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close this book Boiling Point No. 02 - Special Edition April 1991
View the document Smoke Pollution
View the document Dialectics of Improved Stoves by Kirk R Smith, East-West Centre, Hawaii, USA
View the document White Rabbits !
View the document The Chimney Approach to Smoke Pollution
View the document Research Needs- Biofuel Stove Technology
View the document Woodsmoke - who will put it out?
View the document Cookstove Smoke - The Other Side of the Coin
View the document Domestic Air Pollution in Rural Kenya
View the document A Chimney is Not Enough!
View the document Indoor Air Pollution in Rural Malaysia
View the document References:

Woodsmoke - who will put it out?

Reproduced from 'Health for the Millions', the journal of the Health Association of India, February 1987.

For thousands of years people have cooked using firewood and cowdung. Even today, over 90 percent of Indian households use wood, dung and crop residues as fuels. Smoke-filled huts are a common sight across the countryside. During winter, when a temperature inversion prevents the smoke from rising, entire villages look as if they have been tear gassed.

The minuscule efforts so far expended to understand this problem faced by cooks, the second largest occupation in the world (next only to agriculture), is an example of how rural women in developing countries are forgotten. No major group is lower on the global totem pole, say Jamuna Ramakrishna and Kirk Smith of the East-West Centre at Hawaii, in a paper on smoke from cooking fires.

Recognising this major gap, Kirk Smith, A L Aggarwal from the National Institute of Occupational Health (NIOH), Ahmedabad and R M Dave of the Jyoti Solar Energy Institute at Vallabh Vidalaya, decided to carry out a pilot study in four villages of Gujarat. The study was carried out in late 1981 in 36 households in Anand, about 90km south of Ahmedabad. The woman cook in each household wore a sophisticated air sampler which was clamped to her collar, so that the measurement device could move around with the cook and measure her actual exposure: exposures to two major pollutants of wood smoke, total suspended particulates (TSP) and benzo(a) pyrene(BaP) were measured. The results were shocking, showing that both the doses and concentrations being experienced in village homes burning biomass fuels were extremely high by global standards. They show that cooks receive a larger total dose than a resident of the dirtiest urban environment, and receive a much higher dose than the WHO's recommended level or any national public standards.

Gujarati Villages

Estimated annual doses of respirable suspended particulates (milligrammes per individual).





Traffic police in Ahmedabad








WHO recommended level(Source K Smith, East-West Centre).


A number of factors make the level of exposure to pollutants worse. Dwellings in villages are small and badly ventilated. In one of the Gujarat households, when the holes in the roof were closed, as is done regularly in monsoon conditions, ventilation was so reduced that it became impossible for the researchers to remain in the kitchen for more than a few seconds. The woman cook, however, stated that such conditions were normal during the monsoon. The exposures increased manifold and were among the highest recorded anywhere in the world.

Health of Women

What does this mean for the health of women who cook? The most powerful evidence for the ill-effects of wood smoke comes from a survey of a heart disease called cor pulmonale (ITS), in which the right lower chamber of the heart enlarges and fails because of a disorder in the lungs. The survey was carried out over a period of 15 years on hospital patients in Delhi. It found that there was a surprising similarity in the incidence of cor pulmonale (ITS) between men and women even though 75% of men were smokers of tobacco as compared to 10% of women. In addition, the age of onset of cor pulmonale (ITS) in Delhi was much lower for women. Bronchitis and emphysema - abnormal distension of the lungs with air were the main lung diseases in both sexes. Nearly all the women were from the lowest income group. While all the women patients cooked, only 7% of the men claimed that they cooked. The cooking fuels used were mainly dung (63%), wood (25%) and coal (12%).

The authors, Dr S Padmavati and Dr S Aaron, concluded: 'Cigarette smoking is prevalent all over India and must be a contributory cause of bronchitis in men, but not in women as only 10% of them smoke cigarettes. The women are, however, exposed to smoky, primitive fireplaces from childhood. They gave a shorter history of cough and expectoration (coughing up from lungs and air passages); and the onset of cor pulmonale (ITS) and they showed more severe congestive heart failure, greater cardiac (heart) enlargement and greater derangement of pulmonary (lung) function with a severe loss of exercise tolerance.

Though biomass smoke is a complicated mixture of thousands of pollutants, and its impact may be more than the sum of impact of individual pollutants, indirect evidence of the ill-effects of smoke can also be gathered from studies that have been done on individual pollutants. Other than particulates and compounds like BaP, two major pollutants in biomass smoke are carbon monoxide (CO) and formaldehyde.

There is a growing body of evidence that points to a strong link between chronic CO exposures and both heart disease and impaired foetal development. While CO has not itself been found to be carcinogenic, there is concern that it may act to increase the carcinogenic effects of other air pollutants by inhibiting the ability of the lungs to clear themselves.

