Kirk R. Smith, an environmental scientist who traced air pollution to the hearth, finding that one of the greatest international health dangers comes from cooking over open fires in underdeveloped countries, died June 15 at his home in Berkeley, Calif. He was 73.
The cause was a stroke, according to a statement from the University of California at Berkeley's School of Public Health, where Smith was a professor.
In the 1980s, when many people assumed that the worst forms of air pollution derived from automobiles and factory smokestacks, Smith began looking at the problem from the ground up. From his travels throughout Asia and Central America, he noticed that air pollution starts at home - specifically, in the kitchen.
He abandoned his earlier study of the risk of accidents from nuclear power plants to study a more widespread environmental hazard: smoke from solid fuels - typically wood, charcoal, coal or dung. It is a cooking method still practiced in 40 percent of the world's households.
From Nepal, China and India to Guatemala, Mexico and Paraguay, Smith launched dozens of scientific studies showing that smoke from kitchen fires constitutes the world's greatest environmental risk, second only to contaminated water.
"He is literally the most important person in the world in what we call household air pollution," John Balmes, a colleague at UC Berkeley's School of Public Health, said in an interview. "He saved more lives than anyone I know. What he taught me is that the developed world spends billions on cleaning the air from auto emissions and power plants, when more lives are lost in low- and middle-income countries from cooking with solid fuels."
In India, where millions of people still cook their food using dried manure as a fuel, household smoke is the largest source of air pollution.
"We've realized that pollution may start in the kitchen, but it doesn't stay there," Dr. Smith said in 2019. "It goes outside, it goes next door, it goes down the street and it becomes part of the general outdoor air pollution."
The World Health Organization estimates that 4 million people die each year from pneumonia and other diseases caused by household air pollution. Women and young children, often carried on their mother's backs, are at greatest risk from the toxic emissions.
"Indoor fires are like being around a thousand burning cigarettes per hour," Smith said.
Smith was born Kirk Robert Nisbet on Jan. 19, 1947, in Berkeley. His parents divorced when he was a child, and he took the last name of his mother's second husband, an engineer. His mother once worked as a researcher for psychologist Timothy Leary before Leary began his experiments with LSD.
Smith received a bachelor's degree in physics and astronomy in 1968, a master's degree in environmental health sciences in 1972 and a doctorate in biomedical and environmental health in 1977, all from UC Berkeley.
He lived in Nepal and India for extended periods before joining the faculty of UC Berkeley's School of Public Health in 1995. He was elected to the National Academy of Sciences in 1997 and in 2012 received the $100,000 the Tyler Prize for Environmental Achievement, presented by the University of Southern California.
Survivors include his wife of 43 years, Joan Diamond of Berkeley; a daughter; and two grandchildren.
Smith was considered a charismatic figure by students and colleagues around the globe.
"He didn't do science for science's sake," said Balmes, his Berkeley colleague. "He did it to make a difference. He really was trying to save the world."