TOTORABAMBA, Peru—Smoke swirls around the hearth and hangs in the sunny doorway of the adobe kitchen where Espirita Lima Bautista crouches by an open fire, toasting barley grains. Soot dangles from the thatch roof in six-inch stalactites, a grim reminder of the particles she inhales whenever she cooks.

For this 80-year-old grandmother, breathing while cooking for an hour is like inhaling the second-hand soot from 400 cigarettes. Although it only lasts as long as the meal is being prepared, exposure began when she was a baby, slung in a blanket over her mother’s back.

Two decades ago, concerns about cooking fires centered on deforestation from firewood. Now research shows that cookstoves can kill people, too.

Indoor smoke from coal, wood or dung – used as cooking fuel by more than 3 billion people worldwide – ranks ahead of unsafe water as a cause of death in low- and middle-income countries. Almost 2 million deaths a year are caused by cooking smoke, which is linked to pneumonia in children, chronic obstructive pulmonary disease, low birth weight babies and lung cancer, according to the World Health Organization.

These fires also help heat up the planet, emitting greenhouse gases as well as the black carbon that creates the stalactites on Lima Bautista’s ceiling

“There are health and climate co-benefits to changing the way a lot of people in rural areas around the world cook,” said Jennifer Burney, a postdoctoral fellow at the Scripps Institution of Oceanography in San Diego who studies the links between energy and food in poor countries.

Faced with global public health threats, governments and non-profit development organizations are encouraging families to install “improved” stoves. The United States has donated $105 million to a United Nations-led effort that aims to put safer cookstoves in 100 million households by 2020. In addition, leaders of the G8 countries pledged in May to take measures to reduce short-lived climate pollutants that include distributing more efficient cookstoves in developing countries.

The problem is that many newer models on the market do little to reduce harmful emissions and some actually make matters worse.

“It’s a case of the policy getting ahead of the science,” said William Checkley, a researcher from Johns Hopkins University’s Bloomberg School of Public Health, who is coordinating two studies in Peru, including a comparative study of cookstoves in Lima Bautista’s village near the Andean city of Ayacucho.

Research published in March points to huge differences between stove models. Black-carbon emissions from some newer stoves were higher than from traditional fire hearths, said Burney, who co-authored the study.

Cookstove research was originally designed to reduce deforestation, said Tami Bond, an engineering professor at the University of Illinois. Now, she said, “health is really the driver” of clean-stove research.

Indoor smoke mainly affects women, children, the elderly and indigenous people, who have the least political and economic clout, and the least access to safe water, sewer systems and health care, said Agnes Soares, environmental epidemiology adviser at the Pan American Health Organization in Washington, D.C.

For many diseases, indoor cooking fires rank between active and passive cigarette smoking as a risk factor, according to Kirk Smith, director of the Global Health and Environment Program at the University of California, Berkeley.

Globally, the World Health Organization attributes 35 percent of chronic obstructive pulmonary deaths and 21 percent of lower respiratory infection deaths to indoor air pollution from solid fuel. In China, where coal is the main fuel, they are the second-highest factor linked to lung cancer, after smoking. Women who cook indoors over open fires also have thicker carotid artery walls and more arterial plaque buildup than urban counterparts who use liquefied petroleum gas stoves, according to Checkley’s preliminary data. Both are signs of heart disease.

Mayan families in Guatemala use indoor fires not only for cooking, but also to keep women and newborn babies warm, said Lisa Thompson, an assistant professor in the nursing school at the University of California-San Francisco. Wood-fired post-partum saunas expose women to carbon monoxide levels as high as 300 parts per million for half an hour at a time, and babies for about 10 minutes – well above the U.S. Environmental Protection Agency’s maximum limit of 35 ppm in a 1-hour period, she said.

Low-weight babies and stillbirths also are linked to the indoor air pollution from solid fuel. In Guatemala, babies were born on average 85 grams heavier if their mothers cooked using electricity or gas instead of cookstoves, according to one study.

Less is known about other hazards. When Smith saw people tossing plastic bags into their cooking fires, he began testing for other toxics and found dioxins, which are carcinogens. Even when people do not burn plastic, he said, incomplete combustion produces toxic substances in many “improved” cookstoves.

“There are thousands of things in wood smoke,” he said. “You get significant emissions of benzene, formaldehyde and butadiene. Do you need to say anything more than that 40 percent of the world’s children are in kitchens where there are significant amounts of three major carcinogens? If you had those three pollutants being pumped into kitchens in this country at the levels that it happens, even with no particles, you’d have the National Guard out.”

Some research also suggests soot accounts for 30 percent of the recent warming in the Arctic, and the UN’s Global Alliance for Clean Cookstoves reports that a quarter of global soot emissions can be traced back to cookstoves.

Because methane, carbon monoxide and black carbon remain in the atmosphere for a shorter time, some scientists and policymakers consider them “low-hanging fruit.” Reducing them with better technology could have an immediate impact on climate change.

Such efforts, however, could be problematic.

Families in Bangladesh would rather spend a hypothetical subsidy on health care, education, electricity or other needs than on low-emission stoves, according to one study. Even a half-price discount did little to increase demand for stoves.

In Lima Bautista’s community, the Peruvian government encourages women to “improve” their open-hearth cookstoves as part of a program that gives families a cash incentive to keep their children in school and take them for health checkups.

But with no technical advice available, many families simply raise the hearth or install an ineffective chimney, said researcher Elizabeth Klasen. Those measures have no impact or could even make emissions worse. Klasen is working with Checkley on a study comparing locally built and commercially available stoves that are meant to increase fuel efficiency and lower emissions.

Smith doubts that they will see a significant improvement.

“I’ve seen so many ‘improved’ stoves come and go that I’m cynical,” he said. “People use the word ‘improved’ as though it’s magical.”

Engineers and development workers have been experimenting with cookstove designs at least since the 1980s. They come in many styles, from mud-brick hearths to oil drums, with the most common model known as a “rocket stove.”

Because lower emissions depend on more efficient combustion, the secret lies in the stove’s combustion chamber, where “time, temperature and turbulence” are key, said Jim Jetter, an engineer in the U.S. Environmental Protection Agency’s Air Pollution Prevention and Control Division.

“The combustible gases have to have enough time to burn in the combustion chamber, they have to have high enough temperature to completely combust, and there needs to be turbulence, or good mixing in the combustion chamber,” said Jetter, who tests cookstoves in his laboratory.

Even a highly rated model may perform differently in the field.

Some initial efforts have emerged to use carbon credits as an incentive for installing improved cookstoves, but the discovery that some increase emissions highlights a need for international standards. The World Health Organization is drafting limits for indoor air pollution, while the International Standards Organization is developing standards for cookstove emissions, efficiency, safety and durability, said Radha Muthiah, executive director of the Global Alliance for Clean Cookstoves.

But the real answer may lie in a wholesale change in the energy sources available to poor households.

“There’s no mystery about what works,” Smith said. The 60 percent of the global population that does not use wood or dung for cooking has proven that “every cuisine in the world [can be] cooked on electricity or gas,” he said.

The challenge, he said, is to make gas or electricity widely available, with extremely clean cookstoves filling any remaining gap.

“If it’s significantly better, no woman will go back” to cooking over an open fire, and the public health savings should be incentive for governments to put money into the effort, Smith said. “It’s not subsidy – it’s social investment.”

This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.