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: 62

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


You need to be a member of Urgent Evoke to add comments!

Join Urgent Evoke

Latest Activity

Ning Admin is now a member of Urgent Evoke
May 17, 2023
N updated their profile
Sep 25, 2020
Sophie C. commented on Asger Jon Vistisen's blog post Stinging Nettle
"I love that you've brought this to attention. An extensive database of uncommon but resistant and hardy plants/foods could be developed and organized by climate. Ease of growth and processing should also be taken in to account. I will try to…"
Aug 19, 2020
Meghan Mulvey posted a blog post

Fourth of July on the Lake

This past weekend was the annual celebration at the lake house in Connecticut. It is amazing that the lake is still so clear and beautiful after all these years. The watershed association has done a wonderful job protecting these waters from the damaging effects of development.The wood grill was finally ready to cook on, so we didn't miss the propane tank fueled grill anymore. The food actually tasted fresher than in the past and was easy to keep fueled.Dad was very proud of the solar hybrid…See More
Jul 6, 2020
Asger Jon Vistisen posted a blog post

Stinging Nettle

In this blog post I will focus on a plant that is abundant in our nature, and which is immensely nutritious. It's of course the Stinging Nettle. Let's start with the chemical constituents of this plant:37 % Non-Nitrogen-Extracts19 - 29 % Ash9 - 21 % Fiber4 % Fat22 % ProteinOnce the leaves are drid, their protein content can reach an astounding 40 %, which is much higher than beef, which even under the best of circ**stances can never exceed 31 % protein. In addition the Stinging Nettle consists…See More
Apr 13, 2020
Jonathon McCallum posted a blog post

The meal

It is 7'oclock, I was late home from work due to an assignment that i wanted to get ahead on. By the time I get home I am feeling extremley tired and I cannot be bothered to make a proper meal. I walk to the fridge and open it to see what there is for me to eat. All of the out of date foodstuffs have been automaticaly thrown away by the fridge, they will be recycled tomorrow as animal feed or something. I see i have organic local eggs and some local cheese. Foods are vacc** sealded for easy…See More
Mar 10, 2020
Jean Paul Galea shared a profile on Facebook
Mar 1, 2020
Kevin posted a blog post


FutureToday is 2020/1/1. It is just like yesterday. The war is still continuing. It has started since 2010. In 2010, that year was a horrible year. Almost every energy ran out. Every country’s governments were crushed down at the same time. There were riots everywhere. All of the big company’s bosses were killed xdeadx in the riots. Troops fought each other everywhere. Food was bought up xawayx at once. There were no more food supplies in any shops. The economy was all crushed down. All the…See More
Jan 1, 2020
Namwaka Mooto posted blog posts
Jan 13, 2016
T D updated their profile
Sep 3, 2015
Brook Warner posted blog posts
Aug 25, 2015
Santiago Vega posted blog posts
May 5, 2015
Santiago Vega commented on Santiago Vega's blog post Act 8
May 5, 2015
Santiago Vega posted photos
May 5, 2015
Rico Angel Rodriguez posted blog posts
May 2, 2015
Rico Angel Rodriguez posted a photo

public servants

The exchange works directly for state and public workers and servants. It gives them credit in exchange for the amount of public work they contribute to the community. The more constructive they are based off a base rate the more credit they recieve.
May 2, 2015

Follow EVOKE on Twitter

Official EVOKE Facebook Page

EVOKE RSS Activity Feed

© 2024   Created by Alchemy.   Powered by

Badges  |  Report an Issue  |  Terms of Service