Light Pollution (2024)

STEM Explained

Environmental Science, Pollution, Health, Physics, Waves, Sound, Light, Space Science, Astronomy

Curriculum Alignment

Have you ever seen the Milky Way in the night sky? If not, don’t worry. You’re not alone! Over 30% of people in the world can’t see it because of light produced by humans. This is called light pollution.

Light pollution is a waste of energy and money. It can also harm human health, animal health, and ecosystems.

So what can you do to help? As it turns out—plenty!

What is light pollution?

Light pollutionis the excessive and disruptive use of artificial light. Most light pollution comes from outdoor lighting, advertisem*nts and streetlights. Another major source is indoor light from large buildings like office towers.

The three main forms of light pollution are glare, skyglow, and light trespass.

Imagine walking down the street on a really bright day. Suddenly, the windshield of a car reflects sunlight right into your eyes. This is called glare. Glare can make it difficult to see, and can even be painful. At night, glare can be caused by streetlights.

Light trespass is when light shines outside of the area it’s supposed to brighten. Streetlights should only light the street, to make walking and driving safer. But sometimes streetlights can shine into your bedroom. This is an example of light trespass.

Skyglow is a form of light pollution that makes the night sky brighter. It often looks like a yellow halo around a city. Skyglow happens when too much light shines up into the atmosphere. The light scatters and reflects back down to the ground. When there are more clouds, more light is reflected.

Artificial light reflected in the sky looks a lot brighter than the stars. So skyglow makes it very difficult to see constellations or planets.

Chile is one of the best places to study astronomy because its skies are so dark. Astronomers there discovered that supernovas can produce some of the heavy elements on the Periodic Table. They would not have been able to observe this if there had been a lot of light pollution.

Scientists working at the Cerro Tololo Inter-American Observatory were interrupted recently. A new soccer stadium with bright lights had been built nearby. Luckily, those lights were adjusted. They no longer block out the stars!

Did you know?

Parks Canada protects more dark sky than any other organization in the world. Thirteen parks in Canada have official dark sky designations. The Waterton-Glacier International Peace Park is even an International Dark-Sky Park.

In some places, skyglow is so bright that it looks like daylight. Artificial daylight like this can affect the health of both humans and animals.

How does light pollution harm humans?

Photoreceptors are light-sensitive cells in the retina. The retina is found at the back of your eye. Photoreceptors are responsible for converting light into signals. Our brain interprets these signals as images of the world around us. There are three types of photoreceptors - rods, cones and intrinsically photosensitive retinal ganglion cells or ipRGCs. Rods help us see light and dark. They are very sensitive to light. Cones help us to see colours. Glare can hurt your eyes because it can damage or kill rods and cones. This can lead to vision loss or impairment.

Did you know?

The retina has approximately 120 million rods and 6 million cones.

Scientists think ipRGCs help rods respond to light at many different brightness levels. They may also help regulate circadian rhythms. Circadian rhythms are like an internal clock that our bodies follow every day. Many circadian rhythms are controlled by the light signals around us. So light pollution can disrupt our circadian rhythms.

One circadian rhythm is sleep. Our bodies decide when we should be tired based on the amount of light around us. But light pollution, especially skyglow, can make the day seem longer. This means our normal sleep patterns can be disturbed.

If you don’t sleep properly, you may be irritable or anxious. You may have a hard time concentrating. If someone doesn’t sleep well for a long time, they could develop health problems. These include depression, a weak immune system, diabetes, or a higher chance of getting certain cancers.

How does light pollution harm animals?

Circadian rhythms aren’t just important for humans. Light also controls animal behaviours like sleeping, breeding, migrating and hunting.

Light pollution makes migration difficult for many birds. The Prothonotary warbler depends on stars to find its way from Ontario to the Gulf of Mexico. But light from tall buildings and outdoor advertisem*nts hides its view of the night sky. This means fewer birds survive to reach the areas where they breed or find food during the winter.

Did you know?

Many birds are attracted to brightly lit buildings at night. Sometimes they collide with windows, causing injury or death.

Light pollution also affects endangered leatherback and loggerhead sea turtles. On Canada’s Atlantic coast, baby turtles on beaches look for moonlight reflecting from the water. This helps them find their way to the ocean. But light pollution can lead them to cities instead. Because of this, fewer sea turtles reach maturity and breed. This puts the survival of the species at even more risk.

Did you know?

The International Dark-Sky Association estimates that light pollution costs $50 million per year in Quebec. The energy wasted to produce excess light contributes to global climate change too.

How can we reduce light pollution?

Light pollution is preventable! There are a lot of things you can do to reduce your impact. You can also help reduce the impact of your community.

First, you can turn off your lights at night, or close the curtains. Indoor light can cause glare outdoors. Then look at the lights outside your house. Can they be turned off? Or can motion sensors be installed so they only come on when needed? Glare from outdoor lighting can be reduced by shielding light fixtures. You can talk to friends, family, and guardians about making some of these changes at home!

LED lights are often used outdoors. But LEDs can harm humans and animals. Their high-energy blue light reaches far into the eye. This over-stimulates photoreceptors and can lead to vision loss. It’s safer to use lights and filters that are coloured red or yellow.

You can also raise awareness about light pollution in your community. This is a powerful way to make change. The International Dark-Sky Association (IDA) is a non-profit organization that aims to protect the night sky. The IDA website has a lot of resources you can use to help spread the word!

Are the lights turned off in your school at night? Maybe that’s a good place to start. You can discuss effective lighting practices with school administrators. Or you could join an environmental club to advocate as a group. If there is no club, you could even start your own!

Everyone can do something to reduce the impact of light pollution. It can even be fun! Remember, no action is ever too small.