Hi Jack,
Some time ago I used spectroscopy to illustrate the dangers posed by light pollution from white LEDs for astrophotography. My attachment shows how sunlight is filtered by a light pollution filter like the Baader UHC-S filter, to show what wavelengths are let through by the filter. The narrow emission from sodium is of course blocked by the filter whilst the broader emission from a white LED will leak through. However as Paul says background subtraction in spectroscopy would effectively remove light pollution at the risk presumably of introducing more noise. None of the spectra are response corrected
Cheers
Hugh