| Boiling Point No. 29 - December 1992 |
Extracts from "Health Effects of Charcoal and Woodfuel use in Low-Income Households in Lusaka, Zambia". Reprinted with the kind permission of the Stockholm Environment Institute.
by Anders Ellegard and Hans Egneus, Stockholm Environment Institute, 1992
The majority of low-income households in Zambia, as well as in most other developing countries, depend on woodfuels (fuelwood and charcoal) to satisfy their energy requirements for cooking, washing and space heating. In low-income urban areas of Zambia, charcoal is the dominant cooking fuel, accounting for more than 90% of the total. Wood is the major cooking fuel on the outskirts of larger cities, in smaller towns and in rural areas.
There has been growing concern since the late 1970s that pollution from biomass fuels damages the health of women in the third world. Addressing this concern, this study examined some health implications of the use of charcoal and wood as a cooking fuel by women living in low-income, urban areas of Lusaka.
Aim, Objectives and Methodology
With the aim of assisting energy planning, the objectives of this study were:
to analyse the linkage between fuel use and health hazards from exposure to fuel emissions, to improve the database on health hazards of cooking with the fuels, and to interpret indicators of fuel emission exposure and indicators of health status of fuel users.
The study survey used a questionnaire designed to give infortnation on socio-economic conditions, fuel use and health status.
The households investigated used three different fuels for cooking: charcoal, wood and electricity. Households using electricity for cooking are few in low-income areas, but were included as a control group comparable in most aspects except current household fuel burning exposure. In the context of this study, the exposure is affected by a number of factors that are difficult to assess quantitatively, such as:
dietary habits, ea. type of food eaten and whether boiled or grilled; the time factor (long or short cooking times); the cooking situation, ea. ventilation and cooking indoors or outdoors; type of fuel and stove ea. with or without a flue; position while cooking ea. squatting over the fire or standing beside it; climate / altitude / seasonality, and thus whether space heating is required and whether cooking can or must be performed indoors all year round; and social factors, such as who is cooking and whether or not children are exposed.
Economic factors were addressed indirectly through questions about the expenditure on, or amount of, certain basic commodities used in the households, ea. mealie (maize) meal, cooking oil, fuel use, and transportation.
A number of questions were related to the exposure situation such as location of the cooking place, size of the cooking place, number of windows in the kitchen and type of stove used. Information on the type of charcoal stove used was limited to asking whether the stove was traditional, improved or some other type. No charcoal stoves in Lusaka have flues, all are portable. The question for wood users was whether they used a three stone fireplace or any kind of stove. All used a three stone fireplace.
The largest part of the questionnaire was related to questions with a bearing on the health status of the respondents. This part of the questionnaire was designed in order to obtain answers on:
important background factors needed to assess the health status of the respondents, the general health status of the investigated population, and specific health issues related to fuel use and emissions such as acute or chronic effects.
Three different indices were formed: a general health index, an index of breathing problems and an acute effect index. The questions related to each index were selected after consultation with a number of medical experts. The only really good indicator of exposure to smoke is the question on eye irritation. It is not included in any index and could not be treated statistically.
Analysis of selected background parameters:
An analysis of background parameters was performed to identify similarities and differences between sub-groups of the sample. The seven numeric factors chosen for the comparative analysis were:
1. age of the housewife
2. household size (number of persons in the household)
3. number of pregnancies
4. number of children less than 12 years old
5. amount of mealie meal used (calculated per person in the household where each child is counted as half person)
6. litres of cooking oil used (calculated in the same way)
7. number of rooms available for the household.
The analysis shows that the fuel user groups differ from each other in several socio-economic parameters. In general, electricity users are more privileged from a socio-economic point of view and wood users are less well off. Charcoal users appear in between, with traits from both the other fuel groups. The difference is greater between electricity users and the other fuel user groups than between charcoal and wood users.
This has a bearing on the treatment of results from the analysis of health aspects: if differences are found between the fuel user groups, socio-economic implications must be assessed before attributing effects to the choice of fuel.
