Brazil Study: Substituting Gasoline for Ethanol Can Increase PM

09.25.17 | Blog | By:

A study conducted in Sao Paulo, Brazil, has found that substituting gasoline for ethanol leads to a 30% increase in the atmospheric concentration of ultrafine particulate matter (PM) – particles with a diameter of less than 50 nanometers. Paulo Artaxo of the University of Sao Paulo’s Physics Institute, co-author of the study published in the journal Nature Communications, says the polluting nanoparticles are so tiny they behave like gas molecules.

“When inhaled, they can penetrate the respiratory system’s defensive barriers and reach the pulmonary alveoli, so that potentially toxic substances enter the bloodstream and may increase the incidence of respiratory and cardiovascular problems,” Artaxo said in a statement.

Artaxo says between 75% and 80% of the mass of nanoparticles measured in the study corresponds to organic compounds – carbon in different forms – emitted by motor vehicles. Levels of ultrafine particulate matter in the atmosphere are neither monitored nor regulated by environmental agencies, not only in Brazil but practically anywhere in the world. More research is required, Artaxo said, but a consensus is forming in the U.S. and Europe based on recent research indicating these emissions are a potential health hazard and should be regulated.

“These results reinforce the need for public policies to encourage the use of biofuels, as they clearly show that the public loses in health what they save at the pump when opting for gasoline,” Artaxo said.

Meantime, there has also been some recent discussions in the U.S. on the impact of fuel composition on PM emissions with gasoline aromatics as a culprit. Last December, the Health Effects Institute (HEI) held a workshop on the issue to discuss the issues and areas for further research, and released a summary of the workshop this month. Presentations are available here. The bottom line, according to HEI, is that the issues are complex and there is “an important need to better understand the impact of fuel composition — including ethanol blending, and technology — on PM, air toxics, and other emissions, taking into account the various fuels, vehicle and engine parameters.”  According to HEI, further research needs include:

  • The impacts of engine technologies on PM formation, and how this may be affected by fuel formulation;
  • The effects of fuel formulation on the complex chemistry involved with direct PM emissions, as well as on secondary organic aerosol formation in the atmosphere; and
  • The contributions of gasoline (and diesel) on-road vehicles to primary and secondary PM emissions and ambient PM, and their impact on human exposure.

However, it seemed to one of the attendees from that workshop that there is potential for ethanol splash blends to reduce PM, and EPA seemed to admit as much:

“EPA officials grudgingly admitted that there is a direct connection between gasoline aromatics, particulate matter emissions and air toxics. They also conceded that direct injection could make those emissions worse unless gasoline composition was significantly improved… EPA acknowledged that higher-octane ethanol splash-blends would reduce particulate-bound toxic emissions. In the real world, ethanol is splash-blended, so EPA’s devotion to its much-maligned, match-blending protocols is curious, indeed.”

Is the stage being set for future gasoline aromatics improvement and PM reduction through increased ethanol blending? Maybe. It will be interesting to see how the politics and research unfold.


Tammy Klein is a consultant and strategic advisor providing market and policy intelligence and analysis on transportation fuels to the auto and oil industries, governments, and NGOs. She writes and advises on petroleum fuels, biofuels, alternative fuels, automotive fuels, and fuels policy.