Exposure to pollution is uneven in the city of São Paulo

Researchers are measuring differences in pollution levels among buses, automobiles and subway in the metropolitan region.

By Maria Fernanda Ziegler, in New York  |  Agência FAPESP – Inequality in São Paulo, Brazil, also applies when the subject is air pollution. Bus passengers who have long daily commutes are exposed to more pollution than drivers or subway passengers. There is also a significant difference in pollution levels at sites such bus lanes, bus stops and on the city’s main arteries referred to as hotspots.

“Although it is still above recommendations issued by the World Health Organization (WHO), pollution in the metropolitan area of São Paulo has improved in the past 30 years. But this is when looking just at the average. Exposure to pollution is not homogenous among people. Perspectives well above this average exist for individuals, when accounting for time of exposure and places where there is more pollution,” said Maria de Fátima Andrade, a professor at the Institute of Astronomy, Geophysics and Atmospheric Sciences of the University of São Paulo (IAG-USP), in a presentation given at FAPESP Week New York.

The meeting, held at the City University of New York (CUNY) November 26-28, 2018, involved Brazilian and U.S. researchers with the aim of strengthening research partnerships.

According to the WHO, the limit of exposure to particulate matter (PM) is 20 µg/m³. This rate is exceeded by all monitoring stations owned by CETESB, the São Paulo State Environmental Agency. Some attain nearly 40 µg/m³ of particulate matter, such as at the Osasco, Grajaú and Mauá stations. Just above 20 µg/m³ are the Capão Redondo, Mogi, Diadema and Cerqueira Cesar stations.

According to Andrade, among the reasons for the different in pollution levels between stations is the fact that the fleet of vehicles, especially buses, that circulate in the peripheral areas of the city are older – making them bigger polluters.

Andrade has dedicated herself to the study of air pollution in the metropolitan region of São Paulo. In an article published in 2017 in the journal Atmospheric Environment, the researcher and her team have shown that although still at alarming levels, air quality in Greater São Paulo has improved in the past 30 years, thanks mainly to control of vehicle and industrial emissions.

The article is a summary of the findings of the FAPESP-funded thematic project "Narrowing the uncertainties on aerosol and climate changes in São Paulo State: Nuance-SPS".

Social justice

“We are now involved in another thematic project, measuring pollution at specific points in the city. What we have seen is that there are individual differences. Depending on each person’s daily habits, exposure to pollution will be higher or lower. This shows that São Paulo lacks equity from the pollution standpoint as well,” said Andrade, regarding the as-yet- unpublished findings of the thematic project “ASTRID - accessibility, social justice and transport emission impacts of transit-oriented development strategies”.

Two FAPESP grant recipients are directly related to the project. PhD candidate Anne Slovic is studying the aspect of inequality in access to the transportation system and perceptions of air pollution, and PhD candidate Veronika Brand is working to collect data on the cities involved.

The ASTRID project aims at comparing three metropolitan regions: São Paulo, London (England) and Randstad South (which includes The Hague and Rotterdam in The Netherlands) to identify the processes and circumstances that reduce or increase existing social differences, particularly those related to accessibility to transport, perceptions of air quality and conditions of mobility.

In São Paulo, the project is assessing the air quality in the transportation system (bus, automobile and subway), by analyzing four routes that connect the city to its periphery.

Among initial findings of the project collected in São Paulo, is the perception that exposure to pollution is uneven. “Average data are not reflecting the particular population that is more exposed. There are people who breathe polluted air for longer periods while commuting between home and work,” she said.

On the four routes, the subway was the means of transport that had the lowest level of exposure to particulate matter (variation of 12 to 17 µg/m³). Buses and automobiles had similar levels (minimum of 17 and maximum of 35 for buses and 28 µg/m³ for automobiles).

Epidemiological studies relate exposure to particulate matter, including black carbon, with mortality and morbidity caused by cardiovascular, respiratory and neurodegenerative diseases.

“Some people are exposed to more pollution because they spend more time using public transportation for their commute. In that respect, it is important to note that it is the exposure to high concentrations that is generally disregarded when you look at the annual averages, in all parts of the city,” she said.

Pollution and decision making

Andrade also called attention to issues such as the construction of bicycle lanes that fail to take into account more highly polluted routes and sites. “As you see, along a single route, a bus rider would be exposed to more air pollution than an automobile driver because the bus lane is along one of those hotspots. A lot of bicycle lanes are being installed near those hotspots, causing cyclists to be more exposed,” she said.

Measuring the pollution at hotspots may also contribute to the formulation of public policy. One example, according to Andrade, is the discussion regarding the city’s use of electric buses.

“From the standpoint of overall emissions in the metropolitan area of São Paulo, the effect would actually be minor, because it is in relation to total emissions. But when you look at it in terms of the number of people waiting at bus stops throughout the system, it is possible to note some benefit that the measure would bring to people. An assessment of the health effects cannot be made solely on the basis of average concentration, but rather by taking into consideration the public’s routine,” she said.