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October 30, 2005 |
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investigated the relationship between cooking smoke exposure and risk of cataracts among women (who are predominantly the cooks) residing in the Nepal/India border area, (who visited Shree Rana Ambika Shah Lumbini Eye Hospital). That study was a hospital-based, incidence-density case-control study. In that study, 80% of cataracts cases and 57% of the controls (refractive error patients) had reported past and present involvement in cooking in unvented stoves using solid fuel (wood, biomass), where as 22% participants had reported being a past or current smoker. This study provided confirmatory evidence that use of solid fuel in unvented stoves is associated with increased risk of cataract in women who do the cooking. The findings of this study has been published in the International Journal of Epidemiology [12]. In this study, the risk of cataract was found to increase monotonically with exposure duration and across the three exposure gradients (unvented stoves, vented stoves and clean fuel stove). Unfortunately, this study did not document the severity of cataracts quantitatively. Only anatomical positions of cataracts were documented after slit lamp confirmation as usually done in the busy clinical settings.
To further explore whether severity of cataracts increase by the duration of cooking in unvented stoves and in unventilated kitchens, and to explore lens opacity as a potential biomarker of long-term exposure to cooking smoke, I am conducting a cooking smoke and cataract study nested under a separate cooking smoke and tuberculosis study in Kaski, Nepal. This is a questionnaire and medical examination based epidemiological study (case-control design), which is being conducted in collaboration with Department of Ophthalmology at Manipal Medical College (collaborator: Professor Sachet Shrestha) and HMG/N Regional Tuberculosis Center (RTC) (collaborator: Dr. Sharat Verma) in Pokhara. All study participants will be recruited from patients attending these two institutions.
Methodology and purpose of the study
In this study, cases are all female, active pulmonary TB patients between age 20-65 years identified at the Regional Tuberculosis Center and Manipal Medical College in Kaski district. Controls (same age and sex) are being selected from outpatients and inpatients appearing at the Manipal Medical College with in a month of case identification. After obtaining informed consents from cases and controls, the plan is to examine the eye lenses and photographs using slit-lamp fitted with digital camera. The severity of lens opacity will then be scored using a standard set of photographs based on the Lens Opacity Classification System (LOCS) III methods[13]. Later, three sets of lens photographs will be sent to the two ophthalmologists in the School of Optometry at UC Berkeley for grading by those who developed LOCS III method, now widely used in US.
What is LOC III classification?
The LOC III classification system provides an opportunity to classify the lens opacity by type (nuclear opacity, nuclear color, cortical, posterior subcapsular) as well as quantify opacity by severity/grade. Thus this system will enable me to document lens opacity information on continuous severity scale, which will be utilized to see the exposure-response trend between cooking smoke and degree of opacity, after adjusting for potential confounders (exposure to sunlight and level of nutrition). The severity score will also provide an opportunity to explore the possibility of using this information to develop a biomarker of long-term exposure to cooking smoke and early diagnosis of cataracts so that preventive measures could be advised much ahead. If established, this biomarker will help to minimize the misclassification of exposure of cooking smoke, which is very important in the epidemiological studies.
While still in Nepal, I also conducted an indoor air pollution sampling in thirty households of cases and controls. I am trying to study whether Naphthalene in the smoke is a culprit for cataract and formaldehyde as an instigator for irritation. I am trying to capture these compounds using a passive sampling technique. Passive sampling technique will not only be useful in a setting where there is no electricity but also useful in a conflict setting where there is a problem to carry active sampler and where researchers like myself has to go through several checkpoints. Similarly, I am also monitoring particulate matter less than 2 micron size (week long monitoring) and importantly, the level of environmental tobacco smoke (nicotine as a fingerprint). Measurement of environmental tobacco smoke is relevant in the case of Nepal as it has the highest female smoker ratio in the world.
