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Short period in traffic jam already exposes driver to high doses of pollution, indicates study

Publicado em 24 agosto 2021

Por Luciana Constantino | Agência FAPESP

An international study carried out in ten cities, including São Paulo, reveals that a relatively short period in places with a high concentration of pollution is enough to expose car drivers and passengers to significant doses of fine inhalable particles – those that, due to their smaller diameter. that 2.5 millionths of a meter (PM2.5) can reach the pulmonary alveoli and cause even more damage to the body. According to the study, therefore, spending too little time in bottling areas can already have a detrimental impact on health.

The cities with the highest ratio between exposure time and inhalation of pollutants were Guangzhou, China, and Addis Ababa, Ethiopia. These drivers and passengers stayed in areas with a high concentration of PM2.5 less than a third of the time on the route (26% and 28%, respectively), but inhaled more than half (54% and 56%) of the total amount of fine particles. inhaled throughout the trip. In the case of São Paulo, in 17% of the route time — approximately eight minutes — the driver inhaled 35% of the total on the route.

Exposure to these fine particles, also called aerosols, is among the top ten environmental health risk factors, according to the Global Burden of Disease 2019. In the study, it was observed that cities where people were exposed in cars at levels The highest of these aerosols recorded the highest mortality rates per 100,000 vehicle passengers per year.

Dar-es-Salaam (Tanzania), Blantyre (Malawi) and Dhaka (Bangladesh) had the highest mortality rates (respectively: 2.46 deaths per 100,000 car passengers per year; 1.11 and 1.10). The lowest rates were detected in São Paulo, Medellín (Colombia) and Suleimânia (Iraq) — respectively: 0.10 deaths per 100,000 car passengers per year; 0.07 and 0.02.

The distance of the routes ranged between 10 km and 33 km, but, in each of the cities, the researcher always used the same path and the same vehicle. In the case of São Paulo, the route was 12.7 km (about an hour to be completed outside peak hours), leaving the Faculty of Public Health of the University of São Paulo (USP), passing through Ibirapuera Park and through 23 de Maio and Paulista avenues.

In the work, the researchers analyzed a data set of PM2.5 concentrations measured during the journey to assess the relationship between excess pollutants and traffic conditions, fuel prices, health problems and economic losses.

In this case, it was found that, among the places surveyed, the lower the Gross Domestic Product (GDP) of the city, the greater the economic loss, mainly due to health care costs. Dar-es-Salaam also appears among the biggest losses in GDP, followed by Cairo (US$ 10.2 million and US$ 8.9 million per year, respectively). The work also included data on the city of Chennai (India).

The research was carried out within the scope of the Clean Air Engineering for Cities (CArE-Cities) project, by the University of Surrey (United Kingdom), and the results were published in the journal Environment International.

In Brazil, Maria de Fátima Andrade, professor at the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) at USP, who is a collaborating partner of CArE-Cities, doctoral student Veronika Sassen Brand and Thiago Nogueira, took part. It received support from FAPESP through three projects (16/18438-0, 16/14501-0 and 20/08505-8).

“By studying aerosol exposure in the car in several different cities, effective air pollution mitigation measures and best practice guidelines can be developed, including the use of electric buses, actions aimed at public transport and urban mobility” , write the authors in the article, which was coordinated by Professor Prashant Kumar, founding director of the Global Clean Air Research Center (GCARE) in Surrey.

The work cites the need to pay attention to mitigation strategies that meet the United Nations Sustainable Development Goals (SDGs), including good health (SDG 3), clean energy (SDG 7) and sustainable cities (SDG 11 ).

“By identifying places with greater traffic and pollution, it is possible to develop targeted and more efficient public policies to improve air quality in these areas”, adds Brand, in an interview with Agência FAPESP.

In the report “World Cities 2020”, the United Nations Program for Human Settlements (UN-Habitat), citing epicenters of Covid-19, states that “well-planned, managed and financed urban centers help to build resilient cities with capacity to recover from the devastating impacts of pandemics, improve the quality of life of residents and leverage the fight against poverty, inequality and climate change”.

In this context, air quality plays an important role. Even with the pandemic, which reduced economic activities and displacement in 2020, PM2.5 pollution was blamed for about 160,000 deaths in the five most populous capitals in the world, according to a tool developed by Greenpeace and IQAir. The highest estimate is for New Delhi, India, with 54,000 deaths. São Paulo and Mexico City appear with the lowest numbers — 15 thousand deaths estimated in each of them.


To analyze the hotspots in the ten cities (places with more traffic jams), the international study took into account socioeconomic correlations, the impact of fuel prices on levels of exposure to pollution and economic costs. Data were collected in 2019.

A portable laser particle counter (Dylos OPCs) was used in the back seat of a passenger car, which collected per minute, with three configurations for the windows: open, closed with a fan and closed with air recirculation. Samples were collected three times a day: morning peak, afternoon peak and off-peak. The analysis described in the article focused on data collected with open windows, a configuration in which the highest concentrations of pollutants were recorded.

To ensure quality control and data harmonization, the group performed intercomparison measurements over five days, during which time all aerosol equipment was compared with a portable optical particle spectrometer (model GRIMM 11-C).

When analyzing the effect of fuel price variation on pollution concentrations in each city, information such as: specific congestion parameters for each location, average traffic speeds, population size and number of cars per inhabitant were computed.

No significant correlation was found between fuel cost and PM2.5 exposure in the car, indicating that price controls should not be considered as a single policy in air pollution mitigation.

To assess economic losses, the methodology included aerosol concentration data, baseline death rates, car passenger population size, and Value of Statistical Life (VSL).


For Professor Maria de Fátima Andrade, one of the innovative points of the study was measuring the exposure to pollution inside vehicles and bringing to light data from some overcrowded metropolises that have little information, such as in Africa.

“In general, countries with the worst emission control policies end up not having data that consider the various sources of pollution. Measuring exposure within transport, associating time and economic impacts, is important”, says Andrade.

In São Paulo, Cetesb publishes daily bulletins with air quality by type of pollutant and region of the city. This index is a mathematical tool, which includes the following parameters: inhalable particles (MP10); fine inhalable particles (PM2.5); smoke (FMC); ozone (O3); carbon monoxide (CO); nitrogen dioxide (NO2) and sulfur dioxide (SO2).

Depending on the index obtained, the air receives a grade (from good to very bad), identified by colors. For fine inhalable particles, the index ranges from 0 to 25 µg/m3 for 24 hours to be in good quality. Greater than 125 µg/m3 for 24h, the grade is terrible.