Nursemike, you are confusing two styles of filtering.

Physical filtering to remove particulates, which will not work, and exposing the water to absorbents in a bed which, with the correct absorbent, activated carbon, ion exchange resin, etc. will work.

The OPs link statement that filtering to 5 microns will remove dissolved lead is just plain wrong. Very easy to test. Try adding some food colouring dye to the water and see if a particulate filter removes the dissolved material.