Once only a concern for astronomers studying distant planets, the effects of light pollution on human well-being are being examined more closely. In addition to saving energy turning off the lights may be a healthy choice.
How the Circadian Clock Affects the Human Body
The circadian clock or twenty-four hour light dark cycle exerts effects on multiple physiological processes including brain wave patterns and hormone levels. Circadian rhythms control up to fifteen percent of our genes.
Clear links have been made between the presence of light pollution and chronic lack of sleep which in turn decreases the body’s immune response. In the northern latitudes higher levels of suicide and homicide are common in the summer months when there is nearly constant sunlight, as opposed to the expected increase during the months of darkness.
The Link Between Artificial Light and Melatonin Levels
Melatonin is a hormone produced by the pineal gland within the brain. It regulates sleep cycles and has some antioxidant properties. Melatonin levels are highest just before bedtime but melatonin is produced during the night. Exposure to constant artificial light causes melatonin levels to drop.
Cancer, Melatonin and Artificial Light
Melatonin helps control the production of estrogen. When melatonin levels are lowered, as happens with light pollution exposure, estrogen levels rise and the risk of estrogen related tumors such as breast cancer is increased. Melatonin also has been shown to block the growth of prostate cancer cells and in one study it improved survival rates for 9 of 14 patients. Many prostate cancer cases have low levels of melatonin.
Artificial Light, Pregnancy and Neonatal Development
Pregnant night shift workers, exposed to artificial light throughout the night, have a higher risk of late term miscarriage or stillbirths. This may also be linked to the increased estrogen levels caused by reduced melatonin.
In neonatal intensive care units it has been found that infants exposed to constant light are slower to develop a circadian rhythm. Infants in units where lighting was cycled slept through the night sooner and gained weight more quickly. There is also some limited evidence that children’s visual development may be affected.
Research into the effects of early exposure to light pollution on the development of mood disorders is also underway. Constant exposure to light is also a risk factor for the development of myopia, or short sightedness in children. But some are cautious as these same children are likely to be exposed to more television and computer activity as well.
The increasing evidence for negative effects of light pollution on wildlife and human health along with the benefits of reduced energy usage make turning off the lights an easy decision.
Dawn M. Smith - A vet nurse, Dawn has worked in wildlife rehabilitation and conservation around the world in addition to her veterinary hospital ...
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