One is always going to be a little more careful with human research. There are ethics involved that may not apply to other areas of science. I'm ok with that.Another example of anti science, remember the bans on T cell research. Notice all the fantastic discoveries in the last eight years.
I think it is more of a problem for the professor than the student. My stipend was always the same no matter where the money was coming from. The stipend, I thought always comes through the university and at the end of the day they still have to pay it. The university may give the professor a hard time if the grant money dries up and there may be no money for new equipment. Post-doc positions may be another story.
Is it true that if a PhD student is being funded with money from the EPA, they are now SOL?