Household air pollution and the forgotten 3 billion

Oliver Stoner

Photo credit: Nigel Bruce

Air pollution has been described by the WHO as “the most important global environmental health risk”, but this statement does not in fact refer to the typical image of air pollution we hold in developed countries – produced by vehicle exhaust, factories and power stations. In fact, it refers to household air pollution produced by household fuel combustion, for cooking, heating and lighting.

If you are reading this, you are probably fortunate enough to have access to modern household energy services, but around 3 billion people (predominantly in low- and middle- income countries) rely on polluting fuels and technology for day-to-day cooking, heating and lighting. This makes ordinary and essential household activities a significant health risk, attributed by the WHO to millions of premature deaths from respiratory and cardiovascular diseases, and cancer. In fact, the estimated household air pollution mortality just from cooking with polluting fuels (3.8 million deaths per year) is comparable to the contemporary estimate of all premature deaths from outdoor air pollution (4.2 million per year). Indeed, in some countries a significant portion of outdoor pollution may even be the result of household fuel combustion. These major health impacts are compounded by the risk of burn injuries and the time needed to collect fuel, which could instead be spent on work or education – a burden which falls most heavily on women and children.

Figure 1: Estimated global population (millions) using clean and polluting fuels and technologies for cooking (shaded areas) and the estimated global percentage using polluting fuels, with 95% uncertainty intervals (lines). Source: WHO Global Household Energy Model.

To relieve the weight on the societies of developing countries, one of the Sustainable Development Goals (SDGs) is to achieve universal access to clean fuels and technology for cooking by 2030. Here clean refers to specifically to the health impact and the WHO maintains an agonistic stance on the relative merits of clean fuels versus clean technologies. Progress towards this goal is analysed annually in Tracking SDG7: The Energy Progress Report. Over the last few decades, the proportion of the population using polluting fuels and technology combinations has steadily decreased in both urban and rural areas but remains high (around half of the population) in rural areas. While the global percentage using polluting cooking has decreased, the pace of population growth has meant that the absolute number of people using polluting fuels has stagnated, straying little from 3 billion people between 1990 and 2020. In no region is this starker than in Sub-Saharan Africa, due to a combination of high population growth and limited progress in access to clean cooking. Estimated to be less than 500 million in 1990, the number of people using polluting fuels in Sub-Saharan Africa is projected to exceed 1 billion in the next 10 years.

Figure 2: Estimated percentage of each country’s population using polluting fuels for cooking in 1990 and 2020. Source: WHO Global Household Energy Model.

The Global Household Energy Model

Statistical models for solid/polluting fuel use have been employed by the WHO for many years, firstly to monitor clean fuel use for cooking and secondly for estimating  the number of deaths arising from exposure to household air pollution. Affordability, availability, infrastructure and cultural preferences are key determinants of the fuel and technology combination adopted by a household, but these are all served poorly by international monitoring which is limited to the dichotomy of clean versus polluting fuels. Furthermore, for monitoring household air pollution mortality, the use of a single aggregate measure of fuel use lacks accuracy, as it ignores the varying levels of harm associated with different polluting fuels.

Since 2017, researchers at the University of Exeter have worked with the WHO to design a completely new bespoke statistical model for estimating worldwide use of specific fuels (e.g. wood, charcoal) for cooking, the Global Household Energy Model (GHEM). GHEM brings the tracking of SDG 7 up to date with the latest methods and allows fuel use trends to be projected into the future – to act as a baseline against which the effect of interventions can be compared. Researchers at Exeter have also worked with the WHO to help prepare the chapter on clean cooking in Tracking SDG7: The Energy Progress Report which this year, for the first time, includes detailed analysis of worldwide specific fuel use for cooking. Crucially, in the coming years estimates of specific fuel use from GHEM will enable a complete reassessment of the health impacts of cooking with polluting fuels.

This study was commissioned and paid for by the World Health Organization (WHO). Copyright in the original work on which this article is based belongs to WHO. The authors have been given permission to publish this article. The author alone is responsible for the views expressed in this publication and they do not necessarily represent the views, decisions or policies of the World Health Organization.

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