Module 11: Air

Air Pollution

Air pollution is a major environmental risk to health. The WHO estimates that 4.2 million people die each year due to exposure to outdoor air pollution and 3.8 million people die each year due to household exposure to smoke from cookstoves and fuels. Exposure to air pollutants is largely beyond the control of individuals and requires action by public authorities at the national, regional, and international levels. The WHO Air Quality Guidelines contain up-to-date assessments of the health effects of air pollution, and the guidelines recommend targets for air quality at which the health risks will be significantly reduced. It is estimated that 91% of the world’s population live in places that exceed the guidelines for exposure to air pollution.(1)

Indoor Air Pollution

Over 3 billion people worldwide use polluting fuels such as wood, dung, crop residues, or coal in simple stoves with incomplete combustion to heat their meals each day.(2) This indoor smoke contains a range of health-damaging pollutants, including small soot or dust particles that are able to penetrate deep into the lungs. People in developing countries are commonly exposed to very high levels of pollution for 3-7 hours daily over many years. During the winter in cold and mountainous areas, exposure may occur over a substantial portion of each 24-hour period. Because of their customary involvement in cooking, women’s exposure is much higher than men’s. Young children are often carried on their mothers’ backs while cooking is in progress, and they therefore spend many hours breathing smoke. Because  women and children in many parts of the world are exposed to high levels of indoor air pollution every day, they are at increased risk  of chronic obstructive pulmonary disease and of acute respiratory infection in childhood. Exposure to indoor air pollution has also been associated with low birth weight, increased infant and perinatal mortality, pulmonary tuberculosis, nasopharyngeal and laryngeal cancer, and cataract.(3) The WHO estimates that of the 3.8 billion deaths each year attributable to exposure to indoor air pollution, 27% are due to pneumonia, 18% to stroke, 27% to ischaemic heart disease, 20% to chronic obstructive pulmonary disease (COPD), and 8% to lung cancer.(4) 

Indoor air pollution is a major global public health threat requiring increased efforts in the areas of research and policy-making. 
Poverty is one of the main barriers to the adoption of cleaner fuels. Wood is the most common example of biomass fuel, but the use of animal dung and crop residues is also widespread. Many of the substances in biomass smoke can harm human health. The most toxic byproducts are particles, carbon monoxide, nitrous oxides, sulphur oxides (principally from coal), formaldehyde, and polycyclic organic matter. The majority of households in developing countries burn biomass fuels in open fireplaces, or in a poorly functioning earth or metal stove. Combustion is very incomplete in most of these stoves, resulting in substantial emissions which, in the presence of poor ventilation, produce very high levels of indoor pollution. 

Exposure can be reduced by using improved stoves, better housing, cleaner fuels, and behavioral change. Cleaner fuels, especially liquefied petroleum gas, offer the best long-term option in terms of reducing pollution and protecting the environment, but most poor communities using biomass are unlikely to be able to make the transition to these types of cleaner fuels. The use of improved biomass stoves has given varying results and has often been unsuccessful. Until recently, the main emphasis of stove programs has been to reduce the use of wood, and consequently there has been relatively little evaluation of reductions in exposure. Other factors such as seasonal energy requirements and cultural beliefs are also important considerations.

Outdoor Air Pollution

Outdoor air pollution results largely from the combustion of fossil fuels for transport, power generation, and other human activities. Of the 4.2 million premature deaths that occur each year  due to exposure to outdoor air pollution, 91% occurred in low- and middle-income countries, and the greatest number in the WHO South-East Asia and Western Pacific regions. Specifically, the WHO estimates that in 2016, 58% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and strokes, 18% of deaths were due to COPD and acute lower respiratory infections, and 6% of deaths were due to lung cancer.(5) Combustion processes produce a mixture of pollutants that comprise both primary emissions, such as diesel soot particles and lead, and the products of atmospheric transformation, such as ozone and sulfate particles that form from the burning of sulfur-containing fuel. Today, many developing world cities face very severe levels of urban air pollution.

Outdoor air pollution results largely from the combustion of fossil fuels for transport, power generation, and other human activities. Combustion processes produce a mixture of pollutants that comprise both primary emissions, such as diesel soot particles and lead, and the products of atmospheric transformation, such as ozone and sulfate particles that form from the burning of sulfur-containing fuel. Urban air pollution is primarily generated by transportation vehicles and energy production, and this form of pollution kills an estimated 1.2 million people annually. Today, many developing world cities face very severe levels of urban air pollution.

Footnotes

(1) WHO. “Air Pollution.” http://www.who.int/airpollution/en/.

(2) Ibid.

(3) Bruce N., Perez-Padilla R., & Albalak R. “Indoor air pollution in developing countries: a major environmental and public health challenge.” Bulletin of the World Health Organization. (2000). 78(9). http://www.who.int/bulletin/archives/78(9)1078.pdf.

(4) WHO. “Household Air Pollution and Health.”http://www.who.int/en/news-room/fact-sheets/detail/household-air-pollution-and-health.

(5) WHO. “Outdoor (Ambient) Air Pollution and Health.”http://www.who.int/en/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health.