The survivalists tend to worry the most about the government and warfare effects, and ignore more vague environmental concerns---ie they are more militia-slanted and not overly concerned about water quality, air quality, etc. The public_health group was completely dismissive of my post and they seem to be taken with the conventional line from insurance and the pharmaco-medical industry. The so_very_doomed group actually came up with a decent exploration of the side effects of new iodine supplementation (ie bromine release and how to deal with it).

It's my impression that each group tends to accumulate more people who agree with a central set of assumptions, and that they are all different. I join groups whether I agree with their worldview or not, just out of curiosity about the subject matter they entertain. My rare posts are more often disparaged than respected.