Samut Sakhon Province
The most polluted air in Thailand in 2018 was found to be in Samut Sakhon Province. According to the PCD, the level of PM2.5 in the provincial atmosphere in 2019 was unusually high, measuring as high as 195 micrograms per cubic metre (μg/m3). During the air pollution "season" of 2018–2019, PM2.5 levels exceeded the PCD's safe threshold of 50 μg/m3 for 41 days.