Sunlight can transform plastic bags into water-soluble compounds

A new study from the American Chemical Society has investigated the polymers and additives in plastic bags and how these help plastic bags break down in sunlight. The researchers discovered that with the right additives, plastic bags can be made to more easily break down into water soluble chemicals.

When plastic bags are exposed to ultraviolet (UV) light, they release thousands of soluble chemicals and gases. The problem is that plastic bags are not pure plastic but also have additives for color and other attributes. 

“The plastics we use and leak into the environment are widely known to be complex mixtures of polymers and additives, which may influence photochemical behavior. Organic and inorganic additives are common and diverse,” wrote the study authors.

“Little is known about the impacts of plastic formulation on its fate and effects, as studies on marine plastics have generally used pure polymers.” 

“However, several recent studies have shown that additive-containing plastics behave differently than pure polymers: photochemical mineralization to CO2, photo-oxidation pathways, lability of photoproducts to microbes,and leachate toxicity differed between pure and additive-containing polymers.”

For their investigation, the researchers compared plastic bags from big box stores with different additives to a pure polymer film as a control. First, different bags and the polymer film were tested for additives. No additives were found in the film but some of the bags contained titanium dioxide and calcium carbonate, while some contained only calcium carbonate. 

The various bags with different additives were placed along with the polymer film in containers of water. The containers were placed either in the dark or under UV light to simulate the sun. 

The experiment revealed that while only a few chemicals were released in the dark, 5,000 to 15,000 dissolved chemicals were released under simulated sunlight.

When exposed to the UV light, the plastic bags released 1.1 to 50 times the dissolved chemicals compared to bags exposed to dark. 

Of roughly 9,000 chemicals released from the polymer, only about ¼ overlapped with the chemicals released from the bags. These results indicate that plastic bags could degrade into water soluble chemicals in sunshine if the right additives are used in bag manufacturing. 

The study is published in the journal Environmental Science & Technology.

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By Zach Fitzner, Earth.com Staff Writer