Here http://www.survivaltopics.com/survival/making-water-safe-to-drink-video/ is a nice video on water purification. He covers the Millbank Bag (very cool, I think I'll get one), but like most people, when he gets to water boiling OR water filtering, it is just that; either or. My point is that most experts seem to adequately address the pathogen issue but they seem to completely ignore the chemical contaminant issue. I think it is worthwhile these days to consider these steps:

1. Millbank Bag to remove debris;
2. Boiling to kill pathogens;
3. Microfilter to remove heavy metals and other contaminants.

As far as my research is concerned, disinfection via iodine or other means is not universally effective enough to rely on, so I don't mention it.

Step 2 could be eliminated if there is a microfilter that effectively removes all pathogens.

My first question is; How do pathogens and heavy metals and other pollutant molecules differ in size? If recall correctly, viruses are the smallest pathogens. I have no clue regarding pollutants.

My second question is regarding step 3, and is two-fold; Are heavy metals and other potential pollutants a concern to anyone, and is there a microfilter that is known to effectively deal with these?