Light Pollution Environmental Pollution by Paula Mendonça -
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Light Pollution Environmental Pollution

  • Joined Feb 2024
  • Published Books 1
Light Pollution Environmental Pollution by Paula Mendonça -

“Why light pollution is a solvable environmental crisis”

“Excessive outdoor lighting is deadly to animals and takes a toll on human health and wellbeing, too. But when it comes to large-scale environmental problems, this one may be a relatively easy fix.”

It’s not easy to make street lights exciting, but Kelly Beatty is trying. Holding court over Zoom on a spring evening in 2021, he warns citizens of Nantucket island in Massachusetts that the decisions they’ll soon make about their lights are choices they’re “going to have to live with for a long time.”

Beatty often helps advise communities like Nantucket as they transition their streetlights from traditional bulbs to more energy-efficient LEDs, or light-emitting diodes. As communications officer of the Massachusetts chapter of the International Dark-Sky Association (IDA), he’s well aware of the stakes. As this process has been repeated in towns across the world, it has led to a new and preventable environmental problem. LED lights can last 20 years or more, he reminds the group. “It’s important to get it right when you have a chance.”



The IDA defines light pollution as the inappropriate or excessive use of artificial light, with variations including glare (excessive brightness that causes visual discomfort), skyglow (brightening of sky over inhabited areas) and light trespass (light that falls where it isn’t intended or needed). Already a growing problem, light pollution has intensified with the rise of LEDs, which produce blue-intense light in shorter wavelengths that are more susceptible to scatter and thus travel farther. An estimated 99% of U.S. and European populations now live under light-polluted skies, and one third of humanity is unable to see the Milky Way at night. From marine life and plants to birds and insects, the loss of darkness has left deep scars in our ecosystems.

Light Pollution Environmental Pollution by Paula Mendonça -

In recent decades, lightbulbs made with LEDs arrived, a revolution in energy efficiency with seemingly little downside. After all, an LED bulb converts some 90% of the electricity it uses into light, whereas a conventional incandescent bulb only converts about 10%. And LED bulbs are touted as lasting up to 25 times longer.

But the physics of LEDs make them fundamentally different from incandescents. While those traditional bulbs put out warm white light made of all colors mixed together, LEDs filter blue-rich light through a specialized phosphor material, producing light that appears white to the human eye but is still more blue-intense than incandescents’ light.

In January 2013, France created a law to reduce electrical energy consumption and light pollution. “All non-residential properties in France must turn off their interior lights within one hour of the last employee leaving. External lights will be turned off until 1:00 am.” Alei preserves festive dates, such as Christmas, events and all services necessary for the safety of the population. Light pollution, although still little addressed, is already a concern worldwide. The solution to combat light pollution is, mainly, to invest in rational lighting systems, with the appropriate choice in the correct installation of lighting and types of lamps. Correct lighting is that which shines light, solely and exclusively, on the area that needs to be illuminated, using lamps that offer the color definition necessary for the specific application.

Light Pollution Environmental Pollution by Paula Mendonça -

What each of us can do:

Turn on the light only in the room where it needs to be. Use light directed to the location where it is needed.

Install sensors, motion detectors, in dark places – the sensor turns on light only when a person passes by.

Avoid working under artificial lights at night.

Close, whenever possible, the blinds/blinds in the lighted rooms.

A study was carried out in two cities in Galicia in 2017 (Salvador Baráetal, 2018, LR&T) which concluded that 25% of the total sky brightness results from this type of lighting.

It also states that this contribution is maximum in the first hours of the night and that it decreases as the night progresses.

Avoid using superfluous lighting (mobile phone flashes, for example) in dark sky regions.


Have you ever walked around your neighborhood at night and noticed the amount of wasted, and oftentimes unnecessary, artificial light? I think we have all noticed the poorly designed outdoor lighting in our neighborhoods that contributes to light pollution.

According to the DarkSky International (IDA), light pollution is increasing at two times the rate of population growth with 83% of the global population living under a light-polluted sky. In fact, researchers reported that people living in urban areas of more than 500,000 people are exposed to night-time light levels that are three to six times brighter than people in rural areas.


Our night sky is fading – with fewer and fewer dark places to experience a sky full of stars.

Light Pollution Environmental Pollution by Paula Mendonça -

As a solution to this global problem, the IDA and the Illuminating Engineering Society (IES) have published ‘Five Principles for Responsible Outdoor Lighting’. Their shared goal is to prevent and reduce light pollution through the proper application of quality outdoor lighting. The five principles include:

  • Useful: All lighting should have a clear purpose
  • Targeted: Lighting should be directed only where it is needed
  • Low Levels: Light Should be no Brighter Than Necessary
  • Controlled: Light Should Only be Used When Useful
  • Color: Use Warmer Colour Lights

By applying these principles, properly designed lighting at night can be beautiful, healthy, and functional. You will also save energy/money, minimize disruption, and reduce light pollution.

Light Pollution Environmental Pollution by Paula Mendonça -

Light Should be Directed only Where Needed


All lighting should be targeted and directed to light up only the intended area. If you have determined that a light is needed, it should be properly targeted to serve its intended purpose.


Use shielding and careful aiming to target the direction of the light beam so that it points downward and does not spill beyond where needed.

Light Pollution Environmental Pollution by Paula Mendonça -

Did you know that 20% – 50% of outdoor residential lighting is lost to the night sky due to poor shielding alone? Using outdoor lighting with proper shielding alone can make a big difference in reducing light pollution (DarkSky).


There are many negative impacts that result from outdoor lighting that is not properly targeted; including light glare, light trespass, public safety, and wasted energy.


Act Now Against Light Pollution

There are so many options for taking a stand against light pollution. Help reduce the potential harm to human health and protect wildlife, ecosystems, and the night sky.

  • Only use lighting when and where it’s needed
  • Properly shield all outdoor lights
  • If safety is concern, install motion detector lights and timers
  • Keep your blinds drawn to keep light inside
  • Read more about light pollution – a great place to start is the DarkSky International website
  • Become a citizen scientist and help measure light pollution
  • Share this information with your family and friends to spread awareness

The problem of light pollution starts and ends with you. Let’s be responsible and use outdoor lighting that benefits all living things.


Research work for EBIAH students


Light Pollution Environmental Pollution by Paula Mendonça -
Light Pollution Environmental Pollution by Paula Mendonça -
Light Pollution Environmental Pollution by Paula Mendonça -
Light Pollution Environmental Pollution by Paula Mendonça -
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