Hawai’i University researchers report the unexpected discovery that the most common plastics emit traces of methane and ethylene when exposed to sunlight.

Authors of a study conducted at Hawai’i University recently reported another good reason to redouble global efforts to beat plastic pollution: as plastics decay, they emit traces of methane and ethylene, two powerful greenhouse gases, and the rate of emission increases with time. The emissions occur when plastic materials are exposed to ambient solar radiation, whether in water or in the air, but in air, emission rates are much higher.

The researchers tested polycarbonate, acrylic, polypropylene, polyethylene terephthalate, polystyrene, high-density polyethylene and low-density polyethylene – materials used to make food storage, textiles, construction materials and various plastic goods.

“Low-density polyethylene emits these gases when incubated in air at rates about 2 times and 76 times higher than when incubated in water for methane and…