Marcus Eriksen and colleagues compiled surface-plastic samples from 11,777 stations across all ocean basins collected between 1979 and 2019 and used them to model the global surface load over time.
They estimated that in 2019 about 171 trillion plastic particles (range 82–358 trillion), weighing about 2.3 million tonnes (1.1–4.9 million tonnes), were floating on the ocean surface. Levels were roughly stable until about 2005, then rose rapidly. Without action, the surface load could increase about 2.6 times by 2040.
The paper coined the phrase 'plastic smog' to describe a diffuse, mostly microscopic layer of pollution rather than visible islands of rubbish.
The particle count sounds enormous, but the mass is modest compared with total ocean plastic, because most particles are tiny. Uncertainty ranges are wide.