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Reducing your risk from Crypto and other waterborne pathogens

by Kristine Bradof

This article originally appeared in the July 1996 issue of the Wellspring newsletter, published by the MTU Regional Groundwater Education in Michigan (GEM) Center, now the Center for Science and Environmental Outreach at Michigan Technological University.

The 5 to 6 million Americans who have weakened immune systems are at greatest risk of becoming seriously ill from exposure to disease-causing microorganisms (pathogens) in their drinking water. Those at risk include AIDS/HIV or cancer patients, recipients of organ or bone marrow transplants, long-term users of corticosteroids (for asthma, etc.), the elderly, and infants.

If you are in one of the at-risk groups, the surest and least expensive way to make sure your drinking water is safe from pathogens, including chlorine-resistant forms like Cryptosporidium and Giardia, is to boil it for one minute. If you prefer bottled water, which is not necessarily safer than tap water, buy a brand processed by reverse-osmosis or distillation (or boil it, too).

Most home water filters are not intended for use with water that is not safe microbiologically. Look for ones certified by NSF International (800-NSF-8010) for "Standard 53 cyst removal" or labeled "absolute one micron." "Nominal one micron" is not good enough to reliably remove Cryptosporidium. Wording like "Standard 53 applicable" on a filter does not mean the device has been certified by NSF. Once you have the appropriate filter, be sure to maintain it properly. Also be aware that filters sometimes fail, giving no warning that the water is no longer being filtered adequately.

Again, the best advice for protecting your health against pathogens in drinking water is old-fashioned but reliable—boil the water for at least one minute.


Huntoon, E. Water borne disease. Wisconsin Water Well Association Newsletter, January 1995, pp. 8-9.

University of California at Berkeley School of Public Health. Is our water safety going down the drain? University of California at Berkeley Wellness Letter 11(12), September 1995, pp. 1-2.