Thirteen areas in the northern provinces, especially Chiang Mai and Chiang Rai, were found to have PM2.5 dust in the atmosphere at levels which exceed the 50-micron safety standard, with Wiang Pang Kham sub-district in Chiang Rai recording 247 microns.

The Pollution Control Department said, on its “air4thai” website, that air quality in the two provinces is expected to deteriorate tomorrow through Friday, due to stale air.

The 13 areas are:

• Chang Phuek sub-district in Chiang Mai, 74 microns
• Sripoom sub-district in Chiang Mai, 79 microns
• Suthep sub-district in Chiang Mai, 82 microns
• Theprattana Hospital in Mae Chaem district of Chiang Mai, 76 microns
• Wiang Pang Kham sub-district in Chiang Rai, 247 microns
• Wiang sub-district in Muang district of Chiang Rai, 84 microns
• Phra Baat sub-district in Muang district of Lampang, 60 microns
• Ban Dong sub-district in Mae Moh district of Lampang, 52 microns
• Mae Moh sub-district in Mae Moh district of Lampang, 57 microns
• Chong Kham sub-district in Muang district of Mae Hong Son, 109 microns
• Ban Klang sub-district in Muang district of Lamphun, 60 microns
• Ban Tom sub-district in Muang district of Phayao, 74 microns
• Mae Pa sub-district in Mae Sot district of Tak, 56 microns.