photodegrade
v.—Gloss: (of plastics and polymers) to breakdown when exposed to sunlight. Note: A more technical definition of photodegradation is here. «Plastic bags don’t biodegrade. They only break down into tiny toxic little bits that pollute the soil and our waterways. This process is called photodegrade and it takes around 1,000 years for these bags to break down in our landfills.» —“Bush’s Niece Endorses Plastic Bag Recycling” by Sewell Chan New York Times Nov. 5, 2007. (source: Double-Tongued Dictionary)
Further reading
She sells seashells by the seashore. Who is the she in this tongue twister? Some claim it’s the young Mary Anning, who went on to become a famous 19th-century British paleontologist. Dubious perhaps, but the story of her rise from seaside...
Secret signals on the job: Waitresses at some 19th-century restaurants ensured speedy drink service by communicating with a non-verbal code. One server took orders, then placed each customer’s cup to indicate exactly what the customer wanted...
What does photodegrade, mean?
As it hints in the quotation, photodegradation is the breakdown of plastics when exposed to sunlight, although the original source doesn’t seem to explain how this can happen in a landfill, which, presumably, does not expose a great deal of its content to the sun. A more technical definition of photodegradation is here.
Bear in mind that Ms. Bush, quoted there, is probably not an expert on the degradation of trash in landfills. A Google search turns up similar language at this site: http://www.reusablebags.com/facts.php?id=2 – “In a landfill, plastic bags take up to 1,000 years to degrade. As litter, they breakdown into tiny bits, contaminating our soil and water.”
Here’s a bit of explanation: http://www.slate.com/id/2169287/nav/fix/