Environmentalist is often a term used to describe impassioned tree huggers but the word literally means someone who studies the environment so environmentalists can be scientists as well. An ecologist studies the environment and an environmentalist wants to save the environment.
NEIL DEGRASSE TYSON: Just in case our human bodies can't live forever, this computer scientist is trying to design virtual replicas, avatars, that will. JASON LEIGH: An avatar is an instance of yourself that's digital, that will never die. NEIL DEGRASSE TYSON: Jason knows he can't really make you live forever, but he can use computers to preserve your thoughts, memories and even the way you look, for eternity.
So anyway - the answer to your question then is, first, nobody knows if humans can survive zero g for more than two years. And worst case scenario is that you die from the combined effects of all those changes in your body long term. But we might be able to solve all those problems with artificial gravity.