Seeing long-term energy efficiency benefits, many cities and towns have recently replaced their old street lights with new LED technology. But, in doing so, they may be harming sleep patterns and putting the health of humans (and other animals) at risk, says a new American Medical Association "guidance" report.
The AMA says certain high-intensity LEDs can produce a "disability glare" and "prison atmosphere." Residents of Davis, California, Cambridge, Massachusetts, and elsewhere, have complained about "4000K" lights and campaigned to get the lighting replaced with less harsh "3000K" types, or, failing that, at least shielded, so they don't scatter light so widely.
More seriously, the 4000K LED units emit 29% of their luminance as blue light that humans perceive as a harsh type of white light, the AMA says. Research, while not conclusive, suggests this light could have serious health consequences—more so than conventional street lighting.
"Brighter residential nighttime lighting is associated with reduced sleep time, dissatisfaction with sleep quality, nighttime awakenings, excessive sleepiness, impaired daytime functioning, and obesity," the report says. "White LED street lighting patterns also could contribute to the risk of chronic disease in the populations of cities in which they have been installed."
Blue light, whether from street lights, tablets, or phones, is thought to disrupt our circadian rhythm, which, at dusk, normally reduces our body temperature, suppresses appetite, and makes us sleepy. Some researchers even think blue light is associated with certain cancers.
Cities and towns need to balance the financial savings from installing some LED lights with the public health implications. The AMA recommends "3000K or lower lighting for outdoor installations such as roadways," and that municipalities shield their lights, and consider dimming them in off-peak periods.
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