How Cookstoves Research is Changing the World

March 2, 2015 at 12:16 am

Three billion people in the world, a number unchanged in nearly 30 years, cook their food with an open fire, causing respiratory problems such as pneumonia in children and COPD and lung cancer in adults, as well as cardiovascular diseases. Estimates in 2012 from the Global Burden of Disease project, indicate that smoke from these traditional cooking methods causes a staggering four million premature deaths each year.


Even in school, children can be exposed to smoke from open flame cooking. Credit: HANDSTAND Productions.

Until the last decade, this major health issue had gone largely unnoticed by most medical scientists and public health experts. ATS members, in collaboration with organizations, government officials, and institutions across the world, have played important roles in describing the health impacts of cook smoke, conducting clinical trials with cleaner-burning biomass stoves, and highlighting gaps in knowledge of the problem. In recent months, their efforts have gained momentum.

Their findings have contributed to the publication of the World Health Organization’s Indoor Air Quality Guidelines, a report on childhood pneumonia from the Institute of Health Metrics and Evaluation, and a Lancet Respiratory Household Air Pollution (HAP) Commission.


A child hospitalized with pneumonia, a leading cause of death among children worldwide.

“We need to combine a sense of urgency about saving lives now with an optimism that research can provide the evidence for scalable clean cooking solutions needed to reach hundreds of millions of households,” says William J. Martin, II, MD, dean of the Ohio State University College of Public Health and a past president of the ATS.

William J. Martin, II, MD

William J. Martin, II, MD

Dr. Martin serves as a senior author of the HAP Commission alongside ATS member Stephen Gordon, MD, a professor from the Liverpool School of Tropical Medicine. The commission examines the evidence of HAP’s detrimental health effects, strategies for preventing those effects, and priorities for further research. Dr. Martin notes that there are no simple solutions, but there are potentially huge benefits from addressing the adverse health effects of HAP.

There are no simple solutions, Dr. Martin notes, but the health benefits go beyond reducing HAP to improving outdoor air pollution and slowing global warming.

Charting the History of Cookstove Research

Kirk R. Smith, PhD, MPH

Kirk R. Smith, PhD, MPH, advocates focusing on adoption of electric and propane stoves, rather than clean biomass ones.

ATS member Kirk R. Smith, PhD, MPH, a professor of global environmental health at the University of California, Berkeley, pioneered the field of cookstove research. After graduating from Berkeley with a doctorate in environmental health sciences, he found himself working on a rural energy project in India. He was struck by how smoky the houses were in the villages he visited. Without any grant funding, he decided to measure the exposure women received while cooking with open fires and published the results in 1983.

Seventeen years later, in Guatemala, Dr. Kirk conducted the first randomized intervention trial with funding from the U.S. National Institute of Environmental Health Sciences, the World Health Organization, and the Norwegian government to determine if the detrimental health effects of traditional open wood fire cooking could be mitigated by a woodstove with a chimney.


In many remote areas of Latin America, children breathe smoke from open flames in their home. Credit: Trees, Water & People

In 2009, Dr. Kirk, along with co-principal investigator Nigel Bruce, MD, of the University of Liverpool; and investigators Byron Arana, MD, PhD, of the Universidad del Valle de Guatemala and John Balmes, MD, University of California, published the results of the “Randomized Exposure Study of Pollution Indoors and Respiratory Effects (RESPIRE) Trial.” RESPIRE’S primary outcome was a reduction in childhood pneumonia. Choosing this leading cause of death, particularly in children under the age of 5, made the study feasible.

“We needed a health effect that could be the result of short-term exposure to smoke,” Dr. Smith explains. “You can’t easily study changes in lung cancer, for instance.”

The study involved more than 500 households with a pregnant woman or young infant. About half were randomly assigned to the intervention: a woodstove with a chimney. The other half continued to cook indoors with traditional open fires. The wood stove with a chimney reduced indoor smoke by 90 percent and personal exposure by 50 percent (less because household members don’t spend all their time inside by the stove).

Over the course of 18 months, instances of childhood pneumonia were reduced by 22 percent in those homes with the woodstove and chimney; however, that reduction was not statistically significant. What was statistically significant was the reduction by a third of children who developed severe pneumonia.

