAP. Smoky unvented wicks in simple lamps that burn kerosene and in candles can result in substantial black carbon smoke. The increasing availability of light emitting diode (LED) lamps has reduced this form of pollution, but it remains a major problem. Heating needs are highly variable by latitude, altitude, and season. In extreme climates (eg, Nepal, north India), ventilation is deliberately minimised to conserve energy, resulting in extremely toxic amounts of HAP for a substantial proportion of the year. Urban poor people in Africa often bring a simple cooking stove indoors to keep their sleeping area warm at night.

Household behaviour for cooking, lighting, and heating varies by culture, gender, age, and socioeconomic status. These behavioural norms determine both exposure and resulting health risks for women, children, and men. Cultural differences define a fascinating range of cooking methods, from roasting over flame or in an open earthen oven, to boiling, broiling, steaming, and stewing, found almost everywhere. In most cultures, women have a leading role in domestic cooking, with men cooking when at work or away from home. In the typical domestic context, therefore, women have several periods of intense cooking smoke exposure per day. Young children and infants, typically carried on the back or placed near their mother to sleep, are also exposed to these short, very high level, exposures to smoke (figure 1). There is particular concern when young children are exposed to smoke because data suggest that smoke exposure during the window of developmental susceptibility in early life is particularly detrimental. Men in most cultures have greater exposure to occupational, industrial, or agricultural smoke, and higher consumption of tobacco, which is outside the scope of our Commission; however, we note the confounding effect of these exposures on studies of HAP.

Socioeconomic status is a major predictor of exposure to HAP in most cultures. The less expensive fuel options in any context are generally less efficient fuels, produce more smoke, and are used by people with the most poorly designed homes. For example, propane, liquid petroleum gas (LPG), or ethanol often burn very cleanly, but remain too expensive for many households. Electricity is the least polluting form of domestic energy (assuming that households are geographically separated from power stations), but is not affordable to most people. As we descend the energy ladder1 to cheaper forms of fuel (such as charcoal, wood and dung or crop residues), there are polluting fuels with both poor combustibility and highly toxic emissions. Simple homes built with mud, thatch, and animal skins rarely have a chimney and, when present, the chimney is usually a simple vent with no air-drawing flue. In addition, correctly installed flues must be maintained with regular inspections and cleanings, an activity that, when not done, can result in marked increases in HAP.

Poverty, disease, and the use of solid fuel are inextricably linked because poverty is a risk factor for disease in all communities (figure 2). The attribution of disease burden to HAP exposure or other risk factors is complex and needs systemic analysis from multiple perspectives. The 2012 report of the comparative risk assessment2 for the Global Burden of Disease study (GBD) 2010 is the gold standard for such analysis, and its findings attributed nearly 3·5 million deaths to direct exposure to HAP. HAP is also an important contributor to ambient air pollution (estimated to contribute 16% of the global disease burden from ambient air pollution), as detailed in the methods of the report.2 Deaths from air pollution, including from HAP and ambient air pollution, far exceed deaths attributed to other environmental factors (table 1). The great increase in the disease attribution between previous comparative risk assessments and the GBD in 2010 resulted partly from inclusion of cardiovascular and cerebrovascular deaths associated with HAP exposure. The WHO Global Health Observatory report3 updated the estimates and noted that HAP caused 4·3 million deaths worldwide in 2012, and ambient air pollution caused a further 3·7 million deaths.

HAP is associated with many health effects, including both acute and chronic disorders, pulmonary and systemic. Respiratory risks are the focus of this review and so we devote full sections to respiratory infections, chronic lung diseases, and cancers. It is important, however, not to neglect the cardiovascular risks associated with HAP, which have been reviewed elsewhere.4 Data support a role for HAP in the pathogenesis of both myocardial infarction and hypertension-related stroke.5 There are other factors that are also beyond the scope of our Commission. For example, the burning of solid fuel in either open fires or simple stoves results in frequent burns to adults and particularly to children. Burns in children are often severe. There are also indirect health risks to women and children gathering fuel including trauma, assault, and injury.

HAP is now recognised to be a modifiable exposure against which specific interventions such as the use of improved fuels, cookstoves, or heaters, and improved ventilation using improved cooking technology, can improve human health. In practice, culturally acceptable and context-specific solutions involve consideration of many factors including combinations of interventions. In 2011, RESPIRE6 showed, for the first time using a randomised controlled trial (RCT), that a reduction in disease is possible—in this case a reduction in severe pneumonia in children after a chimney stove intervention to reduce HAP. Similar RCTs are continuing elsewhere in the world, from Nepal to Ghana to Malawi, that use different technologies, both to reduce exposure to HAP and to determine the exposure–response. Such data provide the evidence base to understand how much exposure levels need to be reduced to improve health worldwide. Now that such information is becoming available, it will drive commitments by governments, industries, and non-governmental organisations (NGOs) to find culturally sensitive, affordable, and sustainable technologies that households can use to reduce the burden of preventable death.

