According to the World Health Organization (WHO), Worldwide, 9 out of 10 people breathe air that contains high levels of pollutants. The health consequences are dramatic, as the WHO estimates that exposure to fine particles in outdoor air is responsible for more than 4 million deaths per year. The organization also significantly tightened its standards in late 2021, its guiding principles on air pollution.

The countries most affected are low- and middle-income countries, which account for 90% of deaths due to air pollution, but other countries are also affected. According to Santé publique France, in France, air pollution from fine particulate matter (_PM2.5) is estimated to reduce life expectancy by an average of nearly 8 months for people aged 30 and older. Each year, nearly 40,000 deaths can be attributed to it.

These health impacts translate into significant economic impacts. For example, the economic costs of air pollution on health were estimated in 2010 at approximately 1,700 billion dollars in OECD countries, and in France alone, the direct and indirect costs amounted to 100 billion euros per year. Yet the economic argument is sometimes invoked to justify the lack of ambition in policies aimed at reducing air pollution, even though, in France, measures to combat pollution are never subject to an economic assessment of their costs and benefits.

To address these gaps, we developed the interdisciplinary MobilAir project. Its primary goal was to answer two key questions: What measures should be taken to achieve a predetermined target for reducing the health impacts of urban air pollution? What would be the costs and benefits?

Here is the approach that was implemented throughout the Grenoble metropolitan area, along with the results obtained. This approach can, in principle, be adapted to any metropolitan area…

Assessing the Economic Impact of Air Pollution

While no economic assessments are conducted in France to compare the costs and benefits of implementing pollution-reduction measures, this is not the case everywhere: in the United States, for example, the Clean Air Act requires such assessments. These assessments have shown that the costs of reducing pollution are between 3 and 90 times lower than the benefits these measures generate.

The first phase of the MobilAir project therefore involved estimating the human and economic costs of air pollution in the Grenoble metropolitan area through a quantitative health impact assessment (EQIS) supplemented by an economic analysis. This research was published in the scientific journal *Environment International* in August 2019.

The results indicate that the average annual exposure to fine particulate matter (_PM2.5), estimated at 13.9^μg/m3 in 2016, was responsible for 145 deaths each year. The costs associated with these health impacts were estimated at 495 million euros per year.

Reducing emissions by two-thirds is possible

In light of this finding, an initiative was launched in collaboration with local decision-makers to set targets for reducing this excess mortality. In collaboration with researchers, three distinct but equally significant targets were then established: to reduce_{PM2.5-attributable} mortality by 33%, 50%, and 67% in 2021, 2025, and 2030, respectively, compared to the figures recorded for 2016.

The interdisciplinary modeling effort, which spanned three years, brought together air pollution specialistsfrom Atmo Auvergne-Rhône-Alpes, epidemiologists fromInserm, environmental economists from the CNRS, and transportation specialists fromInrae. This modeling chain is based on various data sources: pollution data generated directly by Atmo Auvergne-Rhône-Alpes, data from health surveillance, data from the National Institute of Statistics and Economic Studies (INSEE), data from mobility surveys, and data from the scientific literature specializing in health and economics.

This approach made it possible to identify the policies to be implemented in the two sectors that contribute most to pollution in order to achieve the established goals.

Wood-burning heating and road traffic: major sources of fine particulate matter

Wood-burning heating and road traffic are the main sources of_PM2.5 in the Grenoble metropolitan area. Across the entire Grenoble metropolitan area, these two sectors account for 63% and 17% of emissions, respectively (data from Atmo AuRA).

_PM2.5 produced by road traffic comes not only from diesel combustion (exhaust emissions), but also from brake wear and the resuspension of particles when tires rub against the pavement. While replacing the fleet of diesel vehicles helps reduce exhaust emissions (particularly for diesel vehicles that meet Euro 5 and 6 standards, which were introduced after 2011), this technology has no impact on emissions caused by abrasion and resuspension. As a result, electric vehicles also emit_PM2.5.

When it comes to wood heating, it is primarily inefficient open-hearth fireplaces and stoves that account for the majority of emissions in this sector.

The study indicated that the most ambitious goal—a 67% reduction in the 145 deaths linked to_PM2.5—is indeed achievable. This will require a combined and ambitious approach addressing both wood heating and transportation.

How do I proceed?

As for heating, the goal would be to replace all inefficient wood-burning heating equipment with pellet stoves. These stoves can significantly reduce_PM2.5 emissions.

In the transportation sector, we must aim to reduce car and motorcycle traffic in the metropolitan area by one-third. This could be achieved by establishing a low-emission zone (an urban area accessible only to the least polluting vehicles) for freight transport and passenger vehicles, prohibiting access to vehicles classified as “Crit’air 2” and higher.

Unrealistic? No, because travel data for the Grenoble metropolitan area shows that such a reduction is achievable by increasing the use of active modes of transportation as an alternative to cars. In other words, to improve air quality, the many short trips currently made by car will need to shift to walking or biking. The icing on the cake: these shifts, which will help reduce pollution, will also have positive effects on the health of those who choose to make them.

Combating Air Pollution: Significant Health Co-Benefits Linked to Physical Activity

Walking—including walking to public transportation stops—and biking, whether on a traditional bike or an electric bike, increase physical activity. It’s worth noting that the growing popularity of electric bikes makes it feasible to replace the car for longer trips. And we now know all the health benefits that come from regular physical activity.

Estimates by epidemiologists show that, in addition to the 96 deaths per year (representing 67% of the 145 deaths attributable to air pollution) prevented by reduced air pollution, between 60 and 180 additional deaths could be prevented by increased physical activity. These figures, of course, depend on the modes of transportation used as alternatives to cars: scenarios involving the greatest increase in walking and cycling yield the greatest health benefits compared to scenarios that rely more heavily on public transportation. It should be noted that these figures also take into account the accident rates specific to each mode of transportation.

In total, based on the most favorable assumptions regarding physical activity, up to 270 deaths could be prevented each year among the population of Grenoble (out of an annual all-cause mortality rate of approximately 2,600 deaths).

A Significant Cost-Benefit Ratio

In addition to these significant health benefits, these measures are also highly beneficial from an economic standpoint. The cost-benefit analysis conducted as part of this project compared all costs and all benefits over the next 30 years.

The costs to the community associated with financing the necessary measures and infrastructure were assessed, as was the impact on household spending (purchases of new heating equipment, impact of the modal shift on spending). The economic benefits related to health impacts (reduced pollution and increased physical activity), noise, reduced greenhouse gas emissions, and time spent commuting have also been estimated.

These assessments indicate that the scenarios with the greatest growth in active transportation modes are those that result in the highest total net economic benefit, generating 6.7 to 8.7 billion euros over the 30-year period under consideration (depending on whether or not electric-assist bicycles are included in the modal shift options). This represents a net annual benefit of between 480 and 630 euros per capita per year.

A scenario involving a modal shift that favors public transportation also results in a positive net benefit—albeit a smaller one—of approximately 2 billion euros over the 2016–2045 period (or 160 euros per year per resident). Across all the scenarios evaluated, every euro invested by the local government in transportation infrastructure and subsidies for the purchase of pellet stoves would generate between 1.1 and 4.7 euros in benefits.

It is therefore possible to implement measures in local communities that can significantly reduce pollution and its impacts. The challenge now is to find a way to convince people: driving changes in mobility behavior through environmental policies remains difficult even today. Let’s hope that the prospect of significantly improving their well-being and health—by combating air pollution and engaging in regular physical activity—will encourage city dwellers to hop on their bikes more often…