RESPIRE helped physicians, scientists, and public health experts overcome a major obstacle: A new area of health concern was recognized as worthy of investigation, opening up funding from governments, NGOs, and foundations to support these investigations.

New Randomized Controlled Trials

Since RESPIRE, hundreds of observational studies have been conducted, many by ATS members, and members have launched or are about to launch several new randomized intervention studies, including the following studies.

Cooking and Pneumonia Study (CAPS)

Stephen Gordon, MD

Stephen Gordon, MD

Kevin Mortimer, MB, PhD

Kevin Mortimer, MB, PhD

This trial, the first large cookstove intervention trial in Africa, is being conducted by co-principal investigators Stephen Gordon, MD, and Kevin Mortimer, MB, PhD, both of the Liverpool School of Tropical Medicine, in rural Malawi in 150 villages. They plan to enroll 10,000 children who will be followed for 24 months for exposure to air pollution and episodes of pneumonia. In the interventional villages, all households with a child younger than 4-and-a-half will receive two clean burning stoves to be used for all their cooking. A solar-charge fan is a key element of the stove’s cleaner combustion. The control group will continue their traditional cooking methods.

Although similar to RESPIRE, this study will test a cleaner burning stove in entire villages, with a much larger study group of children up to the age of 5. With this larger study, Dr. Mortimer says, there is a greater chance that a substantial reduction similar to that seen in RESPIRE would prove to be statistically significant. In addition to the incidence of pneumonia younger than 5, the study will also look at measures of air pollution and the economic and social impacts of the stoves.]


Demonstrating an advanced biomass cookstove in Malawi. Credit: HANDSTAND Productions

Burden of Obstructive Lung Disease (BOLD) Study

Building on CAPS, Drs. Mortimer and Balmes will explore how the respiratory health of men and women in the same Malawi villages are affected by traditional and cleaner cooking methods. The WHO estimates that 35 percent of COPD cases worldwide are caused by HAP.

John Balmes, MD

John Balmes, MD

The study will be part of the ongoing BOLD study, which is quantifying the international variation in the prevalence of COPD. Every year for at least three years, and up to 10 years if additional funding is secured, BOLD participants will undergo spirometry and wear an air pollution monitor for 48 hours. The information will be used to assess participant’s respiratory health over time.

Both CAPS and BOLD will benefit from their affiliation with the Biomass Reduction and Environmental Air Towards Health Effects (BREATHE) Africa Partnership, which brings African researchers, both leaders and trainees, together with experts in HAP. The Partnership is building research capacity in respiratory disease in Africa through the Pan African Thoracic Society’s Methods in Epidemiologic, Clinical, and Operations Research (PATS MECOR) course.

Dr. Gordon notes that Norman Lufesi, MPhil, a PATS MECOR student, an independent member of the CAPS Trial Steering Committee, will present his research focusing on childhood pneumonia and the performance of the Malawian health system at ATS 2015. Other PATS MECOR students are being linked with experienced HAP researchers through BREATHE.

“Given the health impact of HAP, the development of skilled African researchers is required to close the large gap in understanding the full dimensions of the health problem that HAP poses,” Dr. Gordon says.

Ghana Randomized Air Pollution and Health Study (GRAPHS)

Patrick Kinney, ScD

Patrick Kinney, ScD

Co-principal investigators Patrick Kinney, ScD and Darby Jack, PhD, of Columbia University, along with Kwaku-Poku Asante, MPH, PhD, of the Kintampo Health Research Centre are conducting this cluster randomized controlled study to understand how cooking might affect the health of pregnant women and their babies. In addition to logging the incidence of pneumonia in the first 12 months of life, GRAPHS will record birth weight.

GRAPHS will study two interventions: a cleaner burning biomass wood stove similar to the one being used in CAPS and a liquefied petroleum gas (LPG) stove. This will be the first randomized trial to consider if LPG, which burns far cleaner than the most advanced biomass stoves, significantly improves health outcomes.

More than 1,400 women in their second or third trimester of pregnancy are being randomly assigned to one of these two arms of the study or to the control.

The In Utero Household Air Pollution and Lung Development Study

Alison Lee, MD

Alison Lee, MD

Nested within GRAPHS, the study conducted by principal investigator Alison Lee, MD, of Mount Sinai in New York, co-investigator Dr. Asante, and colleagues will begin to look at the effects of chronic in utero exposure to household air pollution on lung development. Research indicates that oxidative stress caused in particular by PM2.5 plays a major role in a lifelong assault on lung health, as well as increasing the risk for other diseases, including heart disease, neurogenerative diseases, and immune disorders.

