Spectral energy distribution of common light sources (high pressure sodium, metal halide and LED lights).

Spectroscopy Survey:

The spectral components of light at night are often of interest due to different biological interactions with humans and wildlife. For example, the proliferation of blue-rich white light is of concern since it has been shown in many studies, starting as early as the 1980s that circadian disruption and melatonin suppression peak for blue light in the 450-490nm range. This is precisely the region for which blue-rich white light LEDs spike in their energy output for many of the newly installed fixtures, for street lighting, parking lot lighting (including auto malls), sports lighting, and digital billboards.