Why are UV rays more harmful in the presence of reduced ozone?

UV rays are more harmful in the presence of reduced ozone because the ozone layer absorbs most of the sun's harmful UV radiation.

The ozone layer, located in the Earth's stratosphere, plays a crucial role in protecting life on Earth from the sun's harmful ultraviolet (UV) radiation. It acts as a shield, absorbing the majority of this radiation and preventing it from reaching the Earth's surface. When the ozone layer is reduced or depleted, more UV radiation can penetrate through the atmosphere and reach the Earth's surface, increasing the risk of harmful effects.

UV radiation is divided into three types: UVA, UVB, and UVC. UVC is the most dangerous, but it is completely absorbed by the ozone layer and does not reach the Earth's surface. However, when the ozone layer is reduced, the amount of UVB and UVA reaching the Earth's surface increases. UVB is particularly harmful as it can cause skin cancer and cataracts in humans, harm aquatic ecosystems, and damage sensitive crops and other plants.

The reduction in the ozone layer is primarily caused by human activities, particularly the emission of certain industrial chemicals known as ozone-depleting substances (ODS). These include chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform. These substances are stable and do not break down in the lower atmosphere, allowing them to slowly rise to the stratosphere. Once in the stratosphere, they are broken down by solar radiation, releasing chlorine and bromine atoms which can catalyse the destruction of ozone.

In conclusion, the presence of reduced ozone allows more of the sun's harmful UV radiation to reach the Earth's surface, increasing the risk of harmful effects to humans, animals, and the environment. This highlights the importance of efforts to reduce the emission of ozone-depleting substances and protect the ozone layer.