Non-exhaust emissions: the ignored pollutants

The transport sector is rapidly becoming “green” with innovations in technologies related to electric vehicles, batteries, and sustainable fuels. The focus of policymakers globally has been on achieving net zero exhaust emissions which will help mitigate the greenhouse gas emissions from the sector. However, non-exhaust emissions have been greatly ignored and are yet to be incorporated into sustainable transport policies.

Non-exhaust emissions such as particulate matter (PM) are released by vehicles due to abrasion of tyres, breaks, clutch gear, and from roads such as the wear and tear of asphalt, and the suspension of road dust. The PM emissions from these sources are expected to be much higher than from tail pipe emissions in the near future (Univeristy of Birmingham, n.d.). The global shift from internal combustion vehicles to electric vehicles might reduce the non-exhaust PM 10 emissions by about 20 % but will not reduce the PM 2.5 emissions (OECD, 2020). The total PM based non-exhaust emissions are also expected to increase by over 50% in the next decade and absence of regulations will potentially make these pollutants, the principal cause of air pollution from vehicles in the future.

The composition of these aerosols and PM depends on the source of origin and can include metals, inorganic and organic particles (Institute for Energy and Transport, 2014). Aerosols have been known to reflect sunlight which in-turn help reduce the global warming temperatures (Schiffman, 2018). However, certain aerosols with black and brown carbon can absorb the long wavelength spectrum of sunlight (Feng, n.d.) and can have adverse effects on climate change (US EPA, 2020). The non-exhaust PM significantly contributes to air pollution and microclimate alternations and, pollutants such as PM 2.5, have been known to cause adverse effects on human health including respiratory and cardiovascular illnesses (OECD, 2020).

The principal rationale behind the development of subsidies and benefits for sustainable transport systems and vehicles (e.g., electric, hybrid and hydrogen-based) are based on the fact that these vehicles result in net-zero exhaust emissions contributing to climate change mitigation goals. However, the adverse impacts due to non-exhaust emissions and the true cost of environmental damage of these vehicles are not considered.

Tackling this issue needs a holistic thinking and development of policies related to mobility in general. London, for example aims to have 80% of all trips by 2041 made by foot, cycling, and public transport (Mayor of London, 2020). Bicycles already account for over 25% of daily mode of transport in the Netherlands (Netherlands Institute for Transport Policy Analysis, 2018). Incorporation of circular economy principles into the design and manufacturing of vehicles, especially tyres, brakes, clutch, and other moving gear is the need of the hour. Setting targets and standards for permissible non-exhaust emissions for vehicles will drive the needed change in manufacturing processes such as use of materials, reducing the weight of vehicles and support innovation.

Bibliography

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Institute for Energy and Transport. (2014). Non-exhaust traffic related emissions - Brake and tyre wear PM. European Union.

Mayor of London. (2020). Air quality in London 2016-2020. Retrieved from https://www.london.gov.uk/sites/default/files/air_quality_in_london_2016-2020_october2020final.pdf

Netherlands Institute for Transport Policy Analysis. (2018). Cycling Facts. Ministry of Infrastructure and Water Management.

OECD. (2020). Non-exhaust emissions from road transport. OECD. Retrieved from https://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=ENV/EPOC/WPIEEP(2020)4/FINAL&docLanguage=En

Schiffman, R. (2018). Yale Environment. Retrieved from Yale School of the Environment: https://e360.yale.edu/features/air-pollutions-upside-a-brake-on-global-warming

Univeristy of Birmingham. (n.d.). Sustainable Environments. Retrieved from Univeristy of Birmingham: https://www.birmingham.ac.uk/research/quest/sustainable-environments/brake-dust-and-brown-carbon.aspx

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