Ozone is a gas consisted of of three oxygen atom (O3). It occurs normally in small (trace) quantities in the upper atmosphere (the stratosphere). Ozone protects life on planet from the Sun’s ultraviolet (UV) radiation. In the lower atmosphere (the troposphere) close to the Earth’s surface, ozone is developed by chemistry reactions between air pollutants from automobile exhaust, gasoline vapors, and other emissions. At ground level, high concentrations of ozone are toxic to people and also plants.

Stratospheric “good” ozone

Ninety percent of the ozone in the environment sits in the stratosphere, the great of atmosphere between about 10 and also 50 kilometers altitude. The herbal level of ozone in the stratosphere is a an outcome of a balance between sunlight the creates ozone and chemical reaction that damage it. Ozone is produced when the sort of oxygen we breathe—O2—is separation apart by sunlight into solitary oxygen atoms. Single oxygen atoms deserve to re-join to make O2, or they can join v O2 molecule to make ozone (O3). Ozone is damaged when that reacts v molecules include nitrogen, hydrogen, chlorine, or bromine. Several of the molecules that destroy ozone happen naturally, however people have created others.

The full mass the ozone in the environment is about 3 exchange rate metric tons. That may seem favor a lot, but it is just 0.00006 percent the the atmosphere. The top concentration that ozone wake up at one altitude of about 32 kilometers (20 miles) over the surface ar of the Earth. At the altitude, ozone concentration can be together high as 15 components per million (0.0015 percent).

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The concentration that ozone varies v altitude. Peak concentrations, an mean of 8 molecule of ozone per million molecule in the atmosphere, occur between an altitude of 30 and also 35 kilometers.

Ozone in the stratosphere absorbs many of the ultraviolet radiation native the Sun. There is no ozone, the Sun’s intense UV radiation would sterilize the Earth’s surface. Ozone screens all of the most energetic, UV-c, radiation, and most of the UV-b radiation. Ozone only displays about half of the UV-a radiation. Extreme UV-b and UV-a radiation can reason sunburn and also can lead to skin cancer and also eye damage.

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Solar ultraviolet radiation is largely soaked up by the ozone in the atmosphere—especially the harmful, high-energy UV-a and UV-b. The graph shows the flux (amount of energy flowing through an area) of solar ultraviolet radiation in ~ the top of the setting (top line) and at the Earth’s surface (lower line). The flux is shown on a logarithmic scale, so every tick mark on the y-axis suggests 10 times an ext energy.

raised levels the human-produced gases such together CFCs (chlorofluorocarbons) have actually led to enhanced rates the ozone destruction, upsetting the herbal balance the ozone and leading to decreased stratospheric ozone levels. These lessened ozone levels have actually increased the amount of harmful ultraviolet radiation getting to the Earth’s surface. Once scientists talk around the ozone hole, they are talking about the devastation of stratospheric, “good,” ozone.

Tropospheric “bad” ozone

back ozone high increase in the stratosphere offers a shield to protect life top top Earth, direct call with ozone is harmful come both plants and animals (including humans). Ground-level, “bad,” ozone forms when nitrogen oxide gases from vehicle and also industrial emissions react v volatile necessary compounds (carbon-containing chemicals that evaporate conveniently into the air, such as paint thinners). In the troposphere close to the Earth’s surface, the herbal concentration of ozone is around 10 components per billion (0.000001 percent). According to the environmental Protection Agency, exposure come ozone levels of better than 70 components per billion because that 8 hours or much longer is unhealthy<1>. Together concentrations take place in or near cities throughout periods wherein the environment is warm and stable. The harmful impacts can incorporate throat and lung wake up or aggravation the asthma or emphysema.