BANGKOK — Chiang Mai earned the dubious distinction of being the most-polluted city in the world Tuesday morning as air pollution continues to surge.

Chiang Mai’s air pollution index this morning spiked to the “very unhealthy” level of 234, with ultrafine particulate density nearly 180 micrograms per cubic meter, according to independent monitoring organization AirVisual. Bangkok was ranked the 9th most-polluted city, with average particle concentrations of 80 micrograms per cubic meter.

Read: Chiang Mai’s Foul Air No Priority to Bangkok, North Complains

Rounding out the top 10 were cities including Ulaanbaatar, Mongolia; Lahore, Pakistan; Kathmandu, Nepal; and Hanoi, Vietnam.

On Twitter, #PM25particles became the No. 1 trending hashtag in Thailand. Most comments complained about government inaction, though the problem in the north has persisted for years. PM2.5 particles are the smallest and most harmful type of air pollution.

Several northern provinces also saw air quality deteriorate. Pollution this morning rose to “unhealthy” levels in Nan, Lamphun, Lampang, Mae Hong Son and Prae.

A recent study by the University of Chicago found life expectancy in Thailand is shortened by over two years on average due to prolonged exposure to air pollution.

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