The Sun is the main source of light on Earth, providing us with sunlight that sustains all kinds of life on Earth, from plants to humans. However, radiation from the Sun is actually lethal, which is why the Earth has its own natural sunscreen to protect the surface from excessive UV light. What is this natural sunscreen? It’s a section of the Earth’s atmosphere known as the ozone layer.
What is the Ozone Layer?
Located in the stratosphere, the ozone layer serves as protection for life here on Earth. Acting like a sponge, the ozone layer absorbs most of the sun’s ultraviolet radiation, or powerful, short light waves that can greatly injure living organisms if exposed to a large amount. Ultraviolet radiation has two major types: UVB and UVA. UVB has infamously been recognized as the culprit behind skin conditions like sunburns as well as cancer in various skin cells, such as basal and squamous. UVA, on the other hand, was originally interpreted as harmless due to its inability to cause burns. Nevertheless, scientists have now discovered the possibility that UVA may be more harmful than UVB, as it is able to penetrate deeper into an organism, causing a more lethal form of skin cancer known as melanoma and premature aging. However, because of ozone, a trace gas located in the ozone layer, 98% of this harmful UV light is absorbed, preventing UV radiation from going past the ozone layer and instilling detrimental effects on humans.
Causes of Ozone Depletion
However, the ozone layer has been depleting, or gradually thinning out due to numerous causes that often involve human activities. A prominent reason is chlorofluorocarbons, which are molecules containing carbon, chlorine, and fluorine that are present everywhere, from refrigerants to propellants. Because they are relatively cheap to acquire and nonflammable, numerous companies utilize these chemicals in their products. However, once CFCs evaporate into the atmosphere, they quickly deplete ozone molecules by compromising their ability to reform themselves after they break apart. In addition, because they are noncombustible and highly volatile, CFCS can rapidly evaporate and reach the stratosphere, where the ozone layer is present.
Global warming also plays a crucial role in the depletion of the ozone layer, as an increase in greenhouse gasses lead to heating of the troposphere and cooling of the stratosphere. Lower temperatures result in the formation of polar stratospheric clouds, which house chemical reactions that convert halogen compounds into chlorine, one of the key chemicals in ozone depletion. Continuous ozone loss can also add to the cooling effect, as there is less heat being released in the stratosphere due to a lack of ozone for UV radiation to react with.
Effects of Ozone Depletion
Ozone depletion can instill a myriad of undesirable effects on organisms inhabiting Earth, especially humans. The increase of UV radiation reaching the surface of the Earth can impair an individual’s vision by damaging their eye lens or cornea, leading to conditions such as photokeratitis, cataracts, and even blindness. Additionally, UV radiation can damage DNA by hindering DNA replication and transcription, putting stress on the cells and the organism; they can also promote different types of oxidative DNA lesions as well as DNA breaks, leading to mutations occurring in the DNA strand. The most prominent effects of increased UV radiation exposure however are present on the skin. Because the skin is usually the most exposed to UV radiation, a surge in harmful radiation can result in an increased rate of sunburns and skin cancers such as melanoma, which is often fatal. An increased risk of skin cancer is also due to the fact that UV radiation hampers with the immune system of organisms. In small amounts, UV radiation is only able to limit the skin’s reaction to local attacks, but when radiation is present in large amounts, it is able to lower an individual’s immunological reactions to diseases or germs. With a weakened immune system, individuals are unable to fight off infectious diseases and cancers, which can worsen the effects that these illnesses have on the person or animal.
The effects are not limited to direct impacts on an individual’s physical being. An increase of UV radiation can also disrupt developmental processes of crops and cause mass amounts of these plants to die out. This can result in a shortage of food for the human population and even cause a famine if the issue is not addressed. Furthermore, an increase in production of hydrogen peroxide can occur, which has adverse effects on not only humans, but plants and outdoor materials as well. Hydrogen peroxide can also pollute drinking water, making it unfit for human consumption and causing a shortage of water for humans.
What Has Been Done?
The government has made several attempts to reduce the impact of human activities on the ozone layer. Beginning in 1987 with the Montreal Protocol, which required countries to begin phasing out CFCs, countries who followed the protocol were able to decrease their consumption of ozone-depleting chemicals by 90-95% by 2005. Specifically in the US, the Environmental Protection Agency, or EPA, has created a considerable amount of regulatory programs following the Montreal Protocol, such as ODS Phaseout and Destruction, Exemption, and Labeling programs to name a few. The EPA has also introduced educational and outreach programs to teach the public about health concerns associated with ozone depletion.
How to Protect Yourself
In order to protect individuals from increased UV radiation, the EPA stresses the importance of the UV index, which is a scale used in the US to help people avoid harmful exposure to UV radiation.
