LED street lights have caught the attention of the American Medical Association, which is calling for a ban on certain models of lamp. Paul Skelton reports.

LED street lights are bad for your health; at least, that’s what the American Medical Association (AMA) is saying… kind of.

The AMA is an association of medical professionals that aims to “promote the art and science of medicine and the betterment of public health”. Recently, physicians at the group’s annual general meeting tabled a report conducted by its Council on Science and Public Health entitled The Human and Environmental Effects of LED Community Lighting, which looked at the increasing popularity of LED street lights and the effect it was having on human- and animal-kind.

“Despite the energy efficiency benefits, some LED lights are harmful when used as street lighting,” AMA board member Maya A. Babu says.

“The AMA encourages proper attention to optimal design and engineering features when converting to LED lighting that minimise detrimental health and environmental effects.”

High-intensity LED lighting designs emit a large amount of blue light that appears white to the naked eye. This creates worse nighttime glare than conventional lighting.

Discomfort and disability from intense, blue-rich LED lighting can decrease visual acuity and safety, resulting in concerns and creating a road hazard, the AMA says.

“With the advent of highly efficient and bright LED lighting, strong economic arguments exist to overhaul the street lighting of roadways.

“Valid and compelling reasons driving the conversion from conventional lighting include the inherent energy efficiency and longer lamp life of LED lighting, leading to savings in energy use and reduced operating costs, including taxes and maintenance, as well as lower air pollution burden from reduced reliance on fossil-based carbon fuels.

“Not all LED light is optimal, however, when used as street lighting. Improper design of the lighting fixture can result in glare, creating a road hazard condition.

“LED lighting also is available in various colour correlated temperatures. Many early designs of white LED lighting generated a colour spectrum with excessive blue wavelength. This feature further contributes to disability glare (i.e. visual impairment) due to stray light, as blue wavelengths are associated with more scattering in the human eye, and sufficiently intense blue spectrum damages retinas.”

Accordingly, the report explains, significant human and environmental concerns are associated with short wavelength (blue) LED emission.

“The main reason for converting to LED street lighting is energy efficiency; LED lighting can reduce energy consumption by up to 50% compared with conventional high pressure sodium (HPS) lighting.  LED lighting has no warm up requirement with a rapid ‘turn on and off’ at full intensity. In the event of a power outage, LED lights can turn on instantly when power is restored, as opposed to sodium-based lighting requiring prolonged warm up periods. LED lighting also has the inherent capability to be dimmed or tuned, so that during off peak usage times (e.g. 1am to 5am), further energy savings can be achieved by reducing illumination levels. LED lighting also has a much longer lifetime (15 to 20 years, or 50,000 hours), reducing maintenance costs by decreasing the frequency of fixture or bulb replacement.

“But depending on the design, a large amount of blue light is emitted from some LEDs that appear white to the naked eye. The excess blue and green emissions from some LEDs lead to increased light pollution, as these wavelengths scatter more within the eye and have detrimental environmental and glare effects.

“The first generation of LED outdoor lighting and units that are still widely being installed are ‘4,000K’ LED units. 29% of the spectrum of 4,000K LED lighting is emitted as blue light, which the human eye perceives as a harsh white colour. Due to the point-source nature of LED lighting, studies have shown that this intense blue point source leads to discomfort and disability glare.

“More recently engineered LED lighting is now available at 3,000K or lower. At 3,000K, the human eye still perceives the light as white, but it is slightly warmer in tone and has about 21% of its emission in the blue-appearing part of the spectrum. This emission is still very blue for the nighttime environment but is a significant improvement over the 4,000K lighting because it reduces discomfort and disability glare. Because of different coatings, the energy efficiency of 3,000K lighting is only 3% less than 4,000K but the light is more pleasing to humans and has less of an impact on wildlife.”

Disability glare is defined by the Department of Transportation (DOT) as: “Disability glare occurs when the introduction of stray light into the eye reduces the ability to resolve spatial detail. It is an objective impairment in visual performance.”

“This glare can be greatly minimised by proper lighting design and engineering. Glare can be magnified by improper colour temperature of the LED, such as blue-rich LED lighting,” the AMA says.

“LED lighting is inherently a bright point source and can cause eye fatigue and disability glare if it is allowed to directly shine into human eyes from roadway lighting.

“Much has been learned over the past decade about the potential adverse health effects of electric light exposure, particularly at night. The core concern is disruption of circadian rhythm. With waning ambient light, and in the absence of electric lighting, humans begin the transition to nighttime physiology at about dusk; melatonin blood concentrations rise, body temperature drops, sleepiness grows, and hunger abates, along with several other responses.

“It is estimated that a white LED lamp is at least five times more powerful in influencing circadian physiology than a high pressure sodium light based on melatonin suppression. Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep time, dissatisfaction with sleep quality, nighttime awakenings, excessive sleepiness, impaired daytime functioning and obesity.”

In addition to its impact on drivers, blue-rich LED streetlights operate at a wavelength that most adversely suppresses melatonin during night. It is estimated that white LED lamps have five times greater impact on circadian sleep rhythms than conventional street lamps. Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning and obesity.

The detrimental effects of high-intensity LED lighting are not limited to humans. Excessive outdoor lighting disrupts many species that need a dark environment. For instance, poorly designed LED lighting disorients some bird, insect, turtle and fish species.

Recognising the detrimental effects of poorly-designed, high-intensity LED lighting, the AMA encourages communities to minimise and control blue-rich environmental lighting by using the lowest emission of blue light possible to reduce glare. The AMA recommends an intensity threshold for optimal LED lighting that minimises blue-rich light. The AMA also recommends all LED lighting should be properly shielded to minimise glare and detrimental human health and environmental effects, and consideration should be given to use the ability of LED lighting to be dimmed for off-peak time periods.

The guidance adopted by grassroots physicians who comprise the AMA’s policy-making body strengthens the AMA’s policy stand against light pollution and public awareness of the adverse health and environmental effects of pervasive nighttime lighting.