Bangkok: Haze in Thailand's northern provinces has caused 64,108 people to be hospitalised, while more patients are expected as a result of the air pollution, the media reported on Tuesday. Suraphan Sangsawang, acting director of the Regional Health Promotion Centre, 10 Chiang Mai, said reports from 90 hospitals in the area showed that the number of patients with coronary artery and respiratory diseases has increased dramatically as the region's haze worsened last week, The Nation reported. Suraphan said Chiang Mai had the highest number of patients at 17,359, followed by Chiang Rai at 11,779 and Lampang at 10,228. The volume of particulate matter with a maximum diameter of 10 microns (PM10) rose on Monday above the safe level of 120 micrograms per cubic metre in many northern provinces. According to the Pollution Control Department, the three districts with the highest PM10 levels were Chiang Rai's Mae Sai (276 micrograms), Lampang's Mae Mo (213 micrograms) and Payao's Mueng (188 micrograms). Haze is an annual problem in northern Thailand, where wildfires and fires set by farmers burning fields after harvests choke the air with smoke.