With the differences between fuel user groups revealed above, it appears that type of fuel used is a function of economic status. This linkage is stronger than that with regard to locality. Electricity users are more similar as a group than they are to their charcoal-using neighbours. Electricity is the preferred fuel, followed by charcoal, then wood. Since economic status can itself affect health this implies that findings suggesting that electricity use is associated with better health should be interpreted with care.
Assessment of Exposure to Particulates and Carbon Monoxide:
The dose of a pollutant is the most relevant parameter with regard to possible health effects and in this study the methods used allow calculation of doses on different time bases.
Exposure to particulates depends mainly on the amount of time spent cooking. The calculated average daily dose was arrived at by multiplying the daily cooking time in hours by the average dose per hour.
The women using woodfuel are exposed to the highest doses of Respirable Suspended Particulates (RSP), both because wood is the most polluting fuel and because of the relatively long time spent by the stove. Electricity users are doubly privileged. They use the cleanest fuel and spend less time by the stove. However, even the most heavily exposed women (the wood users) are exposed to less than one tenth of the exposure from one cigarette each hour, corresponding roughly to half a cigarette per day in the majority of cases.
In a review of indoor air pollution in developing countries, Smith (1986) reported levels of Total Suspended Particulates (TSP) at 3,000 - 7,700 g/m³ in Indian rural village kitchens during cooking time. These levels are four to ten times higher than those encountered in the Lusaka study. This is due to differences in ventilation, housing structure, type of fuel and cultural habits.
A number of efforts to improve indoor air quality through improved stove technology have been made in developing countries, but information on achievements has been conflicting. Smith found that though TSP levels were reduced with improved stoves in India, the levels remained high. In another study Smith found no significant reduction with regard to TSP levels in improved stoves (Smith 1987b).
In a study of nearly 200 households in several villages in India, Ramakrishna et al. (1989) found no significant difference between the use of improved or traditional stoves with regard to TSP concentrations in the kitchen. They concluded that improved stoves are nor always associated with improved air quality. Part of this lack of success was attributed to the high outdoor levels of pollution at cooking time because much of the smoke ventilated through the flues was returned inside.
Exposure to carbon monoxide: Charcoal users emerge as the group most strongly exposed to CO, followed by wood users. The electricity users are exposed to the lowest levels of CO. The reason that electricity users are still exposed to relatively high levels of CO is probably to be found in climatic conditions during the period of investigation. July and August are cold months and some housewives among the electricity users had a charcoal stove by their side to keep warm.
Almost one third of the charcoal users were exposed to levels considered by the WHO to be incompatible with good health, while one out of six wood users and one of 25 electricity users were exposed to such high levels, during the time of cooking.
In the present study, too few improved stoves were encountered to warrant statistical conclusion. However, the average CO concentration encountered in those three households using the improved stove was actually higher than in those using the traditional stove.
The investigation shows that the three different fuel-user groups are exposed to significantly different levels of exposure to particulates and carbon monoxide. Wood users are most strongly exposed to respirable particulate matter, followed by charcoal users and with electricity users as the least exposed. With regard to carbon monoxide the order is changed between wood and charcoal users, with the charcoal users most strongly exposed.
The location of the cooking place, whether in a separate kitchen or outdoors, did not yield any significant difference in exposure levels. A slightly significant increase in exposure was encountered among charcoal users cooking in one of the rooms of the house as compared to those generally cooking outside.
In spite of the statistically significant results that have been obtained, the conclusion is that exposure to emissions can vary greatly and be influenced by factors not easily controlled, such as weather, ventilation and cooking habits. It is thus difficult to draw conclusions regarding, for instance, health effects directly from the exposure levels.
Analysis of Health Conditions:
It has been shown that users of different fuels are exposed to significantly different levels of pollution. It has, however, also been shown that the fuel user groups differ in some socio-economic aspects in spite of the fact that all subjects live in what are known as low-income areas. Since it was the aim of this study to link the exposure to household fuel pollution with eventual health effects, this complicated the analysis of health indicators, since factors other than fuel use may be very important.
