This is what the air looked like in Reno, Nevada (aka Truckee Meadows) on December 20, 2013. Isn't it lovely? There are two freeways that intersect in Truckee Meadows: I-80 and 395. Commercial trucks, travelers, tour buses and locals drive on these freeways 24/7. The air, and our lungs, never get a day off.
The preferred personal vehicle in Reno is a full-size pickup. The favorite make is the Dodge Ram, which gets about 11 mpg city and weighs 4,600-5,000 pounds depending on the model. The second favorite is the Toyota Tundra -- the oxymoron of Toyota because it is neither compact nor economical. It weighs in at about 5,500 pounds, again depending on the model and modifications. When I was on the freeway a week ago, I counted four Dodge Rams in my lane and two Toyota Tundras in the lane to my right. These massive pickups outnumber passenger cars in Truckee Meadows about two to one.
I first heard about PM10 in 1995 when I was fresh out of journalism school and working for a newspaper two hours northeast of Los Angeles.
Modern vehicles along with modern tires have created particulate matter at atmospheric levels never seen before on earth. When cars first became common, in the 1920s, the average vehicle topped out at about 45mph and their tires were made from actual rubber from rubber trees. Ford Model Ts weighed about 1,500 pounds and did about 13 to 20 mpg. Tires are now rarely made from rubber trees but rather polyester and nylon -- two prominent petroleum by-products made from crude oil. They're much harder than early tires and they hit the asphalt as they're spinning at twice the speed of early tires. Basically, a car or truck tire, is a spinning crusher that pulverizes sand, dirt and debris and makes it smaller -- usually 10 microns all the way down to 2.5. This ultra-fine dust rises into the lower atmosphere.
If you live in a fairly verdant region that sees a lot of precipitation, like New England or the Pacific Northwest, the particulate matter doesn't stay in the air very long. It's knocked by frequent rains or snow to the ground where it sifts into the water table. Unfortunately, in desert environments like the American West, northern China (Mongolia), the Middle East, Bolivia, etc. -- where there is little or no precipitation, this particulate matter stays in the lower atmosphere. In northern China, cities like Gansu situated near the Mongolian Desert have some of the worst air quality in the world. Granted, this is partly due to the fact the Chinese burn coal to heat their homes but it's also because Mongolia is a desert much like the Great Basin. Also, the booming middle class now own personal vehicles in record numbers. There are even off-road 4x4 clubs in China.
There is very little information on particulate matter -- its sources or where it ultimately ends up. This is not a coincidence. Just as Googling the torque or engine size for a Dodge Ram or a Toyota Tundra readily yields answers, try searching for the mpg or weight of these vehicles and the stats become mysteriously difficult to find.
As populations in desert cities grow, particulate matter accumulates in the air above them.
We inhale this PM10. And all animals (birds, dogs, cats, beef cattle, etc.) inhale it. It drifts down into creeks, rivers and lakes when it rains or snows. Children inhale it.
It's ironic that in the arena of global climate change debate, the issue of particulate matter generated by cars and trucks almost never comes up. Apparently CO2 levels, mercury and withering ice caps are such depressing and huge problems, there's no room left to talk about the most visible form of atmospheric pollution.
Wikipedia - particulate matter
Particulate matter map