Potential environmental impact of the chlorine-containing disinfectants usage during the COVID-19

Chlorine radicals (Cl) play a crucial role in atmospheric chemistry. The COVID-19 (coronavirus disease 2019) pandemic significantly increased the use of chlorine-containing disinfectants in China, leading to enhanced emissions of chlorine gas (Cl₂) and hypochlorous acid (HOCl). In this study, we use the Community Multiscale Air Quality (CMAQ) model with updated chlorine chemistry to evaluate the potential air quality impact of chlorine emissions from disinfectant usage during February 2020, a month with a large outbreak of COVID-19 in mainland China. Results indicate that during the pandemic, there was a sharp increase of reactive chlorine emissions, with Cl₂ and HOCl emissions reaching 773.9 t and 5,913.1 t, making 3 times increase. The emissions of chlorine enhanced atmospheric oxidation capacity (AOC) through the oxidation of VOC by Cl and OH, with the average enhancement in Shanghai, Beijing and Wuhan areas reaching 4.6% ± 1.8%, 10.3% ± 6.6% and 7.4% ± 4.6%, respectively. Consequently, the use of chlorine-containing disinfectants may have contributed to observed increases in the monthly average of the maximum daily 8-h average ozone (MDA8 O₃) and fine particulate matter (PM_2.5) concentrations by up to 1.5 ppbv (5%) and 1.7 μg/m³ (1%), respectively. Especially, the maximum hourly increase values of O₃ and PM_2.5 concentrations were 4.8 ppbv and 11.4 μg/m3, 2.5 ppbv and 4.5 μg/m3 in Beijing and Wuhan, respectively. These results indicate that chlorine emissions from the widespread use of disinfectants have had a significant impact on air quality in certain regions (Beijing and Wuhan) and during specific periods (9:00~12:00).