Depending on where you hike this may be something you ought not to worry about.

If you hike in areas that are practically suburban, here is a pretty significant survey that suggests water treatment is not effective

http://findarticles.com/p/articles/mi_m0689/is_n5_v36/ai_13928819/pg_3?tag=artBody;col1

And here's one that seems to contradict this
informationh

<a href="ttp://www.ncbi.nlm.nih.gov/pubmed/14769284" target="_blank">ttp://www.ncbi.nlm.nih.gov/pubmed/14769284</a>

It sounds like a toss-up......

If you are hiking in real wilderness.... the concern seems much overblown.......