KUALA LUMPUR, Oct. 12 -- Air quality deteriorated across several states this morning, with 22 of the country's 68 monitoring stations recording unhealthy Air Pollutant Index (API) levels as schools in multiple states prepared to resume physical classes.

According to Department of Environment (DOE) surveillance data as of 8.46am, only three stations recorded good air quality while 42 were in the moderate range.

Johor emerged as the hardest-hit state, accounting for eight unhealthy stations, including the nation's highest reading of 170 in Kota Tinggi. Elevated figures were also logged in Pasir Gudang (168), Pengerang (164), Larkin (160), Tangkak (156), Batu Pahat (152), Kluang (152), and Segamat (129).

In Negeri Sembilan, Seremban recor...