Saturday, 21 September 2013

A Thousand Years of Blagging Politicians



Talking of Nick Clegg, the Lib Dems and plastic bags...

The plastic bag was first invented in 1957, as a sandwich bag. By the 1970's it had already replaced the paper bag as our favourite way of carrying shopping.

Radio 4's More or Less quoted Mr Clegg saying, "We all use plastic bags. I do. Everyone does. I think everybody feels that maybe we use too many plastic bags. You might use them for twenty minutes walking back from the shops, but they take a thousand years to degrade."

Do they really? And what's the source of this 'thousand years' claim?

To find out, Tim Harford talked to Ming Tien, Professor of Biochemistry at Pennsylvania State University. 

Prof Tien had no idea where the claim came from, saying that he himself would never make a statement of that kind "as you could never prove it". ("Who's going to do an experiment for a thousand years?", he asked rhetorically.)

The programme then asked Nick Clegg's office for a source for the 'thousand years' figure. The reply came: 
"Scientists agree that it takes a long time for plastic bags to degrade fully. The exact time will depend on the environmental conditions. Typical estimates range from several decades to centuries." 
As More or Less didn't find that a satisfactory answer, they asked again and got this reply:
"There is extensive peer-reviewed literature on the persistence of plastic materials in the environment. Below is a link. Plastic Degradation and its Environmental Implications, with Special Reference to Poly(ethylene terephthalate), Polymers Journal, Volume 5, Issue 1, pp18 available at http {fade out}....[actually, as I've found it for you, should you want to read it, it's also available at www.mdpi.com/2073-4360/5/1/1/pdf
"Gosh, lots and lots and lots of referenciness!", said Tim. 

Still, More or Less didn't give up. They decided to read the paper, and guess what? They found no mention of the figure of a thousand years. 

So they contacted one of its authors, Dr Hayden Webb. He pointed out (in Tim's words):
"First, there's no fixed definition of what it means for plastic to degrade. Second, that different environments will have different effects on plastics. And third, that..well..the study wasn't looking at the plastic that goes into bags. It was looking at the stuff in soft drink bottles, which is a totally different compound. 
"So zero support for Mr Clegg's 'thousand year' plastic bag." 
Fancy that then, a politician spouting nonsense, and a government department trying to bluff its way out when challenged!

I do like More or Less.

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