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examBoard: Cambridge
examType: IGCSE
lessonTitle: Ozone Depletion Health Effects
The ozone layer is a fragile shield of gas that protects Earth from harmful ultraviolet (UV) radiation from the sun. When this protective layer is damaged, more UV radiation reaches Earth's surface, leading to serious health consequences for humans and the environment.
Key Definitions:
The ozone layer acts like Earth's sunscreen, absorbing about 97-99% of the sun's medium-frequency UV radiation. Without this protection, life on Earth would suffer severe damage from the sun's radiation. The ozone layer is naturally thin, equivalent to just 3mm thick if compressed to sea-level pressure, making it vulnerable to disruption.
When ozone-depleting substances (ODS) like chlorofluorocarbons (CFCs) reach the stratosphere, UV radiation breaks them down, releasing chlorine or bromine atoms. One chlorine atom can destroy over 100,000 ozone molecules in a chain reaction before being removed from the stratosphere, creating a significant multiplier effect from even small amounts of pollutants.
Human activities have been the primary driver of ozone layer damage over the past century. Understanding these causes helps us address the problem effectively.
Once widely used in refrigerators, air conditioners, aerosol sprays and foam insulation. CFCs are extremely stable and can remain in the atmosphere for 50-100 years.
Used in fire extinguishers, these compounds contain bromine which is even more destructive to ozone than chlorine - up to 10 times more effective at breaking down ozone molecules.
Methyl bromide (pesticides), carbon tetrachloride (solvents) and hydrochlorofluorocarbons (HCFCs) also contribute to ozone depletion, though at lower levels than CFCs.
When the ozone layer thins, more UV radiation reaches Earth's surface. This increased exposure has serious consequences for human health, particularly affecting the skin, eyes and immune system.
The skin is our first line of defence against environmental hazards, but it's highly vulnerable to UV damage.
Increased UV-B exposure causes painful sunburn in the short term. Over time, it leads to photoageing - premature wrinkles, leathery texture and age spots. This happens because UV radiation damages collagen and elastin fibres that keep skin firm and elastic.
The most serious skin effect is increased risk of skin cancers. These include:
Scientists estimate that for every 1% decrease in ozone, there's a 2-3% increase in skin cancer cases.
Our eyes are particularly sensitive to UV radiation, with several conditions linked to increased exposure.
Cataracts (clouding of the eye's lens) are the leading cause of blindness worldwide. UV exposure accelerates cataract development. Studies suggest a 1% decrease in ozone could lead to a 0.5% increase in cataract cases. Photokeratitis (snow blindness) is a painful, temporary UV burn of the cornea from intense short-term exposure.
UV radiation also contributes to:
Children are especially vulnerable as their lenses allow more UV light to reach their retinas.
Less visible but equally concerning is UV radiation's impact on our immune system's ability to defend against disease.
UV radiation can suppress immune function in several ways:
This immunosuppression can lead to:
Australia has one of the highest rates of skin cancer in the world, partly due to its proximity to the Antarctic ozone hole. Two in three Australians will be diagnosed with skin cancer by age 70. The country spends over AU$1 billion annually on skin cancer treatment, more than any other cancer. In response, Australia launched the successful "Slip, Slop, Slap" campaign (slip on a shirt, slop on sunscreen, slap on a hat), later expanded to include "Seek" shade and "Slide" on sunglasses. This public health initiative has helped raise awareness and reduce skin cancer rates among younger generations.
Humans aren't the only ones affected by increased UV radiation. The environment also suffers significant consequences.
Increased UV-B damages phytoplankton, the foundation of marine food webs that produce about half of Earth's oxygen. It also harms fish eggs and larvae, coral reefs and can disrupt the delicate balance of marine ecosystems. Studies show UV-B can penetrate up to 20 metres in clear water, affecting even deep-dwelling organisms.
Plants exposed to excessive UV-B show reduced growth, smaller leaves and lower crop yields. Some crops like rice, wheat and soybeans are particularly vulnerable. UV radiation can also reduce photosynthesis efficiency and make plants more susceptible to disease and pests, threatening food security.
The discovery of the ozone hole in 1985 prompted unprecedented global cooperation to address the problem.
Signed in 1987, the Montreal Protocol is widely regarded as the most successful international environmental agreement ever. It phased out the production and consumption of ozone-depleting substances. Key achievements include:
While the ozone layer is slowly healing, the process is gradual. The Antarctic ozone hole still forms annually, though its size has generally decreased since 2000. Scientists estimate that without the Montreal Protocol, by 2065 the ozone hole would have been 40% larger and ozone depletion in the mid-latitudes would have doubled. This would have led to UV levels high enough to cause sunburn in just 5 minutes and would have made outdoor activities during midday dangerous in many parts of the world. The successful international cooperation on ozone depletion offers hope that similar approaches can work for other global environmental challenges like climate change.
While the ozone layer recovers, it's important to take personal precautions against UV radiation.
Use broad-spectrum sunscreen (SPF 30+), wear protective clothing, wide-brimmed hats and UV-blocking sunglasses. Seek shade between 10am-4pm when UV is strongest.
Check the daily UV index in weather forecasts. When the index is 3 or higher, take sun protection measures. The scale runs from 1 (low) to 11+ (extreme).
Examine your skin monthly for new or changing moles. See a doctor promptly about any suspicious skin changes. Get regular eye examinations.
Ozone depletion represents one of humanity's greatest environmental challenges, but also one of our greatest success stories in addressing a global threat. While the health effects of increased UV radiation remain serious, international cooperation has put us on a path to recovery. As individuals, understanding these risks and taking appropriate precautions can help us stay safe while the ozone layer continues to heal.
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