What is tropospheric ozone and what effects does it produce

The ozone molecule is made up of three oxygen atoms (O3) and it is a colorless gas with an ocher aroma. The ozone in the highest levels of the atmosphere is called stratospheric ozone and is a protective filter against solar radiation that enters our planet and the ozone existing on the surface is called tropospheric ozone and is a pollutant, therefore It is also known as polluting ozone , as it causes negative effects on human health and the ecosystem .

Tropospheric ozone is a secondary pollutant, it is not emitted directly into the atmosphere, but is formed through complex photochemical reactions, similar to when photochemical smog occurs , in the presence of high solar intensity. These reactions take place between primary pollutants such as some volatile organic compounds (VOC) or nitrogen oxides (NO, NO2). Nitrogen oxides are produced during combustion processes, mainly in vehicle traffic, while volatile organic compounds are produced from various sources such as refineries, dry cleaning, paints, traffic and other activities that use solvent products.

Other compounds involved in the formation of ozone are carbon monoxide (CO) and methane (CH4). Methane is a volatile organic compound produced in the extraction and distribution of natural gas, biomass combustion, wastewater, landfills, coal mining or livestock. In general, the presence of ozone in city centers is lower than in metropolitan belts and rural areas, because it tends to decompose in areas with high concentrations of NO.

In the following lines, we go into detail on the issue of what effects tropospheric ozone produces on human health and ecosystems or, itself, on the environment.

Tropospheric ozone is an important oxidant capable of producing undesirable health effects. Studies show that exposure to ozone can cause the following short-term negative health effects (mainly in summer):

• Lung inflammation
• Respiratory insufficiency.
• Asthma problems
• Bronchopulmonary diseases.
• Cough.
• Irritation of the pharynx and throat.
• Eye irritation.
• Decreased lung function
• General discomfort.

Different investigations have shown that mortality increases with exposure to ozone . There is also evidence linking exposure to ozone with impaired long-term reproductive function. Since 2005, some cohort studies on ozone exposure and respiratory mortality have been published. In addition, the International Agency for Research on Cancer classifies environmental contamination as a carcinogen of the first group (the highest).

Ozone can also interact with other elements such as acetaldehyde, formaldehyde or organic acids and generate pollutants of short duration, but which can be irritating and have health effects.

High levels of ozone can also damage vegetation and impair plant reproduction and development. All this leads to a decrease in biodiversity , the growth of forests and a decrease in crop yields. Ozone also reduces the absorption of carbon dioxide by plants, thus damaging the photosynthesis process.

Damage to crops in southern Europe can be a big problem for the sector. These contaminants can decrease the quality, yield, and value of crops. But not all crops are equally sensitive to ozone pollution, so there are more sensitive crops such as tomatoes, lettuce or cotton. The age of the crops, light levels, soil conditions or degree of humidity also influence. However, the most important factors are ozone levels and exposure time to it. New research suggests that nitrogen and ozone can synergize or antagonize their effects on vegetation and ecosystems, thus they can be unpredictable. Ozone is considered the third most important gas in the greenhouse effect, after carbon dioxide and methane.

Taking into account that sufficient amounts of NOx and VOC are emitted on any day to generate high levels of ozone , the difference in their daily levels is found in different climatic conditions . Some of those that favor are:

• High sunlight.
• High maximum temperatures.
• High differences between the daily minimum and maximum temperatures.
• Low humidity.
• Low wind speed.