No, I don't remember any mention of their lower nastiness on the packaging. It would be a bit of a marketing challenge to make much of it I expect. "NiMH batteries, not as environmentally unfriendly as the others" doesn't really cut it. I tried googling for toxic NiMH and the top 2 hits were:

http://www.buchmann.ca/Article16-Page1.asp

http://michaelbluejay.com/batteries/