In the global COVID-19 epidemic, humans are faced with a new challenge. The concept of quarantine as a preventive measure has changed human activities in all aspects of life. This challenge has led to changes in the environment as well. The air quality index is one of the immediate concrete parameters. In this study, the actual potential of quarantine effects on the air quality index and related variables in Tehran, the capital of Iran, is assessed, where, first, the data on the pollutant reference concentration for all measuring stations in Tehran, from February 19 to April 19, from 2017 to 2020, are monitored and evaluated. This study investigated the hourly concentrations of six particulate matters (PM), including PM2.5, PM10, and air contaminants such as nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO). Changes in pollution rate during the study period can be due to reduced urban traffic, small industrial activities, and dust mites of urban and industrial origins. Although pollution has declined in most regions during the COVID-19 quarantine period, the PM2.5 rate has not decreased significantly, which might be of natural origins such as dust. Next, the air quality index for the stations is calculated, and then, the interpolation is made by evaluating the root mean square (RMS) of different models. The local and global Moran index indicates that the changes and the air quality index in the study area are clustered and have a high spatial autocorrelation. The results indicate that although the bad air quality is reduced due to quarantine, major changes are needed in urban management to provide favorable conditions. Contaminants can play a role in transmitting COVID-19 as a carrier of the virus. It is suggested that due to the rise in COVID-19 and temperature in Iran, in future studies, the effect of increased temperature on COVID-19 can be assessed.
In late December 2019, a new strain of an infectious disease was discovered in Wuhan, China, and was named COVID-19 (Chen et al. 2020a, b, c; Zhang et al. 2021; Afify et al. 2021). This virus, which is a human-to-human transmitted virus (Wang et al. 2020; Wang and Su 2020), causes an acute respiratory infection that can progress to pneumonia if the symptoms are not treated (Jiang et al. 2020a, b; Coccia 2021). The findings indicate that old age is one of its risk factors (Luo et al. 2020; Wang and Zhao 2021) with an approximate 2–3% fatality rate (total infected people who died) (Rodriguez-Morales et al. 2020; Bonilla-Aldana et al. 2020). On February 19, 2020, the Iranian Ministry of Health officially reported that two patients with pneumonia were associated with COVID-19 in the city of Qom. Gilan, Arak, and Tehran were the other provinces where this virus spread widely. Thereafter, the count of infected populations increased rapidly, and within 1 month, the outbreak became a national crisis, with infected individuals diagnosed all over the country (Iran Health Organization 2020). To control this infection, the National Corona Committee was deployed with subcommittees in each province. To prevent the spread of the disease, this committee has enacted measures to ban traffic at different times of the day and close or reduce the operation time of high-risk industries, factories, etc. These measures were lifted from 13 to 20 April. As of 4 May, the confirmed cases are 97,424, and the deaths are 6203 (World Health Organization 2020).
COVID-19 is a human hazard that has had different effects at different times and different places. One of the effects of COVID-19 is its effect on traffic, and its secondary effect is on air quality. This paper examines changes in air quality due to the quarantine caused by COVID-19. This study investigated the hourly concentrations of six particulate matters. Findings indicated that changes in pollution rate during the study period can be due to reduced urban traffic, small industrial activities, and dust mites of urban and industrial origins. Although pollution has declined in most regions during the COVID-19 quarantine period, the PM2.5 rate has not decreased significantly, which might be of natural origins such as dust. The results showed that the increasing percentage of the count of days caused by PM2.5 pollution has a sharp increase, which was at the beginning of the curfew on March 2. The AQI slope showed a further decrease compared to previous years. This rate followed a descending pattern until March 27, and the maximum intensity of the fixed trend index increased until April 12. The results of this study indicate that the quarantine has not been able to significantly affect the mean air quality index; this is because of the use of private cars instead of public transport, which is more evident in areas 6 and 7. On the other hand, the maximum air quality index expressed in Fig. 10 has decreased. Spatial autocorrelation analysis has shown a positive correlation between changes in decrease or increase in indicators. Finally, it can be said that although COVID-19 can affect the rate of contamination in a short period of time, due to the prevalence of COVID-19 in crowded places such as public transport fleets, people have been forced to use personal items, and as a result, pollution has increased.