0-2: individuals do not need protection. People can stand outside safely with minimal sun protection
3-7: individuals should seek shade from late-morning to early afternoon. Sunscreen should be applied on exposed skin and protective clothing should be worn as well as a wide-brimmed hat and sunglasses
8+: extra protection is needed. Along with protective clothing, a wide-brimmed hat, and sunglasses, a minimum of SPF-15 broad spectrum sunscreen should be applied to exposed skin. Seek shade if one’s shadow is shorter than themselves.
A convenient method to interpret how much UV exposure one is exposed to is using The Shadow Rule. If your shadow is longer than you, your UV exposure is usually lower. On the other hand, if your shadow is shorter than you, your UV exposure is high. Individuals should seek shade and protect their skin and eyes
Sun safety is a topic often prioritized when educating the public in order to prevent more serious health problems such as skin cancers or cataracts. Some steps that the EPA recommends are
Apply sunscreen and wear protective clothing when going outdoors. Seek shade when possible.
Avoid sun tanning and tanning beds, as they can cause skin cancer and wrinkling
Do not burn your skin. Sunburns greatly increase an individual’s lifetime risk of developing skin cancer.
Any new or changing moles should be evaluated by a dermatologist, as it may indicate melanoma. Early detection can save an individual’s life
Be careful around environments that reflect the damaging rays of the sun, such as areas of water, snow, and sand
Always check the UV Index when going outdoors, as it provides useful information about the amount of UV radiation outside
Going out in the sun is not the only method of getting Vitamin D. There are safer alternatives such as a diet with foods containing Vitamin D or vitamin supplements
With ozone depletion still being a prominent issue today, it is crucial that individuals are educated on the topic and understand the causes as well as know how to protect themselves if the issue persists or worsens. The Sun may be the thing that keeps life sustained on Earth, but it is also capable of threatening the survival of organisms, which is why the ozone layer must be maintained to protect humans and the environment from receiving too much UV radiation.
Works Cited
(1) “Action Steps for Sun Safety.” EPA, Environmental Protection Agency, 2022, https://www.epa.gov/sunsafety/action-steps-sun-safety.
(2) “Addressing Ozone Layer Depletion.” EPA, Environmental Protection Agency, 2022, https://www.epa.gov/ozone-layer-protection/addressing-ozone-layer-depletion.
(3) Anwar, Fakhra, et al. “Causes of Ozone Layer Depletion and Its Effects on Human: Review.” Atmospheric and Climate Sciences, Scientific Research Publishing, 31 Dec. 2015, https://www.scirp.org/journal/paperinformation.aspx?paperid=63065#ref1.
(4) Costa, Hilary, et al. “Ozone Layer.” Education, 2022, https://education.nationalgeographic.org/resource/ozone-layer/.
(5) “Is There a Connection between the Ozone Hole and Global Warming?” Union of Concerned Scientists, 27 July 2017, https://www.ucsusa.org/resources/ozone-hole-and-global-warming#:~:text=Does%20global%20warming%20have%20an,that%20lead%20to%20ozone%20loss.
(6) Mullenders, Leon H. F. “Solar UV Damage to Cellular DNA: From Mechanisms to Biological Effects.” Photochemical & Photobiological Sciences, The Royal Society of Chemistry, 26 July 2018, https://pubs.rsc.org/en/content/articlelanding/2018/pp/c8pp00182k.
(7) “Suppression of the Immune System from Increased Ultraviolet-B Exposure Due to Ozone Depletion.” Suppression of the Immune System from Increased UV-B Exposure Due to Ozone Depletion, http://www.ciesin.org/TG/HH/ozimmun.html#:~:text=Suppression%20of%20the%20Immune%20System%20from%20Increased%20Ultraviolet%2DB%20Exposure,in%20animals%20and%20human%20beings.
(8) Tang, X., and S. Madronich. “EFFECTS OF INCREASED SOLAR ULTRAVIOLET RADIATION ON TROPOSPHERIC COMPOSITION AND AIR QUALITY.” UNEP Environmental Effects of Ozone Depletion: 1994 Assessment, https://sedac.ciesin.columbia.edu/ozone/UNEP/chap6.html.
(9) “Unusually Cold Stratosphere Causes Substantial Ozone Loss in the Arctic in 2016.” World Meteorological Organization, 6 Dec. 2019, https://public.wmo.int/en/resources/meteoworld/unusually-cold-stratosphere-causes-substantial-ozone-loss-arctic-2016#:~:text=Low%20temperatures%20give%20rise%20to,very%20efficient%20at%20destroying%20ozone.
(10) “UV Index Scale.” EPA, Environmental Protection Agency, 2022, https://www.epa.gov/sunsafety/uv-index-scale-0.
コメント