Here we go again. There is no safe level for PM2.5. The called 'safe level' in Thailand is an arbitrarily selected standard which happens to be well above the WHO guideline. The media have a responsibility to provide accurate information about this, and they are repeatedly not doing so.
There is no such thing as a 'safe limit' for PM2.5. There are arbitrarily adopted national standards, but these are way above WHO guidelines, and WHO makes it clear that there are no thresholds below which PM2.5 levels are safe.
,,,, but the considerably more dangerous component of air pollution is PM2.5, and we already have laws and regulations to control air pollution. The problem is that these are not adequately enforced. Why would a clean air act fare any better?