Episode 1.0: Blue Light Special #1
ADDITIONAL SHOW NOTES:
I didn’t include this in the podcast itself, but here’s how I think of the general ranges of colors within the visual spectrum, as I tend to categorize them, based on the resources I checked and my recollection of studies I have read about the effects of different wavelengths:
Violet is between 380 nm and 450 nm. Note that this includes UV-A light, which is 400 nm and shorter.
Blue light is wavelengths between approx 450 nm and 480/490.
Cyan light (”blue-green”) is wavelengths between approx. 480/490 and 520-ish.
Green light is wavelengths between approx. 500 or 520 and 560 or 570. This includes some light we would perceive as “yellow-green”.
SELECTED SOURCES:
“That Harvard Business Review article”
https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side
About half of the sources I looked at for a definition of blue light wavelengths:
https://www.britannica.com/science/blue-color
https://www.britannica.com/science/light
https://en.wikipedia.org/wiki/Visible_spectrum
https://en.wikipedia.org/wiki/Electromagnetic_spectrum
JOURNAL ARTICLES (NO PAYWALL)
Lamola, A. A., & Russo, M. (2014). Fluorescence excitation spectrum of bilirubin in blood: a model for the action spectrum for phototherapy of neonatal jaundice. Photochemistry and photobiology, 90(2), 294–296. https://doi.org/10.1111/php.12167
Woodgate, P., & Jardine, L. A. (2015). Neonatal jaundice: phototherapy. BMJ clinical evidence, 2015, 0319. Full text available here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4440981/pdf/2015-0319.pdf
An interesting note about this meta-analysis: Even they didn’t really try to talk about or in any differentiate between the wavelengths used in the studies they analyzed, which means that this paper is only moderately useful in helping doctors analyze the best practices for treatment of neonatal jaundice.. They’re clearly and understandable focused on serum bilibrubin levels - but they might be missing some forest for the trees.
An unhappy aside, here: Somewhat buried in this paper they also said: “Reports suggest a resurgence of kernicterus in countries in which this complication had virtually disappeared. This has been attributed mainly to early discharge of newborns from hospital.” I shall leave my astute listeners to connect those dots.
FULL TRANSCRIPT:
Welcome to Episode 1.0 of Starlight and Fireflies, a podcast dedicated to understanding and eliminating the harmful effects of artificial light at night.
This episode is the first of the “Blue Light Special” series. There’s a lot to go into in the topic of blue light - and new stuff is coming out every day - so this is 100% not the last episode about this.
One quick housekeeping note before we dive in: my aim for this podcast is to post one episode every two weeks, going up between Tuesday morning and Thursday night at some point. Didn’t make it this week, obviously, but hey! I got two episodes up!
I wish I could be more specific than that 3-day window, but I’m discovering my workflow in the creation of this thing is both more absorbing and more complex than I anticipated, and my desire and need for balance in my life means it’s gonna have to be bi-weekly.
Also, quick reminder that show notes, resources, and a full transcript are available for perusal at starlightandfireflies.com
First things first: I want to make one thing really clear - there’s a lot of conflicting information out there about blue light.
One study might come out and indicate that blue light exposure can help teenagers with depression or make them alert for morning classes. But then how does that track with the American Pediatric Association guidelines to limit children’s exposure to blue light, or that Harvard Business Review article you vaguely remember that talked about how our addiction to our smartphones is messing with our body clocks?!
I understand the temptation to chuck the whole issue into the bin because it’s all overwhelming and unclear and blue light is unavoidable anyway, right, because Sunlight Is A Thing and also because who, in 2020, is actually gonna give up their screens? Do the people who write these recommendations not understand how we live right now!?
[sigh] I see you, and I hear your frustration.
Generally speaking the questions people have about blue light fall into the same three categories.
1) What exactly is “blue light”?
2) What does it do?
3) Where does it come from?
We will tackle each of these in turn, no matter how many episodes it takes.
Let’s take a minute to define blue light, and then we can use that as a starting-off-point for all of the other complexities.
After all, in the context of any conversation, understanding what words mean is a critical component of communication. I mean, two people can agree on the importance of having a screwdriver handy while assembling a flat-pack bookcase, but there’s gonna be an issue somewhere down the line if one person means “phillips” and the other person shows up with some orange juice.
