Long-term exposure to ambient air pollution, a major contributor to global disease burden, could increase the risk of severe COVID-19 outcomes by several mechanisms. Air pollutants can reduce individuals’ pulmonary immune responses and antimicrobial activities, boosting viral loads. Air pollution can also induce chronic inflammation and overexpression of the alveolar angiotensin-converting enzyme 2 (ACE) receptor,7 the key receptor that facilitates SARS-CoV-2 entry into cells. Exposure to air pollution contributes to chronic conditions, such as cardiovascular disease, that are associated with unfavourable COVID-19 prognosis, possibly owing to persistent immune activation and excessive amplification of cytokine development. Thus, greater exposure to long-term air pollution may lead to severe COVID-19 outcomes.
