Ozone is a colourless, toxic gas. At ground level, it is formed from nitrogen oxides and other volatile organic compounds by solar radiation, through photochemical processes.

• Main sources: road traffic, combustion plants, solvents, agriculture
• Health effects: damage to the lungs, intensification of asthma symptoms or other lung diseases, irritation of the respiratory tract
• Affected risk groups: people with lung diseases, children, seniors, people active outdoors
• Environmental impact: impaired plant growth, quality and quantity of agricultural products

PM10 summarizes all solid and liquid particles with different chemical compositions with a diameter smaller than 10 μm.

• Main sources: road traffic, power plants, stoves / heaters in residential buildings, metal production, agriculture, soil erosion
• Health effects: depending on the size, particles penetrate into the nasal cavity, bronchi or blood circulation and damage the tissue
• Affected risk groups: people at increased risk of lung, heart / circulatory diseases or diabetes, children, seniors, people active outdoors

PM2.5 summarizes all solid and liquid particles with different chemical compositions with a diameter smaller than 2.5 μm.

• Main sources: road traffic, power plants, stoves / heaters in residential buildings, metal production, agriculture, soil erosion
• Health effects: depending on the size, particles penetrate into the nasal cavity, bronchi or blood circulation and damage the tissue
• Affected risk groups: people at increased risk of lung, heart / circulatory diseases or diabetes, children, seniors, people active outdoors

Nitric oxides are by-products of combustion processes. Under sunlight, they are instrumental in the formation of ground-level ozone and are also a source of fine dust.

• Main sources: road transport, combustion plants, solvents, agriculture
• Health effects: irritants and narrows the bronchi, intensifies lung diseases, increases the risk of diabetes and heart/circulatory diseases
• Affected risk groups:  persons with lung disease or increased cardiovascular risk, children, seniors, outdoor active persons
• Effects on the environment: Impaired plant growth, leading to overfertilization and acidification of soils and waters.