The accumulation
of plastic litter in natural environments has
become a serious global issue. Since 1972, mega to micro/nanosized
drifting plastics have been determined to be highly a significant
pollutant in all oceans worldwide. To clarifying numerous problems
such as entanglement or improper ingestion due to drifting and debris
plastic, the amounts of currently drifting plastics should be determined.
For this purpose, chemicals derived from polystyrene (PS) degradation
were analyzed for 4000 sand and water samples taken from around the
world including open sea sites (surface to 5000 m depth) during the
period from 2000 to 2018. All styrene oligomers (SOs) of styrene (styrene
monomer, SM), 2,4-diphenyl-1-butene (styrene dimer, SD2), and 2,4,6-triphenyl-1-hexene (styrene trimer, ST) were found to
contain products from PS degradation. On the basis of survey SO values,
1.4 × 109 metric tons (MT) of SO were found to have
been released into world oceans between 1950 and 2018. This SO subsequently
underwent conversion to 2.7 × 106 MT of PS. Twenty
percent underwent degradation, while 1.2 × 107 MT
of PS apparently continued to drift about in ocean water. Drifting
PS has been clearly shown not only to be crushed into micro/nanoplastic
particles but also to degrade into basic structural units of SOs constituting
PS.