Of many fuels used worldwide, the most popular are electricity and gas; indeed most people living in high-income countries use a combination of electricity for oven use and gas for pot cooking. Both are clean fuels and, although electricity is easily and safely delivered throughout cities and rural areas, the greater immediate control when cooking with gas makes it an attractive option. There are, however, alternative fuel solutions with intermediate cost that have widespread applicability in middle-income regions that retain some of the features of gas cooking. Pellets made of wood or crop residues offer much better burning, particularly in combination with an advanced cookstove, than does wood. Clean liquid fuels such as propane, LPG, and biofuels such as ethanol are all increasingly available, but are not often used because of costs, for cooking needs such as boiling water for tea or similar items. Biogas for villages is another clean fuel possibility that could be an inexpensive and clean energy source for a household, but needs a substantial initial investment, which might well prove cost-effective in time. Ultimately, ideal clean fuels could be made available throughout the world, but they are not presently realistic for most households in LMICs.

Improved cookstove technology for households living in poverty in LMICs has been available for 40 years, initially driven by the need to reduce fuel use that caused deforestation and, more recently, by health risks from HAP. This historical imperative to reduce wood use by improved cooking efficiency led to the invention of many stoves that burn less fuel (usually wood), but, in the absence of known health effects, less consideration has been given to the concentration and toxicity of emissions. Improvements in cookstove design often come as a result of controlling entrainment of air during combustion or with assisted ventilation such as a fan that might use a battery, thermoelectric generator, or another source of electric assistance. Insulated heat direction, correct use of a pot appropriate for the stove, and careful fuel selection (at least dry wood) are other important improvements in design. There are a wide variety of cookstoves available worldwide (figure 3), with equally variable levels of efficiencies that can reduce fuel use or emissions.7 The kitchen performance test that is used to compare alternative technologies typically measures weight of fuel used to heat a defined volume of water to boiling point; improved stoves can improve the percentage of energy transferred from fuel to water from less than 20% (three-stone fire) to more than 80% (advanced cookstoves; figure 4). Unfortunately, available kitchen performance tests do not include a measure of toxicity. Certain innovative and attractive solutions involving renewable energy (eg, solar cookers) can be very effective at reducing cooking-related exposures to zero. However solar cookers have limited use because the cooking is not easily controlled, the time and location of cooking needs access to the sun, and it is often viewed as not being culturally suitable (eg, when staples need to be cooked at night, etc). Many new technologies are being developed that will enhance the efficiencies of various cooking and heating solutions, with particular attention to products that effectively reduce exposures to HAP, improve safety to avoid burns and scalds, and enhance multiple household uses of energy from solid and liquid fuel combustion. Such progress is needed to increase market demand for such improved cooking and heating solutions.

House design is shaped by people developing pragmatic solutions to deal with climate and security with use of materials available locally. Chimneys are far from being universally available and, even when built, chimneys must be correctly designed and installed and have regular maintenance to be effective. In many cultures, the solution to not having smoke from open fires or non-ventilated stoves is cooking outdoors or on simple verandas. This seems like a simple and direct solution, but the exposure to the smoke might remain unacceptably high, even outdoors, and it is dependent on weather and season. Simple ventilation solutions, including air bricks and holes in the roof or eaves, can greatly reduce levels of HAP. Adapted ovens such as the plancha stove in Guatemala or Afghanistan that pipes smoke from a central oven out of the house are also effective interventions to reduce HAP. These interventions need behavioural changes in activities that are held very precious in life, and so there can be immediate resistance to implementation of ventilation.

Even the most efficient technology fails if adoption is only for a brief period after introduction, or if the new technology is used concurrently with traditional methods. This latter behaviour, known as stacking, is common in western kitchens, in which use of an oven, cooker, toaster, and microwave is now usual. Combined use of new and old technologies in households in LMICs at risk from HAP negates any reduction in health risks by new efficient cooking or heating technologies. To reduce HAP, households and communities must share a substantial will to change behaviour at both the household and the community level. This effort involves not only an affordable effective technology but also an appreciation of the benefits of change. In fact, it is unusual for communities to change behaviour to achieve a health-related benefit. More attractive benefits include the convenience in cooking, economy of fuel use, time savings for gathering fuel and cooking, and the value of it being more modern. Modern co-benefits include stoves that also charge a mobile phone or battery light with use of thermoelectric coupling.

