The World Health Organization (WHO) has declared outdoor air pollution a public health emergency,1 responsible for 4.2 million deaths in 2016.2 Traffic is a big part of the problem.

Although most countries have put emissions standards in place, increasing urbanization has led to more congestion3 — and thus the kind of stop-and-go traffic that produces more pollution.

Meanwhile, there are more vehicles on the road than ever,4 each one generating nitrogen oxides, volatile organic compounds (VOCs), particulates, sulphur dioxide and more. In China, for example, the number of vehicles doubled between 2009 and 2011,5 making traffic the single largest source of urban air pollution.6

Hard to escape

Even in high-income European countries, more than three-quarters of residents live in areas where the level of outdoor air pollution exceeds WHO guidelines.7 According to OECD estimates, about half of that is due to road transportation.8

Nor do concentrations need to be high to create health problems. In two recent studies, Harvard researchers found air pollution levels below EPA thresholds still increased the risk of premature death in Americans 65 and older.9

According to the Health Effects Institute, people who live close to high-traffic roadways have the highest health risks. In North America, nearly 45 per cent of residents in big urban centres live within 500 metres of a highway or major road — the zone most affected by vehicle emissions.10

A public health emergency

Traffic-related air pollution can lead to short-term and long-term health problems: asthma, respiratory infections, pulmonary disease, lung cancer, heart disease and stroke.11 A growing body of evidence suggests that it also impairs brain function, affecting school performance in children12 and increasing the risk of dementia in older people.13, 14 Meanwhile, pregnant women exposed to air pollution are more likely to have low-birth-weight babies.15

More than 58,000 premature deaths in the U.S. can be linked directly to poor air quality from the transportation industry.16 And the price tag is high: in OECD countries alone, the health impacts of traffic total an estimated US$85 billion.17

1WHO. 2016. Ambient Air Pollution: A Global Assessment of Exposure and Burden of Disease. Geneva: World Health Organization.

2 WHO. 2018. Ambient (Outdoor) Air Quality and Health.

3 TomTom. 2017. TomTom Traffic Index 2017: Mexico City Retains Crown of ‘Most Traffic Congested City in World’

4Petit, S. 2017. World vehicle population rose 4.6% in 2015. WardsAuto. Oct 17, 2017.

5OECD. 2014. The Cost of Air Pollution: Health Impacts of Road Transport. Pairs: OECD Publishing.

6Zhong, N., Cao, J., Wang, Y. 2015. Traffic congestion, ambient air pollution, and health: evidence from driving restrictions in Beijing. Journal of the Association of Environmental and Resource Economists 4(3): 821:856.

7World Health Organization. 2018. Exposure to ambient pollution from particulate matter for 2016.

8OECD. 2014. The Cost of Air Pollution: Health Impacts of Road Transport. OECD Publishing.

9Di, Q., Wang, Y., Zanobetti, A., Wang, Y., Koutrakis, P., Choirat, C., Dominici, F., Schwartz, J.D. 2017. Air pollution and mortality in the entire Medicare population. N. Engl. J. Med. 376: 2513–2522.; Qian, D., Lingzhen, D., Wang, Y., Zanobetti, A., Choirat, C., Schwartz, J.D., Dominici, F. 2017. Association of short-term exposure to air pollution with mortality in older adults. JAMA 318(24): 2446–2456.

10Health Effects Institute. 2010. Traffic-Related Air Pollution: A Critical Review of the Literature on Emissions, Exposure, and Health Effects. Boston: Health Effects Institute.

11Global Road Safety Facility, The World Bank; Institute for Health Metrics and Evaluation. 2014. Transport for Health: The Global Burden of Disease from Motorized Road Transport. Seattle: WA: IHME; Washington, DC: The World Bank.

12Kweon, B-S., Mohai, P., Lee, S., Sametshaw, A.M. 2016. Proximity of public schools to major highways and industrial facilities, and students’ school performance and health hazards. Environ. Plan B Urban Anal. City Sci. 45(2): 312–329.

13Zhang X, Chen X, Zhang X. 2018. The impact of exposure to air pollution on cognitive performance. Proc. Natl. Acad. Sci. USA. 115(37): 9193–9197.

14Chen, H., Kwong, J.C., Copes, R., Tu, K., Villeneuve, P.J., van Donkelaar, A., Hystad, P., Martin, R.V., Murray, B.J., Jessiman, B., Wilton, A.S., Kopp, A., Burnett, R.T. 2017. Living near major roads and the incidence of dementia, Parkinson’s disease, and multiple sclerosis: a population-based cohort study. Lancet 389 (10070): 718–726.

15Smith, R.B., Fecht, D., Gulliver, J., Beevers, S.D., Dajnak, D., Blangiardo, Marta et al. 2017. Impact of London’s road traffic air and noise pollution on birth weight: retrospective population based cohort study. BMJ  359: j5299.

16Caiazzo, F., Ashok, A., Waitz, I.A., Yim, S.H.L., Barrett, S.R.H. 2013. Air pollution and early deaths in the United States. Part I: Quantifying the impact of major sectors in 2005. Atmos Environ. 79: 198–208.