The first real-world, head-to-head comparison of "improved cookstoves" (ICs) and traditional mud stoves has found that some ICs may at times emit more of the worrisome "black carbon," or soot, particles that are linked to serious health and environmental concerns than traditional mud stoves or open-cook fires.

The report, which raises concerns about the leading hope as a clean cooking technology in the developing world, appears in ACS' journal Environmental Science and Technology.

Abhishek Kar, Hafeez Rehman, Jennifer Burney and colleagues explain that hundreds of millions of people in developing countries in South Asia, Africa and South America are exposed to soot from mud stoves and 3-stone fires used for cooking, heating and light.

The particles can be inhaled deeply into the lungs and have been linked to health problems similar to those associated with cigarette smoking.

In addition, black soot released into the atmosphere is a major factor in global warming. Aid agencies and governments have been seeking replacements for traditional cookstoves and fires to remedy those problems, with ICs as one of the leading hopes.

Until now, however, there have been little real-world data on the actual performance of ICs - which have features like enhanced air flow and a battery-powered fan to burn wood and other fuel more cleanly.

The researchers measured black carbon emissions from five IC models and traditional mud stoves. They did the test in real homes as part of Project Surya, which quantifies the impacts of cleaner cooking technologies in a village in India. Forced draft stoves burned cleaner than any other IC.

However, black carbon concentrations from all ICs varied significantly, even for the same stove from one day to the next. Surprisingly, some natural draft stoves occasionally emitted more black carbon than the traditional mud cookstove.