Climate change and the increasing demand for energy, along with an increasing awareness of pollution having an adverse health effect on women and children, have driven a global interest to reduce HAP. Starting with the US Environmental Protection Agency's Partnership for Clean Indoor Air (PCIA), hundreds of motivated NGOs have joined with government and international organisations to design innovative and regionally specific solutions. In 2010, the US Government, together with the UN Foundation, created a public–private partnership that incorporated the PCIA into the Global Alliance for Clean Cookstoves, enhancing development and implementation of clean cooking solutions for millions of households, to reduce the effect of deforestation and climate change, and to empower women. In addition, the UN launched the Initiative for Sustainable Energy for All in 2011 as a set of plans to provide clean cooking energy for people at the bottom of the world's energy ladder through the advancement of cleaner technologies, such as LPG by the year 2030. Such efforts offer interdisciplinary platforms to promote global change in energy use for poor people that can result in major economic and social improvement, and ultimately, reduce the global burden of disease, especially diseases related to HAP.

Air pollution is the number one environmental cause of death in the world, with HAP being a major contributor to this burden. In this Commission, we discuss evidence to link HAP with respiratory infections, chronic lung diseases, and respiratory tract cancers. We then review issues with quantifying the exposure. Finally, we discuss available interventions and those in development to reduce HAP.

Section snippets

Chronic obstructive pulmonary disease and asthma

Chronic obstructive pulmonary disease (COPD) and asthma are two of the most common chronic diseases worldwide;151 about 80 million people have COPD and 235 million people have asthma.152 In 2005, 3 million people died from COPD, making it the fifth leading cause of mortality. According to GBD 2012, COPD is now the third leading cause of death worldwide, something that WHO had not predicted to occur until 2030.153 COPD and asthma are major causes of morbidity due to persistent symptoms, reduced

Conclusion

Worldwide, respiratory health effects account for nearly a half of the overall deaths and disabilities from HAP. In each section of this Commission, we have focused on how the available published research can inform on specific respiratory disease risk and the complexities that underpin this risk. As is clear from this Commission, severe poverty and fuel use at the bottom of the world's energy ladder are the main risk factors for HAP-related respiratory disease. But this is not simply a story

References (319)

  • HC Chuang et al.

    Protective effects of pulmonary epithelial lining fluid on oxidative stress and DNA single-strand breaks caused by ultrafine carbon black, ferrous sulphate and organic extract of diesel exhaust particles

    Toxicol Appl Pharmacol

    (2013)
  • A Dutta et al.

    Changes in sputum cytology, airway inflammation and oxidative stress due to chronic inhalation of biomass smoke during cooking in premenopausal rural Indian women

    Int J Hyg Environ Health

    (2013)
  • RP Schins et al.

    Inflammatory effects of coarse and fine particulate matter in relation to chemical and biological constituents

    Toxicol Appl Pharmacol

    (2004)
  • TC Wegesser et al.

    Lung response to coarse PM: bioassay in mice

    Toxicol Appl Pharmacol

    (2008)
  • S Becker et al.

    Differential particulate air pollution induced oxidant stress in human granulocytes, monocytes and alveolar macrophages

    Toxicol In Vitro

    (2002)
  • JM Soukup et al.

    Human alveolar macrophage responses to air pollution particulates are associated with insoluble components of coarse material, including particulate endotoxin

    Toxicol Appl Pharmacol

    (2001)
  • A Dutta et al.

    Systemic inflammatory changes and increased oxidative stress in rural Indian women cooking with biomass fuels

    Toxicol Appl Pharmacol

    (2012)
  • A Dutta et al.

    Immune cells and cardiovascular health in premenopausal women of rural India chronically exposed to biomass smoke during daily household cooking

    Sci Total Environ

    (2012)
  • M Lundborg et al.

    Aggregates of ultrafine particles modulate lipid peroxidation and bacterial killing by alveolar macrophages

    Environ Res

    (2007)
  • S Sigaud et al.

    Air pollution particles diminish bacterial clearance in the primed lungs of mice

    Toxicol Appl Pharmacol

    (2007)
  • RE Black et al.

    Maternal and child undernutrition: global and regional exposures and health consequences

    Lancet

    (2008)
  • S Wang et al.

