Light Pollution: What is Light Pollution and Why it is Bad

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What is light pollution? San Francisco Shown at night with lp

Light pollution is not good and what is light pollution (LP) you may ask? It is not like what we normally associate with pollution, like smoke stacks filling up the air with plumes of dirty, chemical laden billowing pillars of smoke. We also commonly associate it with dirty water, as in oil covered waterways, garbage in the water, or toxins and other waste in our water supplies. Generally speaking, pollution is referred to as an impairment of the purity of the environment with purity referring to the state of the environment in its natural unaltered state.

While those images of pollution are the most thought of and associated with it, one thing we typically do not associate as being pollution as a culture and society is light! We are more bright lights, big cities when it comes to our society and culture at this point in time. Most of us [probably look at the night lights and consider it more as scenery and beauty than as pollution in general. However beautiful and, or not harmful it may seem, there is a dark side to this unnatural phenomenon. Before the industrial revolution and our rapid expanses over the last couple centuries, there was no such thing in existence. It has become the price of progress, but is it a necessary price we must pay for progress? No, it indeed is not, at least not if we don’t want it to be.

What is Light Pollution

This is a good question, for as we said earlier, most of us never consider it to be a problem. There are several more technical terminologies associated with it, such as photo pollution or luminous pollution; however all have the same definition, which is simply excessive or obtrusive artificial light. Our friends at the International Dark-Sky Foundation defines it as:

Any adverse effect of artificial light including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste.

Due to the increasing awareness of some of the issues of this phenomenon, they have come up with several scientific definitions for what is light pollution:

The above scientific definitions for what is light pollution are primarily concerned with and describe the state of the environment while the last (fourth) one, which is also the newest (2009), primarily describes the process of polluting by light.

Light Pollution Images

Light pollution has become a side effect of the industrial revolution, primarily located in heavy industrialized areas and densely populated areas in North America, Europe, and Japan. It has common sources, such as exterior and interior lighting, advertising, commercial property, offices, factories, streetlights, sports venues, and even our homes. Even small amounts of light can be noticed and create problems and it does do damage to the environment, however it is not as apparent or prevalent like other forms of pollution such as air, water or noise pollution.

Types of Light Pollution

    • Urban Sky Glow
      • The brightening of the night sky over inhabited areas
    • Light Trespass
      • Light falling where it is not intended, wanted, or needed
    • Glare
      • Excessive brightness which causes visual discomfort, with high levels of glare causing decreased visibility, especially in night driving conditions
    • Light Clutter
      • Bright, confusing, and excessive groupings of light sources, commonly found in over-lit urban areas. The mass proliferation of light clutter contributes to urban sky glow, trespass and glare!
    • Over Illumination
      • The excessive use of light
      • Over-illumination results from several sources:
      • Not using timers, occupancy sensors or other controls to extinguish lighting when not needed;
      • Poor design, especially of workplace spaces, by specifying higher levels of light than needed for a given task;
      • Poor choice of fixtures or light bulbs, which do not direct light into areas as needed;
      • Poor selection of hardware to utilize more energy than needed to accomplish the lighting task;
      • Incomplete training of building managers and occupants to use lighting systems efficiently;
      • Inefficient lighting maintenance resulting in increased stray light and energy costs;
      • “Daylight lighting” demanded by citizens to reduce crime or by shop owners to attract customers;
      • Substitution of old mercury lamps with more efficient sodium or metal halide lamps using the same electrical power;
      • Indirect lighting techniques, such as lighting a vertical wall to bounce photons on the ground.

Light Pollution

There are many different concerns when it comes to light pollution, however it takes a backseat to other forms of pollution in general, and is again, not that prominent in the mainstream media nor in our minds. It should take up more importance though, as it does have harmful effects to both man and animals.

For starters, light pollution makes stargazing extremely difficult if not impossible for those in or nearby cities. It also disrupts ecosystems and has adverse health effects. We can separate LP into two separate but related categories:

  • Annoying light
  • Light that intrudes on an otherwise natural or low light setting.
  • Excessive light (primarily indoors)
  • Light that leads to discomfort and adverse health effects.

