Environmental Factor, March 2010, National Institute of Environmental Health Sciences
Ancient Fires - Modern Dilemma
By Ed Kang
For the modern world, cooking is safe and convenient. A quick turn of the dial on any stove, and within seconds, there's clean, efficient heat. But for millions of families in developing nations, meals are cooked over an open fire, with serious implications for health and the environment. Long-time NIEHS grantee Kirk Smith, Ph.D., recently presented his findings on household fuel use and its connection to indoor and outdoor air pollution and health in a talk at Duke University Feb. 17.
Sponsored by Duke University's Global Health Institute, Smith spoke on "Incomplete Combustion-the Unfinished Global Agenda for Health, Environment and Climate Protection," a subject on which he is a preeminent authority. Smith's talk focused on the health effects of air pollution in developing countries and the urgent need for new and accessible technologies in mitigating exposure.
Cooking up toxic soup
Smith began by mentioning CO2, the by-product of complete combustion. "While CO2 is most important to global warming because of its persistence and quantity, products of incomplete combustion (PICs), such as black carbon emitted from traditional biomass use in the home, are far worse from health, climate, and ecological standpoints."
"Wood smoke is not benign," pointed out Smith. When it burns, 6 to 20 percent is converted into PICs, not heat. "Essentially, it's a toxic soup of classic air pollutants - small particles, carbon monoxide, NO2, and a vast range of other organic materials, including benzopyrene, benzene, formaldehyde, styrene, even dioxin."
Examining the circumstances of exposure reveals the ubiquity of the problem: using solid fuels for cooking is a highly polluting activity. Half the world's households cook several times a day - just when people are present - and the most vulnerable populations, poor women and children, are affected. Smith calls the combination of risk factors "a perfect storm" for health effects.
A panorama of health implications
"We've done the work in Guatemala for what we think is the first randomized trial in air pollution history," explains Smith. That study is now looking at chronic effects of the ancient task of traditional cooking. "There's quite a panorama of things that we're looking at - cognitive effects for children exposed in utero or in early childhood, birth defects, including cleft, and on the adult side, lung cancer and maybe other cancers, tuberculosis, and heart disease."
Smith is quick to note one of the lessons from his research, "The chimney doesn't get rid of the smoke, just moves it." The smoke comes back in the kitchen or the bedroom, or it lingers in the community. He is adamant about the need to replaces stoves now in use with devices that don't produce pollution in the first place. "There are such devices now... even stoves that bring levels down to where a chimney would not be needed."
Immediate returns for health and climate
Products of incomplete combustion present an ancient but large risk to climate and health. Smith estimates 14 percent of global deaths and 10 percent of the burden of disease are attributable to "combustion mismanagement." He also explains the immediate benefit of reducing the cumulative effect of these micro-emissions for the climate. "Unlike CO2, with a lifespan of 100 years or more, if you eliminated all the black carbon today, there would be no black carbon in the atmosphere next week. You can get short-term returns both for health and for climate."
Smith was one of the scientists involved in the NIEHS-sponsored climate change series published in Lancet prior to COP15, and he was a participant in a simulcast workshop and press conference (http://www.niehs.nih.gov/news/events/pastmtg/2009/climate/index.cfm) with partners from the United Kingdom. His University of California, Berkeley programs and publications Web site has links to an impressive number of his publications.
(Ed Kang is a public affairs specialist in the Office of Communications and Public Liaison and a regular contributor to the Environmental Factor.)