LED Street Lights are Harmful to Human Health?

LED streetlights are great for the environment. They consume much less energy than standard high-intensity discharge (HID) lights, last three times longer, and they reduce greenhouse gas emissions and maintenance costs. In general, LED lights also contribute less to light trespass because they emit direct illumination. Because of all their great qualities, many cities have started to convert from HID to LED streetlights.

For example, the City of Davis is located in Northern California and has a population of approximately 66,000 is home to the University of California at Davis. In January of 2014, the Davis city council approved plans to upgrade 2,600 90-watt HPS cobra-style streetlights to LED fixtures. The city was motivated by plans to save approximately $150,000 annually in energy and maintenance costs, reduced CO2, and improved safety.

Sometimes we always hear that street lights are not good for people’s health, is it true? If it is true, then why do so many people prefer using LED street lights?

Surveys about the harmfulness of LED street lights：

The American Medical Association (AMA) provides more information on how exactly the lights can harm travelers. “Despite the energy efficiency benefits, some LED lights are harmful when used as street lighting,” its website reads. It explains that while the lights appear white to the human eye, they are actually blue, which can make nighttime glares more harsh for eyes and can lead to discomfort. Because the lights are so bright, they can also suppress melatonin at night, making it harder to fall asleep or lowering sleep quality. The medical association recommended that all LED street lights be used with proper coverings, and be dimmed during off-peak hours.

Public Health England warned that the LED street lights can disrupt sleep, resulting in a “permanent jet lag.” The blue colour of the lights can also result in damage to the retina. It added that the “uncomfortable” effects of the lights are especially pronounced in the elderly, or those with preexisting eye conditions.

This isn’t the first time concerns have been raised over LED street lights. A similar warning was issued by the Canadian Association of Optometrists (CAO) in May 2017. “Many streets and roadways in Canada are changing their approach to lighting,” the release read. It added that while policymakers shouldn’t ignore the lights’ benefits, they should give more thought to adverse health effects.

“Canadian Association of Optometrists recommends they should also attempt to choose lighting and lighting distribution that reduces light pollution and glare.”

Why are LED street lights not good for people’s health?

Two main problems with LED street lighting:

What some cities have failed to consider, however, is that while LED streetlights are capable of emitting different colors of light, not every color should be used in public outdoor spaces. Bright blue-rich white light can cause some issues for residents, local wildlife, and night sky visibility. When it comes to streetlights, the warmer the color/correlated color temperature (CCT) the better.

CCT will tell you what hue and tone of white to expect from a specific streetlight. It is measured in Kelvin (K), which is similar to degrees in Celsius. Different temperatures on the Kelvin scale represent different colors. For example, light at 2000K-3500K looks more orange/yellow and is called ultra warm or warm white, and as temperature increases in Kelvin, color changes to more of a “paper white” known as natural or neutral white (between 3500K and 5100K) and finally into a bluish-white known as cool white (5100K-20000K).

An incandescent bulb has a color temperature of 2400K, which means it contains far less blue and far more yellow and red wavelengths. Before electric light, we burned wood and candles at night; this artificial light has a CT of about 1800K, quite yellow/red and almost no blue. What we have now is very different. The new “white” LED street lighting which is rapidly being retrofitted in cities has two problems, according to the AMA.

The first is discomfort and glare. Because LED light is so concentrated and has high blue content, it can cause severe glare, resulting in pupillary constriction in the eyes. Blue light scatters more in the human eye than the longer wavelengths of yellow and red, and sufficient levels can damage the retina. This can cause problems seeing clearly for safe driving or walking at night.

You can sense this easily if you look directly into one of the control lights on your new washing machine or other appliance: it is very difficult to do because it hurts. Street lighting can have this same effect, especially if its blue content is high and there is not appropriate shielding.

The other issue addressed by the AMA statement is the impact on human circadian rhythmicity.

Color temperature reliably predicts spectral content of light — that is, how much of each wavelength is present. It’s designed specifically for light that comes off the tungsten filament of an incandescent bulb.

Another system for measuring light color for these sources is called correlated color temperature (CCT). It adjusts the spectral content of the light source to the color sensitivity of human vision.

Suggestions:

A white LED at CCT 4000K or 5000K contains a high level of short-wavelength blue light; this has been the choice for a number of cities that have recently retrofitted their street lighting such as Seattle and New York.

The AMA’s statement recommends that outdoor lighting at night, particularly street lighting, should have a color temperature of no greater than 3000 Kelvin (K). Color temperature (CT) is a measure of the spectral content of light from a source; how much blue, green, yellow and red there is in it. A higher CT rating generally means greater blue content, and the whiter the light appears.

The LED street light itself is not harmful, just need to pay attention to choose a suitable LED street light. A warm white color temperature as much as possible, anti-glare and a great lighting sulution to reduce light pollution. Choosing a suitable LED street light is very important.