Any condition which results in reducing the blood's capability to carry oxygen to the tissues, like anaemia, will also make a person more susceptible to carbon monoxide toxicity. This is particularly bad for Indian women who are anaemic in large numbers. It is estimated that in India 40% to 60% of preschool children, 25% to 30% of women in reproductive age and almost 50% of pregnant women in third trimester (mom than 24 weeks of pregnancy) are anaemic. Chronic diseases will further reduce the capability of the blood to rid itself of carbon monoxide during periods of low or no exposure.

There are several factors that make women particularly susceptible to CO exposure. Women generally have less haemoglobin reserve than men, which makes them more prone to anaemia, which also makes them more vulnerable to lower doses of CO than men. During pregnancy there is additional demand on haemoglobin, further lowering their reserves and making them more sensitive to CO. This exposure can also affect the unborn child leading to reduced birth weight and increased perinatal death rates (that is, deaths at birth or in the first week of life). It is not surprising that respiratory diseases are a leading cause of death among girls and women over the age of five in India.

Formaldehyde is another pollutant in smoke. It causes irritation in the eyes, nose and throat and usually this irritation begins at 0.1 parts per million (ppm) to 1.0 ppm. Some people can become adapted to 2 ppm to 3 ppm for as long as eight hours without undue discomfort. But above 5 ppm most people are extremely uncomfortable and remain so for an hour or more after the end of exposure. Formaldehyde is poisonous to tissues in the lungs and exacerbates skin wounds. It is considered a human carcinogen and there is evidence that aldehydes and BaP can act synergistically to hasten tumour growth in animals. Studies on the effects of smoking also indicate the kind of impact that wood smoke may have on health of women. The longer the history of cigarette smoking, the higher the risk. Women begin cooking as young girls and continue for much of their lives. Young girls may receive significant exposure at their mother's sides even before the often tender age at which they begin cooking full time.

Inhalation of cigarette smoke increases risk. In the case of cooking smoke, inhalation is inevitable because exposure to smoke comes with every breath and not as a puff once every several breaths. Exposure to cigarette smoke during pregnancy and nursing increases the risk to mother and child. Pregnant and nursing mothers generally have no option but to cook and so remain exposed to smoke.

Available Solutions:

Several steps can be taken to cut down the exposures to smoke while cooking and reduce its adverse impact on health: cleaner fuels, improved stoves and better ventilation. As far as clean fuels go one major option may be to speed up the use of kerosene and electricity, but the Government will be unable to supply electricity in the quantities needed for cooking. Moreover, most people are too poor to be able to purchase electricity. Kerosene is cheaper but is used in the rural areas more for lighting than for cooking. It is also a limited fossil resource and can only provide an interim arrangement.

Biogas is another fuel which can greatly reduce the health problems caused by wood smoke. Unfortunately, biogas plants, despite major government programmes, have not spread far and wide.


A second major alternative is to increase the use of charcoal. Particulates and other hydrocarbon emissions are released at the charcoal manufacturing step, and thus charcoal bums relatively cleanly at the cooking stage, except for potentially high emissions of carbon monoxide. Removal of gases through a well-fitted chimney will be essential if charcoal is to be used as a major fuel for indoor cooking.

Smokeless chulhas:

The second major solution to the problem is to so design stoves that exposure to smoke is reduced. A simple chimney can be introduced to take the smoke out of the house but this will lead to increased outdoor air pollution. In a meteorological situation where inversion takes place over many winter months, reducing outdoor pollution is also very important. During these months, exposure to pollutants can increase substantially both for cooks and the village community as a whole.

Stoves can also be designed to improve thermal efficiency, that is to use less fuel to do the same amount of cooking. But recent experiments also show that the steps taken to increase thermal efficiency can sometimes lead to higher rates of emission, and there can thus be a net increase in pollutant emission.

House Design:

A third major aspect of the wood smoke solution is to increase ventilation in the homes of the poor. Ventilation improvement could be the least expensive short-term way to reduce smoke exposure. Relatively minor changes in existing structures, like adding windows, can make substantial changes. Moving the kitchen to a well ventilated area can also make a major difference. Women who cook in a porch, for instance, receive less exposure to smoke. Unfortunately, house designs are usually decided upon by the male in the house who can neglect the problems of women. Also in some cases fear of theft may simply prevent households from making large ventilation holes.

It is equally important to study some of the cooking practices. Most women who cook on wood-fired chulhas generally squat or sit while cooking. This may be an adjustment over years to the high levels of wood smoke. Concentrations of CO and TSP are generally lower near the ground. Thus, it may be much more comfortable being closer to the ground and out of the region of higher smoke density.

There are serious implications for health policy planners in these findings. Just as supply of clean water is now considered an extremely important domestic need in the rural areas, these findings show that supply of clean air is also a matter of high priority to rural women. .