Ozone
Ozone is a gas that exists both at the earth's ground level, and in the earth's upper atmosphere. Its chemical formula is O3. The ozone in the atmosphere occurs naturally and protects life on earth from the sun's harmful ultraviolet rays.
The ozone that occurs on the ground level is formed when sunlight reacts with pollution from motor vehicles, power plants, industrial boilers, refineries, chemical plants, and other industrial sources. Ground-level ozone is the main ingredient of smog, a kind of air pollution found in many U.S. cities, which contributes to climate change.
Ozone has also some positive advantages. Ozone can also be industrially manufactured. Manufactured ozone is a colorless to blue gas with a pungent odor. It is used for purifying air and drinking water; treating industrial waste; drying varnishes and printing inks; deodorizing feathers; bleaching waxes; and making oils and other chemicals. It is used to control mold and bacteria in cold storage, and to age liquor and wood.
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[edit] How are we exposed to Ozone?
We are exposed to ozone in the summer, when the sun and hot temperatures react with pollution to form ozone. We can be exposed to ozone if we exercise or work outdoors during the summer.
As levels of ozone increase, more people are exposed, especially if "ozone alerts" are issued by local governments to warn of dangerous ozone levels. You will be exposed to more ozone in the middle of the day, when ozone levels are highest.
Active children are more likely to be exposed to ozone if they spend a lot of their time playing outdoors in summer. Men are more sensitive to ozone if they exercise or work vigorously outdoors. If you are elderly, or if you have asthma or other respiratory diseases, Ozone may cause serious harm to your health.
People can be exposed to ozone at work if they work in a facility that exposes gasoline vapors, chemical solvents, or processes that produce ozone.
[edit] How can ozone affect our health?
Repeated exposure to ozone may cause permanent damage to the lungs, especially in children whose lungs are still developing. It can cause reproductive and genetic damage. Exposure to ozone may increase the risk of damage to a developing fetus.
Ozone can aggravate chronic lung diseases such as emphysema and bronchitis, and reduce the immune system's ability to fight off infections in the respiratory system. Exposure to ozone can aggravate asthma and heart disease, reduce lung capacity, and cause a build-up of fluid in the lungs, causing difficulty in breathing.
Exposure to ozone can irritate your respiratory system, causing you to cough, feel irritation in your throat, or feel uncomfortable in your chest. Breathing ozone can cause headache, upset stomach, congestion, fatigue, and vomiting.
Having skin or eye contact with liquefied ozone in the workplace can produce severe burns. Moderate exposure to ozone can cause eye irritation, burning of the throat and eyes, and a bitter taste and smell.
[edit] The Chemical Existence Of Ozone
Ozone (O3), or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It's an allotrope of oxygen that's much less stable compared to diatomic allotrope (O2). Ozone within the lower atmosphere is an air pollutant with harmful effects on the respiratory systems of animals and can burn sensitive plants; however, the ozone layer within the upper atmosphere is beneficial, preventing potentially damaging ultraviolet light from reaching the Earth's surface. Ozone exists in low concentrations through the Earth's atmosphere. It's many industrial and consumer applications.
Ozone is an everyday part of the atmosphere and is constantly being created and destroyed in the stratosphere (or ozone layer). The ozone layer protects us from harmful Ultraviolet rays.
Ozone does function as a greenhouse gas, but its contribution to the enhanced greenhouse effect is yet to be calculated.
[edit] History
Ozone, the first allotrope of the chemical element to be recognized, was proposed like a distinct substance by Christian Friedrich Schönbein in 1840, who referred to it as following the Greek verb ozein ("to smell"), from the peculiar odor in lightning storms. The formula for ozone, O3, wasn't determined until 1865 by Jacques-Louis Soret and confirmed by Schönbein in 1867
[edit] Physical properties
Ozone is really a pale blue gas, slightly soluble in water and much more soluble in inert non-polar solvents such as carbon tetrachloride or fluorocarbons, where it forms a blue solution. At -112 °C, it condenses to create a dark blue liquid. It's dangerous to allow this liquid to warm to its boiling point, because both concentrated gaseous ozone and liquid ozone can detonate. At temperatures below -193 °C, it forms a violet-black solid
Running out of energy detect about 0.01 ppm of ozone in air where it features a very specific sharp odor somewhat resembling chlorine bleach. Exposure of 0.1-to-1 ppm produces headaches, burning eyes, and irritation towards the respiratory passages. Even low concentrations of ozone in air are very destructive to organic materials for example latex, plastics, and animal lung tissue.
