Interestingly, weather conditions were found to also affect infection and death rates. A direct relationship was found between air pollution and COVID-19 infection rates. In recent de- cades, air pollution has been a hot topic due to increasing uncontrolled anthropogenic ac- tivities (Sousan et al., 2022). Reports show that air pollution is a major reason for many deaths annually (Norouzi & Asadi, 2022). Although attempts have been made to decrease the emis- sion of pollutants, no serious actions have been taken (Albayati et al., 2021). When COVID-19 began to spread in early 2020, many countries declared a lockdown in an attempt to stop the virus from spreading, and this action benefited the environment in an unprecedented way. Scientists found strong evidence that lockdowns resulted in significantly reduced air pollution emissions (Albayati et al., 2021). In this article, we discuss current issues that link air pollution and COVID-19 in 2 years af- ter identifying this disease (between 2021 and 2022). Our literature review highlighted several relationships that link air pollutants (e.g., PM 2.5 , PM 10 , nitrogen oxides, sulfur oxides, carbon oxides) with COVID-19 infections. In particu- lar, we discuss two relationships between air pollutants and the spread of COVID-19. These air pollutants 1) can contribute to the spread of COVID-19 and 2) have a negative effect on human health. Thus, we focus on the impor- tance of studying the impact of air pollution on human health, using SARS-CoV-2 as a model. Cases Related to Air Pollution and Linked to the COVID-19 Pandemic Impacts of Air Pollution There are different types of air pollutants, and they all negatively influence human health, although to differing degrees. Exposure to some pollutants is harmful in the short term, with other effects appearing only in the long term. Norouzi and Asadi (2022) studied the relationship of PM 2.5 , PM 10 , and nitrogen diox- ide (NO 2 ) levels with confirmed COVID-19 infection and mortality cases in 12 cities in Iran, with a focus on minor changes in cli- mate conditions. This study occurred over the 6 months of March–August 2020. They ana- lyzed patient age, COVID-19 cases, chronic diseases (e.g., hypertension, diabetes, obesity), and air pollutants using Poisson regression
modeling. Results showed that NO 2 had the highest negative effect and was responsible for increasing fatality rates, and that PM 2.5 had an unremarkable effect on death, even when there was a significant increase in the number of infections. Among the chronic diseases, dia- betes showed the highest risk when an infec- tion with a COVID-19 infection. Other factors were found to affect disease transmission, such as a patient’s education level, economic situa- tion, and social class. A similar report from Avellino in Italy cov- ered a wider time interval (January 2020–De- cember 2020), which included a lockdown pe- riod of March 9–May 18, 2020 (Cucciniello et al., 2022). Overall, six air pollutants were ex- amined: PM 2.5 , PM 10 , carbon monoxide (CO), ozone (O 3 ), NO 2 , and benzene. Results were obtained from two monitoring stations, which showed that during the lockdown there was a large reduction in air pollutant levels, except for PM 2.5 and PM 10 . This exception indicates that particulate matter pollution has multiple sources and is not limited to only traffic as a source. The authors conclude it is important to have governmental oversight to control and track pollutant emissions. In summarizing the findings of other re- search, we concluded that all air pollutants have a harmful effect on human health and the environment. By tracking air pollution levels before and after a lockdown, it became clear that lockdowns around the globe resulted in improving air quality. In addition, harmful emissions generated by everyday human ac- tivity have a serious negative effect on human health and the environment. This overuse of natural resources puts us more at risk for seri- ous health consequences from COVID-19. Furthermore, the pandemic showed us that we are ill-prepared for this type of disaster and must plan better for similar future situations. Infection and death rates from COVID-19 var- ied from place to place based on many factors. For instance, people living in industrial areas were exposed to more air pollutants that affect lung health. The work environment also influ- enced if someone became infected with CO- VID-19. Workers in environments that contain chemicals and other pollutants should receive special attention and healthcare. Short- and Long-Term Exposures Exposure to pollutants and chemicals af- fects the human lungs. Of note, there is a
special relationship between lung health and SARS-CoV-2 because the virus affects the re- spiratory system (Albayati et al., 2021). Air pollutants diminish lung function and can lead to an overexpression of angiotensin- converting enzyme 2 (ACE-2) within lung tissue. The virus attaches to ACE-2, which increases the chance of a respiratory infec- tion (Wu et al., 2020). A meta-analysis of 35 papers looked at the effect of short- and long-term exposure to air pollutants (Zang et al., 2022). They concluded that COVID-19 infection was directly related to long-term exposure when an increase occurred of 1 µg/ m 3 in NO 2 , PM 2.5 , and sulfur dioxide (SO 2 ) levels. Fatality rates were directly related to a rise of 1 µg/m 3 in NO 2 and PM 2.5 levels. For short-term exposure, an increase in the Air Quality Index (AQI) by 1 unit and increas- ing the NO 2 , PM 2.5 , PM 10 , and SO 2 levels by 1 µg/m 3 also increased the incidence of CO- VID-19 infections. Prinz and Richter (2022) analyzed data on PM 2.5 and PM 10 from 400 counties in Germany for 2002–2020 and linked the pol- lution data with COVID-19 infection rates. For statical purposes, Kriging interpolation and ordinary least squares (OLS) regres- sions were applied to fill the data gaps and find correlations between average levels of particulate matter and COVID-19 cases, re- spectively. They found that long-term expo- sure of 1 µg/m 3 of PM 2.5 higher than average was responsible for increasing COVID-19 infections by 199.46 ± 29.66 per 100,000 individuals, whereas the same increase in PM 10 resulted in an increase of 52.38 ± 12.99 per 100,000 individuals. Number of deaths due to COVID-19 was also correlated with increased PM 2.5 and PM 10 levels, where 6.18 ± 1.44 and 2.11 were calculated per 100,000 individuals, respectively. Results showed that a longer period of exposure was associated with a higher risk of death and that other pollutants could contribute to health risks. Figure 1 lists particulate matter distribution, COVID-19 infections, and COVID-19 deaths in Germany (Prinz & Richter, 2022). Short-term exposure to air pollutants was also found to have an effect on COVID-19 infections. Xu et al. (2022) confirmed this relationship using data from the U.S. from March 1–June 30, 2020. Among the 806 U.S. counties studied, data from 554 coun-
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March 2025 • Journal of Environmental Health
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