Hello All, I have been concerned about information floating around regarding water sterilization with sunshine.Yes it is true that many pathogens are inactivated by warming them to less than boiling temperatures. But,it depends on the organism and the TIME. The time is also critical when using chemicals (such as chlorine) for disinfection. You have to wait twice as long when the concentration is halved.

I wanted to get some factual information,so I asked the Editor of a magazine that publishes only on the area of cryptosporidium. This is what he had to say Roger

For 140 degrees F (60 degrees C) to inactivate Cryptosporidium, the amount of time at that temperature is critical. One minute may not be adequate whereas five minutes may be.

Solar pots (those designed to pasteurize water by using sunlight)can inactivate Cryptosporidium if the pots achieve pasteurization (usually about 65 degrees C (150 degrees C) within 3 hours).

In fact commercial pasteurizers have been tested for inactivation of Cryptosporidium and found to be effective within 5 seconds, when the oocysts were placed in water or milk. These pasteurizers achieve temperatures of 71.7 degrees C (approximately 161 degrees F). Other studies have demonstrated that one minute at 69.8 degrees C inactivated Cryptosporidium.

We would suggest that to be safe (due to the variability in infectivity between strains, the susceptibility of individuals, etc.) one should boil their water for one minute, even though a lesser temperature may inactivate the oocysts with the same amount of time. 

-- Roger Delano (roger@netdex.com), August 12, 1999