Ozone Layer Depletion

Everyone says that the best way to protect yourself from the sun’s rays is to wear sunscreen. But nothing beats the best sunscreen of all – the ozone layer.

And best of all, no application required.

Since its discovery, we constantly hear those in the science field tell us that it is being destroyed due to human activity. And unless we all do something about it, this ozone layer depletion is bound to get worse – here is everything you need to know about it. 

illustration of science

But if you have been regularly following the news, you may have heard the recent reports saying that the ozone layer hole is the smallest that it has ever been.

This is incredible news that affects the entire world, but why exactly should you be concerned about it?

To better understand why the depletion should be taken seriously and why we need to keep taking measures to replenish it, you must first get a good grasp of what there is to know.

What is it and Why is it Important?

You are probably aware that a shield is created to protect the one holding it from harm. However, other parts of the body are still vulnerable, because the shield can only cover certain areas at a time.

The layer is like that, but it envelops the entire world. This protection is the main reason why this invisible layer is important to every living creature.

It consists of ozone molecules that are naturally occurring. This layer is called as such because it contains the highest concentrations of ozone, and it is where that and oxygen are continuously formed as part of the ozone-oxygen cycle.

This cycle that continuously occurs is essential in the prevention of harmful radiation emitted by the sun from entering the Earth. This ultraviolet light is required in this cycle, which means that most of it will be absorbed by these molecules and what is left will pass through and reach Earth.

Without it, ultraviolet radiation can freely reach Earth without limits. And when it involves UV-B and especially UV-C, this will destroy not just the environment, but it will also cause deaths to living creatures in a short period of time.

blue sky

What Type of Rays are Filtered by it?

The sun produces large amounts of energy in different wavelengths, namely infrared radiation that we feel as heat, light that we see, and ultraviolet radiation or UV rays that cannot be seen or felt. Among these three, it is only the UV rays that get filtered by the ozone layer.

There are three different types of UV radiation, and they come with varying wavelengths:

  • UV-A has the longest wavelength, between 320 to 400 nanometers, and is not fully absorbed by this protective layer, which allows around 95% of it to reach Earth’s surface. However, it is considered relatively harmless.
  • UV-B has a shorter wavelength, measuring between 290 to 320 nanometers, and is considered more harmful. While it can be absorbed, it can also pass through if it the protective layer is depleted; the thinner it is, the more UV-B that can pass through and the greater its environmental and health effects, with sunburn being the most common effect.
  • UV-C is the most dangerous of all and comes with the shortest wavelength, only measuring between 100 to 290 nanometers. With the protective layer, UV-C rays are completely absorbed, why it does not reach Earth, which is a good thing because we do not have any natural defenses against this particular UV ray.

These UV rays can cause great damage especially in large quantities, that is why the presence of this protection is vital to prevent overexposure to it.

What Does it Do?

You are already aware that it acts like a shield for the Earth, but what exactly does this layer do?

While it prevents dangerous UV radiation from reaching Earth, it is not capable of completely blocking all UV rays. What it does is to make it harder for the UV radiation to pass through it, and only allowing the weaker and less harmful ones to penetrate it.

Because of the ozone layer, the most harmful UV-C is absorbed by molecules present and is prevented from entering Earth.

When it comes to the UV-B, it can be absorbed, but not all the UV-B present will be absorbed by these molecules. The amount of UV-B that passes through it will depend on the thickness of the layer itself.

On the other hand, most UV-A can pass through. Although considered the safest, UV-A can still pose harm if you are exposed to it in large amounts or for prolonged periods.

Where is it Located?

To know where it is located, you must first understand what is present above the Earth’s surface.

There are five main atmospheric layers present, but our main concern here is the stratosphere, which is the second layer from the Earth’s surface. While the two lowest layers, namely the troposphere and stratosphere, both contain ozone, the stratosphere contains the largest amount of this molecule. This large concentration is what we call the ozone layer.

The stratosphere is the only layer that is well-equipped to handle these unstable molecules and for longer periods, as it is known as the stable or stratified layer and lacks vertical convection that allows the molecules to move up. However, it is not synonymous to the stratosphere, since this layer is only confined in the lower region that is just above the troposphere.

While the stratosphere is roughly 10 km above the earth’s surface and spans 50 km high, the ozone layer is only found about 20 to 30 km above the earth. Unlike the stratosphere, the thickness of the ozone layer varies depending on the location and the season.

What is the Difference Between Bad and Good Ozone?

