# Changes of Air Pollution between Countries Because of Lockdowns to Face COVID-19 Pandemic
###### Abstract
\begin{table}
\begin{tabular}{l l l} \hline
**Parameter** & **Region, Country** & **Variation in Air Pollutants** \\ \hline \multirow{9}{*}{CO} & Bogota, Colombia & 23–34\% reduction [57] \\  & Quito, Ecuador & 48.75\% reduction [58] \\  & Beijing-Tianjin-Hebei, China & 20.40\% reduction [59] \\  & Dhaka, Bangladesh & 8.8\% reduction [60] \\  & Delhi, India & 30.35\% reduction [61] \\  & Nagpur, India & 63\% reduction [62] \\  & USA and China & 19.28–25.53\% reduction in USA and China [63] \\  & Santiago, Chile & 13\% reduction [64] \\ \hline \multirow{9}{*}{NO\({}_{2}\)} & Bogota, Colombia & 13–22\% reduction [57] \\  & Delhi and Mumbai, India & 60–78\% reduction for Delhi and Mumbai [65] \\  & Barcelona, Spain & 66\% reduction [66] \\  & Quito, Ecuador & 63.98\% reduction [58] \\  & China & 19.11 \(\pm\) 9.4\% reduction [67] \\  & Vietnam & 24–32\% reduction [68] \\  & Nagpur, India & 69.2\% reduction [69] \\  & Makkah, Saudi Arabia & 58.66\% reduction [70] \\  & Beijing-Tianjin-Hebei, China & 37.80\% reduction [59] \\  & Dhaka, Bangladesh & 20.4\% reduction [60] \\  & Bangladesh & 40\% reduction [25] \\  & United Kingdom & 38.3\% reduction [71] \\  & Leeds, Sheffield, and Manchester, England & 37.13–55.54\% reduction [27] \\  & Ankleshwar, Vapi and Gujarat, India & 80.18\% reduction [72] \\  & Delhi, India & 52.68\% reduction [61] \\  & Bengaluru (Bangalore), India & 87\% reduction [62] \\  & USA and China & 36.7–38.98\% reduction in USA and China [63] \\  & Rio de Janeiro and São Paulo, Brazil & 10–40\% reduction [73] \\ \hline \multirow{9}{*}{SO\({}_{2}\)} & Bogota, Colombia & 11–20\% reduction [57] \\  & Delhi and Mumbai, India & 19–39\% reduction for Delhi and Mumbai [65] \\  & Quito, Ecuador & 45.76\% reduction [58] \\  & Nagpur, India & 64.3\% reduction [69] \\  & Dhaka, Bangladesh & 17.5\% reduction [60] \\  & Bangladesh & 43\% reduction [25] \\  & USA and China & 3.81\% increase in the USA–18.36\% reduction in China [63] \\ \hline \multirow{9}{*}{O\({}_{3}\)} & Bogota, Colombia & 31.3–14.1\% increase [57] \\  & Barcelona, Spain & 27\% increase [66] \\  & Quito, Ecuador & 26.54\% increase [58] \\  & Makkah, Saudi Arabia & 68.67\% increase [70] \\  & Morocco & 22–28\% increase [74] \\  & Dhaka, Bangladesh & 9.7\% reduction [60] \\  & Bangladesh & 7\% increase [25] \\  & United Kingdom & 7.6\% increase [71] \\  & Santiago, Chile & 63\% increase [64] \\ \hline \multirow{9}{*}{PM\({}_{2.5}\)} & Bogota, Colombia & 7–15\% reduction [57] \\  & Quito, Ecuador & 42.17\% reduction [57] \\  & Jiangsu, China & 18\% reduction from pre-COVID; 2\% decrease \\  & & post-COVID [75] \\  & Valencia, Spain & 3.1\% increase [76] \\  & Toronto, Canada & 4\% reduction [52] \\  & Beijing-Tianjin-Hebei, China & 21.50\% reduction [59] \\  & Leeds, Sheffield, and Manchester, England & 29.93–40.26\% reduction [27] \\  & New Delhi, Chennai, Kolkata, Mumbai, and & 62\% reduction, followed by Mumbai (49\%), \\  & Hyderabad, India & Chennai (34\%), and New Delhi 26\% [77] \\  & Ahmedabad, India & 68\% reduction [62] \\  & Santiago, Chile & 11\% reduction [64] \\ \hline \end{tabular}
\end{table} 
Table 1: Studies concerning the effects of lockdown measures to cope with the COVID-19 pandemic on levels of different air pollutants. In particular, within the just-mentioned theoretical framework, studies show contradictory results of the above relation across different countries worldwide; these problems are a starting point for further investigation developed here. The study here endeavors to verify whether statistical evidence developed here supports the proposed _research hypothesis_ that the general change (especially, reduction) of air pollutant concentrations between countries can be explained by the measures of control (restriction policy of lockdown) applied to face COVID-19 pandemic. The method of inquiry and results of the study here provide critical implications of strict public policies, beyond health emergencies, as measures of control for environmental pollution in order to foster sustainable pathways of growth.