Han Thomas of the Expat Community of Chiang Mai , Facebook group reports ….

As per Admin request let me write a report on this year’s haze/smog season in Northern Thailand. I’m using values from the downtown station of the Pollution Control Department as it’s had a PM2.5 measuring capability for the longest time so it’s best for year-on-year comparisons.

This year has of course been exceptionally good (or “good”, relatively speaking), both when comparing against previous years where PM2.5 measuring was available as well as when comparing to the past 20 years using PM10 data. (Let that sink in please, this is not a recent phenomenon. The well deserved attention to the problem *is* more recent, and the increased awareness that has led to a ‘burning ban’ for two months in the North came about because of it. It will need even better enforcing, and as the issue is regional to several countries it will also require international cooperation.) It’s good especially considering that there wasn’t major unseasonal rainfall this year. While it’s only the second year that we’ve had a burning ban I’d say it’s encouraging enough to keep that ban in place, and increase enforcement to make it as strict as possible.

The first graph shows monthly PM2.5 values in recent years; it’s also a good indicator of which months are the most problematic. (Typically mid February to mid April, with many spells that are better and worse, arriving at the monthly average.)

The table is the source data for the graph and also converts PM2.5 values to the US EPA AQI scale, which people may be more familiar with and is useful for comparing to other places/countries.

And then the final graph goes back furthest, showing average PM10 values for the year, as well as the number of days per year that the old Thai PM10 standard was exceeded. (That standard I think is pretty much proven as far too lenient now from a health/safety perspective, given the large PM2.5 component in the PM10 level, however it remains useful for multi-year comparisons: this year the old standard was exceeded on 3 days, versus 14 days on average during the past decade, and 20 days on average in the decade before that.

… Breathe easy folks