DUBENDORF, Switzerland, May 25, 2017 (ENS) - Even the newest, cleanest gasoline engines need particle filters to protect public health as diesel engines are required to have, according to a new research study led by Swiss scientists.
The research was led by scientists at Empa, the Swiss Federal Institute for Materials Testing and Research. They found that some unfiltered direct-injection gasoline engines emit just as many soot particles as unfiltered diesel cars did in the past.
Empa researchers Norbert Heeb and Maria Munoz discovered large quantities of benzo(a)pyrene - a combustion product responsible for cutting short the lives of cigarette smokers - in the exhaust gas emitted by gasoline direct injectors.
The carcinogenic potential in one cubic meter of exhaust gas from gasoline direct injectors is up to 1,700 times higher than the European Union limit for clean air. By contrast, diesel cars with particle filters exceeded the limit only 45-fold.
Worldwide, three new cars roll off assembly lines every second – that’s 73 million cars and 18 million utility vehicles per year. Most run on gasoline.
In industrialized nations, the trend is moving towards downsizing engines, making them smaller with direct gasoline injection engines and turbocharging. This technology is kind to the environment and saves fuel, the automakers say.
Experts estimate that by the year 2020, 50 million of these direct-injection gasoline engines will be running on roads all over Europe.
With that in mind, scientists from Empa and the Paul Scherrer Institute, the Bern University of Applied Sciences, the University of Applied Sciences and Arts Northwestern Switzerland, and several industrial partners joined forces to determine which type of fuel - gas or diesel is most harmful to public health and the environment.
In the spring of 2014, the project on Gasoline Vehicle Emission Control for Organic, Metallic and Particulate Non-Legislative Pollutants, the GasOMeP project, got underway to answer that question.
The project was funded by the Competence Center for Energy and Mobility of the ETH Domain, a union of Swiss governmental universities and research institutions.
The research was coordinated by Empa chemist Heeb, who has made a name for himself over the last 25 years by analyzing diesel emissions and studying filter systems.
The team selected seven direct-injection gasoline cars, including a Mitsubishi Carisma (2001 model, exhaust emission standard Euro 3).
The other vehicles were all built between 2010 (the VW Golf, Euro 4) and 2016 (the Citroën C4, Euro 6b).
For comparison, a Peugeot 4008 (2013, Euro 5b) with a diesel engine and a particle filter was also included.
All the vehicles were tested based on the Worldwide Light-Duty Vehicles Test Procedure, which will be mandatory for all newly licensed models as of September 2017.
Every one of the tested gasoline cars emitted 10 to 100 times more fine soot particles than the diesel Peugeot.
Under the microscope, the particles from the gasoline engines were similar in size to the soot particles that have given diesel a bad name - 10 to 20 nanometers in size. They then clump into particle agglomerates measuring 80 to 100 nanometers before leaving the exhaust.
“Once inhaled, these particles remain in the body forever,” explained Heeb. "The evidence shows that they can penetrate the membrane of human alveoli in the lungs and make their way into the bloodstream."
The particles are not the only problem, as Heeb knows. “Liquid or solid chemical toxins from the combustion process, including polycyclic aromatic compounds, accumulate on the surface of the particles, which can then smuggle these substances into the bloodstream – like a Trojan horse," he said.
Munoz, a colleague of Heeb’s from Empa’s Advanced Analytical Technologies lab, took a closer look at the exhaust emissions from the vehicles tested in the GasOMeP project. She discovered the combustion product benzo(a)pyrene, a known carcinogenic substance also found in cigarette smoke.
The World Health Organization considers even the smallest dose of benzo(a)pyrene to be harmful to human health.
The European Union has set an air limit of one nanogram per cubic meter for benzo(a)pyrene. Levels in exhaust emissions were found to be as much as 1,700 times above this limit. Or to put it another way, one cubic meter of exhaust gas transforms up to 1,700 cubic meters of clean air into a mixture considered carcinogenic according to EU standards.
The diesel vehicle with a particle filter fared better. In the test, the Peugeot diesel emitted only 45 nanograms of carcinogenic substances – six times less than the best of the analyzed gasoline cars.
The results of the GasOMeP project were presented during a conference held at the Empa Academy in late March. The researchers concluded that particle filters are established in diesel vehicles and have offered advanced technology for years. They should now also be mandatory for gasoline vehicles.
“At the moment, they don’t incorporate the best available technology,” criticized Heeb, urging haste. “New exhaust emission technologies launched on the market usually take around 13 years to become fully effective. Only then will nine out of 10 cars from the vehicle stock be replaced."
"So," said Heeb, "the sooner particle filters are made mandatory for gasoline vehicles, the better it will be for everyone’s health.”
PHOTO: Empa scientist Norbert Heeb (Photo courtesy Empa)