Air pollution is the third leading cause of death worldwide, and most large cities, have fine particulate matter (PM2.5) levels above WHO health guidelines. Here, we take a closer look at the history of air pollution in Sao Paulo to better understand the current situation, and where things may be heading. 

Since the Industrial Revolution toward the end of the 18th century, energy-intensive tools have spread across the globe and ushered in a new age of exponential growth and technological progress. Unfortunately, because our energy sources are “dirty”, or non-renewable and polluting, we now find ourselves facing the consequences of accumulated particles and gases in our atmosphere: excessive warming and unhealthy air.

While global warming from fossil fuel emissions is more of a long-term problem that will take decades to fix even if we do everything right, air pollution and health can be seen as more of a short-term issue. It has been accumulating and causing death and morbidity for over a century in many places, long noticed yet ignored for lack of hard evidence it was dangerous, and once this was acquired for business interests over public health. 

Large metropolitan areas are usually hotspots for air pollution case studies since they concentrate both industrial activity and transport (the main sources) along with a high density of people who might suffer from it. Sao Paulo is one of these metropolises, having undergone rapid growth in the second half of the 20th century from around 1 million to over 22 million inhabitants.

Its industry boomed between the 1950s and 1980s thanks to the car industry in particular, but also those of chemicals, steel, textile, food and many others. Sao Paulo’s simultaneous urban expansion meant residential and industrial areas often coincided, leading to many complaints in the 60s and 70s. 

The government responded, setting up air pollution control programs which also coincided with less sulfur-heavy fuel, and the rise of hydroelectric and natural gas power plants, resulting in effective pollution reduction. 

As Sao Paulo continued to grow, so did the number of vehicles on the street and the time spent in congestion; industrial emissions were soon overtaken, and vehicular emissions remain Sao Paulo’s largest source of air pollution today. 

Research began linking air pollution to disease burdens in the 80s, but the scopes were not large enough to spur a change in policy. In the last two decades however, evidence has accumulated thanks to studies correlating precise particulate matter (PM) or vehicle traffic density to elderly and child hospitalizations and mortality from respiratory illness. Despite its progress in controlling air pollution, this kind of evidence makes it the government’s responsibility to curb it to the most benign possible levels.  

Most damaging to health worldwide is fine particulate matter (PM2.5) due to its extremely small size (less than 2.5 microns, less than a tenth of a hair’s width) and ability to enter the deepest parts of our lungs and even enter the bloodstream. It causes symptoms similar to those of cigarettes which is why long-term exposure to PM2.5 can be translated into an equivalent in cigarettes smoked (idea and formula courtesy of Berkeley Earth). 

air pollution pm2.5 Sao Paulo

PM2.5 data from 2016 (most recent gridded global dataset).

The situation has kept improving in Sao Paulo and now fluctuates between “Good” (under 10 micrograms per m3), “Moderate” (under 40 mg/m3) and “Unhealthy” (40 to 60 mg/m3) depending on the season.

air pollution Sao Paulo

Source: Berkeley Earth

Indeed, despite the local authorities’ best efforts, smoke regularly wafts over from the Amazon and Cerrado regions to contribute to the poor air quality in Sao Paulo. In fact, a 2020 study found that around 10% of PM2.5-induced premature deaths are attributable to fire smoke pollution.


Air pollution levels and environmental policy go hand in hand, and in Brazil this is truer than anywhere else. They have made great progress but the truth is that air pollution alone has cost the city of Sao Paulo over USD111 million between the years of 2008 and 2017 in medical costs alone, without accounting for the productivity loss of those who were ill. Even from an economical point of view, it is absurd to let the situation continue. Furthermore, Brazil’ wealth of ecological resources gives it unparalleled responsibility as the warden of our last, largest rainforest. We must all set examples where we are in order to change the global standard. Avoid single use plastics and vote. 


This article was written by Owen Mulhern.

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