Originally Posted by
cyccommute
Exactly.
PM 2.5 means particulate matter 2.5µm. The weight per cubic meter doesn't tell the whole story either. From the
EPA
Assuming that the particulate matter is the same density (not an invalid assumption at that particle size), a 10µm particle weighs more than 2.5µm particle which weighs more than a 0.05µm particle. Roughly, you need four 2.5µm particle to weigh the same as a single 10µm particle and you need 200 0.5µm particles to weigh as much as one 10µm particle. But, because of the process by which the particulate is formed, you have many, many more 0.5µm particles than you do 10µm particles. You don't get a 30% reduction in the
number of particles that you breathe in. You might get a 30% reduction in the
weight of particles but the number is far more important. If don't breathe in one 10µm particle but you breathe in 200 0.5µm particles, you aren't doing anything to protect your health.
So, yes, the mask is a placebo.
Are you implying that their 15% reduction number in that is false?
The Guidelines indicate that by reducing particulate matter (PM[SUB]10[/SUB]) pollution from 70 to 20 micrograms per cubic metre (μg/m), we can cut air pollution-related deaths by around 15%.
If not then what would be a proper estimation for the PM2.5-PM10 range?
By the same reasoning as you do there is more 2.5µm than there is in the 10µm range so we can safely assume that a reduction of 2.5µm over a reduction of 10µm particles will decrease the number of air pollution-related death even further over the one for a reduction of 10µm particles.
Plus we can make the assumption that those masks don't stop at 2.5µm and will probably filter 10µm particles and probably some of the lower than 2.5µm particles (due to physics) which are even more harmful than the 2.5µm one.
Though there is unknowns about how much and for how long one of these masks will actually filter these particles for one individual other that the few people who tested them but my estimate of 30-50% reduction of air pollution-related death seems plausible to me.
Having no mask means that there is no way one of these physics events will happen. Having one increase the odds which means no placebo here.