If we talk about ozone, most people think of it negatively – that it only causes harm and should be avoided. However, it is not always bad. There is also some that is good, and it is important to understand the difference between them.

The good stuff is what is found in the stratosphere, specifically in the protective layer. As we already mentioned, this naturally-occurring layer is responsible for protecting us against harmful UV rays emitted by the sun. Because of this, it is important to take measures not to destroy it. The more of it that is present in this atmospheric layer, the better protected we are.

This is not the case for the bad stuff, which is present in the troposphere. The stuff present here is due to pollutants coming from vehicle emissions, industrial facilities, and other sources that produce volatile organic compounds and nitrogen oxide that react with sunlight. This kind of ozone that is produced at the ground level forms what we know as smog, which is known to be harmful to everyone.

Ground level ozone, or the bad stuff, has various health effects if you get exposed to it, such as:

  • May cause respiratory issues or exacerbate already existing conditions
  • Trigger eye irritation
  • Damage or kill plants
  • Make it difficult to breathe
  • Damage lung tissue and cause scarring
  • Increase susceptibility of plants to various stressors, such as diseases and pests
  • Agricultural yield reduction

diseased plant

Complicating matters is the fact that the bad portion is insoluble in water, which means our bodies are incapable of processing it. When the gas is ingested, it will simply pass through the lungs without being broken down. And because it is very reactive, it will immediately trigger various health issues and could even cause death.

The difference between them makes it clear why good ozone must be constantly replenished and bad ozone must be eliminated, or at least limited, with the latter being one of the main reasons for the creation of the Clean Air Act.

How is Good Stratospheric Ozone Formed?

While the bad stuff is man-made in some way because it involves man-made processes, the stratospheric particles we consider good is formed naturally.

21% of the molecules found in the entire atmosphere are oxygen, and this oxygen is crucial in the formation of ozone, together with ultraviolet radiation. The UV rays coming from the sun split up the oxygen molecules in the stratosphere to form two separate oxygen atoms. When a newly unattached oxygen atom collides with an oxygen molecule, it will immediately react and combine with it to form the ozone molecule. This molecule has three oxygen atoms present, two from the existing oxygen molecule and the other one is the free oxygen atom.

Because the air is thinner the higher it is in the atmosphere, the oxygen needed to create it are also fewer in number. On the other hand, the UV light necessary in this process decreases at it moves towards Earth. The stratosphere is the best location to form it because it meets the balance between the required UV light and oxygen molecules.

When Was the Hole Discovered?

Do you recall the time when the ozone layer hole was discovered and everyone was alarmed by it, fearing that it will immediately cause major damage to the whole world? It was a very significant issue back then, but some people are still unclear why this discovery was monumental. Whether or not you already have an idea why its discovery is crucial, it is important to correct any misconceptions about it.

In the past, it was believed to be just another gas found on earth. It was not until years later that scientists began to come up with the idea that this gas is vital to the planet and can absorb the UV rays coming from the sun. And in 1913, two French scientists named Charles Fabry and Henri Buisson discovered the actual presence of a layer abundant in ozone.

Another shocking discovery will be made decades later, but this time spurring the entire world into action.

In 1984, a low level of ozone was discovered in Syowa, Antarctica, as it dropped to less than 200 Dobson Units. This contradicted the belief of scientists back then that levels tend to be steady. After all, records showed that these levels have remained the same for decades. However, this particular drop was not given much attention then, as they believed that this finding is insignificant.

The following year was monumental, as it was then confirmed by Joe Farman, Brian Gardiner, and Jonathan Shanklin that the level has indeed dropped in Antarctica and in more than one station. Initially thought of as incidents of malfunctioning equipment, they discovered that the levels have started dropping beginning in 1979, especially during spring. The historical low was 220 Dobson Units, but the level during that year was 194 Dobson Units and continued to decrease years later.

Unfortunately, the recorded level in 1985 was only 124. Not only that, the layer over the South Pole has dramatically decreased, with its thickness only two-thirds of what it was several decades ago. This thinning in that area then became known as the Antarctic Ozone Hole.

The misconception about the newly discovered hole caused widespread alarm, as the public believed that it is a literal hole that will allow the UV rays to freely reach Earth and cause harm to people, especially to those who are directly underneath the hole.

This “hole” should not be taken literally, as there is no actual hole. What happens is that the amount present drops to less than 220 Dobson Units in a specific area, and this mainly occurs in Antarctica and the Arctic region. The hole being referred to is the areas of the layer that has less than that amount.

