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.
From trafficinfratech.comhttp://www.trafficinfratech.com/traffic-dust-particles%E2%80%93as-dangerous-as-vehicular-emissions/
"Particulate Pollutants
... 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.
