SEATTLE — The U.S. has approved its first new sunscreen filter in more than two decades. But for American fans of Korean skincare, the bigger question is: Is one new filter enough? The Food and Drug Administration in June approved bemotrizinol, a broad-spectrum ultraviolet filter that has been used for years in sunscreens sold in South Korea, Europe and other markets. It is the first new active ingredient added to the U.S. over-the-counter sunscreen monograph since the late 1990s. Also known as BEMT or Tinosorb S, the ingredient protects against both UVA and UVB rays and is highly photostable, meaning it maintains its effectiveness when exposed to sunlight. Its approval marks a significant change for a U.S. sunscreen industry that has long had fewer UV filter options than manufacturers overseas. The FDA itself acknowledged last year that it had “historically moved too slowly” on sunscreen innovation, leaving Americans with fewer options than consumers abroad. That gap is also one reason Korean sunscreens have drawn such a devoted following among American beauty consumers. Fans have