There are two types of UV filters employed in sunscreens. Inorganic UV filters, like titanium dioxide and zinc oxide, are broadly considered safe. Organic sunscreen filters such as oxybenzone and octinoxate have become controversial due to environmental concerns.
In 2018, the Environmental Working Group (EWG) reported that two‐thirds of the commercially available sunscreens in the US contained chemicals, namely predominantly organic filters, that were deemed to be harmful to the environment. The deleterious environmental effects of these filters relate to their impacts on coral reefs, as well as their prevalence in the water supplies and in aquatic wildlife. Furthermore, organic filters have been reported to have negative hormonal effects in animal models. There effects in humans continue to be examined.
For those concerned about the environmental impact of organic UV filters, zinc oxide and titanium oxide containing sunscreens could be used. Note: Zinc oxide and titanium oxide are most often used in combination to provide broad-spectrum UV protection.
Answered by Alex Kelleher, MD