Of course, you can’t entirely resign from using sunscreen. Choose the one which is not harmful to you and for the environment. There is a range of toxic substances which are harmful; however oxybenzone is considered the most dangerous (and the primary coral reefs destructor). Mineral-based sunscreens are a better alternative. The Environmental Working Group (EWG) publishes sunscreen guide every year, below is a link to 2019 version.