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Environmental Sciences Europe
Fig. 11 | Environmental Sciences Europe

Fig. 11

From: Air quality index variation before and after the onset of COVID-19 pandemic: a comprehensive study on 87 capital, industrial and polluted cities of the world

Fig. 11

Differences of AQI parameters in high-income and upper-middle and lower (< UM) income countries by independent-sample t-test. AQI values in high-income countries were significantly lower than those in < UM countries except ozone. Horizontal blue lines represent group median with interquartile range

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