Summer will start in a couple of days. It is good when there is an opportunity to go somewhere far away from the asphalt of cities melting from the heat – to the sea, for example, or to the country for the summer. Unfortunately, for many such luxury is not available: at least five days a week, citizens are forced to spend time in the “stone jungle”. City residents tend to visit city parks and squares as soon as possible, if they cannot get into the forest, then at least more often.
We used to believe that green spaces in cities have a beneficial effect on human life in difficult environmental conditions of cities. Plants help to purify the air, secrete useful phytoncides.
But not everything is so rosy. Factories in cities, of course, have a lot of advantages. But, as it turned out, there is also quite significant harm. This damage was assessed by an international group of environmental scientists from the German Humboldt University. A group of scientists reported on the results of their research.
City plants is guilty of 225 thousand deaths annually
It turned out that urban plants contribute to an increase in surface (tropospheric) ozone. This gas, according to the classification of harmful substances, refers to substances of the highest class of danger that pose a serious danger to humans – up to a possible fatal outcome.
All plants contribute to an increase in the amount of ozone. However, representatives of routine, dogwood and aster are especially distinguished by this. And if oranges and lemons (the Rutaceae family) are not too frequent visitors on our streets, then cornus (the dogwood family), burdock and dandelions (Asteraceae) have spread significantly.
On beneficial and harmful ozone
Scientists distinguish two types of ozone. More precisely, ozone is a gaseous substance consisting of three oxygen atoms. Ozone, which forms the stratospheric layer that protects life on our planet from solar radiation, is useful. Moreover, without it, existence and the very origin of life on Earth would be impossible.
We have all heard about ozone holes – the thinning of the ozone layer as a result of the release into the atmosphere of chlorofluorocarbons, methyl bromide, carbon tetrachloride, hydrochlorofluorocarbons and others.
But the toxicity of the triatomic oxygen compound exceeds the toxicity of fighting substances such as chlorine. Therefore, ozone located in the lower layers of the atmosphere – in the troposphere – is deadly. In addition, the World Health Organization classifies ozone as a threshold substance. That is, any concentration of this substance is dangerous for human health.
What is the “fault” of plants, or how the formation of “harmful” ozone
In general, the plants are not to blame for anything. The blame for the appearance of tropospheric ozone, however, as well as for the destruction of the stratospheric layer, lies with man, his destructive influence on the ecology of the planet.
The formation of ozone is a photochemical reaction that is normal for our planet. Reaction between nitrogen oxides and volatile organic compounds under the influence of ultraviolet radiation. This is how, with the help of plants, this protective shield of our planet – the ozone layer – was formed millions of years ago.
Plants secrete organic compounds – monoterpenes and sesquiterpenes, isoprene, etc. Thanks to them, it smells of pine needles, marsh rosemary, orange. The hotter the sun shines, the more volatile organic compounds are released by plants, and as a result – the formation of ozone, which then rises into the upper atmosphere.
But the trouble is that these volatile organic compounds react with nitrogen oxides, which are contained in the exhaust gases of cars. As a result, in addition to the danger from the exhaust gases themselves (nitrogen oxides are ten times more toxic than carbon monoxide), ozone is formed.
According to scientists, the presence of plants increases the amount of ozone in cities by almost 60%. Given the number of cars in megacities, such a volume of ozone does not have time to escape into the stratosphere.
The dangerous ozone
Being a chemically active oxidizing compound, ozone, entering the body, causes oxidative stress. As a result, an avalanche-like formation of free radicals occurs, which negatively affect living organisms, causing their degradation.
Ozone primarily affects the respiratory tract, causing cough, pneumonia, exacerbation of attacks in asthmatics, emphysema and pulmonary edema. In people who are not prone to respiratory diseases, ozone causes increased fatigue, nausea, headache. And they are also at risk of getting asthma, bronchitis and other problems.
Ozone contributes to the exacerbation or occurrence of allergies. And most importantly, ozone is genotoxic. This means that it is a mutagen or a carcinogen. That is, ozone is a substance that causes gene mutations or tumors.
The most dangerous effects of ozone are on children, the elderly, people with cardiovascular diseases and, as mentioned above, people with respiratory problems.
Well, as a “bonus”: ozone destroys not only living organisms, but also building materials and structures.
How to protect yourself from ozone
Unfortunately, our life is arranged in such a way that most people are forced to live in cities. It is difficult to go against the laws of nature, and the process of ozone formation cannot be stopped. You can reduce its amount only by reducing the amount of exhaust gases. However, for the most part, this is also beyond the power of a layman.
The only thing you can do for your health and the health of your loved ones is to be in the open sun as little as possible, and even more so not to engage in active physical activity in the heat: the hotter the sun shines, the more active the process of ozone formation is. The maximum is in the afternoon hours, the minimum is in the early morning.
The warning to avoid the hot sun applies not only to citizens, but also to summer residents: ozone spreads over a distance of more than 100 kilometers (62 mi) from cities.