But this is the easy part - it is part of the visible spectrum of light, of course, but what are the actual specific wavelengths of blue light, as measured in nanometers? What are scientists and journalists talking about when they talk about blue light? Surely there’s an agreed-upon range of wavelengths that is scientifically defined as ‘blue light’.
Yeah, no. Nope.
I tried. I really tried to find a set definition of “blue light” - I went to no fewer than *8 separate sources* - even broke out some old textbooks! - and I could not find a single definition of blue light that matched *any other* definition. I found a number of ranges that overlapped on one end or the other, but nothing that agreed that “wavelengths between this nanometer and that nanometer are considered blue”.
According to the most specific definition, blue is the light with wavelengths between 436 nm and 495nm.
At the broadest definition I found, ‘blue light’ is any wavelength between 380 and 525 nm - but that also encapsulates all of the violet, and some of the green.
At first, when I was trying to sort through the sources and pin this down, I was just mad, because why couldn’t the science be more specific for crying out loud?
Then I realized: they ARE being so much more specific than “blue”, and that most of the scientific literature talks in terms of specific wavelengths of light, not just colors. But when the studies get digested into media-friendly bites, I think the nuances between blue or violet-blue or green-blue get lost, because the common denominator is “blue” and why devote column inches to the details when it doesn’t really change the message?
But I think as a result of this oversimplification, something weird happens. I think that when scientists and journalists (including me!), talk about the dangers of blue light to health and ecosystems, it’s easy for members of the public to dismiss reports or recommendations as irrelevant because the light they perceive is not what they think of as “blue”, and a consequence of that is that people may be exposing themselves to harmful wavelengths even when they think they are following the recommendations that will keep them safe.
For example: if you use “night mode” on your laptop or smartphone, it will shift over to a more-orange tint - sometimes REALLY orange, like mine is - but it hasn’t stopped emitting harmful wavelengths altogether. It’s still got some blue or green or violet in there, even if it doesn’t look like it.
And even when we talk about “white” light, which is the other color used in articles to talk about light, there are a LOT of people who literally cannot see the difference between a warm white light source and a cool white light source, but the difference in spectra and the possible exposure to harmful light between the two is real.
Or, to put it another way: you know the jokes about people looking at 40,000 different shades of white at the paint store and poking fun at someone insisting on the “distant gray” white over the “soft cloud” white, and how can anyone really tell the difference anyway?
It’s like that. Only in light. Which matters a bit more. Because whether or not you are able to tell the difference between eggshell and ecru paint, it isn’t really a matter of health or safety as far as I know.
But in light, the difference between a 5200k bulb and a 2700k bulb - even if you can’t see the difference yourself - can absolutely affect your health. We really need to talk about “harmful” light vs simply “blue” light because a lot of the sources out there that emit harmful wavelengths don’t look blue.
It may really seem like I’m splitting hairs here, but the being specific about wavelengths is critical in some situations, and I’m going to illuminate that point by talking about a beneficial application of blue light.
Neonatal jaundice, specifically hyperbilirubinemia, is caused by an excess of bilirubin in the blood. It’s a surprisingly common condition effecting up to 80% of pre-term newborns and 50% of full-term babies in the first week of life. It usually goes away on its own, BUT if high levels of bilirubin are left untreated, bilirubin can have neurotoxic effects, called “kernicterus”, which can cause cause an acute or chronic encephalopathy that may result in cerebral palsy, hearing loss, and seizures, among other things.
In really severe cases, the “gold standard” for treatment is a replacement blood transfusion, but there is evidence that even at lower levels of bilirubin in the blood there is the potential for neurotoxicity.
It’s really common, and seems really scary, so it’s more than a little awesome that there is a safe treatment available: phototherapy using blue lights.
In a nutshell, the electromagnetic waves from the light source react with the bilirubin molecule, and a photochemical process called “conjugation” happens, and it goes from a fat-soluble, blood-brain-barrier-crossing-molecule to a one that is water soluble and can be removed harmlessly by the baby’s GI system.
Originally the therapy for this was simply sunlight, but then someone figured out that if you just use blue light by itself, you don’t have to risk newborns getting sunburned. The problem is, light is still energy even if it’s not UV, and there is a real risk of overheating an infant if the intensity is too high or there are too many “wasted” or ineffectual wavelengths present.
