non-toxic paint

This question comes from Beth in Hawaii: 

My boyfriend and I happened to catch your show last night and think everything you're doing to make these green building techniques and tools accessible to people is terrific.

What we're looking for at the moment is your assessment of the best paint to use on concrete. My boyfriend is a builder and also artist who is planning to rip out the tiles in his newly acquired studio and paint the concrete underneath. What paint do you recommend we use? I should add that he has emphysema so it's especially important that we find a nontoxic paint.

Thanks. We'll be tuning in for the rest of the series.