Strategies to combat air pollution are considered one of the biggest challenges all around the world. Large cities in developing world present poor air quality and less restrictive legislation allowing the population to be more exposed to the damage caused by pollutants. In order to study the source and fate of the air pollutants, field campaigns have been made in São Paulo city, Brazil. Sixty PM2.5 samples were collected from July to December 2019 just before the pandemic; other fifty samples were collected during one of the peaks of COVID-19 contamination in this city (from June to August 2020). Polycyclic aromatic hydrocarbons (PAH) and water soluble ions were determined. Concentrations of PM2.5 varied from 5 to 52 µg m-3 in 2019 samples and from 5 to 35 µg m-3 during the pandemic. The most abundant PAH were benzo(e)pyrene, benzo(b)fluoranthene and pyrene. These compounds are ubiquitous in urban atmosphere and present risks for human health. Benzo(a)pyrene equivalent over 1 indicates risk of cancer in the samples collected in 2019, before the pandemic. Sulfate, nitrate, sodium, ammonium, and potassium are the most abundant ions Figure above, shows the concentrations of the most abundant species in 2019 samples. These species are emitted by anthropogenic and natural sources, mainly vehicles, biomass burning and sea salt.