A new study suggests that nation-wide efforts to minimise toxic air pollution across China through limiting emissions from large sources such as transport and power plants could be undermined by an uncontrolled and previously less scrutinized source: household fuel burning.



The study, published in Proceedings of the National Academy of Sciences, focuses on Beijing and its neighbouring provinces, Tianjin and Hebei, whose combined populations exceed 10 million people. Solid fuels such as coal and wood are primarily used in households for everyday tasks such as cooking and heating, and consumption rises during the cold winter months. Household fuels are currently not controlled, are often inefficient and can produce high levels of particle pollution, even if some solids such as wood produce less carbon dioxide than cleaner-burning alternatives like natural gas.

Given the prevalence of these fuels within homes across these regions, researchers found that replacing household fuels with cleaner-burning alternatives may present a more significant opportunity for improving air quality in the North China Plain, including Beijing, than focusing on other, non-residential sectors, such as transport and power.

“You cannot have a clean outdoor environment if a large percentage of the population is burning dirty fuels in households several times a day,” said Kirk Smith, a professor with the University of California, Berkeley’s School of Public Health who co-led the study with Tong Zhu of Peking University and Denise Mauzerall of Princeton University. “The smoke may start indoors, but soon leaves the house and becomes a significant part of regional air pollution.”

Their research demonstrates that eliminating dirty fuel emissions from households within Beijing could contribute an impressive 22% decrease in small particle pollution over the city itself; whilst even more impressively, eliminating these across all three areas would nearly double that reduction in emissions, to around 40%. For comparison, annual reductions in particle emissions from transport and power are 5% and 6% respectively. The study therefore emphasises the need to consider air pollution issues from a holistic perspective, recognising the ability of pollutants to travel long distances, and the consequent need to tackle their sources not only in specific cities or areas, but across wider regions to be most effective.

A 2013 Global Burden of Disease study found that direct exposure to solid domestic fuel burning contributed to 800,000 premature deaths in China, a figure similar to the number of annual deaths from outdoor air pollution, Smith suggests. This new research illustrates the importance of addressing dirty indoor combustion for both indoor and outdoor health, and of collective efforts to clean up the air across larger regions, beyond specific cities.