Brazil is not ready for diesel cars

The Portuguese version of this blog was developed by Instituto de Energia e Meio Ambiente (IEMA).

Sales of diesel passenger cars and commercial vehicles with capacity inferior to 1,000 kg have been banned in Brazil since the 1970s, a step the country took primarily to improve trade balances by reducing their dependence on imported petroleum. But automakers have pressured to reverse that ban, and on September 16, 2015, a government commission was announced to consider the commercialization of diesel cars. It was a kind of miracle of bad timing: Two days later, the U.S. EPA and the California Air Resources Board announced that Volkswagen had admitted to installing a defeat device on diesel passenger cars sold in the U.S. in order to evade clean air regulations.

The worldwide scandal that erupted after that announcement has shaken the global auto industry to its core and perhaps raised questions about the very future of diesel technology in passenger cars. But for Brazil specifically, it highlights a very simple, but essential point: Brazil is not yet in a position to lift its ban on diesel cars without running the risk of major environmental and health impacts. Brazilian officials should keep the restrictions on diesel cars at least until the country adopts world-class vehicle emissions standards, including effective compliance and enforcement provisions, and until there is clarity that diesel vehicles in Europe can comply with regulatory emissions limits under normal real-world driving conditions. Even before the Volkswagen scandal, diesel passenger cars in Europe have been shown to emit on average seven times more NO_x under normal driving conditions than emission limits permit. NO_x has serious adverse health effects, and is a main precursor to ground-level ozone, which leads to respiratory problems that cause premature death. The transportation sector is the largest contributor to ambient NO_x concentrations in Europe (about 40%), where many cities have regularly exceeded the EU’s air quality standards. The poor environmental performance of diesel cars in real-world conditions have led some European governments to enact measures to limit production and sometimes to propose banning diesel cars from specific cities. Paris and London announced that they would work to ban diesel cars in the near future.

The Volkswagen story, and mounting concern in Europe generally over diesel passenger car engines, is about NO_x emissions. An additional concern related to the introduction of diesel passenger vehicles in Brazil is the potential for increased fine particulate matter (PM_2.5) emissions. PM_2.5 contributes to the toxicity of diesel exhaust, which has recently been listed by the World Health Organization as a known human carcinogen. Reducing PM_2.5 emissions from on-road diesel vehicles has long been recognized as an important strategy in reducing the public health burden of motor vehicles, and advances in engine technology and emissions controls have greatly reduced PM_2.5 emissions from modern diesel engines.

Unfortunately, current emission standards in Brazil are not stringent enough to compel the use of the key technology needed to control diesel PM, the highly effective diesel particle filter (DPF). The current PM emission limit for passenger vehicles in Brazil, PROCONVE L6, is 0.025 g/km, equivalent to the Euro 4 standard implemented in the European Union (EU) a decade ago and five times greater than the current EU limit of 0.005 g/km. A review of technologies used to meet the Euro 4 PM standard in Europe suggests that manufacturers will be able to meet the PROCONVE L6 standard of 0.025 g/km without application of DPFs. In addition, DPFs require ultra low-sulfur diesel, and the commercialization of 500-ppm diesel outside of metropolitan areas could prevent automakers from installing DPFs in diesel passenger vehicles. Under current emissions standards and without DPFs, the per kilometer PM emission rate of a new diesel car sold in Brazil would be almost 30 times greater than a new gasoline car.

The potential air quality and human health consequences of lifting the ban on diesel passenger vehicle sales in Brazil are substantial. To provide a sense of what those impacts could be, we performed a preliminary analysis of projected changes in diesel vehicle activity, pollutant emissions, and resultant health outcomes, comparing two scenarios with moderate and fast dieselization rates against a baseline without changes in current diesel passenger vehicle policies.

The moderate and fast dieselization scenarios assume diesel car sales grow at a rate such that diesel vehicles account for 15 and 45%, respectively, of annual light-duty vehicle kilometers traveled in 2050. Based on a well-documented methodology, the fast dieselization pathway results in approximately 150,000 additional premature deaths relative to the baseline scenario between 2015 and 2050. Even in the moderate dieselization scenario, in which gasoline vehicles still dominate total activity, premature deaths are estimated to increase by 32,000 relative to the baseline. These estimates of premature mortality are limited to the impacts of primary PM_2.5 in urban areas, and do not account for health impacts from secondary PM_2.5, ground-level ozone, or other local air pollutants. Since the health impacts quantified in this article are a subset of the expected total, the reported premature mortality from dieselization rates in Brazil should be interpreted as conservative, lower-bound estimates.

Figure 1. Effects of passenger vehicle dieselization on premature mortality in Brazil (Percentages indicate change in 2050 relative to 2015)

The implications are clear enough. Brazil should maintain its restrictions on diesel passenger cars at least until there is clarity that diesel vehicles in Europe can comply with regulatory emissions limits under normal driving conditions.