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Plastic emits greenhouse gases when degraded by sunlight: research

This July 17, 2018 photo shows wrapped plastic straws at a bubble tea cafe in San Francisco. (AP Photo/Jeff Chiu)

BRUSSELS -- Many plastic materials used in daily life emit greenhouse gases such as methane when they are degraded by sunlight, according to a research team at the University of Hawaii. While international attention is now focused on marine pollution by plastics, the team points out that reducing plastic waste is also important to curb global warming.

According to an article published by the team in the online science journal PLOS ONE, the researchers exposed a variety of plastic materials available in the market to sunlight for long periods of time, and confirmed that polyethylene, which is widely used for wrapping and other purposes, emitted the largest amount of methane and ethylene. Methane is a greenhouse gas and has a high impact on global warming second only to carbon dioxide.

The team also tested waste of low-density polyethylene -- a material used for single-use shopping bags -- collected from the sea, and confirmed that the plastic continues to release greenhouse gases, although the amount goes down as time passes. The test results suggest that microplastics produced from waste may continue to emit gasses accelerating global warming.

Past countermeasures against climate change did not incorporate the impact of greenhouse gases originating in plastic waste in the environment. The researchers said the result of their study indicates the need to completely eliminate the production of single-use plastic products.

According to industry group Plastic Europe, the worldwide production of plastics reached 335 million metric tons in 2016, nearly a 200-fold jump from the output in 1950. Some estimates say the figure will double over the next 20 years. Now moves seeking reduction in one-time plastics are spreading rapidly in Europe and the United States among other regions of the world.

(Japanese original by Kosuke Hatta, Brussels Bureau)

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