    Immunomodulatory effects of high-dose alpha-tocopherol acetate on mice subjected to sidestream cigarette smoke

    Toxicology

    (2002)
  • N Büchner et al.

    Unhealthy diet and ultrafine carbon black particles induce senescence and disease associated phenotypic changes

    Exp Gerontol

    (2013)
  • E Rehfuess

    Fuel for Life: Household Energy and Health

    (2006)
  • The Global Health Observatory

  • The top 10 causes of death in the world. Fact sheet number 310

    (2014)
  • SH Hwang et al.

    Environmental tobacco smoke and children's health

    Korean J Pediatr

    (2012)
  • J Bagaitkar et al.

    Tobacco use increases susceptibility to bacterial infection

    Tob Induc Dis

    (2008)
  • MN Bates et al.

    Risk of tuberculosis from exposure to tobacco smoke: a systematic review and meta-analysis

    Arch Intern Med

    (2007)
  • HH Lin et al.

    Tobacco smoke, indoor air pollution and tuberculosis: a systematic review and meta-analysis

    PLoS Med

    (2007)
  • L Downie et al.

    Community-acquired neonatal and infant sepsis in developing countries: efficacy of WHO's currently recommended antibiotics–systematic review and meta-analysis

    Arch Dis Child

    (2013)
  • K Edmond et al.

    New approaches to preventing, diagnosing, and treating neonatal sepsis

    PLoS Med

    (2010)
  • NG Bruce et al.

    Control of household air pollution for child survival: estimates for intervention impacts

    BMC Public Health

    (2013)
  • S Kashima et al.

    Effects of traffic-related outdoor air pollution on respiratory illness and mortality in children, taking into account indoor air pollution, in Indonesia

    J Occup Environ Med

    (2010)
  • JM Tielsch et al.

    Exposure to indoor biomass fuel and tobacco smoke and risk of adverse reproductive outcomes, mortality, respiratory morbidity and growth among newborn infants in south India

    Int J Epidemiol

    (2009)
  • M Dherani et al.

    Indoor air pollution from unprocessed solid fuel use and pneumonia risk in children aged under five years: a systematic review and meta-analysis

    Bull World Health Organ

    (2008)
  • JY Po et al.

    Respiratory disease associated with solid biomass fuel exposure in rural women and children: systematic review and meta-analysis

    Thorax

    (2011)
  • MN Bates et al.

    Acute lower respiratory infection in childhood and household fuel use in Bhaktapur, Nepal

    Environ Health Perspect

    (2013)
  • KR Smith et al.

    Millions dead: how do we know and what does it mean? Methods used in the comparative risk assessment of household air pollution

    Annu Rev Public Health

    (2014)
  • A Adoga et al.

    Chronic suppurative otitis media: socio-economic implications in a tertiary hospital in Northern Nigeria

    Pan Afr Med J

    (2010)
  • LL Jones et al.

    Parental smoking and the risk of middle ear disease in children: a systematic review and meta-analysis

    Arch Pediatr Adolesc Med

    (2012)
  • S Patra et al.

    Passive smoking, indoor air pollution and childhood tuberculosis: a case control study

    Indian J Tuberc

    (2012)
  • J Jubulis et al.

    Modifiable risk factors associated with tuberculosis disease in children in Pune, India

    Int J Tuberc Lung Dis

    (2014)
  • JH Kilabuko et al.

    Air quality and acute respiratory illness in biomass fuel using homes in Bagamoyo, Tanzania

    Int J Environ Res Public Health

    (2007)
  • IL Shrestha et al.

    Indoor air pollution from biomass fuels and respiratory health of the exposed population in Nepalese households

    Int J Occup Environ Health

    (2005)
  • ET Taylor et al.

    Prevalence of acute respiratory infections in women and children in western Sierra Leone due to smoke from wood and charcoal stoves

    Int J Environ Res Public Health

    (2012)
  • LE Bautista et al.

    Indoor charcoal smoke and acute respiratory infections in young children in the Dominican Republic

    Am J Epidemiol

    (2009)
  • K Slama et al.

    Indoor solid fuel combustion and tuberculosis: is there an association?

    Int J Tuberc Lung Dis

    (2010)
  • C Sumpter et al.

    Systematic review and meta-analysis of the associations between indoor air pollution and tuberculosis

    Trop Med Int Health

    (2013)
  • AK Pokhrel et al.

    Tuberculosis and indoor biomass and kerosene use in Nepal: a case-control study

    Environ Health Perspect

    (2010)
  • Cited by (0)

    Section leads

    View full text