The Lighting Research Center of Rensselaer Polytechnic Institute is questioning some of the findings in a report on LED street lighting from the American Medical Association (AMA) – which advocates LED lighting, but urges caution on luminaire selection.
Last month, physicians at the AMA annual meeting adopted guidance on how street lighting planners should select LED lighting.
“Despite the energy efficiency benefits, some LED lights are harmful when used as street lighting,” said AMA board member Dr Maya Babu. “The new AMA guidance encourages proper attention to optimal design and engineering features when converting to LED lighting that minimise detrimental health and environmental effects.”
Cool-white LEDs (~5,000K) are more efficient than neutral white (4,000K) LEDs, which are more efficient that warm (3,000K) white LEDs, but the cooler the colour temperature, the more energy emerges as blue light. This is true of GaN+phosphor LEDs, the most common type by far.
According to the AMA:
High-intensity LED lighting designs emit a large amount of blue light that appears white to the naked eye and create worse night-time 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.
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.
Excessive outdoor lighting disrupts many species that need a dark environment – poorly designed LED lighting disorients some bird, insect, turtle and fish species.
It went on to recommend:
Proper conversion to community-based LED lighting, which reduces energy consumption and decreases the use of fossil fuels.
To encourage minimising and controlling blue-rich environmental lighting by using the lowest emission of blue light possible to reduce glare.
The use of 3,000K or lower lighting for outdoor installations such as roadways.
All LED lighting should be properly shielded to minimise 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.
The full AMA report: ‘2-A-16, Human and environmental effects of light emitting diode (LED) community lighting’, by the AMA Council on Science and Public Health (CSAPH), of is available here on the website of darksky.org.
Reading through it, it is largely a well thought-out report, modest in tone, and many of its points are valid for all lighting.
For example: No one should suffer glare from a streetlamp, nor should too much light from one impinge on the windows of nearby dwellings.
And bearing in mind emerging science on possible links between blue light and poor sleep, it contains the following caution: “Strong consideration also should be given to the use of filters to block blue wavelengths (as used in Hawaii), or to the use of inherent amber LEDs, such as those deployed in Quebec”.
However, it is not perfect, and the Lighting Research Center appears to be most unhappy with the report’s rigour.
LRC’s arguments include:
Predictions of health consequences depend upon an accurate characterisation of the physical stimulus as well as the biological response. Without both nothing meaningful can be stated about the health effects of any light source.
Apart from certain people, blue light hazard from InGaN LEDs is probably not a concern to the majority of people in most lighting applications due to natural photophobic response.
Disability glare and discomfort glare are mostly determined by the amount and distribution of light entering the eye, not its spectral content.
InGaN LED sources dominated by short wavelengths have greater potential for suppressing the hormone melatonin at night than sodium-based sources commonly used outdoors. However, the amount and the duration of exposure need to be specified before it can be stated that InGaN LED sources affect melatonin suppression at night.
Until more is known about the effects of long-wavelength light exposure (amount, spectrum, duration) on circadian disruption, it is inappropriate to single out short-wavelength radiation from InGaN LED sources as a causative factor in modern maladies.
“The LRC’s response attempts to draw attention to the problem of misapplying short-hand metrics to the topic of light and health and also provides the reader with a wealth of references that should inform rational discourse,” said the LRC.
The full Lighting Research Center report is here.
For those interested in street lighting and LED lighting, it is worth reading both reports, which only takes a few minutes in each case.