The D.C. Street Light Task Force was pleased to see The Current’s front-page Aug. 2 article “Push for LED street lighting sees resistance.” However, we’d like to clarify three points.
First, our task force has not opposed the installation of LED streetlights. But we do object to the high blue content of those already installed, at 4000 Kelvin and 5000 Kelvin color temperature. Science has shown us that exposure to blue-spectrum wavelength during the evening and night alters our physiology: It suppresses the sleep hormone melatonin, disrupts circadian rhythm, decreases sleep quality and impairs daytime functioning. Also, some evidence supports an increased risk of cancer, diabetes, cardiovascular disease and obesity.
Second, the fact is:
■ The higher the Kelvins of the LED, the more blue content, and therefore the colder the light appears to the eye.
■ The lower the Kelvins of the LED, the lower the blue content, and therefore the warmer the light appears to the eye.
Thus this statement is incorrect: “Members of D.C. Street Light Task Force … and other observers have said that lights any warmer than 2700 Kelvin would pose health risks to nearby neighbors.”
For comparison, the LEDs already installed in the District at 4000K and 5000K appear white, or cold, because they contain higher amounts of blue. A traditional incandescent light bulb, which appears warmer, is rated at about 2700K. Our conventional high-pressure sodium streetlights, which appear orange or amber, are about 1900K to 2100K (little to no blue content).
Because of the health risks of blue spectrum light exposure, and because its glare can hamper our vision, the American Medical Association has urged us to minimize our environmental lighting to the lowest emission of blue light possible. The D.C. Street Light Task Force is urging the city and the D.C. Department of Transportation to replace the 4000K and 5000K LEDs with the warmer 2700K LEDs, and to use a maximum color temperature of 2700K for the future installation of 70,000 LED streetlights.
A third clarification: Throughout the United States, cities are already installing 2700K streetlights. As of this week, Phoenix has begun installing 100,000 new LED streetlights at 2700K at the request of its residents. There is no need to wait on the warmer 2700K — it is available already.
By using a warmer color (of 2700K or lower) in full cut-off design (which directs the light downward) and in the brightness levels needed for good visibility (but no more than is needed), we will all benefit from protection of our health and safety, reduced energy costs, a better view of the night sky, and a more inviting historic ambiance for the District.
Bonnie Garrity, member, D.C. Street Light Task Force