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A continuing succession of news stories about the possible health effects from “blue” wavelength content in street lighting has kept the topic in the public’s mind. But complexities of the underlying science in both technical and medical terms often lead to misunderstandings and misperceptions of the facts, resulting in erroneous conclusions.

DOE has assembled a variety of valuable, science-based information on the human and environmental effects of LED street lighting.

Where does the actual health risk of blue light fall in the big picture? We don’t know yet, but we do know that blue light is common to all broad spectrum or white light sources (see the linked Table, below). And an informal investigation of interior exposures conducted by Pacific Northwest National Laboratory showed much higher levels presented by interior sources than by exterior sources. Regardless, even though the science remains unsettled, there are commonsense actions that sites can take today to minimize environmental exposure to blue wavelengths while being justified for other reasons (e.g., cost savings).  These include, in order of effectiveness, selecting an appropriate distribution to eliminate uplight and light trespass, delivering just the amount of light needed when it’s needed (e.g., assisted by controls and dimming), and by selecting a low short wavelength content source (note that relying on color temperature to achieve this is not a very reliable approach, however). See Potential Impacts of LED Street Lighting on Sky Glow for more information.