Amidst skepticism: In summary, I had a wonderful time visiting villages though amidst skepticism, whether I will be able to carryout this type of study in present political situation. Initially I had to go through several hassles but at the end it was ok, I got cooperation from all sides. I could visit some places, and some places I could not as patients themselves did not suggest me to visit their villages although they had no objection to participate in the study. More than sixty percent of households that I visited were the houses of TB patients. I noticed one thing common among them, poverty. I am a biologist and I know TB has a biological manifestation but I realized, who gets TB is determined socially. I have a feeling that poverty among other factors is still a very important risk factor. It is important for us to fight against poverty if we are to win the war against infectious as well as non-infectious diseases that is crippling our society.
Reference:
1. Smith, K.R., Biofuels, Air Pollution and Health: A Global Review. 1987: Plenum Press, New York. 452. 2. Shalini, V.K., et al., Oxidative damage to the eye lens caused by cigarette smoke and fuel smoke condensates. Indian J Biochem Biophys, 1994. 31(4): p. 261-6. 3. Christen, W.G., et al., A prospective study of cigarette smoking and risk of cataract in men. Jama, 1992. 268(8): p. 989-93. 4. Hankinson, S.E., et al., A prospective study of cigarette smoking and risk of cataract surgery in women. Jama, 1992. 268(8): p. 994-8. 5. Klein, B.E., et al., Cigarette smoking and lens opacities: the Beaver Dam Eye Study. Am J Prev Med, 1993. 9(1): p. 27-30. 6. West, S., et al., Cigarette smoking and risk of nuclear cataracts. Arch Ophthalmol, 1989. 107(8): p. 1166-9. 7. Mohan, M., et al., India-US case-control study of age-related cataracts. India-US Case Control Study Group. Arch Ophthalmol, 1989. 107(5): p. 670-6. 8. Mishra, V.K., R.D. Retherford, and K.R. Smith, Biomass cooking fuels and prevalence of blindness in India. Journal of Environmental Medicine, 1999. 1: p. 189-199. 9. Zodpey, S.P. and S.N. Ughade, Exposure to cheaper cooking fuels and risk of age- related cataract in women. Indian Journal of Occupational And Environmental Medicine, 1999. (4). 10. Mishra, V.K., R.D. Retherford, and K.R. Smith, Biomass cooking fuels and prevalence of Tuberculosis in India. International Journal of Infectious Diseases, 1999. 3(3): p. 119-129. 11. Padilla, R.P., et al., Cooking with biomass stoves and tuberculosis: a case control study. Int J Tuberc Lung Dis, 2001. 5(5): p. 441-447. 12. Pokhrel, A.K., et al., Case-control study of indoor cooking smoke exposure and cataract in Nepal and India. Int J Epidemiol, 2005. 13. Chylack, L.T., Jr., et al., The Lens Opacities Classification System III. The Longitudinal Study of Cataract Study Group. Arch Ophthalmol, 1993. 111(6): p. 831-6.
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Development Nepal |
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Development and Stability |
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Ongoing Research/ Project |
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I am a biologist and I know TB has a biological manifestation but I realized, who gets TB is determined socially.
Background
This summer, I spent three months in Nepal to investigate the risk factor for cataracts and Tuberculosis. I am exploring whether cooking smoke exposure increases the risk of cataracts and tuberculosis. If yes, my interest is to further explore which chemical/pollutants in particular instigate this process, and, how they do so. I am trying to nail down the answer for these questions because in developing countries including Nepal, poor people, particularly women have limited access to treatment of these diseases. In the case of tuberculosis, there is also stigma attached with it.
Biomass fuel smoke and cigarette smoke: Exposure to biomass fuel (mainly firewood and dung) smoke generated during cooking have many similarities to cigarette smoking [1, 2]. Several studies support the association between cigarette smoking and cataract formation[3-5] and tuberculosis. In the case of cataracts some studies have even documented stopping smoking to have correspondingly reduced the risk of cataract formation[6]. Various existing epidemiological studies also provide evidence of an association between cooking smoke and cataract or blindness[7-9] and tuberculosis[10, 11]. In Nepal, women suffer from cataract and tuberculosis more than men. About three years ago, I had |
Using Lens Opacity (cataracts) as a Biomarker of Exposure to Biomass Smoke in an Epidemiological Study: Lessons from Nepal |
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-Amod Pokhrel amodpokhrel@yahoo.com |
