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.
Lots of positive news these past few weeks on keeping global warming to under 2 degrees Celsius. Both the US and China have ratified the Paris COP21 climate agreement that will help reduce greenhouse gas emissions by the year 2050. The US agreed to cut emissions between 26 to 28 percent below 2005 levels by 2025.
Not to be outdone, Governor Brown signed SB32 into law last week, which sets the state’s emission reduction target at 40% below 1990 levels by 2030. The law extends Assembly Bill 32 that had a goal of lowering emissions to 1990 levels by the year 2020. Besides being the most ambitious climate target in the U.S., it sends a strong signal to the markets about the likely continuation of California’s Cap & Trade program.
This law also likely has implications for local jurisdictions. Lead agencies under the California Environmental Quality Act (CEQA) will continue to have to demonstrate that their projects will not impede California’s greenhouse gas emission reduction goal. Many cities and counties have sought to demonstrate this through a climate action plan or relevant section of their general plan, but almost all of these plans have focused on the year 2020 and its goal. Of the limited number of local jurisdictions that have set goals for target years beyond 2020, few of their plans have proposed specific measures with concrete emission reductions. Local jurisdictions will likely need to revise their plans and add new emission reduction measures to be consistent with the state’s new standards. The good news is that there are many new strategies for reducing emissions that could be added to each plan as well as strengthening existing ones.