For YEARS, Chiang Mai and surrounding areas have made the news with complaints of hazy skies, and dangerously high particle levels in the air. This year again (the period of the year when it occurs seems to be between Januari and April) air pollution levels (yes, quite a few people need hospital treatment) remained poor for many weeks. The reason is the rather medieval practice of burning waste of farm crops. Mostly in Thailand, also in neighboring Burma. On top of that, companies have been accused of burning forest land, to prepare it for planting crops to be used for alternative fuel production. The irony of this statement should not be lost on anybody.
What is most disturbing is that this problem has been there for many years now, and often reported, at least in the local press, but there seems to be no relevant action taken against waste burning. I guess, nobody wants to upset the farmers.
2015 shows the same problem persisting with slightly less coverage in the media. Small particles pollution levels are elevated in some northern provinces. In the English language newspapers, a local cardiologist gives anecdotal evidence of a higher incidence of heart attacks during the 'burning' period between January and April each year.
The advice : Check-out the situation before travelling to Northern Thailand in the early months of the year.