a cheap plastic bag in the sun long enough and it'll eventually crumble
into a powdery mess, its petrochemical fragments destined to be blown far and wide by the elements.
led by researchers from Woods Hole Oceanographic Institution finds
sunlight isn't just capable of breaking plastics down; it can convert
their base polymers and additives into a soup of new chemicals.
process isn't exactly slow either, with the variety of plastic bags
experimented upon leaching a significant mix of soluble organic carbon
compounds after being exposed to sunlight for less than 100 hours.
In spite of so many communities around the globe taking the environmental cost of convenience in a shopping bag seriously, it's still all too easy to find a retailer that's keen to hand over a single-use sack of polyethylene with your purchase.
Once used, there's an all-too-likely chance the bag will find its way into a landfill rather than a recycling plant.
Or, worse, exposed somewhere out in the landscape, where eventually it flutters its way into waterways or the ocean to join the astonishing 640,000 tonnes of plastic dumped by commercial fishing each year.
But many of the details on its distribution and fragmentation have remained unclear.
over the years have hinted at the possibility of more sinister
transformations, with research finding that sunlight can chemically
transform plastics and their additives into new polymers, as well as smaller chemical units that dissolve more easily and are made airborne.
discoveries are one thing. What wasn't known until now is the sheer
diversity of chemical products a plastic item could produce as it sits
baking in the sun.
collected together a sample of consumer polyethylene bags from
commercial enterprises such as Target and Walmart. Researchers also
included a used bag from a CVS in a municipality with a plastic bag ban.
An additive-free, low-density film bag made by Goodfellow served as a
were characterized in terms of organic and metal content and spectral
qualities. Researchers placed swatches from the bags into sterilized
beakers filled with an ionized solution to simulate immersion in
the beakers went into a dark draw for six days. The rest were left in a
temperature-controlled chamber for five days, bathed in a consistent
stream of radiation that mimicked the effects of sunlight.
left in the dark were found to have released a tiny amount of dissolved
organic compounds into the salty solution. Those left in the light,
however, were swimming in new chemicals.
CVS bag presented the greatest difference in concentrations between the
darkened container and the one exposed to sunlight, a measure that only
went up the longer it was left in the light.
apart this plastic soup into a list of its constituent molecules
revealed tens of thousands of dissolved organic compounds, all produced
on a timescale equivalent to just weeks of floating about in the ocean
under the glare of the sun.
entire process is at least ten times more complex than chemists
previously understood, leaving plenty of room for toxic materials we
never even considered to be an issue.
astonishing to think that sunlight can break down plastic, which is
essentially one compound that typically has some additives mixed in,
into tens of thousands of compounds that dissolve in water," says chemist Collin Ward.
to be thinking not only about the fate and impacts of the initial
plastics that get leaked into the environment but also about the
transformation of those materials."
what those compounds do in the environment, or in the tissues of the
organisms living in it, is now the big question. In low concentrations,
there might be relatively little to worry about.
But as plastic waste piles up in
an ever-increasing environmental catastrophe, those concentrations
could climb to levels we wished we'd paid attention to sooner.
goal is to understand the fate and impacts of these materials, we need
to study plastics that are representative of those that are actually
leaked into the environment, as well as study the weathering processes
acting on them," says Ward.
This research was published in Environmental Science & Technology.