*3.1.3 Chemical degradation*

Chemical pollutants are present in the atmosphere (e.g., sulfur dioxide, nitrogen dioxide, ozone, and volatile organic compounds) and the marine environment (e.g., acidity and salinity). The atmospheric pollutants can directly degrade the plastics or catalyze the radical formation by photochemical reactions leading to plastic degradation [73]. Sulfur dioxide and nitrogen dioxide can enhance the formation of ozone in the atmosphere, as a result of UV excitation and photochemical reaction with oxygen [74]. The ozone formed can break the carbon double bonds present in the plastic polymers (chain scission mechanism). In the marine environment, the acidity or alkalinity of the water can catalyze plastic degradation such as polyamides [75].
