Why is sunscreen banned in some countries?

Some sunscreen chemicals have been banned or restricted in specific countries, primarily due to environmental concerns, not human safety issues. Hawaii, Palau, and several other jurisdictions have restricted oxybenzone and octinoxate because of evidence that these chemicals damage coral reefs. These bans are place-specific and ecological in motivation.

The reef-safe sunscreen movement has led to reformulation of many products toward mineral UV filters like zinc oxide and titanium dioxide, which do not carry the same environmental concerns. In terms of human health, these same chemical filters are still considered safe for use and are approved in countries that have not implemented reef-protection bans. In India, where this is not a regulatory concern, the focus when choosing a sunscreen remains on efficacy, skin suitability, and ingredient quality. That said, mineral sunscreens are a good all-round choice for people who want to avoid chemical filters for any reason.

Sources:
National Oceanic and Atmospheric Administration (NOAA), Sunscreen chemicals and coral reefs.