Just a clarification: “white” LEDs do use fluorescent phosphors to generate the wide range of colors that we perceive as “white.” The starting frequency of the “white” LEDs, however, is not red nor green, nor ultraviolet, but blue.
In general, a phosphorescent material cannot generate a color of a shorter wavelength than the impinging wavelength, so red or green LEDs cannot stimulate phosphors to generate blue light, but blue LEDs can stimulate phosphors to generate all visible frequencies of light.
Blue, or other visible light, is not dangerous at any normal intensity used for household illumination.
How this relates to “fluorescent” lights: “fluorescent” lights generate ultraviolet (UV) light (shorter wavelength than any visible light) instead of the blue light generated by LEDs. The UV light then impinges on phosphors to make visible light. This article points out that some of the UV light (dangerous at “normal” intensities) does leak out of the “fluorescent” bulbs. This is a danger not shared by household LEDs which don’t generate UV light.