Blue light is enough of a worry that computer and smartphone vendors such as Apple have introduced a special mode, Night Shift, that shifts the LED displays on devices to warmer colour temperatures.
Astronomers who can no longer see the stars because in many parts of the world night never falls are also up in arms over increased blue light glare interference.
Don't go overboard with lighting up the globe at night and think about the technology used to illuminate places is the common sense message from the International Dark-Sky Association.
Sadly, that message is falling on deaf ears.
We won't be able to avoid LEDs which are are here to stay, Dr John Barentine, the director of conservation at IDA.
"The global lighting market has made its choice, and that choice is LED," Barentine said.
"What we need now is to encourage people to design and deploy LED technology properly", Barentine added.
They will be deployed everywhere too: the New Zealand Transport Authority and local councils want cool temperature LED lamps to light up highways and certain city streets.
This is to replace existing high and low pressure sodium lights which won't be available for much longer.
I asked NZTA why it wants to give us the roadside light blues by switching over to cool white LEDs and Fergus Tate from the authority kindly provided a detailed response.
First, NZTA acknowledges that blue light is an emerging area of concern but Tate said the research is inconclusive, in its early stages and there's no evidence that it is risky.
"The greatest risk is likely to come from interior lighting as the time of exposure is longer, hence a trend toward 3500K ("warm white") for interior LED sources," Tate said.
Barentine also said that he doesn't believe there is evidence that outdoors ALAN from LEDs constitutes a health risk as exposure to it is transient and the doses are relatively low.
However, we don't fully understand what effect low, sustained levels of ALAN exposure has on humans, Barentine said. ALAN disrupts circadian rhythms of living beings with potentially huge negative impact on people's long term health.
Blue moon?
If blue light is a worry, why does the NZTA specification for LED luminaries say they should have a high colour temperature of 3900 to 4250 Kelvin or cool white? Warmer LEDs in the 3000K range emit a great deal less blue light.
The answer centres on the colour of moonlight being pleasant to people.
"Neutral white 4000K LED light mimics moonlight and is generally well tolerated by the human eye," Tate said.
The LEDS are like moonlight argument is found in sales material from vendors such as Phillips Lumens as well, but how true is it?
Barentine disputes that 4000K LEDs are like moonlight in colour, and provided a spectral graph to show the difference between the two.
"The fact that moonlight has a correlated colour temperature of about 4000 Kelvins doesn't mean its light is anything at all like a white LED with a CCT of 4000K," Barentine said.
LED lights bears no resemblance to any natural light on Earth, he added. More to the point, the graphs show that 4000K LEDs emit a large amount of blue light in the 350 to 500 nanometre spectrum - which neither the sunlight reflected from the moon and filtered through the Earth's atmosphere, or warm 2200K LEDs do.
Lee Mauger of the Martinborough Dark-Sky Association did some testing during the last supermoon with a light meter. He pointed it to the moon, and measured under a 4000K streetlight.
"The brightness under a streetlight was more than 100 times than that of a full 'supermoon'!" Mauger said.
On the other hand, cool white LEDs have much better colour rendition than 2700K sodium lamps that "make people look like corpses", Barentine said.
Does better colour rendition make cool white LEDs safer then? Tate said that white light from LEDs for instance is generally considered more safe than the yellow light from high pressure sodium lamps.
Confusingly, that doesn't seem to apply to road lighting though.
"There is no evidence that white light is more or less safe than high pressure sodium [lamps] at route lighting levels," Tate said.
Even though 4000K is NZTA's preferred colour temperature the authority is in fact OK with 3000K LEDs under some circumstances.
"In areas seeking Dark Skies certification to aid astro-tourism activities, the NZ Transport Agency will support the installation of 3000K luminaires, Tate said.
Mauger and MDSA campaigned for 3000K lights on state highway 53, and won that battle.
Warmer LEDs aren't more expensive. Cool white LEDs used to be far cheaper far and easier to find than the warmer 3000K lights.
In 2018 that's no longer the case, Barentine said. Nor are 3000K LEDs any less efficient than their cooler cousins.
NZTA is conducting studies on road lighting, and our Royal Society will issue an advisory publication on the impact of blue light.
LEDs are supposed to have long, 20-30 year life spans (unless their driving electronics give out earlier). Given the strong suggestion that blue light LEDs are bad for us without offering any tangible benefits, why not look to the future and go for warmer road lights instead?
