Major Air Pollutants

The main pollutants whose concentrations are measured at stationary observation posts: nitrogen oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), suspended particles (dust), as well as ammonia (NH3), ozone (O3).

Nitrogen oxide (NO) is a colorless, odorless gas with high reactivity, which by itself is harmless to humans, hazard class 3. However, as soon as the sun warms up the air, the photochemical oxidation converts nitric oxide into a much more hazardous nitrogen dioxide (NO2).

Nitrogen dioxide (NO2) is a reddish-brown gas that forms a “fox’s tail”, a substance of the hazard class 2. The main anthropogenic sources are the processes of high-temperature combustion of various types of fuel (natural gas, coal, gasoline, fuel oil) in thermal power plants, industrial plants and in automobile engines.

Nitrogen dioxide and nitrogen oxide play an important role in the photochemical processes occurring in the troposphere under the influence of solar radiation, often causing photochemical smog, high concentrations of ground-level ozone and formaldehyde, and acid rains.

Human exposure to nitrogen oxides leads to dysfunctions of the lungs and bronchi, to an increase in susceptibility to respiratory tract infections, asthma attacks. Children and adults with cardiovascular diseases are more vulnerable to nitrogen oxides.

Sulfur dioxide, sulfurous anhydride (SO2) is a colorless gas with a characteristic pungent odor (the smell of a burning match), hazard class 3. It is contained in the emissions from enterprises of ferrous and non-ferrous metallurgy, production of ceramics, caprolactam, linoleum, roofing felt, tar felt, glassine, polystyrene, mineral fiber plates; in emissions from the food processing, textile and paper industries, as well as from thermal and power plants (CHP, GRES, boiler houses), etc.

Exposure to sulfur dioxide in concentrations above the maximum permissible level can lead to a significant increase in various respiratory diseases, affect the mucous membranes, cause inflammation of the nasopharynx, bronchitis, cough, hoarseness and sore throat. Especially high sensitivity to sulfur dioxide is observed in people with chronic respiratory disorders, with asthma.

High concentrations of sulfur dioxide cause severe damage to vegetation. Acute damage caused by sulfur dioxide is reflected in the appearance of whitish spots on broadleaf plants (especially spinach, lettuce, cotton and alfalfa) and pine needles. The impact of SO2 on the soil decreases its fertility, because it causes acidification. The presence of sulfur dioxide accelerates the corrosion of metals in the air.

Carbon monoxide (CO) is a colorless, odorless gas, also known as white damp, hazard class 4.

Carbon monoxide is formed as a result of incomplete combustion of fossil fuels (coal, gas, oil) in conditions of lack of oxygen and at low temperatures.

65% of all carbon monoxide emissions are from transportation, 21% from small consumers and the domestic sector, and 14% from industry. Extreme concentrations are often observed in areas of increased anthropogenic pressure on the environment: during peak traffic hours or during inversions (i.e., under conditions of weak air exchange), favorable to the occurrence of smog.

When inhaled, carbon monoxide forms strong complex compounds with human hemoglobin and thereby blocks the flow of oxygen into the blood. This causes headaches, nausea, and, at higher concentration, death.

Ammonia (NH3) is a colorless gas with a pungent characteristic odor (aromatic ammonia odor), hazard class 4. In nature, it is formed during the decomposition of nitrogen-containing organic compounds.

Anhydrous ammonia gas is lighter than air and therefore rises high; as a result, it is generally dispersed and does not accumulate in the lowlands. At relative high humidity, anhydrous ammonia forms vapors heavier than air. These vapors accumulate above the ground or above the lowlands.

Nearly 80% of the ammonia produced by industry is used in agriculture as fertilizer. Ammonia is also used in refrigeration, plastics, explosives, textiles, pesticides, dyes and other chemicals. It is found in many household and industrial cleaning solutions. Household products containing ammonia are made with the addition of 5-10% ammonia, the concentration of ammonia in industrial solutions is higher – 25%, which makes them caustic.

Exposure to high concentrations of ammonia in the air causes a burning sensation in the nose, throat and respiratory tract. This can damage the respiratory tract. Inhalation of low concentrations can cause coughing, nose and throat irritation. The smell of ammonia warns of its presence early on, but ammonia also leads to a weakening of the sense of smell, which reduces the possibility of noticing it in the air at low concentrations.

Ammonia begins to interact immediately after contact with moisture on the surface of the skin, eyes, mouth, respiratory tract, which can cause chemical burns.

Ozone (O3) is a gas that is present both in the upper atmosphere and at the level of the earth, hazard class 1.

Depending on the location in the atmosphere, the ozone can be “good” or “bad” for the environment and human health. Stratospheric ozone protects life on Earth from the sun’s harmful ultraviolet radiation, while tropospheric ozone is an air pollutant that is the main component of urban smog and is very harmful to breathe.

Ground-level (tropospheric) ozone is produced through a chemical reaction caused by solar radiation. The formation of its high concentrations is most likely in the warm season. Inhalation of ozone can cause coughing, shortness of breath, and irritation of the respiratory tract. Children and the elderly are especially sensitive to ozone, and it is also dangerous for those with lung diseases.

Suspended particles (dust) is a widespread air pollutant that includes a mixture of solid and liquid particles in suspension. Suspended particles include fine particles of PM10 and PM2.5.

Fine particles PM10 and PM2.5 are solid microparticles less than 10 microns in size (PM10) and less than 2.5 microns (PM2.5) suspended in the air, which are formed as a result of construction, production (especially cement, ceramics, brick, etc.), erosion of the road surface and wear of brake pads and tires, combustion of solid fuels (coal, oil).

In a large city, there are always PM2.5 particles in the air, and in any case, a person inhales them. Day to day, if more harmful particles enter a person’s body than it loses them, then they will accumulate in the body. The main danger of PM2.5 lies not in drastic jumps in concentration, but in the chronic effect of these particles on the body. Symptoms of PM2.5 “poisoning” will appear imperceptibly. The average city resident inhales 200 billion PM2.5 particles per day. Half of them are deposited in the lungs. One such dose will do without serious consequences. But over time, the deposits of PM2.5 in the body will exceed the critical level, which will lead to an increase in the incidence of respiratory and cardiovascular diseases, for example, worsening of asthma, respiratory diseases, and an increase in mortality from cardiovascular, respiratory and oncological diseases.