How streetlights with LEDs can impact health?
LED street lights are rapidly being deployed across the globe. They provide the advantage of the long lifetimes (mean time to failure: >100,000 hours), reducing the number of field replacements and the costs associated with sending out a repair crew. In the year 2018, the NYC’s Department of Transportation told the Wall Street Journal that switching over to LED bulbs could save the city $6 million a year on energy and $8 million on maintenance. So you can see why many cities, including Seattle, New York and Los Angeles, have been switching over to the new bulbs in recent years. LEDs now make up about 13 percent of public lights in the United States, according to U.S. Energy Department figures. These LEDs have the advantage of being more energy-efficient, producing more Lumens per watt (LPW) than alternative light sources. As a result, the electric utility bills for municipalities are reduced, saving them money over the lifetime of the streetlight. Less energy consumption means that LED lighting is green for the environment. These lights can also be easily modulated (turned ON or OFF), or precisely dimmed under the control of the municipality.
The Street light using White LEDs consists of packaged combinations of red, green and blue LEDs, and more often it not employ the use of blue LEDs because it is usually made of Indium Gallium Nitride (InGaN) and have a phosphorous yttrium-aluminium-garnet (YAG) (Y3Al5O12) mounted on their emitter or emitter’s optic. This phosphor coating creates a new band of coloured light by way of fluorescence and it is known as phosphor light conversion. The original blue LED colour mixes with the colours produced through fluorescence, and white light is produced. White light can be realized and used for white LED streetlights from the base colour of blue light.
But does the blue light used in streetlights with LEDs have any harmful effects on humans?
Well, the American Medical Association (AMA) believes so. Although it does not think that blue LEDs make people feel sad and dark, it does agree that societies should follow strict guidelines to minimize the adverse effects of high-intensity street lighting on humans and the environment.
First, LED streetlights have a high content of blue light and create more night-time glare for humans than traditional lighting sources. The `Glare may lead to safety issues, as the human eye has a hard time seeing clearly when presented with such light. The scattering of blue light can also potentially lead to unnecessary eye strain in humans.
Second, the AMA states that “blue-rich LED streetlights work at a wavelength most adverse to night time melatonin suppression. White LED lamps are estimated to have a five-fold greater effect on circadian sleep patterns than traditional street lamps. “This may have a detrimental impact on human sleep. In other words, this illumination may have a detrimental effect on the circadian clock of the human body, and thus on sleep patterns. It is not just human beings that can suffer from these effects. Owing to the effects of such non-natural illumination, animals may also get their natural systems into confusion.
Cree RSW LED street luminaire, the first of a new generation of streetlights that deliver LED energy savings and reliability in a warm colour temperature that is preferred in many residential applications.
One way to address the issue of too much blue light is to target warmer correlated colour temperature (CCT) for street lights. This is because higher kelvin colour temperatures generally mean higher inherent levels of blue light content, exactly the colour of light that should be minimized at night. Historically, shifting LEDs towards warmer CCTs has resulted in lower efficacy (lumens/watt or LPW) systems. This shift toward warmer CCTs is generally regarded as a negative for street light manufacturers as they wish to be able to claim the highest LPW possible.
The reports about the negative effects of these streetlights on biological agents have not gone unnoticed by the LED manufacturers. Cree, a market leading innovator of lighting-class LEDs, LED lighting and semiconductor solutions, has responded by developing Wave Max technology, an innovative optical waveguide platform, in which its unique design works reduce glare. The Cree RSW series (Figure 1), which utilizes this technology, is the first viable LED streetlight at the warm CCT (3000K, ±175K) and delivers up to 115LPW, enhanced visual comfort with reduced glare, and high colour contrast, leading to improved overall illumination using less energy.
The AMA additionally recommends that manufacturers seek innovative ways to minimize lighting by incorporating intelligent dimming during off-peak time periods. The increased employment of various sensing technologies will likely continue to stimulate developments with respect to this. Other considerations that the AMA suggests include ensuring proper light shielding of all fixtures as well as appropriate directionality in order to minimise light spill over.
The changes in circadian rhythms due to LED’s blue hues may also affect people’s hormone levels. A 2018 study shows that people who live in areas with LED streetlights have an increased risk of developing prostate or breast cancer — both of which are hormone related cancers. The study followed more than 4,000 people in Spain and established a link between high levels of exposure to LEDs and double the risk of developing prostate cancer and 1.5 times higher risk for breast cancer.
Prevent yourself from feeling blue. Understand the impact of light pollution, and take the necessary steps to raise your awareness of the implications to our biological health and the environment. It could be just the panacea we all need to better enrich our lives on this planet.