Wes Siler, writing for Outside Magazine: Actually, Slate, You Really Should Filter Your Water:

The irresponsibility of the don’t-filter argument is exacerbated by two things:

  • While most giardia, e. coli, cyrptosporideum, and waterborne pathogens induce fairly minor illnesses in adults, the effects can be much more severe if the infected person suffers from immunosuppression, is very young or old, or, as with my friend, is simply unlucky. In children, for instance, the CDC says giardiasis can may lead to symptoms as severe as delayed physical and mental growth, slow development, and malnutrition.
  • Effective treatment options are affordable and easy to use. Use an expensive filter because you’re short on time or like cleaner tasting water—cheaper methods will keep you just as healthy.