Emory University | Woodruff Health Sciences Center
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Clearing the air

Researchers tackle indoor pollution from wood and coal burning cookstoves

By Dana Goldman

Story Photo

"Acute Exposure"Steve Sclar 15MPH took this photo while a student at Rollins. He wrote: On this rainy day in a Tibetan yak hair tent, the air became so smoky that I couldn't see from one side of the tent to the other. At this time, my instrument recorded a particulate matter measurement of 118,000 micrograms/m3. WHO designates the safe level to be 10 micrograms/m3. It was an unbelievably acute exposure. Photography by Steve Sclar 15MPH

Whenever Thomas Clasen visits Ethiopia, India, or any of the other low-income countries where he often works on water and sanitation research, the same disturbing scene plays out again and again. Local research participants invite him into their home, and upon entering he is engulfed in thick, acrid smoke.

"People mainly use wood, dung, or crude charcoal-fuel stoves in homes," says Clasen, the Rose Salamone Gangarosa Chair in Sanitation and Safe Water. "The smoke bellows out. Their walls and ceilings are caked with black soot."

For Clasen, those blackened walls and ceilings were a message that his research on household- level environmental health hadn't gone far enough. "Even though I was confident that water and sanitation interventions were important, it became very clear to me that there were other environmental exposures that were potentially more important than the ones I was there to address," says Clasen.

In 2014, Clasen had an opportunity to expand his research to household air pollution by conducting a large randomized controlled trial in Rwanda that combined water filters with improved cookstoves. The work clearly struck a chord with funders. Now Clasen and an international team of researchers are embarking on a $30 million, five-year, randomized, controlled field trial to study the impact of cleaner cooking stoves and fuels on public health. The multi-country study is funded through the National Institutes of Health with support from the Bill & Melinda Gates Foundation.

"Indoor pollution is among the leading risk factors contributing to the global burden of disease," says Clasen, who is a principal investigator for the study. "A low-cost, clean-energy stove intervention could really make a difference."


Participants in the study will wear devices such as those pictured above that measure fine particulates in the air they are breathing.


An estimated 3 billion people around the world cook and heat homes with traditional stoves or open fires that use coal, wood, or animal dung as fuel. Clasen knows that the ubiquitous black soot from these fuel sources doesn't just get on the walls and ceilings. Particulates end up in lungs, increasing the risk of pneumonia, the leading killer of young children.

Evidence suggests that household air pollution contributes to low birth weight and stunted growth, as well as increases in the risk for cardiovascular and other longer-term diseases in adults, such as chronic obstructive pulmonary disease (COPD). Ultimately, that fine particulate matter can be blamed for 4.3 million premature deaths annually around the world. That makes this preventable condition one of the 10 leading risk factors for morbidity and mortality worldwide.

In 2014, the World Health Organization initiated standards for allowable indoor air pollution, setting a standard of 10 micrograms of fine particulate per meter cubed. Compare that with the present-day and commonplace situation that Clasen encounters. "We consistently see 200-500 micrograms per meter cubed; often we see 10 times that," says Clasen. "That means we have to make a very dramatic reduction in exposure levels to reach the WHO targets."

If the problem of household air pollution is massive in scope, so too is this new research trial. Over a 30-month period beginning in 2017, international teams of researchers from 16 collaborating institutions will recruit 800 households to participate in each of four countries: Peru, Guatemala, India, and Rwanda. All households will include a pregnant woman so that researchers can assess the impact of air pollution on growing fetuses and infants. An older adult woman will also be enrolled from a quarter of the households to assess effects in adults.

At the heart of the study is a hypothesis that switching away from fuels like wood, coal, and dung to a lower-emitting liquefied petroleum gas for fuel may significantly decrease household air pollution. That marks a shift in direction for the public health community, which has long worked to encourage the use of improved biomass cookstoves—stoves that used the same fuels but required less of them.

Study co-investigator Kyle Steenland is a professor of environmental health and epidemiology at Rollins. "It's very exciting because no one has done a randomized trial to see whether lowering exposure to indoor pollution via a gas stove intervention can have significant protective effects on a variety of outcomes, including pneumonia, birth weight, stunting, and serious cardiovascular outcomes like blood pressure," he says.


Thomas Clasen working in the field.


Still, the scale of the study presents many practical challenges to researchers. How do you bring stoves and enough gas to remote households and then provide information and education so that family members will set aside their old stoves and fuel sources? "Even though these stoves are beginning to be distributed into these lower-income settings, they are still largely new. There's a big challenge getting these people to use the new stoves as exclusively as possible," says Clasen.

In addition, scientists will give participants wearable devices that can measure personal exposure to air pollution—another challenge. "You have to have people actually wear devices that measure fine particulates in the air they are breathing. Particulates end up deposited on a filter on the device that has to be carefully pre-weighed and post-weighed," explains Clasen. "So just measuring exposure is complicated here." Adults will likely wear sashes or vests with the filters built in; children's devices will be enclosed in backpacks.

As part of the study, researchers will conduct multiple ultrasounds on participating pregnant women to measure gestational growth of fetuses. After the women give birth, researchers will make weekly visits to assess specified health conditions of the adults and growing children. That means the team is preparing for the logistical challenges of bringing ultrasound machines and other equipment to rural villages as well as ensuring ways to refrigerate and store blood and urine samples in remote locations.

While some health outcomes will be possible to study fully within the 30-month study period, scientists are also interested in exploring long-term health outcomes, such as cancers and cardiovascular disease. To that end, investigators—including Rollins professor Dana Barr—will be looking at biomarkers of environmental exposure and disease. Those biomarkers include indicators of cardiovascular function, inflammation, lipids, carcinogens, and risk of diabetes.

These goals are ambitious, given the other sources of air pollution that study participants will continue to be exposed to during the field trial. Says Clasen, "When these people go outside, they're exposed to outdoor air pollution from open fires and waste burning. There's heavy exhaust from motor vehicles. There's kerosene lighting for householders that don't have electricity. There are many sources of air pollution, and we are just addressing one."

Jeremy Sarnat, associate professor of environmental health at Rollins and a co-investigator on the study, says that it is ambitious in scope and scale precisely because the problem of high-polluting fuels is of such global significance. "For me, success is really figuring out if there's a scalable, cross-cultural intervention that shows some success at reducing the burden of disease. That's something that's been very elusive to date with this sort of exposure," he says.

At the end of the trial, the researchers hope to find that the liquefied petroleum gas and more efficient stoves are effective in improving health outcomes. Says Steenland, "We hope to see better birth weight, less childhood pneumonia, and less stunting in the first couple of years of life."

Related Stories

"Rollins researchers receive global environmental research and training award" (10/12/2015)

"Yak dung burning pollutes indoor air of Tibetan households" (1/25/2015)

"A thirst for safe water and sanitation" (6/25/2014)

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