Pollution is often associated with unwanted and harmful chemicals released into the air, soil, and water around the world. A significant amount of time and research has been invested in understanding these types of pollutants. However, the global community also faces another less obvious pollutant known as light pollution. In short, light pollution is the existence of artificial light sources in what would otherwise be a naturally dark setting. Its presence works to change the natural level of light in a particular area. Although light pollution may exist anywhere that artificial light is used, it is primarily identified where that artificial light presents in high concentrations or where it seems to be pointed in indirect or unnecessary positions. Light pollution is found over large urban areas. This article takes a closer look at different types of light pollution as well as its disadvantages.
Types Of Light Pollution
Five types of light pollution have been identified: glare, light trespass, sky glow, light clutter, and over-illumination.
Light pollution can occur as the result of glare, which happens when light is pointed toward reflective surfaces (like glass or mirrored windows). These reflective surfaces do exactly as intended, reflecting the artificial light back into its surroundings. Glare may make it difficult for people to distinguish between objects. This type of light pollution is further divided into 3 subsets: disability, discomfort, and blinding. In disability glare, the reflected light may reduce visibility and can be caused by traffic lights or light reflecting off of fog. Discomfort glare is the least serious, although it has been associated with eye fatigue after long periods of exposure. In blinding glare, the reflected light may actually come from the sun and causes potentially dangerous losses of vision.
The term light trespass refers to light that shines into the personal property or area of a person other than the owner of the light. This type of light is unwanted and may disrupt the sleep patterns or nightly behaviors of the person receiving the light. Light trespass is commonly associated with the light from a street light or advertising signs shining into a personal bedroom. In some countries, local governments have passed regulations to prevent and reduce the instances of light trespass.
Sky glow refers to the aerial view of a city at nighttime. All of the light produced in a city and its surrounding metropolitan area creates a dome shape that hovers over everything. The light shines up into the atmosphere and is reflected back toward the earth. In some cases, the sky glow is so strong that pilots have difficulty flying over a particular region.
Light pollution that is referred to as light clutter is that which occurs in multiple groups. It is associated with poor planning and design and is often seen in lit-up advertising near roadways or in traffic lights that do not follow a uniform plan. Researchers have found a positive correlation between light clutter, visual distractions, and traffic accidents.
Over-illumination is exactly as its name suggests. It is the overuse of artificial lighting, not only in brightness, but also in amount of time left on. The factors that result in over-illumination include: poor design planning, lack of on-off timers, incorrectly directed light, lighting intended to reduce crime, and use of light during day-time hours.
Disadvantages Of Light Pollution
Light pollution disrupts natural light cycles, which can have a disastrous effects on both the ecosystem and on the human population. Additionally, the demand for artificial light in urban areas increases the extraction and use of nonrenewable natural resources. Light pollution also contributes to air pollution in other ways as well.
In terms of the ecosystem, light pollution tends to have the greatest impact on photoperiodic animal species. These animals hunt, breed, and carry out other daily activities based on the time of day. In other words, certain activities are performed at night while other activities take place during the day. Light pollution, however, upsets these circadian rhythms. One example of this disruption is seen in the behavior of newly hatched baby sea turtles. These animals emerge from their nests on beaches around the world and immediately make their way to the ocean. In the absence of artificial light, these hatchlings look for the light of the moon to guide them into the water. The light pollution created in cities and towns located near these special beaches works to distract the baby turtles, confusing them and leading them away from the ocean. A number of other animal species are equally affected by light pollution.
Like other animal species, human behavior is also reliant on circadian rhythms. Generally speaking, humans sleep at night. This sleep pattern is disrupted by light pollution. When people are unable to get a full night of sleep, they tend to experience exhaustion and a loss in the ability to concentrate. Research has also linked exposure to light pollution to a number of other results, such as: obesity, headaches, cancer, depression, stress, anxiety, and sleeping disorders. Many of these diagnoses are associated with a disruption in the production of melatonin, an important sleep-regulating hormone in humans. This same research has found a link between blue light waves (which is emitted by most urban lights) and increased suppression of melatonin production. In addition to these more serious health conditions, light pollution has also been shown to cause eye fatigue, leading to car accidents. When poorly designed street lights are placed on roadways, the glare produced may cause temporary blindness or obstructed vision, which has also been reported as the cause of many traffic accidents around the world.
Urban lighting makes up a large percentage of the demand for electricity around the world. In many countries, the electricity produced for urban lighting is cited as the number one emitter of greenhouse gases. In addition, some research indicates that artificial urban lighting disrupts the natural reduction of air pollution that occurs at night. During this time of the day, nitrate radicals work to break down smog. Light pollution, however, destroys nitrate radicals in the air. This loss of nitrate radicals means that the level of smog within a particular city cannot be reduced at nighttime, leading to increased levels of air pollution as it compounds over time. This increased air pollution, in turn, has a negative impact on human health as well.