The difference is that if the pyrochemical concept is true, it would fill the atmosphere with material inhospitable to most forms of life, and unlike typical pollution or radiation won't be mitigated over time.
If airborne particles could eventually settle after Theia crashed into Earth and created Moon, I'm sure any puny dust cloud kicked up by humans would settle down too.
yeah but would we die before it settled
And we were never alive
before. And by 'we', I mean that maybe 200 million to half a billion
1 years passed between the hypothetical Theia collision and when the
whole of our family tree arose/landed/whatever, with LUCA maybe hundreds of millions of years later.
If the life we have at the moment survives a Theia 2 naturally (deep subterranean, at or around the antipode?) maybe it'll re-arise. Probably has better chance of rearising than ourselves, or anything we would recognise (save for anything our future Martian colonies/etc brought back either deliberstely or on the soles of their spaceboots). But I'd lay odds on the Life Version 2 (the result of the high-speed, highly-parallel frenetic organic experimentation within the boiling and roiling mixing pots of New Earth) coming up with the solution
again, independently, and starting a new competition for life that obliterates any final slow, cold, passive Life V1 that creeps up out of the hiding places. Although it
could go either way, or neither.
1 Short billion, admitedly, but it's still long enough...