This study will enroll at least 150 infants and analyze cord blood samples for markers of oxidant imbalance; those samples will be stored for future immune, hormonal, and epigenetic testing. The study will also test the infants’ pulmonary function through the first year of life. Pending additional funding, children will undergo repeat pulmonary function testing at 6 years of age to assess the relative impact of in utero and early childhood biomass smoke exposure on lung growth.


CAPS field worker checking a child’s carboxyhemoglobin level. Credit: Deborah Havens

Make the Available Clean

The researchers involved in these randomized controlled studies hope that cleaner burning biomass stoves will result in less pneumonia and other measures of improved health that are statistically significant. But researchers note that meeting the new WHO Indoor Air Quality Guidelines (IAQG) will be challenging using currently available biomass stoves. The guidelines call for PM 2.5 exposure to be reduced to an interim target of 35 μg/m3 annual average or lower “to prevent most cases of disease attributable to HAP exposure.”

Dr. Smith is a strong proponent of “making the clean [gas or electric] available, rather than making what’s available [biomass] clean. Gas and/or electricity are already used by 60 percent of humanity and cook every possible cuisine without problem and meet the WHO IAQGs without problem,” he says. “Shouldn’t they have much more of our attention?”

In January, Dr. Smith and his Indian colleagues began a new study, where all the biomass stoves in a north Indian village will be replaced with LPG stoves. By replacing all the stoves, the research team expects to minimize exposure to smoke produced by others.

“If your neighbors are cooking with open fires, you’re still going to get a lot of exposure,” Dr. Smith explains. “We have to think about community interventions, and in this, we’ve learned a lot from those working to improve sanitation in these villages.”

However, other investigators stress the importance of transition technologies using cleaner burning biomass stoves. Dr. Balmes believes that replacing traditional cookstoves in rapidly developing countries like India and China with electric or gas stoves is the best choice but is not yet an option in many regions of the world’s poorest countries including Malawi.

“Malawi won’t have a distribution system for gas or an electric grid for 20 years or more,” Dr. Balmes said. “In fact, the U.N.’s International Energy Agency predicted that most of sub-Saharan Africa won’t have an electrical grid until 2040.”

Given that reality, Dr. Martin believes that implementation at scale of cleaner cooking solutions available today represents a major step forward, and he is encouraged that the Global Alliance for Clean Cookstoves and the International Standards Organization (ISO) in The Hague are developing cookstove standards that will assess stove quality and inform consumers in low resource settings exactly what benefits they can expect.

“Moving up the ‘energy ladder’ for the world’s most disadvantaged populations will occur at a different pace and in different ways depending on the country, its culture, and economic growth,” Dr. Martin adds.

Beyond Resources and Infrastructure

Even if the infrastructure were available everywhere to allow all the world’s homes to have  clean-burning stoves, other obstacles would hinder universal adoption. Cost is the principal one, but champions of the cause recognize that cultural barriers also hinder efforts.

“Stacking” is the term used to describe households that continue to use their traditional smoky stoves even after having acquired a cleaner-burning one. Sometimes this is for economic reasons. Gathered wood is free, cleaner-burning pellets are not, and LPG is even more expensive. There are also cultural hurdles, like a tradition of cooking certain foods a certain way. Interestingly, researchers hypothesize that wider adoption of cleaner cookstoves is likely when the stoves can also be used to generate electricity to charge cellphones, which are nearly universal, even in the poorest households.

Researchers have reported other cultural barriers rooted in gender-ascribed roles. “If you live in a strong patriarchal society and are surviving on a dollar or two a day, and the man of the household wants to spend the money on something other than a clean stove, well, that’s a problem that has to change,” Dr. Martin explains, noting that the Global Alliance for Clean Cookstoves sees part of its mission as empowering women. “There are deeply rooted patterns of behavior and beliefs that create barriers.”

Although the day when all people cook with stoves that don’t harm their health is not yet in sight, incremental gains appear likely and beneficial.

“We need to reach a tipping point of awareness and expectation that every family ought to have a clean cooking solution for their household,” Dr. Martin says.


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