Continue your usual outdoor activities.
PM₁₀ includes both fine particles (PM₂.₅) and larger particles up to 10 micrometres across. Sources include road and construction dust, wind-blown soil, fuel burning and particles formed in the atmosphere. PM₁₀ is not the same as coarse particles alone: those are the fraction between 2.5 and 10 micrometres.
Nitrogen dioxide (NO₂) comes mainly from fuel burning in vehicles, heating, power generation and industry. Gas stoves and other fuel-burning appliances can also release it indoors. It contributes to the formation of ozone and fine particles in the atmosphere.
Ground-level ozone (O₃) forms when sunlight drives reactions involving nitrogen oxides and volatile organic compounds. Levels often rise in sunny weather, and pollution can be transported away from its sources. Ground-level ozone is harmful; it is different from the protective ozone layer high in the atmosphere.