The ozone layer protects life on Earth primarily from the sun’s ultraviolet radiation, specifically the most biologically damaging wavelengths. This thin shield of gas in the upper atmosphere absorbs nearly all of the shortest-wave UV rays (UVC) before they reach the surface and blocks a significant portion of medium-wave UV rays (UVB), the type most responsible for sunburn, DNA damage, and skin cancer. Without it, life on land as we know it would not be possible.
The Three Types of UV Radiation
Sunlight contains three categories of ultraviolet radiation, divided by wavelength. UVC is the most energetic and most dangerous, but the ozone layer absorbs almost all of it before it reaches the ground. UVB, the middle range, is strongly filtered by ozone, though some still gets through. This is the radiation responsible for most of the biological harm we associate with sun exposure. UVA, the longest wavelength, passes through the ozone layer essentially unaffected, which is why sunscreen and physical barriers still matter even with a healthy ozone layer overhead.
The ozone layer sits in the stratosphere, roughly 15 to 35 kilometers above Earth’s surface. It works because ozone molecules are especially good at absorbing UV photons in the UVB and UVC range. When those photons hit an ozone molecule, they break it apart, and the energy is converted to heat rather than reaching the surface. This process is constantly cycling, with ozone molecules breaking and reforming.
DNA Damage and Skin Cancer
UVB radiation is absorbed directly by DNA in skin cells. When it strikes the genetic material, it causes neighboring building blocks in the DNA strand to bond together abnormally, creating structural defects that the cell’s repair machinery has to fix. If those defects aren’t repaired correctly, the result is a permanent mutation. UVB also triggers the production of reactive oxygen species, unstable molecules that cause additional indirect damage to DNA and surrounding cell structures.
Over time, these mutations accumulate in genes that control cell growth, which is how UV exposure leads to skin cancer. Research from Norway quantified this relationship: a 10% reduction in ozone thickness corresponds to a 16 to 18% increase in squamous cell carcinoma rates and a 19 to 32% increase in melanoma rates, with women facing the higher end of that melanoma range. Skin cancer rates also rise steadily as you move toward the equator, where the ozone layer is naturally thinner and UV intensity is greater.
Eye Disease
Your eyes are also vulnerable. Two of the most common UV-related eye conditions are cataracts and pterygium. Cataracts occur when the lens of the eye becomes cloudy, scattering light instead of focusing it clearly. UVB exposure is associated with increased risk of cortical cataracts, the type that forms around the edges of the lens. Pterygium is a fleshy growth on the surface of the eye that can eventually interfere with vision. Both conditions share a common mechanism: UV exposure triggers enzymes that break down tissue in the lens and on the eye’s surface. By filtering UVB, the ozone layer significantly reduces the cumulative UV dose your eyes receive over a lifetime.
Immune Suppression
One of the less obvious effects of excess UVB is its ability to weaken the immune system. Animal studies have shown that UVB exposure suppresses both the initial immune response and the body’s ability to form immune memory. Specifically, UVB reduces the activation and multiplication of key immune cells (T cells) in the lymph nodes closest to the skin. It also reduces the number of immune cells that migrate to the skin when the body detects a threat there.
This matters practically because it means sunburned or heavily UV-exposed skin is less capable of fighting off infections and detecting abnormal cells. The immune suppression isn’t limited to the exposed area either. It can be systemic, meaning UVB hitting one part of your body can dampen immune responses elsewhere. This is one reason excessive sun exposure is linked not just to skin cancer formation but also to the body’s reduced ability to catch and eliminate early cancerous cells.
Crop Yields and Food Production
Plants are no less vulnerable than people. Increased UVB radiation causes measurable changes in plant structure and function, reducing growth rates and disrupting photosynthesis. Research modeling the effects of ozone depletion on wheat found that a 12 to 25% reduction in stratospheric ozone could reduce grain yields by 18 to 57%, with a 30% drop in the weight of individual grains. These aren’t small margins. For a crop that feeds billions of people, even the lower end of that range would be catastrophic.
The ozone layer essentially keeps UV exposure within the range that most crop species evolved to tolerate. Without that buffer, farming as it currently exists in many regions would require entirely different approaches, crop varieties, or protective technologies.
Ocean Life and the Marine Food Chain
Phytoplankton, the microscopic organisms at the base of the ocean food chain, are sensitive to UV radiation. These organisms live near the ocean surface where sunlight is available for photosynthesis, which also means they’re directly exposed to whatever UV reaches the water. Increased UV doesn’t always cause dramatic drops in total biomass, but it significantly reshapes food-web structure because different species of plankton vary widely in their UV sensitivity. Some are killed or inhibited while others are less affected, which shifts the balance of the entire ecosystem.
Since phytoplankton are responsible for roughly half of the oxygen produced on Earth and form the foundation of marine food chains supporting fish, seabirds, and marine mammals, even structural changes in plankton communities ripple outward through carbon cycling, nutrient availability, and fisheries productivity.
Degradation of Materials
Beyond biology, the ozone layer also slows the breakdown of synthetic and natural materials exposed to sunlight. UV radiation is well documented as a primary cause of degradation in plastics, wood, rubber, and fabrics used outdoors. It breaks chemical bonds in polymer chains, causing materials to become brittle, discolored, and structurally weak. The Montreal Protocol, the international agreement that phased out ozone-depleting chemicals starting in the late 1980s, has helped keep UVB levels in check, which in turn extends the useful life of everything from building materials to outdoor furniture.
Good Ozone vs. Bad Ozone
It’s worth noting that not all ozone is protective. The ozone high in the stratosphere is the beneficial kind, absorbing UV before it reaches the ground. But ozone at ground level is a harmful air pollutant and the main component of smog. Ground-level ozone forms when pollutants from cars, power plants, and industrial facilities react with sunlight. It irritates the lungs and is particularly dangerous for children, older adults, and people with asthma or other lung conditions. The EPA classifies stratospheric ozone as “good ozone” and ground-level ozone as “bad ozone,” a simple distinction but an important one. Same molecule, very different consequences depending on where it is in the atmosphere.