As for the health issues, medical research on the effects of excessive light on humans indicates that a variety of adverse health effects may be caused by LP or excessive light exposure. Some design textbooks factor in lighting as an explicit criteria for proper interior lighting. Some of the adverse health effects of excessive lighting include:

  • Increased headache incidence
  • Worker fatigue
  • Medically defined stress
  • Decrease in sexual functions
  • Increased anxiety

Animals also suffer from light pollution, demonstrating adverse effect on moods and anxiety. LP also poses a serious risk to nocturnal wildlife, resulting in negative impacts on plant and animal physiology. It has been attributed to confusion in animal navigation, alter competitive interactions, change predator-prey relations, and cause physiological harm. For further information on nocturnal wildlife look at the following: Ecological Consequences of Artificial Night Lighting .

In a study by Travis Longcore and Catherine Rich on Ecological LP, they cited that the natural rhythm of life is orchestrated by the natural diurnal patterns of light and dark, so the un-natural disruption to these patterns impacts the ecological dynamics.

In June of 2009, the American Medical Association adopted resolution 516 which according to the adoption:


RESOLVED, That our American Medical Association advocate that all future outdoor lighting be of energy efficient designs to reduce waste of energy and production of greenhouse gasses that result from this wasted energy use; and be it further

RESOLVED, That our AMA support LP reduction efforts and glare reduction efforts at both the national and state levels; and be it further

RESOLVED, That our AMA support efforts to ensure all future streetlights be of a fully shielded design or similar non-glare design to improve the safety of our roadways for all, but especially vision impaired and older drivers

Newer research into dark-phase light contamination such as unnatural night lighting may disrupt circadian rhythms, which is the 24-hour cycle of day and night that regulates biological functions for all life on Earth! Studies have also suggested that circadian disruption linked to breast cancer.

There are also other adverse effect from LP, such as the fact that it destroys nitrate radicals which prevents the normal nighttime reduction in atmospheric smog produced by exhaust fumes from cars and factories and boosts pollution. It also creates problems for astronomers, as astronomy is highly sensitive to LP. This could adversely affect our search for heavenly bodies which pose a risk to our planet, such as asteroids or comets which could potentially strike us someday.

These are all legitimate concerns; however, we consider the energy waste and related energy use issues the largest concern. On a global scale, it is estimated that LP is responsible for one fourth of all electricity consumption worldwide. In the United States according to a practical guide to LP by the International Dark-Sky Association and a report by Florida Atlantic University estimate that one third of all lighting is wasted which costs around $2.2 BILLION dollars annually, not to mention wasting 30 million barrels of oil, 8.2 million tons of coal, and spewing 14.7 million tons of CO₂ into the atmosphere in the U.S. alone, which contributes heavily to the ongoing climate change crisis we are currently experiencing.

A source from the U.S. Dept. of Energy confirms that lighting energy account for roughly four to five millions barrels of oil (equivalent) per day, with energy audits demonstrating that roughly 30 to 60% of lighting energy consumption is either unnecessary or gratuitous. If we can reduce these numbers by 50% alone, we could save a great deal of money and eliminate the nearly 8 million tons of CO₂ that would otherwise be needlessly pumped into the atmosphere, and those figures are from the US alone. In Australia, it is estimated that 2 million tons of CO₂ are wasted on this problem.

While these problems persist, some are making strides forward. I could cite many, many sources of positive examples of people tackling the issues of LP, however there are so many I don’t know where to begin, but trust us, they are there and plentiful, but we can all do our part in helping to reducing the easiest form of pollution to reduce on our planet, LP.

Light Pollution Solutions

Solutions to reducing and eliminating LP may imply many different things like reducing sky glow, reducing glare, reducing light trespass or reducing light clutter. The methodology for reducing LP therefore is best when applied to an exact problem in any given instance, and not when applied generally.

  • Utilizing light sources of minimum intensity necessary to accomplish the light’s purpose.
  • Turning lights off using a timer or occupancy sensor or manually when not needed.
  • Improving lighting fixtures, so that they direct their light more accurately towards where it is needed, and with fewer side effects.
  • Adjusting the type of lights used, so that the light waves emitted are those that are less likely to cause severe light pollution problems. Mercury, metal halide and above all first generation of blue-light LED road luminaries are much more pollutant than sodium lamps: Earth atmosphere scatters and transmits blue light better than yellow or red light. It is a common experience observing “glare” and “fog” around and below LED road luminaries as soon as air humidity increases, while orange sodium lamp luminaries are less prone to show this phenomenon.
  • Evaluating existing lighting plans, and re-designing some or all of the plans depending on whether the existing lighting is actually needed or not.


We hope that light pollution gave you more insight into what is light pollution and for how best to proceed forward in helping to reduce this problem and making for a better home for every living creature on the planet, including us! Peace my friends!

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