Will My Plastic Bag Still Be Here in 2507?
News reports have cited a statistic that the ubiquitous receptacles take 500 years to break down in landfills. How do we know?
Actually, we don't. Plastic bags have only been around for about 50 years, so there's no firsthand evidence of their decomposition rate.
So, where does the 500-year statistic come from? Although standard polyethylene bags don't biodegrade, they do photodegrade. When exposed to ultraviolet radiation from sunlight, polyethylene's polymer chains become brittle and start to crack. This suggests that plastic bags will eventually fragment into microscopic granules. As of yet, however, scientists aren't sure how many centuries it takes for the sun to work its magic. That's why certain news sources cite a 500-year estimate while others prefer a more conservative 1,000-year lifespan. According to some plastics experts, all these figures are just another way of saying "a really, really long time."