Thursday, November 3, 2011

Light Pollution’s Medical Effects

Excessive light is a problem for everyone, not just amateur astronomers-

People  well aware of the  many problems associated with light  pollution, such as energy waste, sky glow, and environmental impact. But not many  people know about the burgeoning growth  of research that demonstrates direct  human-health issues related to excess  light. In fact, health effects might ultimately be the most important reason to  control light pollution. The energy wasted  by excessive lighting is produced mainly by burning fossil fuels, leading directly to air pollution that causes higher asthma  rates and increased respiratory problems  for people with lung disease and other  medical issues.   
Glare is the most common health  safety problem resulting from poorly  designed outdoor lighting. You have probably noticed poor vision stemming from  glare on a dirty windshield. Over time, calcifications build up in the lenses of  our eyes, which eventually develop into  a cataract. These calcifications and other  lens and eye imperfections scatter light  in a similar fashion to a dirty windshield.  This effect grows more severe with age,  and it’s the primary reason why elderly  people have a diffi cult time driving at  night near poorly designed streetlights.  Most people with this problem are not  even aware that glare is the main cause  of their poor night vision, and that they  could drive more safely if streetlights were  properly designed. Recognizing this fact,  the American Medical Association (AMA)  adopted a resolution in 2009 urging full  shielding for all public street lighting.
A hot new area of research is how  night light disrupts our circadian rhythm.  Numerous papers over the past 15 years  have led medical researchers to conclude  that night light increases the incidence  of certain cancers, most notably breast  cancer. In fact, researchers now estimate  that up to 30% of breast cancers may be  due to light at night suppressing circadian rhythm. The research basis for this  conclusion has become so compelling that  the World Health Organization recently  declared circadian-rhythm disruption to  be a class 2A carcinogen — placing it on  the same level of severity as the effects of  tobacco smoke on lung cancer.
The biochemical mechanism for this  problem has been thoroughly researched  and is thought to result from the suppression of melatonin production by the  pineal gland in the center of our brain.  This gland produces melatonin while we sleep. Repeated exposure to light at night  markedly suppresses melatonin production. Previous research has shown that  this hormone helps the immune system  suppress the development of several types of cancers.



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