ADVANCEMENT OF THE SCIENCE
the roads increased from 2.7 to 9.1 million in the last decade (Mehmood et al., 2020). The World Economic Forum in 2012 reported Karachi and Peshawar to be among the top 20 highly polluted cities in the world (Iftikhar et al., 2018). Lahore is currently the most polluted city of Pakistan. The amount of particulate matter in the atmosphere fre- quently exceeds WHO and national air qual- ity guidelines: 25 μg/m 3 24-hr mean and 35 μg/m 3 24-hr mean, respectively (Ahmad et al., 2020; Pakistan Environmental Protec- tion Agency, 2008; World Health Organiza- tion, 2021). Various studies have been conducted in different countries to identify the impacts of lockdown on the environment and air quality. This study focused on evaluating the impact of the COVID-19 lockdown on air quality in terms of particulate matter (PM 2.5 ) in four major cities of Pakistan.
FIGURE 3
24-Hour Average of PM 2.5 Concentrations Pre- and Post-Lockdown in the Selected Cities in Pakistan
WHO Limit
A: Karachi
100 120 140 160
Pre-Lockdown
Post-Lockdown
0 20 40 60 80
1/1/2020 2/1/2020 3/1/2020 4/1/2020 5/1/2020
6/1/2020
Date
WHO Limit
B: Lahore
100 150 200 250 300 350 400
Effect of Lockdown on Global Air Quality
Pre-Lockdown
Post-Lockdown
Human health is greatly impacted by air qual- ity. Thus, the unprecedented growth and development in recent years and the subse- quent impact on the environment—especially in air quality—has attracted the attention of global researchers. Short- and long-term expo- sure to air pollution has been linked to health issues such as chronic obstructive pulmo- nary disease (COPD), asthma, inflammation, and SARS (Xu et al., 2020). Fine particulate matter emissions (e.g., NO 2 , CO 2 ) from vari- ous sources such as power plants, industrial manufacturing, coal burning, and vehicles are known to cause severe health impacts. According to WHO, 92% of the world’s pop- ulation lives in areas with air quality below specified limits. In 2016, 4.2 million deaths worldwide were reported due to ambient air pollution, which is approximately 8% of global deaths. Additionally, 29% of lung can- cer deaths, 25% of heart disease deaths, 24% of stroke deaths, and 43% of lung diseases were attributed to ambient air pollution. In addi- tion, 26% of deaths related to respiratory infec- tion, 25% of deaths due to COPD, and 17% of deaths due to stroke and ischemic heart dis- ease were attributed to air pollution (Isaifan, 2020). A study conducted by Fang et al. (2016) reported that air pollution was responsible for 32% of reported deaths in China, with a 2% mortality rate associated with PM 2.5 in China.
0 50
1/1/2020
2/1/2020 3/1/2020
4/1/2020 5/1/2020
6/1/2020
Date
continued
Following government-imposed lockdown or as a personal response to COVID-19, trav- eling was majorly reduced (Muhammad et al., 2020). Air travel decreased by 96% due to COVID-19, the lowest ever rate in 75 years (Wang et al., 2020). In addition, manufactur- ing, transport, and the industrial sector were affected. Global oil demand also was drasti- cally reduced (Muhammad et al., 2020). As a result, air pollution levels in New York dropped by approximately 50% in March 2020 as compared with March 2019 (Hen- riques, 2020; Saadat et al., 2020). In Rio de Janeiro, Brazil, in the first week of quarantine, public transportation use decreased by 50%, accompanied by significant reductions in particulate mat-
ter. Similar results were reported in China, Spain, Italy, France, and India. Reduction of economic activity and road traffic in Rio de Janeiro led to a decline in NO 2 and CO levels (Dantas et al., 2020). Similarly in São Paulo, Brazil, during lockdown, reductions of up to 77% in NO, 54% in NO 2 , and 65% in CO concentrations were reported (Nakada & Urban, 2020). In China, COVID-19 led to lockdown of major commercial and industrial activi- ties and a reduction in travel, which led to a remarkable reduction in air pollutant emis- sions to levels that had not been recorded in years. Lockdown resulted in a 25% reduction in carbon emissions by February 2020. A dramatic reduction in NO 2 levels (i.e., 30%)
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Volume 85 • Number 6
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