CHIANG MAI, Thailand -- When it comes to air pollution in the north of Thailand, there are plenty of canaries in the proverbial coal mine.
Red flags indicating the seriousness of this perennial problem -- which flares up during the increasingly unpredictable open burning season -- include a rising incidence of pulmonary cancers in the young and fit. Residents and visitors to the city known as the "Rose of the North" can also point to the daily evidence of their own senses: directly felt or observable phenomena such as haze-shrouded buildings, itchy eyes and the dense grey dome of particulate matter that engulfs inbound planes when they begin to descend.
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