These models combine our understanding of how ozone-depleting substances affect the ozone layer, of how changes in ozone affect UV radiation and of how UV radiation affects the incidence of skin cancers. For example, one global model suggests that by the successful implementation of the Montreal Protocol will be preventing about two million skin cancers every year.
A longer-term model focussed on health effects in people born in the USA between and This model estimates that protecting the ozone layer will have prevented a total of approximately million cases of skin cancers and 2.
This includes million cases of malignant melanoma. As yet there are no long-term world-avoided models for skin cancers globally. However, all the existing models lead to the same conclusion. Uncontrolled ozone depletion would have substantially increased the risk of skin cancers worldwide. Exposure to high levels of UV radiation leads to an increased risk of cataracts.
Cataracts are responsible for around half of blindness world-wide, equivalent to about 20 million people in [WHO6]. At the moment a world-avoided model for cataracts is only available for the USA. This model indicates that failure to control ozone depletion effectively would have led to almost 63 million additional cataract cases in people born in the USA between and As well as skin cancers and cataracts UV radiation can have other health effects.
These effects include the production of vitamin D in the skin that is beneficial to health. In the world we live in now, with effective protection of the ozone layer, there is a balance between the positive and negative effects of UV-B [WHO4]. Had we failed to protect the ozone layer that balance would have swung dramatically towards the negatives, above all the increased risks of skin cancer and cataracts.
By avoiding these negative consequences, the Montreal Protocol has made a major contribution to good health and well-being, one of the sustainable development goals adopted by all United Nations Member States in Over the course of evolution, animals, plants and microbes have developed mechanisms that allow them to cope with the variation in UV-B radiation that they experience in their normal environments, protected by the intact ozone layer.
This includes the plants and animals that we all rely on for our food. Crops need sunlight for photosynthesis, so cannot avoid exposure to UV-B. As with human health, there is a balance between the positive and negative effects of UVB on plants. Uncontrolled ozone depletion would have shifted this balance very much towards the negative. Increased exposure to UV radiation can damage aquatic food chains and cause direct damage to crustaceans and fish eggs.
As a result, uncontrolled ozone depletion would have threatened fisheries and other aquatic resources that make a significant contribution to global food supply. These suggest that a 10 per cent reduction in stratospheric ozone might reduce plant production by about 6 per cent.
If this relationship holds for the very severe ozone depletions expected in the world avoided then uncontrolled ozone depletion would have substantially reduced crop production globally.
Overall, while we cannot yet quantify the loss in food production, it is clear that without the Montreal Protocol ozone depletion would have made it progressively harder to deliver the sustainable development goal of zero hunger.
Just as uncontrolled ozone depletion threatens food production, it also threatens plants, animals and microbes in natural ecosystems. As with crops, wild plants are able to cope with current levels of UV-B radiation, but their growth can be reduced by large increases in UV-B.
Most animals also seem to be able to avoid the damaging effects of current levels of UV-B radiation. Even so, damage to plants would reduce the food available for herbivores, with consequences for the whole food web. They contain micro-organisms, animals and plants that provide us with half of the oxygen we breathe and much of the food we eat.
A healthy ocean is vital to our survival. In the oceans, lakes and rivers UV-B has adverse effects on many different aspects of the biology of organisms across the food web. Through these effects on ecosystems, large-scale increases in UV-B could alter the exchange of carbon dioxide between the atmosphere and the biosphere.
Increased UV radiation also stimulates the breakdown of decaying leaves and other organic matter. Together, the effects of increased UV-B would reduce the ability of ecosystems to trap carbon dioxide, including carbon dioxide produced by human activities.
In this way, large-scale ozone depletion would have worsened the build-up of carbon dioxide in the atmosphere that is causing climate change. Changing UV-B also alters the cycling of nitrogen and other chemicals in the environment, which may worsen air pollution.
Exposure to UV-B also damages natural and synthetic materials. Vulnerable materials include wood, plastic, rubber and even the materials used in some solar panels. These materials, widely used in buildings, agriculture and commercial products, are already designed to minimize the damage caused by UV.
This would have led to more rapid deterioration and the need for additional UV protection, increasing the cost and reducing the reliability of many products. In the s, the global community decided to do something about ozone depletion. With growing evidence that CFCs were damaging the ozone layer and understanding of the many consequences of uncontrolled depletion, scientists and policy makers urged nations to control their use of CFCs. They are the first international environmental treaties to be universally endorsed by nations of the world.
The Vienna Convention for the Protection of the Ozone Layer was adopted in and entered into force in Where ozone is formed, peak concentrations usually occur during afternoon hours, when sunlight is the most intense.
However, areas downwind of major sources of VOC and NOx may experience ozone peaks in the afternoon and evening, after wind has carried ozone and its VOC and NOx precursors many miles from their sources.
