Current Research Current Research


Current Research

Studies of the Effects of Household Air Pollution in Nepal
Photo by Jean-Marie Hullot

1. TB Case-Control Study

This research concerns the intersection of two of the world’s major health and environmental problems: tuberculosis (TB) and household air pollution. Tuberculosis remains one of the world’s most difficult diseases, with 2 billion people infected with the causal agent Mycobacterium tuberculosis. Infection rates in South Asia, including India and Nepal, are very high.

Much of the world (about 2.6 billion people), particularly in South Asia, is too poor to afford clean fuels—electricity or gas—for heating or cooking, and still use solid fuels (e.g., wood, animal dung, crop residues) for these purposes. Many families also use kerosene for cooking or lighting. Solid fuel burning emits much smoke, and kerosene, particularly in inexpensive wick stoves and lamps, emits fine particulates and chemicals. Previous epidemiology investigations, including our work in Nepal, has produced evidence that burning solid fuels or kerosene may promote TB, but uncertainties remain. The present case-control study, in the Kaski District of Nepal, will be the largest and most comprehensive epidemiology study ever to have investigated this issue. We anticipate that it will provide definitive evidence about whether emissions from solid fuel or kerosene are risk factors for TB disease or TB infection.

This study is funded by a grant from the National Institute of Environmental Health Sciences of the U.S. National Institutes of Health.

2. Epidemiologic Investigations of Cataract, Dry Eye Disease and Macular Degeneration

The impact of household air pollution from cooking, heating and lighting fuel use on eye diseases has not been extensively investigated, although cigarette smoking is associated with a number of eye diseases. About 90% of visually impaired and blind people live in developing countries and in every part of the world, females are at higher risk at all ages.

The co-occurrence of household fuel combustion product exposure and high prevalence of blindness in developing countries underlines the importance of understanding any causal relationships between the two. The fact that cigarette smoking is a well-established risk factor for cataract and age-related macular degeneration (AMD), the first and third leading causes of blindness worldwide, lends credibility to such associations. There are also other ocular conditions of public health importance, such as those causing chronic ocular pain, including dry eye disease (keratoconjunctivitis sicca).

This research comprises two concurrently running epidemiology studies in Kaski District, Nepal:

  • A cross-sectional study of 900 women using a variety of fuel types for cooking and heating, to investigate possible associations with cataract of the eye and dry eye disease.
  • A case-control study of macular degeneration to investigate possible associations with household fuel use, involving 300 cases and 300 controls.

Both studies will include comprehensive hospital-based eye examinations of participants. The studies are funded by a grant from the National Eye Institute of the U.S. National Institutes of Health.

3. Cross-Sectional Study of Cardiopulmonary Disease

There have been few epidemiologic studies of the relationship of household air pollution and chronic respiratory or cardiovascular diseases. This study is carrying out a hospital-based cardiopulmonary examination of 300 women participants in the cross-sectional study in Kaski District of cataract and dry eye disease.

The cardiopulmonary examination includes measurement of blood pressure, spirometry, EKG, echocardiography and ankle brachial index measurement. Taking advantage of equipment provided by the eye study, we will also take photographs of the retinal vasculature—the only place in the body where the vascular is directly visible using non-invasive procedures. Photographs will be examined for evidence of occlusion of the blood vessels.

This study is funded by a grant from the United Nations Foundation and the Global Alliance for Clean Cookstoves.


Providing Solar Lamps to Kerosene Lamp-Using Families in Kenya

Simple kerosene lamps are widely used, particularly in rural areas, in low and middle income countries around the world. Well-known are the risks of fire, explosion and poisoning associated with kerosene, and, in more recent years, evidence has been accumulating that the soot and fumes emitted by kerosene used for cooking and lighting are associated with health problems. Although solar lamps are increasingly available in the same countries, there have been no studies of whether adoption of these lamps sufficiently reduces exposure to air pollution that there are health benefits.

As a first step towards investigating possible health benefits of transitioning from kerosene lamps to solar, we investigated changes in usage and exposure to small particulates (PM2.5) when 20 kerosene lamp-using households near the city of Busia in Kenya were each provided with 3 solar lamps.

Our investigation showed (i) that kerosene lamp use was associated with substantial measureable exposure to PM2.5, both in adult and school pupil lamp users; (ii) these exposures were of such a magnitude that they had high potential to cause adverse health effects; and (iii) provision of 3 solar lamps per household provided a successful means of reducing these exposures and likely mitigating health impacts of household air pollution. 

Demonstrating health improvements and the sustainability of any such solar lamp intervention would require a much larger and more sustained study, for which the present study provides a basis for design and sample size calculation.

This study was funded by a grant from Google Ireland Limited and SolarAid (London).

The final report of the study is available here (PDF).


A collaborative study between the University of Otago, the University of California, and Stanford University

Hydrogen sulfide (H2S) is an odorous gas (the ‘rotten eggs’ smell) produced by many industrial processes and from natural sources. Exposures to high H2S concentrations can have serious effects. However, it is unknown whether long-term exposures to much lower concentrations have any health effects. The city of Rotorua, New Zealand, is the only city in the world that is sited on an active geothermal field. Around the city can be found geysers, boiling mud pools, and steaming, near-boiling water pools, with the ubiquitous odor of naturally-emitted H2S. The Rotorua population is regarded as the largest anywhere exposed to naturally occurring ambient concentrations of H2S and provides a unique natural experiment in which the relationship between H2S and health can be studied. We have taken advantage of this to carry out the largest study ever undertaken of possible long-term health effects of H2S.
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Bay Area Solvent Study (BASS)

Solvents are widely used in industry yet, surprisingly, much is still unknown about whether prolonged exposures to these chemicals cause health effects. The Bay Area Solvent Study (BASS) is an epidemiologic research project designed to find out whether exposure to solvents has caused health effects, particularly nervous system effects or reproductive problems, among male motor vehicle mechanics. These mechanics frequently use solvents, often in spray cans, to clean brakes and engine parts. The results of the study will be used to help establish appropriate exposure limits for solvents in workplaces.

Michael N. Bates, PhD, MPH
Adjunct Professor, Epidemiology

School of Public Health
Epidemiology and
Environmental Health Sciences
University of California
783 University Hall, MC 7360
Berkeley, California 94720-7360

Office: 510-643-1627
Mobile: 510-504-5424
Fax: 510-642-5815
Skype: mnbates
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