Study Reveals Connection Between Air Pollution and Sleep Disturbances in São Paulo

São Paulo is the city with the most automobiles in the world, with more than 9 million vehicles, according to data from the National Traffic Department. All this number of engines generates high emissions of pollutant gases, associated with the greenhouse effect and worsening of lung health, and can even lead to poorer quality of sleep. USP professors Jaime Oliva, from the Institute of Brazilian Studies, Adalgiza Fornaro, from the Institute of Astronomy, Geophysics and Atmospheric Sciences, Regina Markus, from the Institute of Biology, and Paulo Saldiva, from the School of Medicine, explain why the Metropolitan Region of São Paulo is home to so many cars and how the health consequences appear.

The preference for automobiles

As Jaime Oliva explains, the preference for private cars over public transportation is the result of a city model that is more focused on the isolation of citizens than on the interaction of people and pedestrian culture. “There is no simple reason to understand the entire process and the social legitimacy that has developed for the use of automobiles. Since the 1970s, the city government of São Paulo has focused its main expense on the road system to accommodate private automobiles. The government has never sought to encourage other mobility alternatives.”

On the other hand, sectors of civil society have not shown interest or deep support for other ways of getting around the city. The automobile economy was stimulated as a driver of the development of São Paulo’s industry, and the construction industry has also adapted and stimulated the automobilization of the metropolis. “The entire real estate sector, the entire civil engineering sector has also been creating the means to accommodate this mass of automobiles that not only drive, but also need to be parked. We have a set of new buildings that have been under construction since the 1980s, with parking infrastructure being one of their major attractions,” explains Oliva.

Gases emitted

This large number of combustion engines generates a large amount of polluting gases released into the atmosphere. According to data from the 19th Inventory of Greenhouse Gas Emissions of the Municipality of São Paulo, the transportation sector is responsible for approximately 60% of GHG emissions in the city.

Adalgiza Fornaro explains that car emissions are the result of complete and incomplete combustion of fuel: “ A perfect engine would only generate energy, water vapor and CO2. But the machine is not perfect and will end up emitting other gases that are products of incomplete combustion and the composition of the air itself.”

The researcher explains that polluting gases can be divided into three groups: carbon dioxide and carbon monoxide, nitrogen gases (NO and NO2) and particulate matter, very fine grains of impurity that disperse through the air. While carbon is associated with global warming, gases containing nitrogen have other consequences for the climate: “In the presence of solar radiation, photochemical reactions of NO, NO2 and carbon monoxide will produce tropospheric ozone (O3), which is a strong oxidant, a very serious pollutant that contaminates the soil through rain and has consequences for human health”, explains Adalgiza. The type of fuel also influences the amount of emissions. Diesel vehicles tend to emit more particulate matter, observed, for example, in the black smoke that comes out of truck exhaust pipes.

Health consequences

In addition to polluting the atmosphere, contributing to global warming, amplifying problems such as heat islands, and causing acid rain that contaminates the soil and harms agricultural productivity, particulate pollution also has serious consequences for human health, which science is still trying to understand in detail.

Professor Regina Markus’ research team found links between breathing polluted air and the unregulated production of melatonin, a hormone associated with both sleep regulation and the immune system, in addition to other physiological functions. “My area of ​​research involves any system that acutely attacks the body, so it could be a bacteria, a virus or a fungus, for example. Our surprise was that some of the body’s responses to pollution are the same as the response we got with viruses and bacteria.”

The professor explains that one of the lungs’ reactions to the aggression of a pollutant particle is the release of alveolar macrophages, which, like Pac-Man , swallow the aggressor to prevent it from entering the bloodstream and spreading throughout the body. These macrophages then begin to form mucus, a dark phlegm that is expelled from the airways in the form of coughing and sneezing.

However, this response does not occur in all subjects. Regina Markus noticed that, in some subjects, the macrophages are not stimulated, so the diesel enters the bloodstream through the lungs, which worsens the quality and regulation of sleep: “This causes a series of reactions in the pinealocytes, cells of the pineal gland, which ‘turn on the alert signal’ and prevent the enzymes that produce melatonin. It is a cause and effect relationship: diesel particles in the bloodstream, the pineal gland does not produce melatonin at night,” explains the professor.

Complex solution

Although government measures have been taken to regulate pollution emitted by cars, such as mandatory vehicle inspections, and automotive technology has advanced with improvements, for example, in palladium catalysts that filter the air released from the exhaust, the pollution emitted remains high enough to bring undesirable consequences for the environment and human health.

According to Paulo Saldiva, another problem caused by the colossal number of cars in the city of São Paulo is the increase in stress caused by traffic, which is increasingly intense in the metropolis. The solution is complex and involves both the chemistry and mechanics of automobiles and the urbanization of the city: “I have no doubt that we have to reduce the need for mobility. When you concentrate a city and move people far from their work, they will have to move around, sometimes spending four hours a day on public transport. We need to not only reduce emissions from transport, but also reduce the need for motorized transport.”