February 22, 2019

Confused about the health impacts of LEDs? Here's what an engineer has to say about it

The technology behind light emitting diodes (LEDs) has advanced so quickly that these small light sources have found a place in just about every electrical device one might own.

All of our screens (TVs, phones, tablets, etc.) are now backlit with LEDs. General lighting in our homes and workplaces are moving to LED. Every appliance, whether necessary or not, seems to have at least one small colored LED embedded in it, resulting in a home where darkness has been replaced with small pools of primary colored light. Research about the effects of our new LED environments on our health are now starting to come to light (pardon the pun). However, without proper context, the findings can cause undue confusion and concerns.

Much of the research to date revolves around “blue light,” which is a key phrase that gathers many areas of research under one umbrella. Unfortunately, it is easy to explore one facet of blue light without the others and develop a black or white stance about the use of LEDs.

On the other hand, some reports try to cover all aspects of blue light without going into depth on each subtopic, making LEDs in general sound like one big concern.

For example, a recent report from the American Medical Association titled “Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting” did just that. While the intentions were good, the report caused a stir in the lighting industry resulting in responses from key organizations, including the Illuminating Engineering Society and the Lighting Research Center.

To clarify the blue light topic, some of the facets below offer a more holistic viewpoint on the issue.

• Correlated Color Temperature (CCT)

CCT is a metric to describe white light. It is based on the color that iron emits when heated to certain temperatures. Lower temperatures produce yellowish or warmer light, while hotter temperatures produce blueish or cooler light. A gas flame from a stove or barbeque behaves similarly.

It is important to note that “warm” and “cool” refer to the color of the light, and not temperature — the cooler or more blueish the LED, the greater the spike in blue energy. It is important to note that different CCTs of white light produce different behavioral responses. In brief, warmer light is more relaxing (think intimate restaurant) while cooler light is more energetic and (think sports).

• Blue Light Hazard

Exposure to high intensity 430nm light can damage the eye. However, it would usually take looking at a high intensity LED at a close distance for around 10 seconds to cause damage. This is longer than a person will likely tolerate without squinting or another natural response to avoid damage. Typically, the LEDs in our environments are not installed in ways that put our eyes at risk.

• Circadian Rhythms

It has recently been discovered that our eyes contain a third photoreceptor (in addition to rods and cones) called intrinsically photosensitive retinal ganglion cells (ipRGCs). These ganglion cells are not responsible for any vision, but are responsible for controlling our circadian response. They are sensitive to light peaking around 480nm, which is blue light, but closer to green than the blue from standard LEDs.

In short, our bodies need a certain amount of this light during the day to tell us that it is daytime. However, at night, this light can suppress melatonin production, and prevent someone from falling asleep. This is why many sources suggest limiting screen time at night.

• Dynamic White Lighting

Light sources that are able to control the CCT of their light from warm to cool are referred to as Dynamic White Lighting. These new fixtures are touted for use in the realm of circadian and behavior response. It is important to note that circadian response is a result of the underlying spectrum while behavior response is more so due to the apparent color of the light.

• Glare

Glare is not specific to color and not a specific problem with LEDs, but due to the small point source of LEDs it is more common with larger LED fixtures. Glare is commonly part of the blue light hazard conversation. While many of the other factors discussed above have advantageous uses, glare is almost never desirable.

This discussion of lighting and health is complex but important. More and more new discoveries are revealed about the links between lighting and health.

But, LEDs are here to stay as an important part of a greener future. They provide more solutions than any previous lighting source, and they have potential to solve health problems at an equal or greater level than the problems their early versions created.

To continue progress in the field of LED lighting and health research, it is important to distinguish cause and effect relationships between appropriate lighting variables. Here are a few simple pointers.

1. During the day, our bodies need a dose of appropriate blue wavelengths of light. Daylight is best, however not always available, If designed appropriately, LED sources can help deliver this.

2. In the evenings and at night, blue wavelengths are not desirable. If you have screen time at night, enable the appropriate night mode on your device to filter out unwanted blues.

3. When reading about lighting and health, consider the source. Not only the author of the piece, but the light source (or fixture type) discussed and its use to clearly identify the pros and cons.

4. If you will be involved in a lighting project in the future, have a conversation with your lighting designer and share your questions and concerns. Other local resources include the Lighting Design Lab and the IES Seattle/Puget Sound Chapter.

DLR Group Senior Associate Sean Avery, P.E., is the electrical engineering leader in the Northwest region, and a member of the Illuminating Engineering Society's Seattle/Puget Sound Chapter.