It's fairly well sourced. Some examples of harm from plastics, mostly on the environment:
> Degradation (changes in the ecosystem state) and modifications of marine systems are associated with loss of ecosystem services and values.
> in 2019, production and incineration of plastic will contribute greenhouse gases in the equivalent of 850 million tonnes of carbon dioxide (CO2) to the atmosphere
> For example, in Bangkok flood risk increases substantially because of plastic waste clogging the already overburdened sewer system.
> Marine wildlife such as seabirds, whales, fish and turtles mistake plastic waste for prey; most then die of starvation as their stomachs become filled with plastic. They also suffer from lacerations, infections, reduced ability to swim, and internal injuries.
> When analyzing the effect of polyethylene microbeads (origin: cosmetic exfoliants) on the aquatic macrophyte L. minor, no effect on photosynthetic pigments & productivity was found, but root growth and root cell viability decreased.
But this one's about humans:
> By affecting the thyroid hormone axis, BPA exposure can lead to hypothyroidism.
For perspective on the numbers in that map, the first meter of each of those square kilometers of water weighs 1,024,000,000 kg. (At least, using the first number for sea water density I could find.)
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...