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The composition of polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs), hexachlorobenzene (HCB), pentachlorobenzene (PeCB), and organophosphate flame retardants (OPFRs) present in the gas-phase fraction of the atmosphere of Barcelona was analyzed during the SARS-CoV-2 coronavirus disease (COVID-19) lockdown and prior to this period. The changes in daily concentrations of CO, NO, NO 2 , O 3  and particulate matter smaller than 10 μm (PM 10 ) were considered for comparison. Bayesian analysis considering serial dependencies and seasonality showed statistically significant decreases of CO, NO, NO 2 , and PM 10  (between −28 and −76%) and O 3  increases (+45%) during lockdown. However, the lockdown concentration decreases of PeCB (−90.5%, from 8.5 to 0.8 pg m –3 ), HCB (−79%, 25.5–5.4 pg m –3 ) and some PAHs, such as benz[a]anthracene (−87%, 120–17 pg m –3 ) and pyrene (−81%, 3,500–680 pg m –3 ), were even stronger. The PAH depletion ranged between −68 and −87% that could be primarily associated with the strong reduction of traffic mobility during this period (−80%). Besides traffic reduction, the observed air quality improvements could be related to lower generation of solid urban residues (−25%) and the subsequent decrease of urban waste incineration (between −25 and −28%). Tributyl phosphate also showed a reduction in concentration during lockdown but the other OPFRs were seemingly not affected by this restriction, possibly as a result of the uniform release from the emission sources, e.g., construction material, industrial applications, and household products.

Changes in Urban Gas-Phase Persistent Organic Pollutants During the COVID-19 Lockdown in Barcelona