Air pollution contains much higher levels of emissions from motor vehicles than researchers previously believed, indicate the findings of a new study.
Canadian researchers indicate 50% to 90% of air pollution chemicals in Toronto, Canada, and likely other cities worldwide, come from vehicle emissions; much higher than prior studies, which estimated these levels at only 10%. The findings were published March 11, in the journal Atmospheric Chemistry and Physics.
Researchers conducted a study of levels of benzene and polycyclic aromatic hydrocarbons (PAHs) in air pollution in Toronto. They used a new method and computer model to determine air pollution levels in the region, which includes much of southern Ontario and the northeastern United States.
The researchers estimated the absolute and relative contributions of motor vehicles to ambient pollutant concentrations. Both benzene and PAHs are toxic air pollutants and are associated with motor vehicle emissions.
According to the findings, the average concentrations of benzene and PAHs ranged from 4% to 21% in the spring and summer and from 14 to 24% in the fall and winter. However, levels of the two pollutants rose as high as 90% in some locations.
Cars and other gasoline-powered vehicles are responsible for a large portion of these two air pollutants, which are highly toxic. However, prior estimates and studies indicated roughly 10% of PAHs and benzene in air pollution concentrations came from vehicles and the remainder from other sources. Those studies used national averages which concluded the major share came from agricultural burning, wood smoke and industrial sources.
Using the new method, researchers were able to make a much more specific measurement of air pollution. They found that levels of PAHs and benzene which could be attributed to motor vehicles are at least five times larger than previously thought.
The new research method is more geographically specific, and determines the exact composition of air pollution in a range of areas, the researchers report. Comparatively, national averages don’t represent every area of the country and communities can differ from each other. Concentrations would be much higher in large cities than in rural areas.
While this study was done in Toronto, researchers indicate the findings will likely to be similar in any large urban area or highly populated city.
Benzene is known to cause blood cancer and blood disorders, such as anemia, and is also associated with other cancers. PAHs also cause cancer from both inhalation and skin exposure and have been shown to harm pregnancy in mice. Long term exposure to air pollution can increase a person’s risk of stroke and cardiac arrest.
Both chemical levels were routinely higher across all measurements during the study than the recommended safe levels.
“This finding is particularly relevant to the study of public health in the urban areas of our model domain where human population, ambient concentrations, and traffic volumes tend to be high,” the researchers wrote.
The study’s authors called for a switch to zero-emissions vehicles to help reduce the pollution levels and the effects on humans.