Light Pollution
A new phenomenon
Light pollution is a relatively new phenomenon, found mostly where city lights diminish the view of the nighttime sky. As urban areas grow, so does this form of pollution. According to the U.S. National Park Service, the glow from some cities due to outdoor lighting has been shown to diminish views of night skies in national parks over 200 miles away. Light pollution exists in two forms, sky glow, which is the brightening of the night sky due to outdoor lighting scattered in the atmosphere, and glare, which is the direct shining of light. Light pollution results from outdoor lights aimed upward or sideways, with the light scattering in the atmosphere and reflecting back to the ground. Particles in the atmosphere responsible for air pollution accentuate light pollution by increasing the amount of light scatter. According to the International Dark-Sky Association, light sources that emit blue light are particularly disruptive to night skies due to greater light scattering.
What is an LED?
You’ve probably heard the term “LED” before but what exactly is a light-emitting diode and how does it differ from other lighting products. LEDs are semiconductor devices that produce visible light when an electrical current passed through them. Incandescent bulbs, on the other hand, produce light using electricity to heat a metal filament until it becomes “white” hot or is said to incandesce. Fluorescent lamps, meanwhile, work by ionizing mercury vapor in a glass tube. This causes electrons in the gas to emit photons at UV frequencies. LEDs are used in a wide range of applications, from traffic lights and vehicle brake lights to TVs and refrigerators. LEDs are “directional” light sources, which means they emit light in a specific direction, unlike incandescent and compact fluorescent bulbs, which emit light and heat in all directions. For this reason, LED lighting is able to use light and energy more efficiently in many applications.
Street lighting
Although many would argue that replacing conventional street lighting with light-emitting diodes would cuts costs and save energy, the American Medication Association last year warned of potential hazards related to LEDs. High-intensity LED lighting emits a large amount of blue light that appears white to the naked eye and creates worse nighttime glare than conventional lighting, according to the AMA. Discomfort and disability from intense LED lighting can decrease visual acuity and safety for drivers, resulting in concerns and creating a road hazard. Faulty LED lighting has also been shown to disorient some bird, insect and fish species. Due to the threat poorly designed LED lighting holds, the AMA has encouraged local bodies to control blue light-rich environmental lighting by using the lowest emission of blue light possible to reduce glare. The AMA also recommends an intensity threshold for optimal LED lighting that minimizes blue-rich light.
Too much light?
According to a recent article in the journal Scientific Reports, extreme exposure to light at night can have an adverse effect on a person’s immune and endocrine systems. Using nocturnal hamsters as their subjects, Ohio State University researchers divided the animals into two groups. One experienced days and nights as usual, the other was exposed to dim light during their regular sleeping period. The scientists found that the hamsters exposed to light pollution gained a noticeable amount of weight. They also found that the offspring of those hamsters, raised in normal conditions, had impaired immune systems and decreased endocrine activity compared to the offspring of the hamsters kept in normal conditions. The researchers concluded that the hamsters’ DNA was altered by the negative effects of light at night and that the study reinforced research tying light pollution to certain forms of cancer and other fatal medical conditions.
Saving energy
According to the U.S. Department of Energy, the average American household wastes .5 kilowatt hours of energy every night on outdoor lighting, enough to power a 50-inch plasma TV for one hour. To reduce the problem of light pollution in your community, consider installing fixtures equipped with motion sensors or incorporating timers that provide you with light only when you need it. Dimmer switches will allow you to softly illuminate areas where you spend time outdoors after dark. The type of light fixtures you install around the exterior of your home greatly affect the amount of light pollution you generate. Shielded fixtures prevent light from spreading upward, where it isn’t needed. Since these types of fixtures concentrate light where it is used, lower-wattage bulbs are often sufficient. And if you’re constantly disturbed by a neighbor’s bothersome lighting, don’t be afraid to suggest that more efficient lights could help you as well as their energy bill.
Trusted by thousands of listeners every week, T. Glenn Pait, M.D., began offering expert advice as the host of UAMS’ “Here’s to Your Health” program in 1996. Dr. Pait began working at UAMS in 1994 and has been practicing medicine for over 20 years.