Light Pollution

Cities and towns are shifting their outdoor lighting to LED bulbs (Light Emitting Diodes) because they use less energy and fuel to burn and are more environmentally friendly.  They last longer and ultimately will be cheaper. The cities of New York and Seattle have replaced, or are in the process of replacing, all their street lights with white LED bulbs at a color temperature of 4000 – 5000k.  Why then did this environmentally friendly and economically sound decision result in the American Medical Association (AMA) issuing a statement condemning this practice?

It seems that the older less efficient street lamps or incandescent bulbs had a color temperature of 2400 K or less Candle light is actually a bit less than 1800 CT. At the higher color temperature the light contains more of the blue spectrum of light which has a shorter wavelength than the former incandescent bulbs which had more yellow and red. The result is that the new bulbs produce significant glare resulting in pupillary constriction and reduced vision. In addition, blue light scatters more on the retina and at sufficient levels can damage the retina in addition to making driving and night walking more difficult.

The American Medical Association believes the white LED light suppresses natural production of melatonin by the brain more than five times what the former bulbs were capable of. This has a major effect on human’s circadian rhythm and ability to fall asleep. For the animal kingdom it can adversely affect the migratory pattern of animals and can adversely affect aquatic animals such as turtles and their nesting and reproductive habits.

The AMA statement called for using the lowest level of blue wavelength light possible to reduce glare. They encourage the use of 3000k or less CT for outdoor lightings and roadway lighting to reduce glare and improve safety.  They additionally asked for dimming of these lights for off peak periods. They did not condemn or call for a ban on LED lights just for municipalities to be aware of the dangers of using the products with a high color temperature (CT) above 3000k and blue wave length predominant light.

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