Ozone is diamagnetic, which means that its electrons are all paired. In comparison, O2 is paramagnetic, containing two unpaired electrons.
[edit] Structure
According to experimental evidence from microwave spectroscopy, ozone is a bent molecule, with C2v symmetry (similar to the water molecule). The O - O distances are 127.2 pm. The O - O - O angle is 116.78°. The central atom is sp² hybridized with one lone pair. Ozone is a polar molecule with a dipole moment of 0.5337 D. The bonding can be expressed as a resonance hybrid with a single bond on one side and double bond on the other producing an overall bond order of 1.5 for each side.
[edit] Effects
[edit] Air pollution
There's a great deal of evidence to exhibit that ozone, created by high concentrations of pollution and daylight Ultra violet rays at the Earth's surface, can harm lung function and irritate the respiratory system. Contact with ozone and the pollutants that produce it is associated with premature death, asthma, bronchitis, heart attack, and other cardiopulmonary problems.
Long-term exposure to ozone can increase risk of death from respiratory illness. A study of 450,000 people living in United States cities showed a significant correlation between ozone levels and respiratory illness over the 18-year follow-up period. The study revealed that people residing in cities with high ozone levels such as Houston or Los Angeles had an over 30% increased risk of dying from lung disease.
Air quality guidelines for example those from the World Health Organization, america Environmental Protection Agency (EPA) and also the EU provide detailed studies made to identify the amount that may cause measurable ill health effects.
Based on scientists using the (EPA), susceptible people could be adversely affected by ozone levels as little as 40 ppb.
In the EU, the present target value for ozone concentrations is 120 µg/m³ which is about 60ppb. This target pertains to all member states prior to Directive 2008/50/EC. Ozone concentration is measured like a maximum daily mean of 8 hour averages and also the target shouldn't be exceeded on a lot more than 25 calendar days each year, beginning with January 2010. Whilst the directive requires in the future a strict compliance with 120 µg/m³ limit (i.e. mean ozone concentration not to be exceeded on any day of the season), there isn't any date set for this requirement which is treated as a long-term objective.
The Climate Act directs the EPA to create National Ambient Air Quality Standards for many pollutants, including ground-level ozone, and counties out of compliance with one of these standards have to take steps to reduce their levels. In May 2008, the EPA lowered its ozone standard from 80 ppb to 75 ppb. This proved controversial, since the Agency's own scientists and advisory board had recommended lowering the conventional to 60 ppb, and the World Health Organization recommends 51 ppb. Many public health insurance and environmental groups also supported the 60 ppb standard. On January 7, 2010, the U.S. Environmental Protection Agency (EPA) announced proposed revisions towards the National Ambient Quality of air Standard (NAAQS) for that pollutant ozone, the principal element of smog:
... EPA proposes that the level of the 8-hour primary standard, that was set at 0.075 ppm within the 2008 final rule, should instead be set in a lower level inside the range of 0.060 to 0.070 parts per million (ppm), to supply increased protection for children along with other ‘‘at risk’’ populations against a range of O3- related adverse health effects that vary from decreased lung function and increased respiratory symptoms to serious indicators of respiratory morbidity including emergency department visits and hospital admissions for respiratory causes, and possibly cardiovascular-related morbidity as well as total non- accidental and cardiopulmonary mortality. ...
The EPA has developed an Air Quality Index to assist explain air pollution levels towards the general public. Underneath the current standards, eight-hour average ozone concentrations of 85 to 104 ppb are referred to as "unhealthy for sensitive groups", 105 ppb to 124 ppb as "unhealthy" and 125 ppb to 404 ppb as "very unhealthy".
Ozone may also be present in indoor polluting of the environment, partly due to electronic equipment for example photocopiers. A connection has also been known to exist between the increased pollen, fungal spores, and ozone caused by thunderstorms and hospital admissions of asthma sufferers.
A typical British folk myth dating back towards the Victorian times holds how the smell of the sea is brought on by ozone, which this smell has "bracing" health benefits. Neither of these is true. The characteristic "smell from the sea" is not caused by ozone but by the presence of dimethyl sulfide generated by phytoplankton which, like ozone, is toxic in high concentrations.
[edit] Reactions
[edit] The natural ozone cycle
Ozone is created and destroyed by ultraviolet light from the Sun. It is created from oxygen by high energy rays, while low energy rays destroy it.
[edit] The impact of human activities
Some ozone is man-made by various kinds of air pollution, which then reacts in sunlight. This low level ozone is harmful to human health.
[edit] Other Greenhouse gases
Also see: Stratospheric Ozone Depletion, Ozone layer
