Friday, February 28, 2014
Consider what a cloud of traffic-dust-particles looks like.
Here's is photograph of roadway dust in Santa Barbara, California. A late afternoon sun setting behind an apartment building illuminated this frenetic cloud.
Keep in mind that traffic dust is composed of a myriad of small, large, and ultrafine shards of particulate matter, most of which is toxic. Benzene, asbestos, diesel soot, heavy metals, tire wear, crankcase and cargo drippings are some of the contaminants that either make up the dust or adhere to dust particles.
... finely divided solids or liquids. Since the larger particles tend to get settled quickly, they are called settleable or Dustfall particles (particles more than 1µ). Smaller particles, on the other hand, remain suspended for longer periods and hence, are called Suspended Particulate Matter (particles less than 1µ). The smallest particles, almost like gasses, are readily transported by wind currents to longer distances without getting deposited anywhere. While dust, smoke and fumes fall under solid particles, mist and spray come under liquid particles. Suspended Particulate Matter (SPM), most abundantly present in the atmosphere, is the cause of major concern for health. The SPMs can enter very deep into the lungs, severely affecting a person’s health. Since they are small in size, they do not settle anywhere and remain in the breathing zone of human beings. The settling velocity of this particle size range is very low and, therefore, the particles, composed of several toxic compounds, remain suspended for long periods. Metallic fumes, droplets of oil, tar and acid, black soot and local oil particles are some of the examples of these particles."
This is a normal and acceptable circumstance but this should not be so.