LED Highway Lighting: Quality Issues (new AMA warning)

“While there are many positives for LEDs, the AMA looked at the light output quality and the potential health impact. The AMA committee that examined the issue and issued the health warning explained in great detail how LED lights operate and how they may impact humans and nocturnal wildlife by increasing glare and disrupting the circadian rhythm of humans.”

US cities that have installed or are considering installing new light emitting diode (LED) highway lights are now dealing with a recent warning from the American Medical Association (AMA) about the health issues from this lighting for drivers and residents. Currently, cities have converted about 10% of their highway lights to LED lights, primarily switching from high pressure sodium (HPS) lights. They were considering accelerating the pace of conversion–until the health warning.

Advantages LED Lighting

The advantages of converting to LED lights are numerous. First, they consume about 50% less energy than HPS lights. Second, LED lights require no warm up time and have a rapid “turn on and off” at full intensity capability. They also are able to fully turn on immediately after power is restored after having been lost.

LED lights have much longer lifespans – 15–20 years, or 50,000 hours, some 2–74 times the lifespan of HPS lights – reducing the maintenance cost of having to replace bulbs more frequently. Also, LED lights do not contain mercury or lead and thus do not release any toxic substances if damaged, unlike mercury or HPS lights.

Many of these positives for LEDs are why cities have been switching to them, and also why LEDs are taking market share from compact fluorescent light (CFL) bulbs, which do contain mercury and produce harsh light qualities, in household and commercial applications.

AMA Concern

While there are many positives for LEDs, the AMA looked at the light output quality and the potential health impact. The AMA committee that examined the issue and issued the health warning explained in great detail how LED lights operate and how they may impact humans and nocturnal wildlife by increasing glare and disrupting the circadian rhythm of humans.

According to the AMA report:

LED lighting is inherently narrow bandwidth, with “white” being obtained by adding phosphor coating 18 layers to a high energy (such as blue) LED. These phosphor layers can wear with time leading to a 19 higher spectral response than was designed or intended.

The AMA said that excess blue and green emissions from LEDs can increase light pollution. The light pollution comes because the LED wavelengths scatter more within the eye, creating detrimental health and glare effects.

How these detrimental effects may be mitigated comes from understanding the light range of LED lights and their characterization by their correlated color (CCT) temperature index. The lights are measured by their heat, or kelvin (K), rating, although it is really not heat as much as a measure of light brightness. Daylight is equivalent to 6500K, while HPS lights have CCT ratings of 2100K.

Most of the highway LED lights are 4000K, in which 29% of its light spectrum is emitted as blue light, which the human eye perceives as a harsh white color.  This light increases glare for drivers and can create long-term health issues for residents.

Interestingly, the energy efficiency of 3000K lights is only 3% less than 4000K, but the light is perceived as more pleasing to humans and it produces less of an impact on wildlife. The AMA cited many cities where the residents have complained about the 4000K LED lights and are demanding that they be replaced.

Cities Adjust

Many cities are changing them out in response. The health problems citied relate to the disruption of the human circadian rhythm that can be detrimental to sleep quality. This problem can also come from television and computer screen light in the evening.  The AMA also stated:

Although data are still emerging, some evidence supports a long-term increase in the risk for cancer, diabetes, cardiovascular disease and obesity from chronic sleep disruption or shiftwork and associated with exposure to brighter light sources in the evening or night.

The AMA committee recommended that LED lights be adopted for their energy efficiency and related reduction in the use of fossil fuels. It also recommended that the lowest blue-output LED bulbs be utilized. It encouraged the use of 3000K or lower light bulbs for outdoor installations such as highways, and that they be properly shielded to minimize glare and harmful human and environmental effects.

If you haven’t shopped for light bulbs lately, expect to see much more emphasis on the quality of the light emitted by the more energy-efficient light bulbs – both CFLs and LEDs.  How many cities will be replacing the early LEDs they installed remains to be seen, but we expect most will over time.

More LED lights will lead to reduced electricity consumption. But there are health effects to now consider, another example of tradeoffs.