I don't like that title
First, man is one of the few creatures in the world that removes his fresh feces from the environment.
Think of what whales do. If we defecated into our atmosphere it would get pretty weird.
Also look at the terpenes put out by a pine tree. One pine tree can create more photochemical smog on a hot day than several cars.
ALL LIVING THINGS pollute their own environment, and by comparable biomass, man is a leightweight.
Ya know what? One of the first mass extinctions was caused by the O2 pollution excreted by plants.
At one time on this planet, oxygen was pure poison to all life.