*3.3. Coarse Particulate Matter (PM10)*

*3.3. Coarse Particulate Matter (PM10)* PM10 is one of the leading driving factors of air pollution‐caused deaths in Tehran. The contribution of traffic flow emissions to particular matter concentrations and their negative impact on human health has been explored in many studies [52–54]. In Tehran, PM10's usual concentration is 90.6 μg/m3 [1]. The mean annual PM10 concentration in 2020 decreased from 56.7 μg/m3 to 55.8 μg/m3 in 2019, which is not a significant reduction (*p*‐ value > 0.05) (Figure S4). This indicates that PM10 in Tehran was approximately three times higher than the standard threshold recommended by WHO (annual mean of 15 μg/m3) [55]. In 2020 (2019), the highest concentration of PM10 was 139 μg/m3 (204 μg/m3) at station 7 (4) and in December (August). In addition, in 2020 (2019), the minimum concentration of PM10 was 5 μg/m3 (8 μg/m3) at station 2 (2), and it was observed in February (March). The results showed an increase in the mean PM10 concentration in six stations (Stations 5, PM<sup>10</sup> is one of the leading driving factors of air pollution-caused deaths in Tehran. The contribution of traffic flow emissions to particular matter concentrations and their negative impact on human health has been explored in many studies [52–54]. In Tehran, PM10's usual concentration is 90.6 µg/m<sup>3</sup> [1]. The mean annual PM<sup>10</sup> concentration in 2020 decreased from 56.7 µg/m<sup>3</sup> to 55.8 µg/m<sup>3</sup> in 2019, which is not a significant reduction (*p*-value > 0.05) (Figure S4). This indicates that PM<sup>10</sup> in Tehran was approximately three times higher than the standard threshold recommended by WHO (annual mean of 15 µg/m<sup>3</sup> ) [55]. In 2020 (2019), the highest concentration of PM<sup>10</sup> was 139 µg/m<sup>3</sup> (204 µg/m<sup>3</sup> ) at station 7 (4) and in December (August). In addition, in 2020 (2019), the minimum concentration of PM<sup>10</sup> was 5 µg/m<sup>3</sup> (8 µg/m<sup>3</sup> ) at station 2 (2), and it was observed in February (March). The results showed an increase in the mean PM<sup>10</sup> concentration in six stations (Stations 5, 7, 8, 9, 11, and 13) in 2020 compared to 2019, especially in March, June, July, and November (*p*-value < 0.05). In general, the lowest PM<sup>10</sup> concentrations were

7, 8, 9, 11, and 13) in 2020 compared to 2019, especially in March, June, July, and November

may be a sign of stability in the atmospheric boundary condition and is consistent with

the behavior presented by other researchers [56] (Figure 5).

observed in February and March, whereas the highest levels were observed in September and October. This pattern may be a sign of stability in the atmospheric boundary condition and is consistent with the behavior presented by other researchers [56] (Figure 5). *Sustainability* **2022**, *14*, x FOR PEER REVIEW 10 of 23

**Figure 5.** *Cont*.

**Figure 5.** (**a**) Distribution map of the mean monthly PM10 concentration at each station and (**b**) spa‐ tial distribution of variations in the mean monthly PM10 concentration in 2020 compared to 2019. **Figure 5.** (**a**) Distribution map of the mean monthly PM<sup>10</sup> concentration at each station and (**b**) spatial distribution of variations in the mean monthly PM<sup>10</sup> concentration in 2020 compared to 2019.
