Key words: Toxic microclimate, carbon monoxide, nitrogen oxides, sulfur dioxide, ozone, smog, formaldehyde

TOXIC MICROCLIMATE

Air is a mixture of different gases, of which nitrogen, oxygen, argon and carbon dioxide predominate. These gases make up 99.99% of the atmosphere. In addition, air contains various dopants such as ozone, carbon monoxide CO, sulfur oxides, ammonia and dust. Toxic substances present in the internal environment will be originated either from the exterior or in the interior itself.

Sulfur oxides (SO2 and SO3 as byproducts of fossil fuel combustion), nitrogen oxides (gas engines, heat plants, gas burning), carbon dioxide (gasoline and incomplete combustion), ozone, hydrocarbons and smog come from the outside.

Toxic gases in indoor air generated by anthropogenic activities and released from building materials (NO₂, CO). The most common toxic component of indoor building environments is carbon monoxide (CO). Its source is most often the combustion processes and the combustion of tobacco. In the case of good combustion, flue gases contain approximately 0.2-0.5% of carbon monoxide. In the case of incomplete combustion, these concentrations are considerably higher. Gas appliances without exhaust are also sources of nitrogen oxides. In addition, plastics in the interior are a source of toxic gas, for example, styrene is the emissied of polystyrene, volatile organic compounds evaporate very often from the coatings on heating surfaces.

Carbon dioxide is the product of incomplete combustion for oxygen access. The sources include solid fuel stoves, gas appliances without exhaust, fireplaces, non-fired kitchens with a gas stove, and others. Natural gas, which is used in the Czech Republic for cooking, heating or heating water, contains 5% of carbon monoxide. Smoking of tobacco is also a significant source. Carbon monoxide binds to the red blood dye and thus reduces the amount of oxygen transmitted by the blood. Lighter poisoning is manifested by headaches, pounding blood in the head, chest pressure, dizziness. Total nausea and vomiting are typical. In the case of heavier poisoning with carbon monoxide, there is a considerable tendency to fainting. At first, weak legs, a person stops feeling the ground under his feet, objects appear to be larger. Body temperature rises to 42 ° C.

The source of sulfur dioxide can be, for example, a domestic furnace in which coal is burned. In the 1970s and 1980s, sulfur dioxide was the main component of air pollution, but since the mid-1990s, its concentrations have been declining, due to improved flue gas desulfurization technologies for large sources of pollution. Sources include thermal power plants, heating plants and industrial boiler. Higher concentrations of SO₂ irritate the upper respiratory tract, cough and increase respiratory illness.

The sources of nitrogen oxides are emissions from automobile transport and from stationary sources burning fossil fuels at high temperatures. Eight nitrogen oxides can be found in the indoor environment. Only two cause health damage. They are nitrogen dioxide (NO₂) and nitrous oxide (NO).

Smog is the chemical pollution of the atmosphere caused by human activity. The atmosphere is enriched with ingredients that are not normally in it and which are harmful to health during a phenomenon. Smog (smoke and fog produced by nitrogen oxides) arises because of air pollution, which is degraded by exposure to ultraviolet radiation to other toxic substances, such as ozone. Ozone is not a pollutant directly discharged into the air and therefore, to reduce its increased concentration, it is necessary to reduce the emissions of the substances it needs to produce itself.

Ozone (O₃ or triatomic oxygen) is natural gas, which binds to the oxidized organic compounds. It is a reaction with other elements in the atmosphere. Ozone concentrations in the indoor environment tend to be half that of the external environment. There are two types:

• Atmospheric ozone, which is in the atmospheric layer and protects us from harmful ultraviolet rays. Its loss causes the so-called ozone hole.
• Tropospheric ozone, which is contained in the ground air zone and at high concentrations, is harmful to humans.

Volatile Organic Compounds (VOCs) are defined as organic substances in the solid, liquid or gaseous state that, at normal temperature and pressure, enter the atmosphere in the form of vapor with a pressure greater than 0.13 kPa. According to the World Health Organization (WHO), volatile organic compounds are defined as organic compounds boiling in the range of 50 - 100 ° C to 240 - 260 ° C.

Volatile organic compounds are compounds, which, in the presence of solar radiation, react with nitrogen oxides and form photochemical oxidants. They have a demonstrably negative impact on the environment and air quality with negative impacts on human health. In the environment, they usually occur together as a sum of the compounds (TVOC). Their sources include, in particular, adhesives, solvents, paints, coatings, and the like. VOCs icnlude for example toluene, xylene, styrene, ethylbenzene, chlorinated hydrocarbons, phthalates and terpenes.

The sources of formaldehyde in the interior of buildings can be furnishings (furniture, carpets, wallpaper, etc.) or used building materials. Furthermore, cleaning and cosmetics used in households or plants, coal combustion, gas burning and smoking can be a source of formaldehyde.  Outside sources are primarily transport industry. The concentration of formaldehyde in the interior depends mainly on the number of people, the interior fittings, the temperature and humidity of the environment. The presence of formaldehyde, thanks to its pungent odor appearing in small concentrations, is perceived by the smell. Therefore is considered one of the safest indoor pollutants. Its impact on human health cannot be underestimated.

Polycyclic aromatic hydrocarbons (PAHs) represent a group of more than 100 chemical compounds. Polycyclic aromatic hydrocarbons form carbon and hydrogen, two or more benzene nuclei. They are characterized by long-term inertia capability in the indoor environment. These are substances with significant medical severity. Their characteristics include toxic, carcinogenic and mutagenic properties. They have a strong ability to bind to solid sorbents or particles (dust) even in living organisms (bioaccumulation capacity). They are able to form other compounds that can be even more carcinogenic.

OPTIMIZATION OF TOXIC MICROCLIMATE

Optimization of the toxic microclimate can be done by interfering with a source of pollutants, interfering with the field of transmission or by interfering with the subject. The basic method of optimization is ventilation.

In case of interference with the sources of pollutants, it is necessary to prefer materials of construction without toxic ingredients and volatile organic compounds. For technological heating installation, it is necessary to regularly carry out maintenance and cleaning in order to avoid reduction in the efficiency of the combustion process, and excessive production of carbon monoxide.

Intervention into the field of transmission constitutes a restriction on the spread of toxic substances in indoor environments. Methods of limitation of spreading include ventilation, filtration and decomposition of toxic substances into non-toxic or removal of toxic substances by intense air ionization.

The intervention in the subject exposed to the toxic microclimate involves the use of gas masks.