A century ago, biofuels (wood, dung and crop residues) provided the great majority of household energy worldwide. With the advent of fuels such as oil and gas, and the more widespread availability of electricity, the share of household energy from bio-fuels has fallen to around 15%. However, this small percentage hides the fact that around half of the world's population (rising to three-quarters of people in developing countries) still rely on bio-mass energy. This is more so in poor household uses very much less fuel than each wealthy one. With over 30 percent population below poverty line and relying on agriculture labour for subsistence even the neighborhood of mega cities like Jaipur Mumbai, Kolkatta and Chennai have large thickets of mud houses besides the 70 percent of the population residing in villages use biofuel as the fuel for the cooking.
• Thus bio-fuel use, especially wood, is typically associated with poor rural households which comprise almost 700 million or 70 percent of the population of India Wood is also extensively used -often in combination with other fuels - in the urban slums that characterize the rapidly expanding cities of many developing countries.
Figure 1: Biomass fire over which beer is being brewed near Gondar, Ethiopia (Nigel Bruce). This is not much different than rural Indian homes of over 300 million rural poor.
Most of this biomass is burnt in open fires or poorly constructed stoves, usually inside the home (Figure 1). Pollution levels inside the home and kitchen areas are therefore high. Women, with their young children, work in these heavily polluted environments for many hours each day and are thus most heavily exposed to smoke (see front cover). The effect that this pollution has on the health of mothers and their very young children is a considerable cause for concern. Growing efforts are now being made to determine just how serious this problem is, and to promote economically, socially and environmentally sustainable ways of reducing this hazard.
Evidence shows that the levels of smoke pollution in biofuel-using households are at least 10 times and sometimes 100 or more times higher than anything experienced in homes using 'clean' energy systems. the level of particulate matter (PM), although other components of smoke are also injurious to health. Measures of PM10 describe the weight of particles smaller than 10 microns in each cubic metre of air. Indoor biofuel combustion results in PM10 levels of thousands, and frequently tens of thousands, of µg/m3 during use. A second measurement, PM2.5, describes the concentration of 2.5 micron particles, which can penetrate even more deeply and are likely to cause the most damage. The 24 hour average is considerably higher than the EPA standard.
The EPA standard recommends a maximum annual average of 50 µg/m3 PM10.
Since fires will be used in a similar way every day of the year (allowing for seasonal variations in cold areas, special occasions, etc.), the annual average will in general be similar to the 24 hour average. This is therefore also dramatically higher than the EPA standard.
Evidence for health effects of smoke on infants and young children
Since levels of exposure are considerably in excess of standards, it would be very surprising if indoor air pollution from biofuels was not a serious hazard. Indeed, the supply and use of household energy affects the health of children, women (and men) in a range of ways, but we will focus here on the effects of smoke on young children.
Pneumonia, the most common type of Acute Lower Respiratory Infection (ALRI), is now the single most important cause of death worldwide among children under 5 years of age. The risk is highest in the first year of life, and especially in the first six months. A growing number of studies have reported an increased risk of ALRI associated with exposure to bio-mass smoke, although for a number of reasons to do with the methods and study design, the evidence from these studies is not reckoned to be particularly strong. (EHP 1997, Bruce 1998).
Irritation of the eyes by smoke is frequently seen, and reported by mothers. It is not certain whether this places the child at higher risk of eye disease, but it might be expected that such children would be more susceptible to eye infection, such as trachoma, which is spread by rubbing and wiping eyes with contaminated material, such as cloths.
How much benefit to health will there be from feasible reductions in smoke pollution?
This is a crucial question for those working in the household energy field. Over a twenty four hour period, open fires typically yield PM10 values of at least 1000 µg/m3. Experience has shown that improved stoves which have been in operation for some months or years rarely yield twenty four hour PM10 values of less than 500 to 600 µg/m3. These values are about ten times higher than the recommended levels. The fact is, we have little or no idea whether reductions across this range of exposure levels would make any difference at all to the incidence of ALRI, or to any of the other key health problems associated with smoke.
Conclusions - what needs to be done?
Indoor air pollution is an important health hazard for young children. Given the very large numbers of children and their mothers who are exposed to high levels for many hours each day, substantial reductions in exposure should have an important public health impact. However, we do need to establish the levels of exposure at which benefits can be obtained. This has important practical implications for household energy programmes, which include the goal of reducing exposure. Health considerations can help to identify means of achieving effective and sustainable change, and the following points highlight key areas of action:
• Increase awareness among health and development policy makers of biofuel pollution as a health hazard, especially for women and young children.
• Support practical household energy initiatives which can reduce human exposure
• Obtain clearer evidence of health improvements resulting from reduction in smoke pollution using measures available to poor communities
• Encourage development projects involving household energy to assess exposure levels. There is a need to develop and evaluate valid and robust methods of exposure measurement to support this objective.
• Further develop programmes for the management of childhood illness, including ALRI, to combine control of pollution and other social/environmental risk factors with case-management and vaccination.
• Evaluate implementation projects to identify and disseminate experience of effective and sustainable ways of reducing exposure among young children. This should go beyond purely technical performance, and include the economic and social aspects.
While the use of stoves and the effects of smoke appear to be substantial health hazards, it must not be forgotten that fuel provides vital functions upon which life and health depend, including food, clean water (where boiled), warmth and light. The fire is often at the heart of the home, and contributes directly and indirectly to the health and security of the growing child. The health hazards of smoke must therefore be balanced against these benefits.
Two divisions of the World Health Organisation (WHO), Child Health and Development and the Office of Global and Integrated Environmental Health are currently collaborating on a programme of work that is designed to address these health issues. WHO is working with a wide range of development and research groups to ensure that this programme is effective and relevant, and further details of this work can be obtained from the author.
Abridged from http://www.hedon.info/SmokeFromBiomassAndItsEffectsOnInfants