Within the framework of the National Scientific Program " Environmental Protection and Reduction of Risks of Adverse Events and Natural Disasters" funded by the Ministry of Education and Science, the System for Chemical Weather Forecast (air pollution) was created. The System present the 72 hours forecast for air pollution in real-time, starting from 00:00 of the current day and extending two more days ahead for the territory of Bulgaria, with a spatial resolution of 3 km and for three selected cities - Sofia, Plovdiv, and Varna, with a resolution of 1 km each.

For each of the mentioned domeins, one of the five main pollutants can be selected - Nitrogen Dioxide (NO₂), Ozone (O₃), Sulfur Dioxide (SO₂), Fine Particulate Matter with a diameter below 10 µm (PM₁₀), Fine Particulate Matter with a diameter below 2.5 µm (PM_2.5), from which the Air Quality Index (AQI) is calculated and visualized. The system also forecasts the Universal Thermal Comfort Index (UTCI), indicating the thermal comfort/discomfort of the human body.

Fine Particulate Matter (PM₁₀)

Sources

Dust is a major atmospheric air pollutant. Its harmful health effects mainly depend on the size and chemical composition of suspended particulate matter, the chemicals adsorbed on their surface, including mutagens, DNA modulators, and others, as well as the portion of the respiratory system in which they deposit. Major sources of dust include industry, transportation, and energy production.

Impact on Human Health

Dust enters the body mainly through the respiratory system, where larger particles are retained in the upper respiratory tract, while finer particles (under 10 µm - PM₁₀) reach the lower parts of the respiratory system, leading to damage to lung tissues. Children, the elderly, and people with chronic respiratory diseases, the flu, or asthma are particularly sensitive to high levels of PM₁₀.
The harmful effect of dust pollution is more pronounced when Sulfur dioxide is simultaneously present in the atmosphere. Their synergistic action on the respiratory organs and mucous membranes has been established. It manifests with irritant effects and depends on the duration of exposure. Short-term exposure to 500 µg/m³ of dust and Sulfur dioxide increases overall mortality in the population, while concentrations half as low result in increased morbidity and impairment of lung function. Prolonged exposure to Sulfur dioxide and dust leads to increased non-specific lung diseases, mainly upper respiratory tract infections and bronchitis - at significantly lower concentrations (30 - 150 µg/m³), which is particularly pronounced in children. The most vulnerable to the combined effects of dust and SO₂ are individuals chronically ill with bronchial asthma and cardiovascular diseases.

Legislation

Information on the impact of atmospheric pollutants on human health is coordinated with the Ministry of Health (MH) and the National Center for Public Health and Analyses under Art. 44, para. 2 of Regulation No. 12 of July 15, 2010, and Order No. RD-09-159/14.04.2003 of the MH.
Regulation No. 12 of July 15, 2010 (prom. SG, No. 58 of July 30, 2010) establishes norms for Maximum Permissible Concentrations (MPC) for nitrogen dioxide, ozone, sulfur dioxide, and fine particulate matter. The introduced MPCs aim to protect against their harmful effects on human health and the environment. The following norms are regulated for different types of pollutants:

Annual Average Standard - 40 µg/m³;
Average Daily Standard - 50 µg/m³ (not to be exceeded more than 35 times per year);

https://eea.government.bg/bg/output/daily/2004-air/november/30-11.html