Replacing older streetlights with more efficient solid-state lighting—more commonly referred to as light-emitting diodes or LEDs—is a greenhouse gas reduction measure included in nearly every climate action plan. A recent report by the American Medical Association (AMA), however, casts new light (pun intended) on a potentially serious drawback with LED street lighting.
New LED streetlights can significantly reduce energy use and resulting greenhouse gas emissions (GHGs) compared to standard high-pressure sodium (HPS) lights they replace. Streetlights with HPS bulbs consumes about 560 kWh annually assuming an average 4,100 hours of operation (PG&E/USDOE 2008). This is the same amount of electricity consumed annually by a standard ENERGY STAR refrigerator so imagine a fridge sitting in place of a street lamp for a year – that’s a lot of energy and a lot of indirect GHGs! However, LED streetlights consume between 50 and 70 percent less electricity (ibid.). When a local jurisdiction replaces hundreds or even thousands of its older HPS fixtures, these energy savings and reduced GHGs can be significant. Given their long lifespan, LEDs also significantly reduce replacement costs and are usually one of the most cost-effective measures recommended in local climate action plans.
The potential downside to LED lighting is beginning to be taken more seriously, though, as illustrated by the AMA report. Recent concerns center around the very intense levels of blue light—greater than 4,000 kelvin (K)—emanating from the LEDs and the potential health effects on people. According to the AMA report, very intense blue-rich LEDs can increase nighttime glare and reduce visibility for drivers. This could have possible adverse effect on safety for all road users. In addition, the wavelength of blue-rich light in white residential LED fixtures is also known to suppress melatonin, which the AMA notes is associated with “reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning and obesity.” It is estimated that blue-rich LEDs in residential areas have an adverse impact on circadian sleep rhythms at levels five times that of HPS streetlights. This concern is not limited to public lighting. Even companies like Apple have taken steps to minimize the amount of blue light on their devices’ LED screens long before lawsuits or government regulations force any change.
It is important to note that reducing the correlated color intensity of LEDs to levels similar to HPS (~2,200 K) could significantly distort color perception and affect visibility. The AMA’s guidance recommends minimizing blue-rich outdoor lighting by using LEDs that do not exceed 3,000 K, which given the trade-offs of lower intensity levels, should probably be an ideal target for local jurisdictions.
Bottom line: Local jurisdictions should still include emission reduction measures that recommend replacing outdoor lighting with LEDs as soon as feasible, and they should explicitly acknowledge the AMA’s recommended limit as a goal when selecting replacement lights.