Every year, towards the end of March, the world at large observes Earth Hour. The concept is to switch off all unnecessary lights, thus saving electricity in order to raise awareness for environmental problems throughout the globe. This is a unique event in which major centres of urban populations switch off lights for an hour.

The event highlights willingness of the human race to do something about the increasing problem of pollution in the world. It has also brought to light a problem that has seldom received much-needed attention before – light pollution.

Man’s dependence on (once) cheap electricity has led to our unrestricted use of artificial lights. This has resulted in problems that we have become oblivious to. Though we may have conquered the demons of darkness and illuminated our cities, towns and villages, we have done so at an expense that is still being calculated.

The simplest way that light pollution can be defined is: the introduction, consciously or unconsciously, of man-made (artificial) light into the environment. Contrary to what we may think, this light pollution does not start when we turn the switch on, or dissipates when we switch the light off. The effects are long and lingering. The disruption to the environment has reached such levels that man-made light is now competing with starlight in the night sky, and in the process interfering with ecosystems, resulting in ill-health effects. It is also threatening the science of astronomy, which is steadily being pushed out of urban centres of learning.

Light pollution is the result of our poor understanding of artificial light. Indoor and outdoor advertising, building lighting, factories, street lighting and sporting arenas have artificial light that is poorly designed to meet our needs and is thus polluting the environment. The resulting consequences are financial, health and of course, environmental.

Economically, the problem is immense, yet is not being addressed. According to some estimates, global lighting is responsible for one-fourth of all electricity consumption. If artificial lights are designed and managed in a way that it serves the needs of the particular area it is needed for, and is not intrusive, then it saves energy. In 2007, the Italian electricity provider Terna reported a saving of 645.2 million kWh in electricity consumption during the daylight saving period from April to October. It attributed this saving to the delayed need for artificial lighting during the evenings.

One problem of light pollution that we are most familiar with is sleep deprivation. The glare of poorly designed street lights often ends up in our bedrooms, causing immense irritation and loss of sleep for all. Other health-related issues include worker fatigue, medically defined stress and increase in anxiety. Night-shift workers have been the focus of a number of studies. Some have documented a correlation between night shift work and the increased incidence of breast and prostate cancer. Headlights from oncoming cars is bad for the eyes – not to mention very annoying!

A study has also suggested that light pollution destroys nitrate radicals, thus preventing the normal night time reduction of atmospheric smog produced by fumes emitted from cars and factories.

For plants and animals, artificial light have caused critical problems, thus leading to problems for humans as well. Light pollution poses a serious threat to nocturnal wildlife. It is known to have caused confusion to animal navigation, and change predator-prey relations among other things. Light pollution around lakes prevents zooplankton from eating surface algae, causing algal blooms that can kill off the lakes' plants and lower water quality.

Night-time light interferes with the ability of moths and other nocturnal insects to navigate. Night-blooming flowers that depend on moths for pollination may be affected by night lighting, as there is no replacement pollinator that would not be affected by the artificial light. This can lead to species decline of plants that are unable to reproduce.

Lights on tall structures can disorient migrating birds. Estimates by the US Fish and Wildlife Service of the number of birds killed after being attracted to tall towers range from 4 to 5 million per year. The Fatal Light Awareness Program (FLAP) works with building owners in Toronto, Canada and other cities to reduce mortality of birds by turning out lights during migration periods. Lighthouses along the Canadian east coast report thousands of migratory bird deaths every year.

Sea turtle hatchlings find the ocean by moving away from the dark silhouette of dunes and their vegetation, a behaviour with which artificial lights interfere. It is also responsible for the reduction of the polarization of the moonlit sky, which is believed to be used by many animals for navigation.

The science of astronomy has been one of the biggest victims of light pollution. Skyglow (the scattering of light in the atmosphere) reduces the contrast between stars and galaxies and the sky itself, making it much harder to see fainter objects. This is one factor that has caused newer telescopes to be built in increasingly remote areas. In addition, light trespass can impact observations when artificial light directly enters the tube of the telescope and is reflected from non-optical surfaces until it eventually reaches the eyepiece. This direct form of light pollution causes a glow across the field of view which reduces contrast.

So what is the solution to these problems? Possible solutions include:

• Utilising 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.
• Adjusting the type of lights used, so that the light waves emitted are those that are less likely to cause severe light pollution problems.
• Evaluating existing lighting plans, and re-designing some or all of the plans, depending on whether existing light is actually needed.

No matter what is done, it is mostly about educating society about its responsibilities, which if not tackled now, will have severe consequences in the future.