Air pollution particulate matter (PM) is associated with SARS-CoV-2 infection and severity, although mechanistic studies are lacking. We tested whether airway surface liquid (ASL) from primary human airway epithelial cells is antiviral against SARS-CoV-2 and 229E-CoV (responsible for common colds), and whether PM (urban, indoor (IAP), volcanic ash) affected ASL antiviral activity. ASL inactivated SARS-CoV-2 and 229E-CoV. Independently, urban PM also decreased SARS-CoV-2 and 229E-CoV-2 infection, and IAP decreased 229E-CoV infection. However, in combination, urban PM impaired ASL’s antiviral activity against both viruses and the same effect occurred for IAP and ash against SARS-CoV-2, suggesting PM may enhance SARS-CoV-2 infection.