Scientists have discovered that this occurs seasonally, particularly during spring, because temperatures increase and more reactions occur in Antarctica, which then affects the levels that will also affect the size of the hole.

What Causes The Depletion and the Hole?

Over the years, we have been told that certain chemicals cause the depletion and create the hole. However, this is not fully understood by most people, largely owing to the confusion about what exactly the hole is. Since we have already clarified what this hole is, what happens next is to understand what causes this phenomenon.

You may be wondering why it is typically associated with Antarctica. Aside from being where the hole was discovered, this location also provides the ideal condition for ozone depletion to occur.

The main culprit for this depletion is the CFCs, or chlorofluorocarbons. Scientists discovered that these chemicals that were widely used in aerosols and common household appliances, like refrigerators and air conditioning units that use freon, did not undergo any form of decay nor had any reaction with other chemicals while in the troposphere, even for years; they just remain stuck in the atmosphere. It is when these CFCs reach the stratosphere where they wreak havoc.

A specific type of cloud known as nacreous clouds, often called ‘mother of pearl’ clouds, is one of the main causes of the holes. These clouds, including ice crystals, can only be formed in the layer and during wintertime when the temperature drops to -78 ℃ in the stratosphere. Prevalent in Antarctica, these conditions are ideal for surface chemistry to occur, while the ice crystals present in these clouds draw CFCs closer to it.

When CFCs reach the stratosphere and react with UV radiation, it breaks apart these CFCs and releases various gases, the most dangerous of which is the highly reactive chlorine. Once a chlorine atom interacts with an ozone molecule, it destroys it by getting the third oxygen atom from the molecule and produces the unstable chlorine monoxide molecule (ClO).

Once this new molecule meets a free oxygen atom, the oxygen atom part of the chlorine monoxide molecule will interact with it and form a new oxygen molecule. Because the chlorine is now a free atom once more, it can again interact with another molecule and destroy it. This destruction occurs faster than the time it takes to replenish lost molecules, causing depletion and increasing the size of the hole.

Unfortunately, it is not just chlorine that can destroy these molecules. Bromine, which is also often released by CFCs together with chlorine, as well as other chemicals and compounds like hydrofluorocarbons, halons, methyl chloroform, hydrocarbons with bromine, and carbon tetrachloride, are also known to cause ozone depletion.

With all these depleting substances, it is no wonder we were all caught off-guard when the hole was discovered and at an already noteworthy size.

What is Happening to the Hole?

Since its discovery, scientists have begun taking a closer look to understand what is happening to the hole. After the events in 1985, they realized that the problem is more serious than they initially thought, and that this worldwide problem has been the result of human activities over the years.

Using products and equipment that contain ozone-depleting substances, especially CFCs, were so widespread for decades, nobody expected that it would greatly affect the layer in a matter of time. And as more research came, it became evident that unless the world does something about it, the hole is bound to get bigger. Worst of all, it can have fatal consequences in the future.

To put a stop to this, world leaders decided to craft policies that will limit the depletion. The first one was the United Nations Vienna Convention for the Protection of the Ozone Layer, which was ratified in March 1985. While the Vienna Convention was a landmark agreement because all countries involved in it also became signatories and promoted the increase in research involving the ozone layer, it did not take an active stance in terms of its protection.

The Montreal Protocol on Substances that Deplete the Ozone Layer that was created in September 1987 is a different story. It supplemented the Vienna Convention by aiming to phase out the depleting substances, or ODS, in terms of both its manufacture and consumption. Like the Vienna Convention, the Montreal Protocol was also a landmark agreement because 196 countries ratified the agreement and it was adapted worldwide.

It initially aimed to cut down the production and use of CFCs and other substances that destroy the ozone layer in the entire world by 1999. Over the years, the Montreal protocol has been revised many times and they eventually came up with the goal of completely banning these substances by the year 2000. The urgency was felt by some countries, that they even started the ban years before the set deadline.

Even with the protocol in place, scientists are aware that it will take time before it can recover. Because these substances are stable, which means they remain in the atmosphere even after decades, scientists do not expect it to be gone until around 2040 to 2070.

After all, record lows in levels were discovered in the mid-1990s when chlorine and bromine present in the atmosphere reached peak levels. And this is why it seems impossible for the hole to disappear in just a few years.

