by approximately 60% and 40%, respectively, while NO 2 and CO decreased by 52.68% and 30.35%, respectively, compared with the pre- vious year (Mahato et al., 2020). Moreover, in major cities in India such as Pune, Mumbai, and Ahmedabad, NO 2 emissions decreased by approximately 40–50% in March 2020 compared with March 2019 (Paital, 2020). In Almaty, Kazakhstan, a 30–34% reduction in PM 2.5 was observed during the lockdown compared with the same time period in 2018–2019 (Kerimray et al., 2020).
FIGURE 3 continued
24-Hour Average of PM 2.5 Concentrations Pre- and Post-Lockdown in the Selected Cities in Pakistan
WHO Limit
C: Peshawar
100 120 140 160 180
Post-Lockdown
Pre-Lockdown
0 20 40 60 80
Methods
Study Area Four major cities of Pakistan were selected for the study: Karachi, Lahore, Peshawar, and Islamabad (Figure 1). These cities have been reported to have very high concentra- tions of particulate matter (Sanchez-Triana et al., 2014). Karachi, the capital city of Sindh Prov- ince, is the biggest metropolitan city and is located along the Arabian Sea (Chen et al., 2020). It is the most industrialized and urbanized city of Pakistan. The urbanization rate of the city is approximately 3%. It is also the most populated city of the country, with a population of approximately 14,910,352 according to provisional summary results of the Population and Housing Census (Gov- ernment of Pakistan, 2017). Karachi has a large industrial base, including cement factories, steel mills, oil refineries, found- ries, railroad yards, petrochemical indus- tries, shipping, automobile assembly plants, printing and publishing plants, food pro- cessing plants, brick kilns, tanneries, solid waste incineration, open burning of munici- pal waste, oil-fired power plants, metal recy- cling plants, and some light industry (Chen et al., 2020; Parekh et al., 2001; Shahid et al., 2016). In addition, Karachi has more than 3.6 million vehicles, the largest num- ber in the country (Khan et al., 2018). These sources contribute to high particulate emis- sions in the city and severe air quality, and thus pose health risks to residents of the city (Chen et al., 2020; Gurjar et al., 2010; Parekh et al., 2001). Lahore is the capital of Punjab Province and is situated along the Ravi River. It is the second most populated city of Pakistan with a population of approximately 11,126,285
1/1/2020
2/1/2020 3/1/2020
4/1/2020 5/1/2020
6/1/2020
Date
WHO Limit
D: Islamabad
100 120 140 160 180
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 = World Health Organization.
was also observed following lockdown (Myl- lyvirta, 2020; Tahir & Masood, 2020). According to the National Aeronau- tics and Space Administration, a decrease in NO 2 concentrations was first observed over Wuhan, China, which then spread to the entire country and ultimately the whole world (Dutheil et al., 2020; Wang & Su, 2020). In Shanghai, Beijing, Guang- zhou, and Wuhan, reductions in PM 2.5 were found to be 6.37, 9.23, 5.35, and 30.79 μg/ m 3 , respectively (Wang et al., 2020). Satel- lite images show a drop in NO 2 emissions in UK, Spain, and Northern Italy (Saadat et al., 2020). According to the European Space Agency, NO 2 concentrations in China, Spain, France, and Italy dropped by approximately
20–30% due to lockdown (Muhammad et al., 2020). In the northern U.S., NO 2 concentrations dropped by approximately 30% due to lock- down (Paital et al., 2020). And in the U.S. overall, CO 2 emissions dropped by approxi- mately 40%. Particulate matter concentra- tions also decreased in the U.S. and UK com- pared with the previous year (Child, 2020; Paital, 2020). Air quality in India also improved due to lockdown: people from the northern Indian state of Punjab reported that they could see the Himalayas from 100 mi away due to improved air quality (Ramasamy et al., 2020). Air quality of Delhi, India, also improved dur- ing lockdown: PM 10 and PM 2.5 were reduced
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January/February 2023 • Journal of Environmental Health
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