Blog del Direttore Lorenzo Pagliano

Will Electric Vehicles contribute less Particulate Matter (PM10 and PM2.5) to air we breath? Recent analysis conclude: only negligibly, and policies to reduce number and weight of vehicles are needed.

22/10/2017

Recent scientific literature on the issue of PM10 and PM 2.5 pollution challenges the assumption that electric vehicles can create a significant change in PM levels. We quote below a few original studies and reviews. We would be glad to receive information from readers on other studies about the subject.

Highlights:

In many cities the concentration of Particulate Matter in air is largely above the annual legal limits in micrograms/cubic meter, and World Health Organisation is recommending to make limits stricter ("recent long-term studies show associations between PM and mortality at levels well below the current annual WHO air quality guideline level for PM2.5, which is 10 μg/m3").

A large fraction (50-85% and up to 90%) of traffic generated PM10 and PM2,5 is not due to the exhaust emissions by the motor, but rather to non-exhaust emissions (brake wear, road wear, tyre wear and road dust resuspension)

Non-exhaust emissions are found to be proportional to the mass of the vehicle

EVs emit the same amount of PM10 as modern gasoline and diesel cars. Analysis that compare PM2.5 emissions, conclude that EVs bring about a negligible reduction in emissions. Compared to an average gasoline ICEV, the EV emits 3% less PM2.5. Compared to an average diesel ICEV, the EV emits 1% less PM2.5.

Hence it appears that only policies to reduce the number and weight of motorised vehicles can reduce PM concentrations in air. Policies to remove barriers to, and create conditions for, safely walking and cycling within cities and increase use of Public Transport have been highly successful where implemented (e.g. in Copenhagen only 9% of travels to work or school are made by car, 62% by bicycle, and policies to promote cycling are transforming the cities of Oslo, Paris,…)

Excerpts from peer reviewed publications

Urban air quality: The challenge of traffic non-exhaust emissions Review Article Journal of Hazardous Materials, Volume 275, 30 June 2014, Pages 31-36, Fulvio Amato, Flemming R. Cassee, Hugo A.C. Denier van der Gon, Robert Gehrig, Mats Gustafsson, Wolfgang Hafner, Roy M. Harrison, Magdalena Jozwicka, Frank J. Kelly, Teresa Moreno, Andre S.H. Prevot, Martijn Schaap, Jordi Sunyer, Xavier Querol, http://dx.doi.org/10.1016/j.jhazmat.2014.04.053:

“There is no doubt about the serious environmental impact of non-exhaust emissions. Ambient air measurements across Europe have revealed a total non-exhaust contribution (wear emissions + resuspension) to PM10 comparable to that of tailpipe emissions, with a clear exacerbation in Scandinavian and Mediterranean countries due to winter tyres and drier climate, respectively [2,27–29].
Ketzel et al. [30] estimated that in several European countries a large part (about 50–85% depending on the location) of the total traffic PM10 emissions originates from non-exhaust sources. Moreover the lack of abatement measures for non-exhaust emissions has led to their increasing contribution to the PM air-shed.

no actions are currently in place to reduce the non-exhaust part of emissions such as those from brake wear, road wear, tyre wear and road dust resuspension. These “non-exhaust” sources contribute easily as much and often more than the tailpipe exhaust to the ambient air PM concentrations in cities, and their relative contribution to ambient PM is destined to increase in the future, posing obvious research and policy challenges.

Soret, A., Guevara, M., Baldasano, J., 2014. The potential impacts of electric vehicles on air quality in the urban areas of Barcelona and Madrid (Spain). Atmos. Environ. 99, 51-63. http://dx.doi.org/10.1016/j.atmosenv.2014.09.048:

…“fleet electrification cannot be considered a unique solution, and other management strategies may be defined. This is especially important with respect to particulate matter emissions, which are not significantly reduced by fleet electrification (<5%) due to the high weight of non-exhaust emissions.”

