In the Washington Post story Some cities are taking another look at LED lighting after AMA warning I noticed the phrase "unseen blue light" in the first full paragraph:
The American Medical Association issued a warning in June that high-intensity LED streetlights — such as those in Seattle, Los Angeles, New York, Houston and elsewhere — emit unseen blue light (my emphasis) that can disturb sleep rhythms and possibly increase the risk of serious health conditions, including cancer and cardiovascular disease. The AMA also cautioned that those light-emitting-diode lights can impair nighttime driving vision.
I searched the linked American Medical Association related news item AMA Adopts Community Guidance to Reduce the Harmful Human and Environmental Effects of High Intensity Street Lighting for the word "unseen" and couldn't find it.
Most (but not all) white light LED systems use powerful blue LEDs to illuminate a broadband phosphor. When the light from both are combined, a double-humped spectrum is produced - a narrow blue peak and a broad bump including enough green and red to stake a claim as being white. In the lighting industry, it's common to express the 'color' of the light using an effective color temperature.
Is the term "unseen blue light" just a poor choice of words to express the idea that we don't realize that yellowish light has less blue content than white light does, or is there something more subtle going on here? Does the particular choice of the wavelength of the blue light used have implications? In other words, if two different wavelengths were used for the blue light, and balanced to produce the same effective color temperature and brightness, would they still have different implications as far as the AMA's concern about sleep is concerned?
While most of the AMA warning talks about "blue-rich" LED lighting, especially when it is intense, they do use the term "wavelength" once:
In addition to its impact on drivers, blue-rich LED streetlights operate at a wavelength that most adversely suppresses melatonin during night. (my emphasis)