Imissions

Imissions are generated as a result of emissions being in contact with the environment, leading to their storage in the soil, plants and organisms. Their concentration is lower than the concentrations of emissions and imissions’ concentrations in cities are monitored.

Solid air imissions
Solid air imissions include dust and aerosols. The most frequent agents are various inorganic powders, such as metal particles, silicates, fluorides, chlorides and sulphates. Dusts of organic origin such as tars, bacteria and pollens. General harm of solid air imissions are mainly:
 * 1) Reducing visibility
 * 2) Toxicity to living organisms
 * 3) Corrosive effect on materials.

These substances also adsorb gas particles and thus contribute to then increase of the reactivity of particles and secondary emissions. In industrial areas they are responsible for the condensation of water droplets → an increased incidence of fog and clouds. The specific degree of harm depends on many factors:
 * 1) Particle size (and dispersity which depends on it). According to these parameters depends the substance retention in the lungs.
 * 2) Biological aggressiveness (react or not reacting with lung tissue? Formation of coniosis?).
 * 3) Physical properties: especially particle shape, crystalline structure and surface wettability.

Harmful solid air imission depending on particle size:
 * Particles larger than 100 μm have relatively little importance to the health of individuals, because they quickly settle due to their considerable weight. For this reason, considerably limited their interaction with other pollutants in the air.
 * Dust particles in the size of 10 μm are referred to as an aerosol. Mass content is relatively low in the air. They have great biological significance. They are inhaled by humans, but for the most part are already captured in the upper respiratory tract. They settle in a layer of mucus that is moved by cilia toward the nasopharynx and then swallowed. If these particles have a toxic chemical nature, they have a significant health impact.
 * Particles smaller than 10 μm in the air are present in small quantities, but have great biological significance. The respiratory tract in 24 hours they will receive up to 0.01 g. The molecular size of 1-2 micron penetration into the bronchioles and alveoli, where they are sometimes captured in more than 90%. These particles are therefore in terms of retaining the aerosol in the lungs the most dangerous.
 * On the contrary, particles smaller than 0.01 micron in the lungs begin to behave like gas molecules and are largely exhaled.

Chemical composition of dust as a factor of harmfulness
Biologically inert powder doesn’t have a specific biological effect and thus does not harm the lungs. Conversely, biologically aggressive dust has specific effects thanks to its chemical composition. Examples:
 * Inhalation of silica (SiO2) → fibroplastic effects. If the air contains about 10% of the dust, occurs when the long-term inhalation of progressively to chronic airway inflammation, increased connective tissue in the lungs, honeycombed lungs, increased blood flow resistance in the pulmonary circulation, and consequently right heart hypertrophy and failure. These expressions are summarized under the name of lung silicosis.
 * Long-term inhalation of asbestos fiber dust is to develop asbestosis, and increases the risk of pleural mesothelioma.
 * Dusts containing beryllium inhaled during immunosuppression can lead to beryllosis.
 * Dusting powder iron in the lungs is known as siderosis.

Physical properties of dust as factor of harmfulness
Physical properties of particles are the answer to the question of why silica dust causes silicosis in the glass industry, while the population of the Sahara, which is exposed to inhalation of large quantities of silica dust, is not suffering. Sahara dust is predominantly silica, but due to the age of particles and their mutual abrasion they become amorphous. Dust particles in glass are newly created and predominantly crystalline having many edges and tips → far more toxic.

Gaseous air imissions
Gaseous air imissions include compounds of various elements, mainly sulfur compounds, nitrogen oxides, carbon oxides, halogen compounds and various organic compounds. They have diverse origin:
 * Sulfur oxides (SO2 and SO3), sulphide, carbon disulphide - resulting from the burning of fossil fuels (mainly coal), burning fuel oil as the product of different technologies (especially in chemical industry)
 * Oxides of nitrogen, ammonia - result from burning at high temperatures (heat and power plants on fossil fuels), the cylinders of piston engines;
 * Carbon oxides (CO and CO2) - formed by incomplete combustion of carbonaceous fuels (mainly car traffic), as significant concentrations in the boiler;
 * Halogen compounds (HF, HCl) - released into the atmosphere in metallurgical processes (aluminum), also arise in the manufacture of phosphate fertilizers;
 * Organic compounds (saturated and unsaturated aliphatic and aromatic hydrocarbons, formaldehyde, formic acid, acrolein) - in the atmosphere occur in large nožství(?). Major sources are automobile engines (two-and four-stroke gasoline engines).

Detection of most of these substances is significant because:
 * Nitrogen compounds are highly irritating to the body after inhalation and the change in the blood are the cause of methemoglobin.
 * They participate in photochemical reactions that lead to the formation of secondary emissions.
 * Organic compounds in air pollution is a large amount, especially saturated and unsaturated aliphatic and aromatic hydrocarbons and their oxygen derivatives, as well as indoor. They are emitted as vapors or volatile compounds.
 * Many polycyclic aromatic hydrocarbons have proven carcinogenic properties.

Radioactive air imissions
Radioactive air imissions include strontium, caesium and iodine isotopes and other substances. These imissions, threatened the man by air almost exclusively in a nuclear accident (such as in Chernobyl in 1986). If properly operated, nuclear power plants are, in terms of radioactive emissions into the atmosphere, less dangerous than normal coal fired thermal power plants.

=Smog=

Related articles
Primary and Secondary Emissions