Arabia Weather - The ozone layer in the Earth's upper atmosphere protects human health, crops and ecosystems from damage caused by excessive ultraviolet radiation. But in the lower atmosphere, the scenario is different, where human activities can cause a lot of ozone, which threatens human health, crops and ecosystems, so how can one gas carry a harmful effect and another beneficial?!
Ozone (O3) is a gas naturally produced in the atmosphere. Most of the ozone in the Earth's atmosphere is formed in the stratosphere, about 15 km above the Earth's surface.
The ozone here forms the ozone layer, which acts as a natural shield that protects the earth from the harmful rays of the sun. This ozone depletion caused a lot of concern in the seventies and eighties, when scientists discovered that gases used in sprays and refrigerants, such as chlorofluorocarbons (CFCs), were It causes a huge seasonal hole in the ozone layer.
Then the world moved and countries signed the Montreal Protocol to phase out these gases, the agreement was a huge success, and now scientists are watching the ozone layer recover. This is good news for the planet, as the ozone layer prevents the risks caused by harmful rays from the sun, including: cancer and cataracts, and protects agricultural crops and ecosystems.
As it is said, there are two sides to the same coin, and ozone has two sides, one harmful and dangerous, and the other beneficial and necessary. How is that?!
After we got to know the beneficial ozone in the stratosphere, which forms a concentrated layer that contains 90% of the ozone in the earth's atmosphere, ozone gas is also present in the troposphere near the surface of the earth, but in lower concentrations, and this is the harmful ozone, which constitutes 10% of the total ozone in the atmosphere.
Most of the tropospheric ozone is located at an altitude of less than 2-3 km, so it is also referred to as "surface ozone". Surface ozone is described as harmful ozone because at high concentrations it poses a threat to human health and the production of crops and natural plants, including forests.
In 2010, the Environmental Effects Assessment Panel (EEAP) reported that 1-1.25 million deaths globally can be attributed to surface ozone pollution. While long-term exposure to high levels of surface ozone may contribute to cardiovascular disease — including high blood pressure, heart disease and stroke — the most well-known link is respiratory disease.
Inhaling ozone causes inflammation and damage to the airways and lungs. This can lead to problems even in people who do not have any pre-existing respiratory diseases, but is more harmful for those with existing diseases. Globally, up to 20 percent of all asthma emergency room visits may be due to surface ozone. In its 2020 update report, the EEAP also noted preliminary evidence that high levels of air pollution may be associated with worse health outcomes from COVID-19 infection.
Many plants, from lichens to forest trees, are damaged by exposure to surface ozone. Estimates of global yield losses in soybeans, wheat, rice and maize due to surface ozone range from 4-12 percent. Some studies have found greater yield reductions in some areas, for example up to 24 percent in rice and 36 percent in wheat. High concentrations of surface ozone also harm the growth and productivity of forests. This reduction in growth reduces the ability of forests to absorb carbon dioxide, including from human activities - a major driver of climate change.
Very low concentrations of surface ozone occur naturally in even the cleanest air, but much larger amounts can be produced in polluted air. Ozone is produced by chemical reactions between a mixture of air pollutants we produce, including nitrogen oxide (NOx), carbon monoxide (CO), and hydrocarbons. Higher temperatures and bright sunlight speed up these reactions, so surface ozone concentrations are usually higher in warm, sunny conditions.
In general, surface ozone tends to be greater in urban areas where emissions from industry and transportation lead to high concentrations of nitrogen oxides and hydrocarbons. Surface ozone may then be spread from urban to rural areas by wind.
Unlike the Montreal Protocol, which protects good ozone, there is no global treaty that protects us from the effects of bad ozone. However, many countries include surface ozone as part of air quality standards and clean air systems—such as reducing and regulating emissions from industry, power plants, and vehicles, and measures to reduce hydrocarbon emissions such as organic solvents and unburned vehicle fuels.
So while there is only one type of ozone, depending on where it is located - whether in the stratosphere or the troposphere - it will have very different effects on humans, crops, animals and ecosystems. So it is important to note this distinction. We need to make sure that we continue to implement the Montreal Protocol to protect the "good ozone" in the stratosphere which is our sunscreen.