Blue light and our bodies

by Simon Jones

This week I want to look at two applications of blue light. One, we talk about regularly in our popular biomedical Engineering for Life show; using blue light as a means of treating the disease jaundice. The other you may have come across on the news recently, that blue light could be disrupting the sleep patterns of millions. So what is it that makes this blue light so special?

Let’s start with light as a source of energy…

In fact, light is energy, in the form of an electromagnetic wave. But there isn’t just one standard type of electromagnetic wave doing the rounds in our lives – there are actually many different kinds of light (indeed, the electromagnetic spectrum is continuous, so you could argue there are infinite variations of light). But keeping things straightforward; we know there are different ‘kinds’ of light, from the obvious visible light that we see, to UV radiation which burns our skin, or X-Rays or radio waves, or even gamma rays as emitted in some nuclear reactions. All these different types of wave are a kind of light, which are situated on the electromagnetic spectrum.


Image: InductiveLoad (CC-BY)

The shorter the wavelength of light, the more energy it carries. From the spectrum above, we can see that gamma waves carry more energy than X-rays – both of which carry enough energy to be quite harmful to human cells in high doses. These in turn have more energy than visible light, which again has more energy than radio waves.

Looking at a spectrum of just visible light, we know it is made up of the ‘rainbow’ colours. The wavelengths of each of colours varies too. At one end of the spectrum we have red light, and at the other end blue light. That light appears blue to us precisely because it has a shorter wavelength than the red light on the electromagnetic spectrum.

Image: science made simple (CC-BY)

Image: science made simple (CC-BY-NC)

This therefore allows us to reach the conclusion that blue light has energy, and that it has the highest level of energy of the visible spectrum (i.e. what humans can see).

Blue light as a friend :)

So blue light has lots of energy, excellent! Luminous blue coffee all round. The great thing about blue light is that it is broadly speaking harmless, unlike its next door neighbour UV light who goes around causing harmful sun burns.

As engineers, we’ve made good use of blue light to solve a particular problem – the disease jaundice, which is common in new-born babies. Jaundice often occurs when a baby is born prematurely and is not fully developed, but plenty of full-term, fully developed babies are also born with mild jaundice. One of the last parts of a baby to develop is the liver, which in premature babies may not be fully developed, and thus not working properly. And, one of the jobs of the liver is to breakdown a waste product called bilirubin into proteins (which you can then effectively wee out). If a baby doesn’t have a working liver, this bilirubin chemical builds up in the body, and can appear in the skin as a yellow substance. This has the effect of giving the baby’s skin a yellow tinge.

Having waste products build up in the body is never good, but with blue light we found a solution. Blue light has enough energy that it can break down the bilirubin in the skin, just by shining on it. Believe it or not, this simple but effective solution really works. Engineers have designed special ‘blue beds’ on which babies can sleep and recover at the same time, without any discomfort. The chemicals in the skin are broken down effortlessly, and the solution is simple enough that it can be done at home – no need for lots of hospital visits! Here’s a photo of this happening in action:


“When I grow up I want to be a Na’vi”
Photo: Dave Herholz (CC-BY-SA)


Blue light as an enemy >:(

So that’s a man-made, directed solution which can help our bodies through jaundice. But recently in the news, there have been a lot of stories about the blue light of smart phones and other electronic devices disrupting our sleeping patterns. How does this work?

First of all it is still exactly the same science at play here; the same blue light on the electromagnetic spectrum. Our backlit gadgets often make use of light tinged slightly blue, even if our screens don’t look it, because blue light appears very bright whilst using relatively low battery power, which is desirable for consumers.

Here’s the problem: Just like the blue light energy was able to break down bilirubin in the skin with jaundice, blue light can also break down another chemical in our skin called melatonin. Melatonin is a hormone which helps us to sleep by regulating our sleep cycle. It makes us feel more awake when we are exposed to bright light (such as sunlight) and drowsy in the dark – effectively it is one of our own little biological clocks.

Now, if you’re a clever cookie you can see where the problem lies here. If we expose ourselves to blue light late at night, for example by reading emails on a laptop, then in the process we might be breaking down our melatonin levels, which in turn makes it harder for us to feel sleepy. This disrupted sleep might not make much of a difference, but consider how many people use backlit screens and how regularly they might do this before bed, and the problem starts to become a little more concerning. Not to mention that often we are using these devices in dark rooms, causing our eyes to squint and focus on a little bright screen, which isn’t doing our eyes any good either!


“Curse you infernal WhatsApp, I’ll never get a good night’s sleep now.”  Illustration by John Leech 1843 (Public Domain)

So – here’s a modern day challenge for us as software developers, product designers and the electronics engineers. How can we make our devices retain the same level of comfort in terms of brightness, but be healthier in the scheme of our lifestyles? These are the challenges we regularly discuss about in our Tomorrow’s Engineers: Around the World secondary school show. For more information on careers in engineering, be sure to check out the Tomorrow’s Engineers project!

Or, perhaps the easier option is just a shift in our attitudes, to one of not using bright lights in dark rooms for prolonged periods of time!


Curriculum Links

KS3 Biology in England and Wales:

Organ systems and how they support vital life processes.

How organisms affect, and are affected by, their environment, including the accumulation of toxic materials.

The tissues and organs of the human digestive system.

KS3 Physics in England and Wales:

The similarities and differences between light waves and waves in matter

light transferring energy from source to absorber, leading to chemical and electrical effects.

colours and the different frequencies of light, white light and prisms.

Scottish KS3 Biology:

Knowledge and understanding of the structure and function of organs of the body

Scottish KS3 Physics:

Learners explore the nature of sound, light and radiations in the electromagnetic spectrum.

Understanding of the properties of light and other forms of electromagnetic radiations.

Explain how light can be used in a variety of applications.

Northern Ireland KS3 Physics:

Sound and Light

We have a wide variety of engineering shows for primary, secondary and family audiences.

We also work in partnership with Tomorrow’s Engineers to inspire the next generation of engineers!


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Posted in Biology, Engineering, Physics