Thus, high ozone concentrations can occur in remote areas and at various times of day, including during the early evening or night. Figure 1: U. This map depicts ozone concentrations by U. All orange, red, and purple areas exceeded the 8-hour ambient air quality standard for ozone during The map illustrates how likely it may be for a particular area to experience air quality advisories for ozone.
Ozone has two properties of interest to human health. First, it absorbs UV light, reducing human exposure to harmful UV radiation that causes skin cancer and cataracts. Second, when inhaled, it reacts chemically with many biological molecules in the respiratory tract, leading to a number of adverse health effects. This course addresses this second property.
Review Key Points. Skip to main content. Giuliana: This was , before you could just plot something in Excel and email it to your adviser or your coworkers.
Susan said the researchers were charting their data and pinning it to bulletin boards in the airplane hangars at the Punta Arenas airport. So you had all these scientists testing different theories, plotting the concentrations of everything from chlorine monoxide radicals to nitrous oxide, but pinning the plots to the same boards, then standing around and comparing notes with each other. OK, so what if we, you know, we plot these things together? What is that telling us? These things are correlated.
What does it mean? She also describes the collaborative nature of the field campaign as a truly formative experience for an emerging scientist. Susan Strahan: We were just excited that we were getting the answers.
This is really important. This matters to all of us. Kerri: Wait, but if Susan Strahan was making her measurements in , that means the Montreal Protocol was ratified before we knew that CFCs were causing the ozone hole? Giuliana: Actually, yes. The work to put the Montreal Protocol into place began as a way to put an end to the kind of slow ozone depletion that Sherry Rowland and Mario Molina proposed.
Mario Molina, Sherry Rowland, and Paul Crutzen were jointly awarded the Nobel Prize in Chemistry for their work showing how CFCs and other industrial chemicals were depleting stratospheric ozone—the first time the prize had been awarded for environmental science.
Giuliana: Well, sort of. Because the ozone-depletion reaction in the Antarctic is dependent on the presence of those tiny ice particles in the stratosphere, the size of the hole is controlled by the stratospheric temperature. This year happened to be an exceptionally warm year, so the hole was pretty small.
The best estimate says that the ozone hole should be fully recovered by the end of this century. Susan Strahan: The road to recovery is really bumpy. We are. But if you wait and you look at decade-over-decade changes, then you start to see a trend. Giuliana: And some of the bumps along the way are caused by humans, too.
In fact, the rate of decline had slowed to half of what it should have been. The Chinese government and an international organization called the Environmental Investigation Agency have begun to crack down on these manufacturers.
So despite the immense success of the Montreal Protocol and the ensuing healing of the ozone hole, we have to be vigilant. Susan Strahan: Even though we think of the ozone hole, or the ozone layer, as sort of a solved problem—because we did come up with an effective solution—this was a reminder that that solution is only effective as long as everybody plays by the rules.
Mario Molina: What is common to these two problems is they are both global—namely, they are consequences of the emission of certain compounds, gases, that remain for quite some time in the atmosphere.
You cannot solve climate change or stratospheric ozone just by stopping emissions in a few countries. You have to do it all over the planet.
Giuliana: As an aside, because CFCs are also very potent greenhouse gases, the Montreal Protocol is the global policy that has had the biggest impact on slowing climate change. Kerri: Oh, nice. It shrinks the ozone hole and it slows warming. How did the world get on board with banning them and then show so much reluctance to do the same with greenhouse gas emissions?
Burning fossil fuels is much more central to our entire way of life. And ozone depletion happened much more quickly than climate change, which made it harder to ignore. Susan Strahan: The ozone hole was a really dramatic phenomenon. It was like, bam, half the ozone layer over Antarctica is gone and comes back later, but every year it goes away. It makes it a lot harder to get everybody on board.
Giuliana: Well, Susan Strahan was careful to say that evidence-based policy making requires really good, unambiguous, unbiased science. And Mario Molina said something similar.
Science can only tell us what will happen if society does certain things. Ozone depletion was a real, potentially catastrophic issue, and the world came together to solve it. Susan Strahan: The big lesson is science and policy can work together to solve big problems. Ozone destruction was an existential threat. Scientists did their science, they wrote up a big consensus report to show to policy makers around the world. We can implement these and go forward to solve this problem.
I think the climate change problem is harder. Tune in next month for another exciting episode. This episode was written by me, Giuliana Viglione, and produced by me and Kerri Jansen. Sabrina Ashwell is our copyeditor. Contact the reporter.
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How the world came together to heal the ozone layer—and the lessons learned that can help in the battle against climate change by Giuliana Viglione December 17, Maps of ozone concentrations from September left and October right show the gradual healing of the ozone layer.
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