They can be.
On June 14th, 2016 the American Medical Association (AMA) issued an official new policy statement regarding the use of energy-efficient LED streetlights…and it comes with substantial words of caution.
About 10% of existing U.S. streetlights have been converted to LED lighting in an effort to cut costs, save energy, and reduce reliance on fossil-based fuels. And while these are very real and worthy benefits, the conversion to LED streetlights comes with a hefty health cost. The AMA puts the spotlight on proper design and engineering features to curtail the significant health and environmental hazards associated with high-intensity LED lighting.
How LED Streetlights Can Harm Health
LED streetlights emit high levels of blue light, which we see as white light. But blue light actually dissipates more in the human eye and high levels can damage the retina, producing a far worse nighttime glare than conventional streetlights do. The AMA warned that blue light can cause discomfort and decrease visual acuity, which can be hazardous to safety. LED streetlights may quite literally be a road hazard!
Blue light from LED streetlights also suppresses melatonin production in the body. This is why sleep experts recommend avoiding digital stimulation, such as working on computers, at night, as the blue light emitted from a computer screen can significantly lower melatonin, the hormone that promotes sleepiness. Large-scale studies link the use of artificial lighting at night to lack of sleep, reduced sleep quality, excessive sleepiness, impaired daytime functioning, and even obesity. Researchers estimate that blue-rich LED streetlights alter our circadian sleep rhythms more than conventional high pressure sodium lamps do by a factor of 5!
The AMA’s Recommendations
According to the AMA, safe LED lighting is all in the design. The AMA recommends using a color temp (CT) of no more than 3000 Kelvin (K). Color temp measures how much blue, green yellow, or red is emitted from a light. The higher the CT, the more blue light is emitted. However, in cities such as Seattle and New York City, which have already begun converting their streetlights to LED, the CT falls in the 4000-5000 K range.
And 3000 K may not even be a low enough recommendation, as it doesn’t account for the relative amount of each color produced. Another measurement to be considered is correlated color temp (CCT), which changes according to the content of each wavelength of light. So two different 3000 K LED streetlights could actually be emitting vastly different outputs of blue light.
The AMA’s specific recommendations include: “minimizing and controlling blue-rich environmental lighting by using the lowest emission of blue light possible to reduce glare…and the use of 3000K or lower lighting for outdoor installations such as roadways. All LED lighting should be properly shielded to minimize glare and detrimental human and environmental effects, and consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods.”