This study evaluated the pollutant levels (NO2, SO2, CO, and O3), air quality index (AQI) and the influence of meteorological variables and coronavirus disease (COVID-19) pandemic on the air quality in Rio de Janeiro. The data set used comprises periods before (March-April, 2019) and during pandemic (March-April, 2020). According to the AQI results, on most days, the air quality was ranked as “good”. Brazilian air quality standards for SO2, O3, and NO2 were not exceeded in any of the monitoring stations during partial lockdown, while CO exceeded in all periods in one site due to industrial emission. Comparing both periods, descriptive statistics for the meteorological parameters presented no differences, which suggests similar conditions. However, when evaluated week by week in 2020, weather conditions presented some differences that probably affected pollutant concentrations. The correlations between O3 and NO2 and some meteorological parameters indicate that variations in both favored ozone formation, since it is a photochemical process favored by temperature and solar radiation and that, in Rio de Janeiro, low NO2 concentrations lead to increased O3. The improvements on air quality during the partial lockdown may be attributed mainly to a reduction on emission sources rather than weather conditions.

For the accomplishment of Olympic and Paralympic Games in Rio de Janeiro city (Rio 2016), the government of the Rio de Janeiro state has undertaken to monitor air quality before and during the events. In Beijing, China, and Athens, Greece, the air quality was monitored in Olympic venues in order to evaluate the athletes’ performance in relation to the environment in which they were exposed. This study has the same proposal to Rio de Janeiro, Brazil. The air quality scenario of the three previous years (2013, 2014, 2015) of Rio 2016 was considered. Coarse (PM10) and fine (PM2.5) particles and O3 were monitored continuously on the stations located near to competition venues, as required by International Olympic Committee (IOC). The levels registered ranged from 6 to 96 μg m-3 for PM10, 1 to 44 μg m-3 for PM2.5 and 121 to 269 μg m-3 for O3. These concentrations exceeded the national and international air quality standards. These high concentrations are associated with uncountable civil works to build Olympic arenas and the urban mobility´s improvement. However, the concentrations for all the pollutants monitored in Rio de Janeiro city were in lower concentrations than in Beijing Olympic Games 2008.