Inhaling particulate matter is a health risk. Estimates of excess early mortalities may range from 100 thousands to 100 millions. Clearly this shows that science is in very early stages, but that is the current situation. In cities this PM 2.5 can get up pretty high. Research grade monitoring equipment is expensive. I was interested to read about a low-cost "citizen science" approach to this. Public Lab: Measure coarse and fine air particulates with a DustDuino At the heart is a sensor Buy Grove - Dust Sensor [SEN12291P] | Seeedstudio that seems pretty nifty. They can sell that for $16? Dang. Even if you don't care at all about PM 2.5, seed studio looks like an interesting outfit.
Ambient particulate matter is quite a tricky issue. Inhaling high levels of PM2.5 is certainly a health issue, but ambient particles are absolutely essential to life on earth (terrestrial earth at least). Small particles suspended in the atmosphere serve as cloud condensation nuclei (CCN) for heterogeneous cloud nucleation. Without CCN, only homogeneous nucleation can take place, and that only occurs at about -40 degrees C, which occurs far too high in the atmosphere for precipitation to take place (reach the ground). I suppose there's some level of ambient particles below which no health issues are observed. Don't know for sure if the U.S. National Ambient Air Quality Standards (NAAQS) for PM2.5 is at or below that level.
Thanks. It certainly seems correct that the 'setpoint' for droplet accretion would be higher without terrestrial sources of CCN. Marine slat aerosol and dimethyl sulfide -> sulfuric acid droplets also play a role, and planet surface ~70% water covered. On the health side, I don't think any aspect is marked by 'scientific consensus' The mortality estimates vary by about 3 orders of magnitude. One can certainly find people outside the field suggesting that there is no excess mortality at all. I recall it was Roy Spencer who argued thus in a Congressional hearing (may have been one of his functional equivalent though). My interest here is not on the medical side, rather to draw attention to a device with apparently unique capabilities and an absurdly low price It would be interesting to know the concentration range over which this sensor is accurate. The website indicates it can be used to monitor the effectiveness of clean rooms, which suggests a very low 'floor'.
