Excessive blue light emitted by light emitting diodes (LED) can adversely impact human health, according to a report recently released by the American Medical Association (AMA) Council on Science and Public Health. The report looked at LED street lighting on U.S. roadways. While LED lighting has several advantages, the excessive blue light it emits can be harmful. The human eyeperceives the large amount of blue light emitted by some LEDs as white. Blue light directly affects sleep by suppressing the production of the hormone melatonin, which mediates the sleep-wake cycle in humans.
Compared with conventional street lighting, the blue-rich white LED street lighting is five times more disruptive to sleep cycle, the report said. Although more research is needed, evidence available suggests a long-term increase in the risk for cancer, diabetes, cardiovascular diseases and obesity caused by chronic sleep disruption due to exposure to blue light.
The excessive blue wavelength contributes to glare effects as a result of larger scattering in the human eye.
Contrary to the popular notion that bright LED lighting increases road safety, the report says discomfort and disability glare caused by unshielded, bright LED lighting negatively impacts visual acuity, thus “decreasing safety and creating road hazards”.
Glare forms a veil of luminance that reduces the contrast, thus in turn reducing the visibility of a target. The report also notes that unshielded LED lighting causes papillary constriction, leading to “worse night-time vision between lighting fixtures.” Intense blue spectrum can even damage the retina.
The correlated colour temperature (CCT) of first-generation LEDs, which are currently used, is 4,000K. Higher CCT values indicate greater blue light emission, and in the case of 4,000K LED lighting, 29 per cent of the spectrum is emitted as blue light.
However, at 3,000K, the blue light emitted is only 21 per cent and appears “slightly warmer in tone”. While discomfort and disability glare is reduced, there is only a 3 per cent drop in energy efficiency compared with 4,000K LED lighting.
More attention should be paid to proper design, shielding and installation so that no light shines above 80 degrees from the horizontal, the report says.
Unless blue-light emission from 4,000K LED street lighting is restricted, retrofits using these lamps could result in 2.5 times increase in lighting pollution, said a study (World Atlas of Artificial Night Sky Brightness) published in the journal Science Advances,
“Strong consideration should be made for effective shielding and limiting CCT of outdoor lighting to 3,000 Kelvin or lower,” the AMA recommends.