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What is PM10?
PM10 is dust in the air made of particles up to 10 microns across. This page explains what it includes, where it comes from, what the WHO guideline says, and how the map shows it.
What PM10 is
PM10 means particulate matter up to 10 microns across. It is measured in micrograms per cubic metre of air (µg/m³). In Bulgarian it is called ФПЧ10. PM10 includes PM2.5, plus the coarser particles such as road dust, soil and pollen fragments.
Where PM10 comes from in Bulgaria
In winter, burning wood and coal for heating raises PM10 together with PM2.5. All year, road traffic stirs up dust and wears tyres, brakes and road surface. Construction, industry, farming and natural dust from soil add to it. The European Environment Agency (EEA) describes these as the main sources across Europe. Dry and windy days can raise PM10 without any burning at all.
What it means for health
The World Health Organization (WHO) explains that PM10 particles can be breathed in and reach the lungs. They are linked with breathing problems, and the smaller PM2.5 part is linked with the more serious effects. People with asthma or heart and lung conditions are the most sensitive. One reading on its own does not describe your personal risk.
Guideline values and map colours
The map colours follow the bands of the European Air Quality Index. For PM10, good is up to 15 µg/m³, fair up to 45, moderate up to 120, poor up to 195, very poor up to 270, and above that extremely poor. Grey means there is not enough data.
The WHO 2021 Global Air Quality Guidelines recommend a PM10 yearly average of no more than 15 µg/m³ and a 24-hour average of no more than 45 µg/m³. The index bands apply to hourly values, so they are not the same test as the WHO guideline. Always check the official source for legal limits.
How Kanarche measures it
Most readings come from low-cost optical sensors that volunteers run in the Sensor.Community network. The value for an area is the median of the sensors that reported recently, and we show a value only when at least three separate locations report. Official stations of the Executive Environment Agency (ИАОС) are shown too where they exist, with data from the European Environment Agency. Low-cost sensors are not reference instruments and high humidity makes them read higher, so the numbers are indicative. They show change over time and differences between places well.
What to do when the level is high
On a day with high values, people usually cut down strenuous activity outdoors, keep windows closed during the worst hours, and ventilate when the level drops. People with heart or lung conditions should follow their doctor's advice. This map gives no health advice. For official alerts, follow the Ministry of Health, the regional health inspectorates (РЗИ) and the Executive Environment Agency (ИАОС).