Household Air Pollution from Solid Cookfuels and Its Effects on Health

Abstract

Since the earliest human times, humans have used wood as fuel for fires to cook their food. Indeed, learning to control fire is considered the defining moment between the pre-human and human condition (Wrangham 2009). With the agricultural revolution some 10,000 years ago, agricultural residues (including animal dung) were brought to the hearth as well. Around 1,000 years ago, coal became used in areas where it was mined easily—for example, the British Isles and China (Smil 1994). These three fuels—wood, agricultural residues, and coal—constitute the solid cooking fuels used by about 40 percent of humanity today (Bonjour and others 2013). Typically burned in simple cookstoves, these fuels produce smoke that is now understood to cause a large burden of disease (Smith and others 2014).Cleaner fuels (coal gas, natural gas, liquefied petroleum gas [LPG], and electricity) began to make inroads only in the late nineteenth century. Although today 60 percent of the world’s population uses these modern fuels (which are relatively clean in household use, even in simple cookstoves), growth in their use has never kept up with global population growth, primarily because of the persistence of biomass use among the poor. Today, almost 3 billion people use solid cookfuels, which probably is more than at any time in world history (Bonjour and others 2013) and more than the entire world population before 1960.Household air pollution (HAP) is now understood to be a major risk factor for health. According to the 2013 Global Burden of Disease Study (GBD), HAP is ranked as the single most significant environmental health risk factor globally. In poor countries where many households rely on biomass for cooking (such as in Sub-Saharan Africa), HAP is ranked among the top risk factors examined in the GBD assessments. Depending on which set of estimates is used, some 3 million to 4 million premature deaths are thought to be caused annually by HAP. Between 3 and 5 percent of the GBD in terms of disability-adjusted life years (DALYs) is attributed to it, about one-third in children younger than age five years and the rest divided between adult men and women (for background on DALYs, see Salomon 2014).This chapter relies on two major reviews published in recent years. One was done as part of the Comparative Risk Assessment (CRA) of the GBD project (Lim and others 2012; Lozano and others 2012; Smith and others 2014), and the other was done as background documentation for the World Health Organization’s (WHO) Indoor Air Quality Guidelines (IAQGs) (WHO 2014b). This chapter summarizes what is known about effective and cost-effective interventions to reduce the health effects of exposure to HAP from solid cooking fuels and then explores some of the issues regarding framing, interactions, and viable interventions. The discussion follows the classic environmental health pathway described in box 7.1.Most of the older literature and even some modern studies refer to the problem as one of indoor air pollution, but the CRA (Lim and others 2012) carefully redefined it as HAP for several reasons (Smith and others 2014): Much of the health-relevant exposure to air pollution from cooking fuel occurs in the environment around households, not just indoors. Solid cooking fuel is sufficiently polluting to affect widespread ambient (outdoor) air pollution levels appreciably and, thus, to cause ill health far from the source. The term indoor implies that an effective chimney or other venting would solve the problem entirely, when the basic problem is dirty combustion near people. In some parts of the world, incompletely combusted solid fuels are commonly used for space heating or lighting, as well as for cooking, thus confusing the attribution of risk and assessment of appropriate interventions unless the household uses being considered are specified. The term indoor air pollution overlaps with much research on indoor pollution from other sources (for example, from household furnishings and consumer products). For example, the CRA now separately includes risks from indoor exposure to radon. This chapter focuses on the evidence base for health effects, because the causality between HAP and ill health is only now being firmly established. This is unlike contaminated water and poor sanitation, for which the connection to ill health was established in the nineteenth century. The causality and scale of the effects from HAP have only recently received recognition in health effects studies, which are now appearing in large numbers. This recent appearance perhaps explains why there are relatively few evaluations of large-scale interventions to date. Initiatives presently under way provide excellent opportunities to do so.