How much light is enough?

Nighttime lights are a given in today’s urban environment, but don’t assume their glow is always rosy.

It’s an idea that triggered for me while I was reading The Big Tiny: A Built-It-Myself Memoir by Dee Williams — one of my favourite books. Dee builds herself a tiny house as a means to reclaim meaning in her life after she is diagnosed with congestive heart failure. Along the way, she reconsiders many “taken-for-granted” aspects of her previous “big-house” existence, including electric light.

Dee writes:

In my estimation there are far too many lights in the world; streetlights, car lights, tiny lights in the glove box; front and back porch lights, lights in the ceiling, under the cabinets, and in the refrigerator; lights working their way across undulating surfaces, so you could guess the couch cushions are soft and the bathroom sink will bruise your hip if you totter into it in the middle of the night.

I wondered if all that light was somehow causing us to forget things, blinding us to the truth that a little darkness can be a good thing.

In fact, a regular dose of darkness — real darkness, untouched by the glow of streetlights, nightlights, appliance lights and device lights — is a good thing, a very good thing, for both people and the planet. These days, however, it’s in short supply.

According to a 2016 study published in Science Advances, over 80 per cent of the world’s population lives under light-polluted skies. The Milky Way is completely blocked out for almost 80 per cent of North Americans. In large Canadian cities, over 95 per cent of stars that can be seen with the naked eye are no longer visible. [1]

Light pollution is defined as the inappropriate or excessive use of artificial light, particularly at night. Today, light pollution is largely caused by lights that shine too brightly, too widely and too long for their intended purpose. Excess light waves careen in all directions, bounce off surfaces and reflect up into the atmosphere, where they converge to form an ever-present glow. Heavy light pollution in urban centres can lighten a dark sky over 60 kilometres away. [2]

Blue light — today’s energy-efficient choice — is especially problematic. Emitted by LED light bulbs, most outdoor lighting and device screens, blue light packs more energy than other frequencies and bounces and scatters more. The more blue lights we flick on, the greater the polluting effect.

What does this glut of nighttime light mean for us, and for the environment we live in? It doesn’t look good.

As humans, we have a number of biological processes that depend on darkness. Hormone secretion, metabolism, sleep-wake cycles, emotion and mood regulation and gene expression all require some amount of darkness (complete darkness) to function correctly. Research has linked regular exposure to artificial indoor nighttime light to illnesses like diabetes, depression, heart disease and some forms of cancer (particularly breast cancer). [3]

The natural environment also takes a beating. According to a 2017 study published in Translational Psychiatry, there is “a growing body of ecological research [that] points to nighttime lighting near urban centres as a major disruption to wildlife migration, foraging activities, reproduction and immune functioning.” Studies show that exposure to bright and/or consistent nighttime light can cause frogs to inhibit mating calls, zooplankton in lakes to stop eating algae that prevents deoxygenation of the water, birds to veer off migratory paths, and trees to struggle with seasonal adjustments. [4]

Light pollution affects our mental health, too. Think back to the last time you experienced a nighttime power outage. You probably sat and talked with family or friends, visited or checked on neighbours, lit a candle, let go of your “to-dos,” let your body and mind rest. You probably felt more relaxed that usual — lighter, less harried, more content, more grounded, more present. I bet most of these sensations disappeared the instant the lights flicked back on.

What can you do to help reduce light pollution? Here are a few tips offered by National Geographic:

  • Use lower temperature LED or compact fluorescent light bulbs with a rating of less than 3,000K.
  • Use dimmers, motion sensors and timers on outdoor lights, and install fixtures that shield light bulbs from shining in unintended directions.
  • Turn off all unnecessary indoor lights. (Timers and dimmers work great indoors, too!)
  • Turn off all devices at least one hour before bed, and install apps or screens that filter blue light when you’re working at night.
  • Don’t turn on lights when you get up at night. If you need a light source (in the bathroom, for example), use a red light that will not disrupt your nighttime physiology.

And once in a while, do your best to live your day by the rise and fall of the sun. Get up when it’s light out, and turn in when it gets dark. If necessary, use a candle, headlight or single dim light to carry out your early morning or evening activities. Welcome darkness back into your life. Reclaim its value.


  1. ASTROLab du parc national du Mont-Mégantic. Light Pollution. Canada Under the Stars.
  2. Drake, Nadia. “Our nights are getting brighter, and Earth is paying the price.” National Geographic. Published 3 April 2019.
  3. Ibid.
  4. Chepesiuk, Ron. “Missing the Dark: Health Effects of Light Pollution.” Environmental Health Perspectives, 2009 Jan; 117(1): A20-A27.
    ASTROLab du parc national du Mont-Mégantic. Light Pollution. Canada Under the Stars.


All sources last retrieved 27 October 2020.

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