Browse Publications Technical Papers 2005-01-2215
2005-05-11

CLEAN DIESELS: the key to clean air in São Paulo 2005-01-2215

Despite progress in air quality for many conventional pollutants, the São Paulo Metropolitan Region continues to exceed health-based standards for particulates and ozone. In 1986, the Federal government established the Vehicle Air Pollution Control Program (PROCONVE), which created tighter emissions standards for all new vehicles and mandated improved fuel quality. As a result, considerable progress has been made with regard to certain pollution problems, particularly with carbon monoxide (CO) and sulfur dioxide (SO2).
Two pollutants continue to threaten public health in São Paulo: particulate matter (PM) and ozone. For particles, standards are set and a monitoring program is in place for PM10 (particles of 10 μm or smaller, also known as inhalable PM). PM10 concentrations in São Paulo continue to exceed air quality standards on a regular basis. Because fine PM or PM2.5 (a subset of PM10 which includes particles of less than 2.5 μm) are able to lodge more deeply in the lungs, these particles are more dangerous to human health. Standards have not yet been set for these particles in Brazil and high readings of fine particles PM2.5 have recently been recorded in São Paulo. Levels of ozone also remain very high and consistent (over 200 μg/m3 at the peak hour). Solving the ozone problem will require very significant reductions in volatile organic compounds and NOx.
This report will explore the current air pollution problem in the São Paulo, lay out strategies to reduce mobile source emissions in order to meet air quality standards, and explore the technology options needed to reduce emissions. Clean air in São Paulo requires control of direct particulate matter emissions and precursors for ozone and secondary PM. We argue that, in order to meet air quality standards in São Paulo, diesel vehicles need to be much cleaner and that reducing the amount of sulfur in diesel fuel, which will enable clean new vehicle standards, is one of the critical first steps, followed closely by wide scale retrofit programs for in-use vehicles.
Our analysis shows that clean air goals will require a nationwide shift to diesel fuel with sulfur content below 15 ppm, allowing Brazil to take advantage of the best pollution control technologies available today.
High sulfur in fuel makes it virtually impossible to use the advanced technologies (filters and traps) to control particulate matter (PM) and ozone precursors - the pollutants that most threaten the health of Brazilians. When ultralow sulfur fuels are used in combination with advanced control technologies, the emissions reductions from diesel vehicles are dramatic. For example, catalyzed filters can reduce particle emissions from diesel vehicles by up to 95%. This technology could reduce levels of these life-threatening pollutants in São Paulo and save thousands of lives throughout the country each year. With low sulfur fuel, filters can also be placed on many existing vehicles and can reduce emissions by 80-95%, making it one of the most cost effective ways to clean up the air in the near term.

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