Questions to Ask Before Switching on the Lights

For most of human existence, our ancestors lived with the natural 24-hour light-dark cycle, spending each day in natural daylight and sleeping in the dark at night. But since the widespread introduction of electric light, more than 90% of our time is spent indoors, under unhealthy and human-unfriendly electric light, which disrupts our circadian clocks and greatly increases the risk of cancer, obesity, diabetes, heart disease, and hundreds of other disorders.

Today’s LED and fluorescent lights are designed for energy efficiency with little regard for human health. Like DDT and asbestos, static blue-rich lights are a dangerously flawed technology.

The science is extensive, and the risks well established, yet most people are largely unaware of the risks to their health from artificial light. By 2007, the first 10,000 scientific studies of the impact of light on circadian clocks led a World Health Organization agency to classify exposure to light at night as a probable carcinogen.

In 2021, another 10,000 scientific publications later, the National Institutes of Health’s National Toxicology Program identified the culprit: excessive blue-rich light at night (and insufficient blue daylight exposure), which is delivered by today’s LED and fluorescent lights.

We don’t have to give up electric light. But we need to get healthier by using electric lights that are sky-blue-rich during the day and blue-depleted at night. Because fewer than 0.5% of lights sold today meet this standard, the rates of diabetes, heart disease, and cancer are climbing. There is no good reason why obesity, sleep disorders, and fatigue should continue to be an international epidemic.

I bring a unique perspective from the forefront of the battle against unhealthy lights. While a professor at Harvard Medical School, I led the team that discovered the location of the circadian clock in the human brain and how it is synchronized by light.

Our recent discovery of the narrow sky-blue signal that synchronizes circadian clocks under normal lighting conditions led to the invention (and patenting) of evidence-based circadian lighting and the demonstration of its effectiveness in many major companies. The circadian lights that we developed are already installed in the safety-critical workplaces of over 50 Fortune 500 companies with documented improvements in workforce alertness and health.

One problem is the lack of communication about harmful lighting from scientists. As one industry leader said about circadian lighting, “Nobody knows about it … Scientists know, but they talk only to each other. If you talk to your neighbor, they won’t know.”

Another problem that slows the introduction of healthy lighting is the lighting industry itself, wrestling with how to introduce circadian lighting without opening the door to potential liabilities for the billions of unhealthy lights they have already installed. It doesn’t help that government agencies, such as the U.S. Department of Energy, promote lighting policies that place energy efficiency at a much higher priority than human health. However, you do not have to sacrifice your health for the health of the planet.

Ultimately it is up to each of us to demand healthy circadian lighting. Don’t leave your lighting decisions to your local hardware store, electricians, and building maintenance or to a corporate sustainability executive who is paid bonuses solely for energy-savings goals. You need to know the real story and understand the impact of the wrong versus right lights on you and your loved ones.

You need to know the practical information necessary to counteract the risks at home, in business, and medical offices, and in public spaces, hospitals, and care facilities.

Healthy light bulbs and fixtures are becoming available for both residential and commercial space. Display screens are being developed with different light spectrum, and blue doses you need for evening and night use versus daytime; and how to obtain energy-efficient light that is also safe and healthy. You will also need to learn which outdoor lights to install to avoid harmful effects on wildlife, another inadvertent consequence of the LED revolution.