How Can the City of Sao Paulo Avoid More than 11,000 Annual Deaths? With a Better Urban and Transport Planning

South America is the world’s most urban continent, with almost 85% of the total population already living in cities. Nevertheless, evidence on the health effects of urban planning policies in South American cities is limited when compared to cities in high income countries. Additionally, no South American country has institutionalized the use of health impact assessment (HIA) for decision and policy-making.

In a recently published study, we aimed to assess the health burden related to urban environmental exposures in Sao Paulo, Brazil. This city has a population of more than 12 million residents and is densely-constructed, with a high use of impermeable surface materials, high motorized traffic, and an unequal distribution of green and blue spaces, which has been associated with the urban heat island effect.

In a recently published study, we aimed to assess the health burden related to urban environmental exposures in Sao Paulo, Brazil

We estimated the number of deaths caused by not following internationally-recommended or locally-preferable levels for air pollution, green space and temperature, and we determined the spatial distribution of these deaths.

The Health Impact Assessment Study

We created exposure models to estimate air pollution –nitrogen dioxide (NO₂)– and ambient temperature distribution across the city, and we used satellite data at a fine resolution to estimate green space. We also included particulate matter with a diameter of 2.5μm or less (PM_2.5) air pollution at the city level. Then, we retrieved population and mortality data.

We compared the current, real distribution of urban exposures with a hypothetical, ideal scenario if the guidelines below were followed:

• Air pollution: NO₂ concentrations not above 10 μg/m³, and PM_2.5 not above 5 μg/m³, according to WHO guidelines.
• Green space: assuming the entire city was as green as the two centric districts known as the Garden Districts, which were developed according to the Garden City concept.
• Excess heat: a reduction of 1°C in ambient air temperature, assuming an increase in vegetation and permeability, and reduction in motorized traffic.

Figure included in the study. It shows major road network and environmental exposure maps at the census tract (CT) level of Sao Paulo. (A) Sao Paulo major road network. (B) Air pollution: NO₂ annual mean concentrations (μg/m³) estimated for 2017 at CT level. (C) Green space: NDVI level for CT level, garden districts highlighted in yellow. (D) Excess heat: Maximum daily mean temperature (°C) between 10/05/2018 and 09/05/2019 at CT level.

We associated the difference in exposure level between the baseline and ideal exposure level with mortality to quantify the attributable mortality burden of breaching these exposure levels. We also assessed the exposure and health impact distribution by socioeconomic vulnerability of the population, based on an index that includes different dimensions of poverty (income, education and life cycle).

We created exposure models to estimate air pollution and ambient temperature distribution across the city, and we used satellite data at a fine resolution to estimate green space

Towards a Healthy, Sustainable and Equal City

Our analysis shows that 17% of Sao Paulo’s annual total natural-cause mortality –11,372 attributable deaths– could be prevented if the city complied with internationally-recommended or locally-preferable exposure levels for air pollution, green space and temperature. The largest mortality burden was attributed to exceeding air pollution limits –8,409 deaths–, followed by insufficient green space –2,593 deaths–, and excess heat exposure –370 deaths–.

We found larger adverse health impacts in areas of lower socioeconomic vulnerability, due to demographic profile –older populations and with highest baseline natural mortality–, residential area configurations –living around central areas, close to work and services–, and traffic density –most of residents work in the city-center, presenting higher traffic density and air pollution levels in central areas than in peripheral areas–. However, since the central area is where most of the population spend their day –working, studying, for leisure time, etc.–, we expect the real burden of those living in the peripheral areas to be higher than our estimations; as well as actions in the city-center might positively affect the entire Sao Paulo population.

Our analysis shows that 17% of Sao Paulo’s annual total natural-cause mortality –11,372 attributable deaths– could be prevented if the city complied with internationally-recommended or locally-preferable exposure levels for air pollution, green space and temperature

Reducing air pollution in Sao Paulo requires a multisectoral and multi-level approach that targets the regulation and monitoring of wood and waste burning, construction (i.e. especially for PM_2.5), the remaining industrial activities close to the city, motorized transport (i.e. especially for NO₂), and integrated planning and collaboration with other municipalities. The promotion of public and active transport, improvement of traffic safety and multi-modal connectivity, as well as decentralized job opportunities, are needed to reduce car-dependency and travel distances.

Cycle lane at Paulista Avenue, Sao Paulo, Brazil. Photo: Mirthyani Bezerra.

For green space, Sao Paulo should consider increasing its green areas in an equitable way, not only in terms of availability, but also in terms of quality, maintenance and use of these spaces. Depending on the exact location of those green areas, they are associated either with recreational activities, agricultural initiatives serving self-subsistence and food markets, or with informal settlements and poorer social infrastructures, which require different and integrated actions for appropriate response. Since the city is densely constructed, green space policies could include providing pocket parks, general greening of squares, streets, patios and public areas, recovering historic green spaces, and enhancing the provision of areas for peri-urban agricultural activities to support local food production.

We believe that changes towards more sustainable, climate-friendly, equitable and health promoting approaches are needed and can remedy negative effects in Sao Paulo

Finally, daily temperatures varied across the city, with milder temperatures being found in areas with more green space. Increasing vegetation, enhancing permeable surface areas, and reducing motorized traffic, might contribute to the control of excess heat in areas most impacted by heat stress.

We believe that changes towards more sustainable, climate-friendly, equitable and health promoting approaches are needed and can remedy negative effects in Sao Paulo. Cities need integrated urban planning and a multi-level governance strategy in order to improve environmental quality and justice, while simultaneously reducing the associated ill-health burden.