I believe you are asking, "what social activities pollute our environment?"
Monster truck racing is a very social activity. It burns a large large large amount of diesel fuel. Now, albeit races and tournaments do only happen on the occasion, there is still much damage done during the short period of time that these trucks run. After many races, there is a smoggy haze drifting over the area in which the race took place. Only a few hours time, and there is already smog hovering over the race joint.
Now, you may look at monster track racing and say, "How on Earth is this a social activity?!" Well, just like soccer or basketball, monster truck racing has fans. Fans gather in the same area to view an event and SOCIALIZE as a unit. They share a common interest of that individual activity and enjoy talking and exchanging information about it.
I personally enjoy watching monster truck racing. Will I ever drive one? The world will never know. . . Until . . . The day I drive one.
-Noah
