If you look at the pipes coming out of your roof, those are plumbing vents.
Vents need to be 12 feet away from an open window, or up on the roof.
Having an open cleanout at ground level means that sewer gas lifts up into your open windows.
I don't know that it's that dangerous, there are vents on the roof, that disperse the same gases into the wind. The idea being that by the time it reaches the next house, it is diluted, and even gains elevation.