Just like radium, tritium is also radioactive, albeit with a much lower level of radiation, and also a shorter half life.
With a half life of 12.5 years, tritium paint on watch dials and hands will lose their ability to glow over a few decades. Moreover, as tritium ages, its color changes, creating a yellowish patina on luminous markers of vintage Rolex watches.
While they are substantially safer than radium, tritium watches are still radioactive, that’s why watchmakers marked the dials with the level of radioactivity emitted by the watch. Most Rolex watches with tritium markers have the symbols “T Swiss T” or “SWISS T<25” below 6 o’clock to indicate that it uses the radioactive material.