How Does Straw Burning Affect Urban Air Quality in China?

Over the past decade, straw burning has been debated as one of the causes of severe air pollution in developing countries. However, the magnitude and pattern of its impact on air quality have not been precisely estimated. This study employs remote sensing data on straw fires from different satellite sources and examines its overall impact on urban air quality in China. Exploiting daily variations in straw burning activities and air pollution with a difference‐in‐differences strategy across 290 cities and 620 days, I find a clear temporal pattern for the straw burning effect. On the first day after burning, the index of air pollution increases by 6.5 in urban areas, equivalent to 9.4% of the mean. This impact decreases over time and remains significant for at least eight days. The effect is larger for fires located in the upwind direction relative to urban areas and is limited with lower wind speed. In terms of distance, pollution is mostly driven by straw fires within 100 km from urban centers but could also be influenced by fires as far as 600 km away. Among different pollutants, particulate matters are increased most by straw fires. The effect is largest and most persistent in October and November, when straw burning prevails in the north after harvest, but is also non‐negligible in other seasons.