Older recommendations for this specific blue-light therapy were as broad as between 400-500 nanometers, which is the entirety of the blue band, from violet to green. But in 2011 the American Academy of Pediatrics recommended a much narrower spectral range of between 460 and 490 nm, which is more of what we would perceive as “cyan” or blue-green light.
In 2014, in a study published in Photochemistry and photobiology, Angelo Lamola and Marie Russo found the specific wavelength that best ‘conjugated’ bilirubin in blood - 476 nm. This study looked at bilirubin levels in blood samples only, not in babies; but the calculations they made in the in vitro model replicated the results of a separate, earlier, clinical study which found that a fluorescent light source that peaked near 490 nm - or more blue-green - is significantly more effective than one peaked near 450nm, or more pure blue.
These findings added even more support to the AAP’s narrower recommendations, and they conclude: “light between 460 and 490 nm is most effective for phototherapy of neonatal jaundice and that light outside this range is primarily absorbed by hemoglobin and uselessly heats the infant.”
Then in 2015, a meta-analysis authored by Drs. Woodgate and Jardine, published in The BMJ Clinical Evidence, looked at 14 different in vivo studies to try and determine any best practices for hospital phototherapy of hyperbilirubinemia.
They ended up with a list of unanswered questions, but they DID find that LEDs meant less time under the lamps compared to quartz or halide bulb, which makes sense and is a great use of LED tech. They also found that “blue-green light was more effective than blue light” for treatment, which echoes both the AAP recommendations and the 2014 in vitro study.
And THIS is where the specific wavelengths MATTER.
Because if you’re a parent with a jaundiced infant and you are reassured that this safe and simple treatment might be able to save your precious child from brain damage, wouldn’t YOU like to know that the lights the hospital is using are the ones that are, at the very least, following the American Academy of Pediatrics guidelines?!
In that 2014 study, the authors cited the “super-blue lamp” as being the preferred lamps in hospitals for neonatal phototherapy , and specifically mentioned the Philips TL20W/52. This sounds like it should be fine, but it has a peak wavelength emission at 450nm, which is absolutely NOT the clinically, evidence-based recommended wavelength for this application.
What’s even WORSE is that this bulb’s spectral range is, according to the manufacturer, between 400-500nm, which is the old guidelines, and means it’s not only emitting a much much wider range of wavelengths than recommended, it’s getting into low-energy UV territory of 400nm.
And I know this because of the manufacturer’s own data sheet/sales leaflet; I’ve got the PDF linked in the show notes if you want to see it, but THEY ACTUALLY CALL IT THE “JAUNDICE TL/TL-D”
I wish I could say the leaflet I found is outdated and that they re-jiggered it to reflect the clinical best practices AND the AAP recommendations but, no, it’s from October 2019.
Remember - the entire point of the recommendations limiting the range of wavelengths from the entire blue side of the spectrum to the narrowest, most effective band is to avoid overheating newborns while treating them for jaundice to avoid damage to their brains.
Do YOU want to bet a baby’s health that a hospital administrator who is ordering fluorescent light bulbs for an older machine in a NICU unit will double check the claims of a manufacturer?
Or that a busy neonatalogist is going to be 100% up on the latest recommendations AND ALSO know what wavelengths are being emitted by the machines they are using?
Talking about neonatal care with relatively high stakes is a really dramatic example of what I’m talking about: blue light is blue light is blue light, except when it isn’t - it’s cyan. Or violet. Or green. And which wavelength is more prevalent in the lights used for this therapy can make an actual difference in the outcomes for babies and their families. So doesn’t it seem important to be more specific than “blue light”?
Light can heal, and it can harm. I think it’s important that when we talk about the light that is in our environments and bathing our bodies, we talk about the wavelengths that are most prevalent, and do the most harm.
There is low hanging fruit there, in terms of ridding our environment and spaces of wavelengths that are damaging, and we will start with those.
And we shall, beginning next episode. We’ll tackle the exact wavelengths that can either mess up our circadian rhythms or make us bright-eyed and bushy-tailed on a dark winter morning, depending on who you ask.
In the meantime, remember that light is powerful. Use it carefully.
