In Brazil, states are responsible for monitoring air quality, with state environmental agencies each implementing and managing their own monitoring system. Based on the information contained in the Air Quality Platform, the interactive panel below shows where there are or have been monitoring stations in the country¹, which pollutants are being and have been monitored, the state agencies in charge, and the type of technology used. It is possible to choose the pollutant(s) and view all the stations that monitor it on the map. Currently, the Platform provides air quality monitoring information for ten Brazilian states and the Federal District. See the monitoring coverage present in the Air Quality Platform over the years:

An overview of the daily air quality assessment in several stations, simultaneously, can be consulted in this panel. Each square is colored according to the Air Quality Index classification (and WHO air quality guidelines, as in the previous panel) for each season and pollutant on the day. By selecting “All” in the “Pollutant” filter, it is possible to see the overall air quality classification defined based on the pollutant with the worst classification. For example: if in a certain season the air quality for a pollutant was evaluated as “Very bad”, for another pollutant it was evaluated as “Moderate” and for all others it was evaluated as “Good”, the overall classification will be “Very bad”. Select station group via panel commands. Identify critical periods and areas.

In a second tab on the panel, it is possible to see the daily information aggregated by month, making it easier to observe the behavior of pollutants throughout the seasons. For example, generally the winter months in the southern hemisphere (between June and August) have higher concentrations of particulate matter. To switch between views, select the desired tab at the top of the left panel.

Air quality standards are reference values of concentration of pollutants that act as targets in air quality management. In Brazil, air quality standards are established by a Resolution of the National Council for the Environment (CONAMA, the acronym in Portuguese) No. 491/2018 and are organized into levels. There are intermediate standards (IS), from 1 to 3, which represent provisional or temporary values for a given polluted region, which over time should aim to continue advancing to higher standards, improving air quality in stages until reaching the final standard. The final standards (FS) follow the 2005 World Health Organization definitions. However, the WHO revised its recommendations and for PM10 and PM2.5 the recommended values became more restrictive in 2021⁵. Thus, for the other pollutants, the AQG overshoots are equal to the FS overshoots.

In the panel below, it is possible to see how many days in the year exceeded air quality standards at a station for a given pollutant, as well as the number of days with average concentrations higher than WHO recommendations. The panel also shows the number of days when there was no effective monitoring to assess air quality on a daily basis.

After a year has ended, air quality can be evaluated based on an average value, calculated through daily concentrations for each pollutant, considering representativeness criteria⁶. The higher the average value, the more polluted the air was throughout the year. Unlike the daily assessment of air quality, the air quality index (AQI) is not applied in the annual assessment. However, there are air quality standards adopted in Brazil for assessing air quality on an annual scale, as well as values guidelines by the WHO.

Currently, Brazil has up to 4 standards, depending on the pollutant. Three standards are interim or intermediate (intermediate standards 1, 2 and 3) and there is the final standard. In addition to demonstrating the lines (limit values) of the standards in force by the National Council for the Environment (CONAMA), the visualization below shows the limit value recommended by the WHO (Air Quality Guideline, AQG). In this panel, when choosing a monitoring station and a pollutant, we can assess whether or not the level of air pollution in the year exceeded the value recommended by the WHO, or the air quality standards in Brazil, in addition to observing the representativeness of the data on the yearly scale.

This panel presents the air quality assessed on an annual scale for each monitored station, locating it on the map. With the data identified with their latitudes and longitudes on the map, critical regions are observed, where most stations have conflicting values according to the WHO recommendation, i.e., most stations present concentrations of at least one pollutant with values that can be harmful to the health of the population.

An air quality monitoring network is composed of a set of stations installed in strategically defined locations. According to the Brazilian Ministry of Environment (2019), monitoring stations should be classified according to their spatial representation, in increasing order of scope: microscale, medium scale, neighborhood scale or urban scale. This spatial representativeness class for each station is defined according to the pollutant monitored and the characteristics of the surroundings. Microscale stations are characterized by the presence of intensive emission sources in their immediate surroundings and aim to observe the most direct effect of these sources on air quality. In turn, an urban scale station, the one with the greatest spatial coverage, seeks to measure the background pollution of the city, which represents the minimum levels of environmental atmospheric pollution to which the population is chronically exposed. Mid-scale and neighborhood-scale stations are intermediate classes. On the panel, it is possible to consult the scale classification when placing the cursor over each station.