Table 2. Descriptive statistics of the spatial variation of PM₁₀, PM_2.5, NO₂ and O₃, according to the municipality class.

Municipality class	PM10 (μg/m3)		PM2.5 (μg/m3)		NO2 (μg/m3)		O3 (μg/m3)
	Median	Min-Max	Median	Min-Max	Median	Min-Max	Median	Min-Max
Class 1	23.7	14.2–52.6	22.3	12.7–49.7	28.4	15.5–64.8	106.3	94.8–114.1
Class 2	16.8	10.7–37.2	15.9	9.6–35.3	17.2	8.2–47.9	106.4	100.0–112.7
Class 6	15.6	10.7–31.2	14.8	9.6–29.6	15.0	4.0–38.2	104.5	93.5–114.8
Class 5	13.5	9.8–28.0	12.6	8.7–26.5	12.6	3.4–32.8	103.1	86.5–114.6
Class 4	12.0	6.5–23.4	11.3	6.1–22.3	7.8	2.7–25.5	101.2	86.2–113.5
Class 3	10.7	6.0–18.2	10.1	5.6–17.4	5.2	1.9–15.5	99.8	85.5–110.1

Class 1: most populated regional capitals (Turin, Milan, Venice, Genoa, Bologna, Florence, Rome, Naples, Bari, Cagliari, Palermo, Catania); Class 2: municipalities within regional capital metropolitan areas; Class 3: municipalities with less than 2,000 resident inhabitants; Class 4: municipalities with 2,001–10,000 resident inhabitants; Class 5: municipalities with 10,001–50,000 resident inhabitants; Class 6: municipalities with more than 50,000 resident inhabitants.

The classes are ordered by decreasing air pollutants concentration levels.