Unfortunately, the only way to remove chemical pollution from water in the field is through distillation. For all intensive purposes, distallation is impractical because it requires a huge amount of fuel.
If I were hiking through an area where the water is known to be chemically polluted, I would: 1) do my due diligence to find out where confirmed, clean water sources are, 2) carry in more water (water is heavy, so I'd probably have to sacrifice other conveniences to make room for the weight).
Carbon filters may get rid of some of the chemical pollutants, but not all.
BTW, correct me if I'm wrong, but I find it highly unlikely that any developed country would use lead pipes in transporting water.