Center for International Environmental Law (CIEL) uses international law to fight plastics, toxics and climate harm; its lawyers are in the room at every plastics treaty session and it publishes the analyses many non-governmental organisations (NGOs) rely on. Donations fund legal staff and treaty work.
It is a 501(c)(3) (Employer Identification Number 52-1633220) rated 4 stars by Charity Navigator (charitynavigator.org/ein/521633220) and publishes annual and financial reports at ciel.org/about-us/financial-annual-reports/
How to start: ciel.org/donate/