Physician warnings about LED street lights come as Xcel and the City of Minot already are making the switch to the new lighting.

In June, the American Medical Association released guidelines for use of LED lights, stating that there can be adverse safety consequences in converting from conventional street lights to the energy efficient LED lights. Specifically, glare and eye discomfort can occur if light is allowed to shine directly toward the eye, the association stated.

Xcel Energy has launched a multi-year effort to upgrade all its cobra head, high-pressure sodium street lights to LED solid-state units. In April, Xcel Energy finished converting 3,500 street lights across North Dakota, including about 1,200 in Minot, to LED.

Minot doesn’t have many city-owned LED lights at this time, said Lance Meyer, city engineer. The main areas are on 37th Avenue Southeast. New LED lights also will be going in as part of work on 37th Avenue Southwest. The downtown is being converted to LED lights as construction on the infrastructure proceeds. Meyer estimated 115 to 120 LED lights will be installed downtown as part of that three-year project. A subdivision being developed in northwest Minot also will have some LED lights.

Both Xcel Energy and Minot have installed LED with the intensity of 4000 Kelvin. The AMA’s recommendation calls for 3000K, although it states the design, shielding and installation techniques can mitigate for a brighter light.

Matthew Lindstrom, media relations representative for Xcel Energy in Minneapolis, said the company did a thorough analysis before beginning its conversion program. The analysis included a review of LED lighting standards and best practices, examining data on the potential energy savings from LED lights, public safety, pedestrian and traffic benefits and neighborhood and community livability issues. Pilot programs were conducted in West St. Paul, Minn., Amarillo, Texas, and Denver.

“We evaluated a wide range of LED lights available and selected 4000K LED fixtures, which closely resemble the color of natural moonlight. They offer significantly more energy savings than other light sources that were evaluated at the time,” Lindstrom said in a prepared statement in response to an inquiry.

In its guidance, the AMA acknowledged that LED lighting leads to cost and energy savings. About 10 percent of existing U.S. street lighting has been converted and more is coming.

However, the AMA stated high-intensity LED lighting emits a large amount of blue light that appears white to the naked eye. Discomfort and disability from intense, blue-rich LED lighting can decrease visual acuity and safety, creating a potential road hazard.

Cities have been installing lighting that typically is 4000K or 5000K. The Kelvin scale is the measurement of temperature required to heat a metal object to that color. It does not refer to temperature of the LED, which is cool to the touch.

In comparison, daylight is equivalent to 6500K, and high pressure sodium lighting used in the street lights being replaced is 2100K, according to the AMA.

It is the amount of blue light in LEDs, which the human eye perceives as harsh white, that raises the AMA concern. The association reported 29 percent of the spectrum of 4000K LED lighting is emitted as blue light, which studies have shown leads to discomfort and disability glare.

The AMA recommends more recently engineered LED lighting of 3000K or lower. At 3000K, the human eye still perceives the light as white, but it is slightly warmer in tone, and has about 21 percent of its emission in the blue-appearing part of the spectrum.

“This emission is still very blue for the night-time environment, but is a significant improvement over the 4000K lighting because it reduces discomfort and disability glare. Because of different coatings, the energy efficiency of 3000K lighting is only 3 percent less than 4000K, but the light is more pleasing to humans and has less of an impact on wildlife,” the AMA stated in its guidance.

The AMA noted other concerns with LEDs are disruption to wildlife that require dark environments and the suppression of melatonin in humans, creating sleep disturbance. Surveys show brighter residential night-time lighting affects sleep.

Meyer, who only recently became aware of the AMA report, said the city’s LED lights are focused on the street to avoid impact to nearby houses. Light stops at the back of the neighboring sidewalk. Because the LEDs are more directional with less scattered light, there have been perceptions in the public that the lights aren’t as bright, he said.

Lindstrom said Xcel Energy’s LED street lights light the roadway and only three to five feet behind the pole to ensure that there is no light spilling into homes or businesses.

The new AMA guidance encourages proper attention to optimal design and engineering features to minimize detrimental health and environmental effects of LEDs.

In addition to using the lowest emission of blue light possible to reduce glare, the AMA recommends all LED lighting be properly shielded and be dimmed for off-peak time periods. To limit light shining directly into the eyes, installation should ensure that no light shines above 80 degrees from the horizontal.

Xcel Energy reports its lights meet that standard.

Meyer said the city relies on federal guidance, which is based on expert research, in determining the type of lights it installs and the angle of that lighting. He said the city has not received any complaints from the public related to eye discomfort because of the LED lights.