The ozone hole affects humans primarily by allowing more ultraviolet-B radiation to reach Earth’s surface, which increases rates of skin cancer, cataracts, and immune suppression. For every 1% decrease in ozone thickness, melanoma incidence is projected to rise 1% to 2%, and squamous cell carcinoma incidence by 3% to nearly 5%. These aren’t abstract risks: without the international treaty that began repairing the ozone layer, an estimated 443 million additional skin cancer cases would have occurred among people born in the United States alone between 1890 and 2100.
How the Ozone Layer Protects You
The ozone layer sits between 10 and 50 kilometers up in the stratosphere. If you compressed it to ground level, it would be only about 3 millimeters thick, yet that thin shield efficiently absorbs UV radiation up to about 310 nanometers in wavelength. This is the UV-B range (280 to 315 nanometers), the portion of sunlight energetic enough to directly damage DNA in living cells.
Chemicals called chlorofluorocarbons, once common in refrigerators and aerosol cans, release reactive chlorine in the stratosphere. That chlorine breaks ozone into ordinary oxygen molecules, which don’t block UV-B. The result is straightforward: thinner ozone means more UV-B reaches your skin, your eyes, and the ecosystems you depend on for food.
Skin Cancer Risk
UV-B radiation is absorbed directly by DNA, creating structural damage in skin cells that can accumulate into cancer-causing mutations over a lifetime. The World Health Organization considers the link between UV exposure and skin cancer, both melanoma and non-melanoma types, to be supported by strong evidence.
The numbers vary sharply by geography and skin tone. Simulations based on the Montreal Protocol’s timeline project that Australia will see the greatest increase in additional skin cancer cases: up to 200 extra cases per million people per year by the mid to late 21st century. New Zealand follows closely at 100 to 150 per million, then China at 90 to 120 per million, the Mediterranean at 90 to 100, the southwestern United States at 80 to 110, and western Europe at 30 to 40. Regions near the equator with predominantly darker-skinned populations, like the Congo, are expected to see no measurable increase, because higher melanin levels provide natural UV protection.
Overall, modeling based on ozone trends predicted a 10% increase in skin cancer incidence by mid-century due to ozone depletion, even with international controls in place.
Eye Damage and Cataracts
Your eyes are vulnerable to the same UV-B radiation that harms skin. When UV-B penetrates the eye’s lens, it generates reactive oxygen species that damage and kill lens cells. Over time, this causes the lens to cloud, scattering and absorbing visible light instead of transmitting it clearly. That clouding is a cataract.
Cataracts remain the leading cause of blindness worldwide, responsible for roughly 35% of all blindness cases. The Montreal Protocol’s protections are estimated to have prevented 63 million cataract cases in the U.S. population alone. Of those, 33 million were specifically prevented by the treaty’s later strengthening through amendments that further restricted ozone-depleting chemicals.
Immune Suppression
UV-B exposure doesn’t just damage skin and eyes. It also suppresses immune responses, both locally at the skin and throughout the body. Research has shown that UV-B reduces the effectiveness of immune cells that normally detect and destroy abnormal cells and fight off infections. This matters in two ways: it may make your body less effective at catching early-stage skin cancers before they grow, and it could increase susceptibility to certain infectious diseases. The full extent of this effect in real-world populations is still being quantified, but the underlying biological mechanism is well established.
Impacts on Food and Agriculture
The ozone hole also affects humans indirectly through its impact on the food supply. Elevated UV-B damages plant DNA and disrupts normal growth processes, altering plant structure and reducing crop yields. Cereals, which supply more than 50% of the world’s dietary energy and are the foundation of food security in both developing and developed nations, are particularly important in this equation. Global cereal production accounts for roughly 26 million tonnes annually, and any UV-driven decline in yields puts pressure on a food system already strained by population growth and climate change.
Beyond crops, increased UV-B penetrating the top layers of the ocean affects marine ecosystems, including the phytoplankton that form the base of oceanic food chains. Changes at that level ripple upward to the fish and seafood that hundreds of millions of people rely on for protein.
The Vitamin D Tradeoff
UV-B isn’t entirely harmful. Your skin needs it to produce vitamin D, which is essential for bone health and immune function. About 90% of the body’s vitamin D comes from sun exposure rather than food. This creates a genuine tension: strong sun protection prevents skin damage but can contribute to vitamin D deficiency.
In practice, the tradeoff is less dramatic than it sounds. Your body produces a day’s worth of vitamin D (about 400 IU) in roughly one-third the time it takes for your skin to start turning pink. For most people, that means 10 to 15 minutes of sun exposure on uncovered skin, two to three times a week, is sufficient. After your body reaches adequate vitamin D levels, it begins breaking down the excess, so prolonged sun exposure beyond that window provides no additional vitamin D benefit, only accumulated DNA damage that raises lifetime cancer risk.
Where the Ozone Layer Stands Now
The Montreal Protocol, signed in 1987 and strengthened through subsequent amendments, banned the chemicals responsible for ozone destruction. It has been remarkably effective. NASA and NOAA scientists confirmed that the ozone hole continued healing through 2024, with its severity falling below the average of the past three decades. Full recovery of the ozone layer is projected by 2066.
The health benefits are enormous. Comparing the strengthened Montreal Protocol to a scenario with no regulations at all, an estimated 443 million skin cancer cases and 2.3 million skin cancer deaths have been or will be avoided among people born in the United States between 1890 and 2100. Strengthening the original 1987 treaty through later amendments alone accounted for 230 million fewer skin cancer cases and 1.3 million fewer deaths. The ozone layer is still far from fully healed, but the trajectory is moving in the right direction.
Protecting Yourself From UV-B
The WHO recommends taking protective measures whenever the UV index reaches 3 or above. At that level, unprotected skin can begin accumulating damage in relatively short periods. The higher the UV index, the faster harm occurs.
The most effective protection is structural: staying out of direct midday sun and seeking shade. After that, clothing matters more than sunscreen. A broad-brimmed hat protects your face, ears, and neck. Wraparound sunglasses that block 99% to 100% of both UV-A and UV-B protect your eyes and the delicate skin around them. Sunscreen is best used on skin that clothing can’t cover, and it should never be treated as a reason to spend more time in the sun. Artificial tanning devices, which deliver concentrated UV radiation, should be avoided entirely.