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Biomass smoke and ill-health in India: preliminary results from a national survey
[top] [end]IntroductionIndia's health situation is different from that in other regions in a number of ways. It has a special burden of ill-health due to three particular disease conditions which are of interest with regard to the possible influence of bio-mass smoke exposures:
All these disease categories have a number of risk factors associated with them.
Tuberculosis, which has been ominously re-invigorated by the AIDS epidemic and new drug-resistant strains, has sometimes been linked to outdoor pollution, but never to biomass smoke and never at the national level. [top] [end]National Family Health Survey (NFHS)Recently, a national survey done in India has produced information by which these connections can be tested statistically. In 1992-93, the ambitious National Family Health Survey (NFHS) carefully chose 88 562 households containing 514 827 people all over the country. They were chosen in such a manner that they represented accurately some 99% of the total population (Kashmir and Sikkim could not be visited). An extensive questionnaire was completed for each household, by interviewing the head of household for more than two hours. Although the principal purpose of the survey was to understand better the factors that affect fertility and population growth, much other information on socio-economic, health, demographic, and household conditions was gathered as well.Among the questions asked was one on household fuels, which found that 93% of the rural population and 32% of the urban population lived in households relying primarily on biomass fuels for cooking. As shown in the table, this is similar to the results in the 1991 Indian Census, where the percentages of households using biomass fuels were 96% and 37% respectively. Having such a large and carefully done survey of both household fuel use and health conditions allows, for the first time, an exploration of what meaningful relationships might exist between them at the national level. This article presents a preliminary comparison of the disease rates in those households primarily using biomass fuels with those in households using other fuels. Simple comparisons between these groups could be misleading, however, because the two groups of households probably differ in other important ways as well. In particular, biomass-using households are generally poorer, and poverty itself is an important risk factor for disease (through poorer nutrition, lower education levels, less access to healthcare, etc.). To correct for the effects of poverty and other important socio-economic factors, the results reported here have been adjusted to take into account house type, crowding, place of residence, education, caste, and religion. Since nearly all diseases are strongly related to age and sex, these corrections have been made as well. All the differences reported here meet accepted requirements for statistical significance. [top] [end]Acute Respiratory Infection (ARI)Children under 3 years in households using biomass fuels had about 30% more respiratory infections in the two weeks previous to the survey compared to children living in households with cleaner fuels. This level of risk is not nearly as high as has been observed in detailed, but small-scale, studies in Africa and Asia. In these studies, elevations of ARI risk of 100% to 500% for young children exposed to biomass smoke from household cooking compared to those who are not have been reported. However the studies in Africa and Asia looked at moderate and severe ARI cases that can be life-threatening. The incidence of mild cases of ARI, on the other hand, do not vary much by location in the world. Even children living in the richest and cleanest societies have a number of mild ARI episodes per year. Since the NFHS did not determine the severity of cases, it is not surprising that it found a lower risk for all cases than the other studies found for more serious cases.[top] [end]BlindnessAdults over 30 years old living in households using biomass fuels had about 30% more partial blindness than those living in households using cleaner fuels. There was no statistically significant difference for complete blindness. Cataracts, the major cause of blindness in India, are thought to be caused by cumulative damage to the lens of the eye, which can occur through exposure to cigarette smoke or sunlight, and drying due to episodes of diarrhea, among other factors. Laboratory studies have also found cataracts to be produced in rats exposed to high levels of wood smoke.
In addition, however, other causes of blindness may have links to biomass smoke. Trachoma, for example, is caused by infection of the eye, which might be enhanced if people are rubbing their eyes due to irritation by smoke. Conjunctivitis, another source of blindness, is thought to result from long-term irritation such as might occur due to the aldehydes, acrolein, and other irritating chemicals in bio-mass smoke. Table: Primary cooking fuel (%) in Indian households according to 1991 census
[top] [end]TuberculosisAdults over 30 years old living in biomass households had 170% higher TB rates than those in cleaner households. This is an unexpected finding, which, if confirmed, would have major public health implications because of the terrible toll of TB in India and elsewhere in the developing world. Coming down with this disease is the result of two events: first, contracting the TB infection; second, conversion of the infection to active disease. Many people who are TB positive never actually contract the disease.India has one of the highest rates of TB infection in the world, about half the population, only a fraction of whom will ever convert. It is not clear from the NFHS, however, which of these events might be influenced by biomass smoke. The coughing produced by biomass smoke irritation might increase the rate of infection. On the other hand, damage to the immune system from prolonged breathing of biomass smoke could well increase the rate of conversion from infection to disease. [top] [end]ConclusionThe nature of such broad spectrum national studies is that, in the terminology of science, they serve more as hypothesis-generating efforts, rather than being by themselves hypothesis-proving. Focused studies examining the ill-health outcomes in more detail would be needed, since the NFHS relies on self-reporting of illness, which can be inaccurate and subject to bias. Better determination of actual exposure, rather than just reported primary fuel used, would also be required, since many households use multiple fuels and there are many types of stoves and kitchen arrangements. It would also be important to determine smoking patterns to make sure that greater ill-health in biomass-using households is not due to differences in tobacco use.Nevertheless, if confirmed and accepted into the peer-reviewed scientific literature, these NFHS results will go a long way toward establishing the potential relationships between biomass fuel use and these important causes of ill-health. [top] [end]References
[top] [end]Contents: Boiling Point 40: Household energy and health
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Page created:
02 August 2007; Last edited:
04 December 2008; Version: 2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Pagename: BiomassSmokeAndIll-healthInIndia-PreliminaryResultsFromANationalSurvey @HEDON: FEGA | |||||||||||||||||||||||||||||||||||||||||||||||||||||
