At long-term summer temperatures, the toxic gas ozone can form. But what is ozone in general and from which limits will it be dangerous for your health? We explain here what ozone layer, ozone hole and high ozone levels are all about.
What is ozone?
Ozone is a gas mixture that consists of three oxygen atoms (O 3 ) - so it has one oxygen atom more than the oxygen in our breathing air (O 2 ). The colorless gas is an important component of the Earth's atmosphere and protects us as such - 20 to 30 kilometers from the Earth's surface - from the dangerous ultraviolet radiation of the sun.
In strong sunlight ozone can be formed near the ground. Too high a concentration of the gas is dangerous to humans and animals because it can irritate the respiratory system and eyes.
At which ozone levels does it become dangerous?
Since 1990 very high levels of ozone rarely occur and, if so, peak concentrations have decreased. However, even if high peaks have decreased significantly, the annual mean value of ozone pollution has increased in comparison.
The threshold for informing the population about ozone levels is 180 μg / m 3 (micrograms per cubic meter of air, measured in the one-hour average). From this concentration, people who are sensitive to airborne pollutants should avoid unusual and intense outdoor activities in the afternoon. For the rest of the population, this applies from the threshold value of 240 μg / m 3 .
Under a daily load (mean value over 8 hours) of 120 μg / m 3 is not to be expected with health impairments.
Ozone and its by-products
Ozone is counted among the so-called photo-oxidants. In sunny weather in the ground-level air, this category forms further substances - this is called the summer smog. The summer smog typical photo-oxidant mixture contains a variety of irritants, but not always in the same composition.
The strong irritant effect of this smog on the eyes and mucous membranes of the upper respiratory tract (nasopharyngeal space) is only partially due to ozone, but also to other photo-oxidants, which are a byproduct of atmospheric ozone formation. These include, for example:
These substances are - in contrast to ozone - well soluble in water. In terms of their health effects, however, they are less significant than ozone because they occur in lower concentrations and are less toxic (toxic).
Effect of ozone on the respiratory tract
Ozone itself reacts almost exclusively at the point of impact, that is on the surfaces of the respiratory tract. Due to its low water solubility, it is retained to a much lesser extent than, for example, sulfur dioxide in the upper respiratory tract. As a result, ozone penetrates much further into the lungs.
In the lung periphery, the irritant gas encounters tissue that is not protected by a layer of mucus. This can lead to damage of the cell membrane with the associated inflammatory processes.
When does ozone harm?
About ten percent of the population is particularly sensitive to ozone. Health impairments are to be expected all the more:
- the higher the concentration of ozone in the inhaled air
- the longer you are exposed to the ozone
- the higher the minute ventilation (volume of air inhaled or exhaled for one minute) during exposure
When we make a physical effort, the minute volume increases. It is therefore easy to understand why ozone is a particular problem for people who spend a lot of time outdoors in summer smog episodes and are physically demanding.
But also infants and toddlers are at risk because they have, based on their height, a relatively high respiratory minute volume. In addition, their immune system is not yet fully developed: additional irritation by ozone may increase susceptibility to respiratory tract infections.
In addition, asthmatics, people with lung or cardiovascular diseases and the elderly are particularly at risk.
Ozone: symptoms and health effects
Depending on the concentration and the dose, human ozone may cause sensory effects (odor), effects on lung function and physical performance.
The following symptoms occur only after several hours of exposure to simultaneous physical activity:
- Changes in lung function
- Reduction of endurance capacity from 240 μg / m 3
- inflammatory reaction of the lung tissue from 160 μg / m 3 at 6.6 hours exposure with intermittent exercise
- Increase in the frequency of asthma attacks (240 to 300 μg / m 3 )
These functional changes and impairments usually return to normal within one to three hours after the onset of action. However, under particularly heavy loads, slight deviations can still be detected after 24 to 48 hours. Inflammations of the lung tissue can last longer.
A permanent increase in the ozone concentration in the breathing air increases the risk of developing a respiratory disease. Other long-term consequences are not excluded. For example, ozone is suspected to trigger cancer and promote Alzheimer's.
Irritation symptoms due to high ozone levels
The following mood disorders are mentioned from 200 μg / m 3 :
- Tears (caused by the accompanying substances of ozone)
- Irritation of the respiratory tract
- to cough
- a headache
- difficulty breathing
The acute symptoms of irritation to the eyes and mucous membranes are largely independent of physical activity; their extent depends primarily on the length of stay in the ozone-depleted atmosphere.
5 simple rules against the summer smog
To avoid health problems caused by high ozone concentrations, the following rules should be observed:
- Since high ozone concentrations usually occur at high temperatures, the rule of thumb is that reasonable behavior with regard to high temperatures is also reasonable with regard to ozone.
- Before you go on hot days, you should inform yourself about the ozone weather conditions.
- Longer physical effort should not be placed in the midday and afternoon hours, if possible at other times of the day. In the morning, the ozone concentration is lowest.
- If necessary, drain in a well-ventilated room. Indoors, the ozone concentration is lower.
- Take more breaks and relax in the shade.
Daily updated ozone levels
The Federal Environment Agency (UBA) publishes several daily updated ozone values and nationwide ozone forecasts, even on weekends. The air data comes from numerous measuring stations in Germany and reflects not only the current ozone levels but also the particulate matter pollution.
We also provide up-to-date information on ozone levels for today and tomorrow in our bioweather.
How is ozone created?
The ozone levels are always dependent on the weather. If the sun shines long and intense, ozone can form. In the formation of various pollutants in our air play a role, which are released for example by the road, power plants or solvents in paints and varnishes.
Usually, ozone breaks down again after a few days, especially in busy areas, as the substance reacts with car exhaust - outside of cities, ozone depletion takes longer.
Use of ozone
In addition to the weather-related formation of ozone, the gas can also be formed specifically. For example, there are room air purifiers that use ozone to remove the smell of cigarette smoke, for health reasons, experts advise against the use of such air purifiers.
Even some washing machines have a so-called ozone generator to rid the laundry of bacteria and odors. In addition, ozone is used in the treatment of water, such as in waterworks or for water treatment in the swimming pool. The advantages and disadvantages of this method are currently being researched.
In alternative medicine, the disinfecting and germicidal gas is used as part of the so-called ozone therapy. For example, it is injected or used for external fumigation of wounds. However, the healing effect of ozone is not considered proven, the therapy with ozone is therefore controversial.
Ozone hole - what's up with that?
As already mentioned, ozone is also in the earth's atmosphere. This layer in the lower part of the stratosphere is called the ozone layer.
However, there are influences that can lead to ozone depletion in the ozone layer and make the ozone layer thinner - this is called the ozone hole. One of the triggers for ozone depletion is CFCs (chlorofluorocarbons), a group of gases previously used, for example, as propellants in spray cans. The connection between the greenhouse effect and the ozone hole is also much discussed in science.
Since the ozone layer protects us from the damaging effects of the sun's rays, an ozone hole can have serious consequences for our health. However, it is unrelated to elevated ozone levels near the ground, which occur in the summer smog.