The questions included in the general health index are those that could be connected to general ill-health, but not explicitly connected to household fuel pollution. The reason for including these questions is to find whether there is any difference in health status in general between the fuel user groups that could confound the conclusions with regard to the effects of fuel use.
The most notable feature of the resulting data is the similarity between the fuel user groups, though there are some differences. The wood users have higher prevalence of tiredness and concentration difficulties and more surprising - lower prevalence of headaches, breathing problems, stomach pains and loss of appetite. Electricity users have relatively lower prevalence of sleeping problems, concentration difficulties and night sweat, but higher prevalence of worries than the other fuel user groups.
Acute effect index and eye irritation:
The acute effect index was designed to capture symptoms possibly related to the cooking fuel used (electricity, charcoal, wood). The frequencies of positive answers to the questions (ie. Felt dizzy after cooking, Concentration difficulties, Muscle weakness, Headaches, Lips change colour, and Eyes watered when cooking) give a split impression. Users of biofuels appear to have high prevalence of most of the symptoms that could be associated with carbon monoxide exposure, though prevalence of headaches is similar and muscle weakness is lower than in electricity users. Eye irritation is associated with the use of wood as a cooking fuel.
Breathing problem index:
The breathing problem index was designed specifically to catch symptoms related to respiratory function, because respiratory impairment is considered to be a major effect of exposure to biomass fuel pollution. Since exposure to woodfuel smoke is so similar to tobacco smoke, the smokers have been excluded from this analysis.
The results show that the prevalence of respiratory symptoms is similar in the three groups. The prevalence of cough is also remarkably similar in all fuel user groups, but the nature of the cough appears to be different. With regard to the symptoms of bronchitis the woodfuel users show higher prevalence. In this case it should be noted that charcoal users have the highest prevalences, though bronchitis (whether chronic or not) is rather expected to be associated with particulate pollution and such exposure was lower among charcoal users than among wood users.
Another important symptom of respiratory impairment is wheezing breath and here the ranking order is what would be expected from our hypothesis; wood users highest and electricity users lowest.
Comparison between smokers and non-smokers reveal higher prevalence of all major breathing symptoms in smokers than in non-smokers. With regard to productive cough there is a similar prevalence in smokers and in charcoal users. A tentative conclusion might be that the exposure to tobacco smoke causes more severe breathing problems than does the use of woodfuels.
Thus, while the health indices are capable of detecting significant differences among smokers and non-smokers, no difference could be detected between different fuel user groups. This is not to say that biomass smoke is not harmful to health, but that under the conditions prevailing among women in low-income areas of Lusaka - such effects cannot be substantiated in this survey.
In this study an attempt has been made to link information on the health status in a population with exposure measurements for the same population.
Since there was a significant difference in exposure to both particulates and carbon monoxide between the fuel user groups, the fuel use was taken as an indicator of exposure level. The different fuel user groups were compared with regard to different health aspects both directly, by comparing the prevalence of symptoms, and statistically through health indices that were compiled over groups of symptoms.
The conclusion from this investigation is that fuel use does not seem to be a major factor with regard to the health symptoms of women in low-income areas in Lusaka as measured here. This is true both for general health symptoms and for such symptoms that could be associated with exposure to smoke or carbon monoxide.
Smith, K R. 1986. Biomass Combustion and indoor air pollution: The bright and dark sides of small is beautiful. Environment Management 10:61-74.
Smith, KR. 1987b. Difficulties in achieving and verifying exposure reductions in village households with improved biofuel-fired cookstoves. Indoor Air '87, Berlin 17-21 Aug., pp. 115-120.
Ramakrishna, J., M B. Durgaprasad and K R Smith. 1989. Cooking in India: The impact of improved stoves on indoor air quality. Environment International 15:341-352.