Friday, 28 December 2012

Plastic not so Fantastic: Water Bottle, Plasticizers and Surface Tension

I was in the lab yesterday and wanted to compare the surface tension of water from our MilliQ system and water that is in these plastic bottles.  I used the Kibron EZ-Pi Plus in static surface tension mode.  The surface tension of water is 72.8 mN/m.  This was the value from the MilliQ water.  However, when I did the same test with the plastic from the water bottle it lowered the surface tension to 71.0 mN/m.  These water bottles and other materials like a silicone septum may contain plasticizers, silicone or other surface active materials.  This leaching of these chemicals may cause false positives or add confusing results to when measuring surface active substances from drugs to lipid molecules.  Particular precautions should be made in order to limit the leaching from these bottles (eg. working with glass or ceramic, degassing water, working with the water touching the plastic within a small time period). 

Even if you do not work in a lab or care about surface active substances this result can still affect you.   You likely at some point have had a drink from a plastic water bottle at some point in your life.  Sure it has a nice little sticker printed on the front of it.  It says the it pours from some glacier you have never heard about.  It could also come from a local well that is said to be a fountain of youth.  It has a sealed cap.  It must be good stuff.  Anything that is branded has a name and is in my local market must be good.  Right? 

Wrong.  Even if the water is said to be pure, a plastic container may leach chemicals such as phthalates or bisphenol A (an industrial chemical linked to increased risk of birth defects, miscarriage, baldness and prostate cancer) into the bottled water. Scratches in the plastic, harsh detergents, and boiling liquids exacerbate the leaching. 

However,  tap water is probably better which in the end you are just buying in bottled form.  In the end some say that up to 40% of bottled water is tap water.  In addition some brands contain chemical contaminants at levels above strict state limits. If consumed over a long period of time, some of these contaminants could cause serious health problems.

What is the best water bottle to drink from?  For personal health, the ideal water container is glass. However, glass bottles are rare, heavy, and breakable. Many believe polycarbonate (PC) plastic is a good option due to its durability and lack of odor, but it can still leach bisphenol A into its contents and with a recycling code of number 7, is rarely recyclable. A better health option may be one of the new bio-based alternative plastics (such as those made with corn starch)—not really a plastic, but with similar properties, yet reusable and readily biodegradable.

If you can’t avoid drinking water from plastic bottles, make certain it has not been exposed to high temperatures, such as being left inside a locked up car or near a glass window. 0.001 ug/L with LC/MS.  However some of the degraded BPA may be present as well which might be just as harmful.  To find the total organic carbon.  Measuring surface tension will allow you to see if there are any of these leached substances quickly and easily.