Non-exhaust PM emissions from electric vehicles, Victor R.J.H. Timmers , Peter A.J. Achten, Atmospheric Environment 134 (2016) 10-17 http://dx.doi.org/10.1016/j.atmosenv.2016.03.017:

“By analysing the existing literature on non-exhaust emissions of different vehicle categories, this review found that there is a positive relationship between weight and non-exhaust PM emission factors. In addition, electric vehicles (EVs) were found to be 24% heavier than equivalent internal combustion engine vehicles (ICEVs). As a result, total PM10 emissions from EVs were found to be equal to those of modern ICEVs. PM2.5 emissions were only 1-3% lower for EVs compared to modern ICEVs.”
“However, these differences are likely to disappear completely as exhaust emission standards become even stricter. “
“Therefore, it could be concluded that the increased popularity of electric vehicles will likely not have a great effect on PM levels. Non-exhaust emissions already account for over 90% of PM10 and 85% of PM2.5 emissions from traffic. These proportions will continue to increase as exhaust standards improve and average vehicle weight increases. Future policy should consequently focus on setting standards for non-exhaust emissions and encouraging weight reduction of all vehicles to significantly reduce PM emissions from traffic.”

"By using the data from Simons (2013) on the effect of weight on emissions and the average exhaust and non-exhaust emission from the various emission inventories, we can compare the total PM emissions from EVs with those from gasoline and diesel cars. When we do this, we find that EVs emit the same amount of PM10 as modern gasoline and diesel cars. See Table 5 for the comparisons.
When we compare PM2.5 emissions, we can see that EVs bring about a negligible reduction in emissions. Compared to an average gasoline ICEV, the EV emits 3% less PM2.5. Compared to an average diesel ICEV, the EV emits 1% less PM2.5. See Table 6 for the comparisons.
From these calculations, it is clear that EVs are not significantly less polluting than modern ICEVs in terms of PM. We can also see that non-exhaust emissions currently account for more than 90% of PM10 and 85% of PM2.5 emissions from traffic. These proportions are likely to keep increasing in the future as increasingly strict emission limits result in higher exhaust standards (EU, 2007).
Several studies have reached the same conclusion on the importance of non-exhaust emissions. Rexeis and Hausberger (2009) predicted that the percentage of non-exhaust PM of the total PM emissions will increase from 50% in 2000 up to 80-90% by 2020. Joerß and Handke (2007) modelled non-exhaust emissions of PM2.5 in Germany and found that non-exhaust sources accounted for 25% of traffic PM2.5 emissions in 2000 and are expected to contribute 70% of traffic PM2.5 by 2020. This conclusion was also reached by Denier van der Gon et al. (2013), who predicted non- exhaust will likely be the dominant source of total PM emissions from traffic by 2020.
Worryingly, over the last decade, we have seen a steady increase in vehicle weight in almost all segments (International Council on Clean Transportation, 2015). See Fig. 2. This trend is expected to apply to EVs as well, as demand for longer range EVs increases. In order to achieve a longer range, EVs need larger batteries and require more structural weight to accommodate these batteries (Shiau et al., 2009).
Therefore, non-exhaust emissions from EVs and ICEVs are likely to keep increasing in the future. Strategies designed to reduce PM pollution by restricting vehicle exhaust emissions alone will no longer be very effective (Kousoulidou et al., 2008). "

Review of evidence on health aspects of air pollution – REVIHAAP Project technical report (2013). The World Health Organization WHO/Europe.
http://www.euro.who.int/en/health-topics/environment-and-health/air-quality/publications/2013/review-of-evidence-on-health-aspects-of-air-pollution-revihaap-project-final-technical-report

“The adverse effects on health of particulate matter (PM) are especially well documented. There is no evidence of a safe level of exposure or a threshold below which no adverse health effects occur… additional studies linking long-term exposure to PM2.5 to several new health outcomes, including atherosclerosis, adverse birth outcomes and childhood respiratory disease; and
emerging evidence that also suggests possible links between long-term PM2.5 exposure and neurodevelopment and cognitive function, as well as other chronic disease conditions, such as diabetes.”
“As the evidence base for the association between PM and short-term, as well as long-term, health effects has become much larger and broader, it is important to update the current WHO guidelines for PM. This is particularly important as recent long-term studies show associations between PM and mortality at levels well below the current annual WHO air quality guideline level for PM2.5, which is 10 μg/m3.”

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