If you recall, we have received some very good news recently. Because the number of CFCs present in the atmosphere have been in constant decline over the years after reaching record highs, the hole has also begun to show signs of being repaired, which has now led to the smallest hole since this hole was discovered. This is proof that the Montreal Protocol is effective.

While it was human activities that caused the depletion, it is also human intervention that is now fixing it.

How Does It Affect Human Health?

Depletion became such a big deal for everyone because of its perceived impact on the human health, especially due to the misconceptions. Because the term ‘hole’ was used, the general public took it literally and believed that this hole will allow all the sun’s rays to get to earth. They thought that since they already get bad sunburns now, how much worse would it be if it has a hole?

If more ozone molecules are being destroyed than replenished, severe sunburns are the least of your worries. You can look forward to the following health issues with the increased exposure to the UV rays, particularly to UV-B, brought about by depletion:

  • Skin cancer, including the non-melanoma kind
  • Development of melanoma considered malignant
  • Cataracts, which often lead to blindness
  • Snow blindness and other forms of photokeratitis
  • Damage to the cornea, retina, conjunctiva, and lens of the eyes
  • Compromised immune system
  • Polymorphic Light Eruption
  • Eye diseases
  • Premature skin aging and other forms of skin damage
  • Pterygium

sun screen

You may have noticed that the health impacts brought about by depletion are limited to the skin, eyes, and the immune system. It has also been discovered that while everyone can experience these health effects, those who are fair-skinned are more vulnerable to the various skin conditions mentioned here. This is because darker-skinned people have more melanin that also serves as protection against UV rays.

Many of these health issues have permanent effects, that is why it should be taken seriously. And if you are not yet aware, it can even have fatal consequences.

Remember all these when you go outside in a particularly hot day without slathering on some sunscreen.

What Impact Does It Have on Plant and Animal Life?

Think again if you believe that the impact of depletion is limited to humans. Sadly, plant and animal life are also vulnerable to the effects of too much exposure to UV radiation.


While certain plants are resistant to UV-B, many of them also have properties that protect them from radiation. Think of these plants having their own version of the ozone layer and only allowing small amounts of radiation to pass through.

Despite these defenses, scientists have confirmed that plants can still be badly affected by a depletion of 10% or higher. If this happens, certain plants may experience the following negative effects:

  • Cell changes that can result in irregularities with the pollination cycle, varying flowering times, and stunted plant growth
  • Greater susceptibility to plant diseases
  • Imbalance in terms of plant and herbivore competition
  • Decrease in yield
  • Issues with photosynthesis
  • Decline of nitrogen-fixing bacteria

Do note that because plants have different reactions to UV-B, exposure to it even in large amounts will have an unequal impact to these plants; some may be severely affected while others may have little reaction to it. UV-B can also be beneficial to some plants, but not if it gets overexposed to it, which is the case if the depletion continues.

turtle swimming in the ocean


Animals are also not spared from the harmful effects of UV-B overexposure due to depletion. Its effects on animals is quite similar to that of humans, as it also mainly affects their eyes, skin, and immune system.

If it is depleted and they get overexposed to UV-B, animals may acquire the following:

Humans and animals seem to be more affected by this scenario than plants, since only plants get to recover during the months when the hole is smaller. This respite is crucial because if plants are not given time to recover from too much UV-B exposure, which is what will happen if the ozone stops being replenished, it can drastically affect the food supply of both humans and animals alike.

Fortunately, we are likely to avoid this scenario because we are already reaping the benefits of the Montreal Protocol. With the banning of the depleting substances, the hole is getting smaller, which reduces our chances of experiencing these impacts, or at least experiencing them less severely.

We are one step further away from the worst-case scenario that we were all afraid of.

2 Minute Summary:

There is more to fear about the depletion than getting extremely sunburned.

Scientists have proven that the size of the hole is detrimental to all living things here on Earth.

The bigger the hole present, the greater its negative impact.

With the continuous depletion, we are all prime candidates for the acquisition of various health issues, particularly involving our eyes, our immune system, and our skin.

How does getting cataracts and becoming blind sound to you?

Or the acquisition of various illnesses because you have a weaker immune system?

But worst of all, we can also die from it, because skin cancer is a very real possibility.

Not only that, we can also die from starvation, as both plants and animals alike are also affected by it.

They can also die from it.

And when they die, our food source is affected.

One of the worst things you can possibly do is to underestimate the impact of the depletion.

Because if you do, you can get first hand experience of its fatal consequences.

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