Urgent Evoke

A crash course in changing the world.

This month's National Geographic issue is all about water. I was so excited to get it in the mail last Friday because I knew there would be something to spark me off for EVOKE. Plus, I just love NatGeo. I wouldn't be the person I am today if I hadn't read hundreds of those little yellow bordered magazines as a kid.

Anyway, I opened up to page following the Visions of Earth section and immediately got inspired by SODIS. This Swiss engineering group has figured out how to disinfect water in 6 hours using only sunlight and plastic water bottles. Seriously. And they have the scientific research to back up their work.

The Method:
Basically, you find a discarded water bottle and clean it out with soapy water. The bottle must be clear or blue, with few scratches. Remove the label and fill it with water from a puddle, creek, or standpipe that isn't terribly murky. Then stick it out on a piece of metal in full sunshine. The picture in my NatGeo shows a bunch of old Evian bottles full of water on a piece of corrugated roofing in a Nairobi slum. In 6 hours the UVA kills the viruses, bacteria, and parasites in the water. Wow!


Then I got to thinking, what about toxins from the plastic? They might leach out if the plastic gets hot. In the past couple of years, people have switched water bottles in the US from regular plastic to metal and special plastics over the fear of endocrine disruptors leaching from plastics. There is no direct proof of harm to humans, but fish, frogs, and other animals are showing signs of toxicity from pollution in our water supplies. A 2009 research article by Leonard Sax (free online) suggests that PET plastics may leach endocrine disruptors like antimony and phthalates. These affect hormonal levels and can mimic estrogen. Sax's research suggests that high temperatures can cause leaching into water, but he ends with a "more research is needed" comment.

I then went to SODIS to see if this issue was addressed. They did! It was a relief to find that they had considered possible harms like this. From their website, they write

"Reports from around the world regarding substances in PET bottles that cause cancer are worrying users of the SODIS method. Therefore, a number of research institutions tested the scientific accuracy of these reports and carried out their own analyses of the materials. Studies have been produced for the following substances: antimony, adipates, phthalates, acetaldehydes and formaldehydes. These studies show that when the SODIS method is applied correctly with PET bottles, there is no danger to human health."

Since their method is amazingly simple, this method of disinfection both works and does not harm. This is followed by a description of all the different chemicals and links to several scientific articles that summarize the tests in greater detail.

So why do I care? This summer I will be working in rural Africa. I plan to take this information with me and pass it on. Plus, it doesn't hurt that I will have a cheap and safe way to clean my own drinking water in the field.

Photo from SODIS.

Views: 61

Comment by John D. Boyden on May 9, 2010 at 7:07pm
+1 KS added the link to my URL stash
Comment by Ternura Rojas on May 9, 2010 at 7:33pm
This is a good idea to solve extreme, urgent situations. I am very concerned about the potential toxic effects that this practice could bring about on the long term. I suggest every one who proposes this idea to fill a bottle with tap water (please refrain from experimenting with fresh water from a near river or spring) Then put the bottle under the sun for 4-6 hours and then drink, let me know about the plastic taste of that water. This flavor gets enhanced as the bottle is re-used an used again. Do you think that you should (or ever could) rely on this method to obtain healthy drinkable water?
This idea is good but not sustainable :-) T

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