[kemaru]

The 85 % figure is from Environ. Sci. Technol. 2011, 45, 21, 9175–9179 https://pubs.acs.org/doi/abs/10.1021/es201811s

The 200-500 kiloton/year is from https://pubs.acs.org/doi/10.1021/acs.est.3c05955

For a deeper dive you can peruse the works that cite these articles, there's lots of research into microplastic population dynamics. Unfortunately most reach similar conclusions.

[pseudalopex]

> The 85 % figure is from Environ. Sci. Technol. 2011, 45, 21, 9175–9179 https://pubs.acs.org/doi/abs/10.1021/es201811s

The abstract said a large proportion of microplastic fibers found in the marine environment may be derived from sewage as a consequence of washing of clothes. Not is derived. And not microfiber solely.