Diffusion of Phtalates during SODIS exposure

Regula Meierhofer - Monday 22 May 2006

Mindy Weimer has raised questions on the inactivation pattern of pathogens during solar exposure and the extent of diffusion of Phtalates into the water from PET-bottles.

1) Inactivation pattern of pathogens during solar exposure

A great number of SODIS experiments have been carried out in the laboratories of Eawag, Swiss federal institute of aquatic research, and other research institution such as for example the Royal College of Surgeons in Ireland, the University of Northumbria in England, the MIT and others. The laboratory research has been complemented by many field tests of partner organisations of Eawag/Sandec in more than 20 developing countries. You can find references of research results on the POU bibliography that has been compiled by Dan Campell (http://www.ehproject.org/PDF/Others/pou_bibliography2.pdf) or on the SODIS website (http://www.sodis.ch/Text2002/T-Papers.htm)

An increase of Faecal coliforms or other pathogens during solar exposure has never been observed nor could we find any regrowth of E.coli within one week after the water had been treated with SODIS. Could it be that your test samples were recontaminated during sampling? What kind of testing methods did you use? You may contact me directly for further discussions.

2) Diffusion of Phtalates into water from PET bottles

The discussion on the diffusion of Phtalates and Adipates goes back to a masters thesis by D. Lilya, College of Graduate Studies, University of Idaho . During her work she conducted an assessment on organic chemical migration from reused PET plastic bottles and claimed a possible carcinogenic risk of reusing PET-bottles due to the migration of DEHA (di(2-ethylhexyl)adipate) and DEHP (di(2-ethylhexyl)phthalate).

Worried about those statements, Eawag/Sandec in collaboration with the Swiss Federal Laboratories for Materials Testing and Research (EMPA) studied the migration of organic components DEHA and DEHP from new and reused bottles (heavy use during 6 months in the field (Honduras, Nepal and Switzerland) to the water under the conditions of solar water disinfection (SODIS). Bottles were exposed to sunlight at a water temperature of 60°C. Total time of exposure to sunlight was 17 hours.

The levels of the plasticizers di(2-ethylhexyl)adipate (DEHA) and di(2-ethylhexyl)phthalate (DEHP) detected in the water were 0.010 – 0.046 µg/L for DEHA and 0.10 – 0.71 µg/L for DEHP. These detected levels are in the range of background levels detected in pure water stored in glass bottles without any previous contact with PET. Background levels are found even in pure water due to the ubiquitous presence of traces of these plasticizers. Such low concentrations of DEHA and DEHP are distinctly below the WHO guidelines for drinking water quality (80 µg/L for DEHA and 8 µg/L for DEHP).

The report of diffusion of phtalates and adipates can be downloaded from:
http://www.sodis.ch/files/Report_EMPA.pdf

°°°
Regula Meierhofer
Eawag
Water and Sanitation in Developing Countries (Sandec) Ueberlandstrasse 133 8600 Duebendorf Telefon +41 (0)44 823 50 73 regula.meierhofer@eawag.ch www.sodis.ch; www.sandec.ch; www.eawag.ch

SODIS related response

Mindy Weimer - Tuesday 30 May 2006

Dear Regula, Kevin, and Prajwal,

Thank you for your prompt response to my inquiry last week. I apologize that it has taken me this long to reply.

The method I used to test for total FC is that prescribed in the DelAgua field kit manual. I have been using that frequently over the past year to test a full range of water samples. My reasoning for not attributing this detection to the method was because I ran them in triplicate.

The simplest explanation of course is to attribute the detection to experimental error. However, I am pretty confident in my water testing skills as I trained Oxfam field engineers how to use the DelAgua kit and water test; so I thought it best to not assume I made an error without inquiring to see if others had seen a similar trend somewhere.

“An increase of Faecal coliforms or other pathogens during solar exposure has never been observed nor could we find any regrowth of E.coli within one week after the water had been treated with SODIS. Could it be that your test samples were recontaminated during sampling?” –Regula

I honestly cannot think of another explanation. I needed that confirmation from you though, and am actually pleased to learn that I can attribute those results to experimental error and not need to worry about regrowth.

“Nevertheless we changed our protocol to recommend that the SODIS water is consumed as soon as possible after exposure and not left for more than 24 hours before consumption.” –Kevin

I have been monitoring the water quality of 4 SODIS users in 4 different Jakarta slums each week this month. A couple of the users have been treating 16 bottles at a time to refill their dispenser containers, so have not been drinking the water the very next day. Of the 5, 4, 2, and 2 days post-treated, all results show 0 FC/100mL. I still encourage them not to wait so long to drink the water, but just thought I would share that with you.

Thanks for you Kevin and Regula for insight re: thalates leaching from the plastic.

“In the beginning days, I could not believe and trust on this technology being so simple but after consulting some related professional I get satisfied on this technology. Basically, I am interested to familiarize this simple technology in most of our rural areas so I'd like to hear more detail information and your realistic experience so that I could do some thing for the people who are not able to adopt this very simple technic in their daily life.” –Prajwal

I too had to prove it to myself, and ran tests of my own before I introduced SODIS to the urban communities I work with. I will email the results of my tests, and I am still working on my report covering more detailed information of my “realistic experience” implementing and monitoring SODIS with community members. I will be happy to send it to you, though likely at the end of July.

Respectfully,
Mindy