Respiratory risks from household air pollution in low and middle income countries

Abstract

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.

Figure 1. Exposure of children to household air pollution at home and at school

(A) An infant in Malawi is exposed to very high levels of cooking smoke. Both mother and child had evidence of eye irritation. (B) Household air pollution exposure continues at school. Used with permission of CAPS/Handstand productions.

Figure 2. WHO map of household air pollution and mortality

World map of poverty (not shown) shows nearly identical geographical distribution. © WHO 2005. All rights reserved.

Figure 3. Cookstove types used around the world

(A) Three-stone, minimally tended, wood fuel. (B) Berkeley–Darfur, wood fuel. (C) Envirofit G-3300, wood fuel. (D) Onil, wood fuel. (E) Philips HD4008, wood fuel. (F) Philips HD4012, wood fuel. (G) Sampada, wood fuel. (H) StoveTec GreenFire, wood fuel. (I) Upesi Portable, wood fuel. (J) GERES, charcoal fuel. (K) Gyapa, charcoal fuel. (L) Jiko, ceramic, charcoal fuel. (M) Jiko, metal, charcoal fuel. (N) KCJ Standard, charcoal fuel. (O) Kenya Uhai, charcoal fuel. (P) StoveTec prototype, charcoal fuel. (Q) Belonio Rice Husk Gasifier, rice hull fuel. (R) Mayon Turbo, rice hull fuel. (S) Oorja, biomass pellet fuel. (T) StoveTec TLUD prototype, wood pellet fuel. (U) Jinqilin CKQ-80I, corn cob fuel. (V) Protos, plant oil fuel. Photo is courtesy of James Jetter, US Environmental Protection Agency, NC, USA.

Figure 4. Improved cookstoves offer greatly reduced household air pollution exposure

(A) A woman in Malawi using the Philips improved cookstove as part of the Cooking and Pneumonia Study (CAPS) funded by the Joint Global Health Trials of the Medical Research Council, Wellcome Trust, and Department for International Development. (B) Taken at the same location in Malawi, non-invasive monitoring, in this case od carboxyhaemoglobin, can be used to objectively assess cookstove effect. Used with permission of CAPS/Handstand productions.

Figure 5. Household air pollution and other risk factors for respiratory infections

ALRI=acute lower respiratory infection.

Figure 6. Forest plot of studies to assess the link between lung cancer and exposure to household air pollution

Figure 7. Forest plot of studies to assess the link between nasopharyngeal cancer and exposure to household air pollution stratified by adjustment for tobacco smoking status

Al/Mo/Tu=North Africa (Algeria, Morocco, Tunisia).

Figure 8. Exposure monitoring is essential to properly assess the effect of an intervention

(A) A simple clay stove implemented in community studies to reduce fuel consumption and hence improve livelihoods for women. (B) The effect of stacking (use of several different energy sources in cooking) on air monitored in four households before (left) and after (right) the introduction of a simple clay stove to reduce fuel consumption. Households have used both the stove and fire, resulting in increased household air pollution being measured after the intervention. Reprinted with permission of the International Union Against Tuberculosis and Lung Disease.

Figure 9. The energy ladder

Adapted from Rehfuess. © WHO. All rights reserved.

Figure 10. Integrated exposure–response models for acute lower respiratory infection, lung cancer, and COPD

Predicted values of integrated exposure–response model for acute lower respiratory infection incidence in infants (A), lung cancer mortality in adults (B), and COPD mortality in adults (C). Shaded boxes for COPD mortality and lung cancer mortality represent uncertainty (height) and exposure contrast (width) of RR for HAP estimates for men (smaller darker boxes) and women (larger lighter boxes). HAP=household air pollution. RR=relative risk. PM_2·5=particulate matter smaller than 2·5 μm. COPD=chronic obstructive pulmonary disease. Adapted from Burnett and colleagues.

Figure 11. Seven key domains (D) of factors affecting adoption and sustained use of household energy interventions

Adapted from Puzzolo and colleagues.