LED streetlights have the potential to reduce energy consumption by about 50 percent compared to traditional high-pressure sodium lights. According to a U.S. Department of Energy (DOE) survey of governments and utilities, 62 percent of respondents reported using LED sources in their streetlighting. Eight percent said it was the most prominent technology in their inventory; 30 percent said second-most. An estimated 10 percent of U.S. streetlights have been converted to LED technology.
However, LED sources have some concerning characteristics not found with high-pressure sodium. Earlier this year, the American Medical Association (AMA) issued guidance to communities installing LED streetlighting, acknowledging the benefits—notably the reduction in energy consumption and resulting reduction in air pollution—while cautioning against possible health and safety effects of poorly designed “high-intensity,” blue-rich LED streetlighting.
One concern is disability glare resulting from poor luminaire design and light emission saturated in short (“blue”) wavelengths. Another is disruption of human circadian rhythms and animal and insect populations. The organization cited surveys correlating brighter residential streetlighting with reduced sleep and related health issues.
“Despite the energy-efficiency benefits, some LED lights are harmful when used as streetlighting,” said Maya A. Babu, AMA board member. “The new AMA guidance encourages proper attention to optimal design and engineering features when converting to LED lighting that minimize detrimental health and environmental effects.”
The AMA advised communities to select LED lighting that minimizes blue spectral content. Luminaires should be properly designed and shielded to prevent glare and have a correlated color temperature (CCT) of 3,000 Kelvin (K) or lower. Only about 20 percent of the spectral emissions in these warmer-toned, white-light sources is in short wavelengths while sacrificing only about 3 percent efficiency.
Finally, communities should consider implementing dimming during off-peak operating times, presumably based on traffic density patterns.
The AMA press release and guidance received a great deal of media coverage—some of it misleading as to the effects of LED lighting—immediately causing concern in the lighting industry. Notably, the Illuminating Engineering Society (IES), was not consulted in the creation of the guidance.
Nobody disputes that streetlighting should be properly designed and controlled to minimize light level and energy for the task, place light only where it’s needed and avoid glare. The AMA’s evaluation of indium gallium nitride (InGaN) LED sources and recommended CCT, however, created instant controversy.
“The AMA recommendation for 3,000K or lower is not an appropriate solution for all applications, nor is it supported by the current body of research,” a National Electrical Manufacturers Association (NEMA) press release stated. “NEMA will issue additional technical guidance specific to the issues and trade-offs related to the spectral content of lighting solutions.”
The IES also responded.
“Of primary concern to the IES is the potential for this report and its ensuing press to misinform the public with incomplete or inaccurate claims and improper interpretations,” the IES stated. The IES hopes to work with the AMA to ensure lighting recommendations involve discussion with the IES.
Mark S. Rea and Mariana G. Figueiro of the Lighting Research Center at Rensselaer Polytechnic Institute, Troy, N.Y., indicated that InGaN LED sources, whose spectral content is rich in short wavelengths, have greater potential than high-pressure sodium to suppress production of the hormone melatonin, which regulates sleep.
However, they added, the amount and duration of exposure need to be known before it can be definitively stated that InGaN LED sources affect melatonin at night. Looking at CCT alone is insufficient to characterize the light source’s effect; it’s misleading to take CCT, which was developed for one purpose, and apply it to another: light and health. Also, glare is mostly determined by the amount and distribution of light entering the eye, not the light’s spectral content.
The DOE stated there is nothing inherently dangerous about LED streetlighting. In fact, LED sources offer advantages such as precise optical control, tailored spectral content and relative ease of dimming.
“Some media coverage can give the impression that LEDs are the enemy when, in fact, they’re a critical part of the solution, which the AMA acknowledges,” said Jim Brodrick, SSL program manager, DOE. “The key takeaway from the AMA’s guidance is the importance of properly matching lighting products with the given application, no matter what technology is used. More than another technology, LEDs offer the capability to provide, for each application, the right amount of light, with the right spectrum, where you need, when you need it.”
The AMA is well intentioned and raised some legitimate concerns but reached questionable conclusions and a solution that may be oversimplified. It would benefit from involving the lighting industry in future lighting recommendations.
To learn more—including links to the report and industry response—visit www.lightnowblog.com/?p=11697.