Trains And Pollution: What's The Real Damage?

Trains are widely considered to be one of the greenest modes of transportation available. However, this is only true of electric trains, as diesel trains emit pollutants that negatively impact air quality and threaten the health of passengers, workers, and communities living near railway infrastructure. While the entire transport sector contributes about 22% of global emissions, rail accounted for only 0.8% of this between 1990 and 2009, according to the European Environment Agency (EEA). Nevertheless, the use of diesel engines in trains has been linked to poor air quality and health issues, with a particular focus on the emissions of nitrogen oxides, hydrocarbons, and carbon monoxide.

Electric trains are emission-free, but diesel trains produce pollution

Trains are often considered a greener mode of transportation compared to flying or driving. However, not all trains are emission-free. While electric trains are emission-free at the point of use, diesel trains produce pollution and contribute to poor air quality, particularly in enclosed stations.

Diesel engines are the primary source of pollution from trains. About 20% of Europe's rail traffic is hauled by diesel locomotives, with countries like the UK, Greece, Estonia, Latvia, and Lithuania highly dependent on diesel traction. Diesel trains operating in enclosed stations, such as London's Paddington Station, can emit levels of nitrogen dioxide (NO2) that exceed European recommendations, impacting the air quality and the health of passengers and workers.

The emissions from diesel trains include pollutants like particulate matter, nitrogen oxides, hydrocarbons (HC), and carbon monoxide (CO). These pollutants have been linked to serious health issues. For example, particulate matter can burrow deep into lungs, while nitrogen oxides contribute to the formation of smog, which is associated with heart, lung, and cardiovascular disease and asthma.

To address this issue, there have been efforts to transition to cleaner locomotives and reduce pollution from train operations. California, for instance, has passed rules to fund cleaner, zero-emission locomotives, aiming to improve air quality and protect communities from the health impacts of locomotive pollution. Additionally, initiatives like the Low Carbon Sustainable Rail Transport Challenge aim for cutbacks in energy consumption and CO2 emissions from train operations by 2030.

In contrast to diesel trains, electric trains are emission-free. While the percentage of electrified rail networks varies across Europe, the shift towards electrification is crucial for reducing pollution and improving air quality in the railway sector. Electric trains contribute to making rail travel one of the greenest modes of transportation available, even with the current reliance on diesel locomotives in some regions.

Rail travel is one of the greenest modes of transportation

The transport sector contributes about 22% of global emissions, but rail travel only accounts for a tiny fraction of this, at 0.8% between 1990 and 2009. Rail and waterborne transport have the lowest emissions per kilometre and unit transported, while aviation and road transport emit significantly more.

However, it is important to note that diesel trains operating in enclosed stations can emit large quantities of pollutants, leading to poor air quality and health risks for travellers and workers. For example, a study found that emissions at London's Paddington Station far exceeded European recommendations. The University of Cambridge, the University of Minnesota, and Minnesota State University Mankato also found that air quality at the station was in breach of European limits for outdoor air quality in terms of nitrogen dioxide (NO2).

To improve sustainability, the rail industry is working to become even greener. For instance, paper tickets across the UK's National Rail network are being produced using a water-based system, reducing environmental impact by 87%. Additionally, free water fountains at stations are saving the equivalent of 400,000 plastic bottles from landfills each month.

Overall, rail travel is one of the most environmentally friendly modes of transportation, and its widespread adoption can play a critical role in tackling climate change.

Diesel trains operating in enclosed stations emit large quantities of pollutants

The use of diesel engines is the primary cause of pollution from trains. Electric trains, on the other hand, are emission-free. According to the European Commission, about 20% of Europe's rail traffic is hauled by diesel locomotives, with countries like the UK, Greece, Estonia, Latvia, and Lithuania being highly dependent on diesel traction.

Another study published in the journal Environmental Research Letters evaluated the air quality in London Paddington train station over five days and found it to be in breach of European limits for nitrogen dioxide (NO2) for outdoor air quality. Similarly, a study conducted at Edinburgh Waverley and London King's Cross stations, which had 59% and 18% of their train services powered by diesel engines, respectively, found elevated concentrations of NO2 and particulate matter (PM2.5) inside the stations, especially near the platforms with a higher frequency of diesel services.

The impact of diesel trains on air quality is not limited to enclosed stations but also affects communities living near rail lines. A study in Washington State, USA, found that residents living near rail lines were exposed to higher levels of diesel particulate matter (DPM) and airborne coal dust, with a significant increase in PM2.5 exposure. Similarly, in the United States, freight trains and truck routes often run through or parallel to communities of colour and low-income communities, exposing them to locomotive pollution and poor air quality, impacting their health.

While the transport sector contributes about 22% of global emissions, rail accounted for only 0.8% between 1990 and 2009, according to the European Environment Agency (EEA). However, with the health risks associated with diesel emissions and the potential for enclosed stations to have poor air quality, there is a growing need for improvement in emission reduction, especially in the rail sector.

Locomotive exhaust contains harmful pollutants like nitrogen oxides and particulate matter

While railway travel is considered one of the greenest modes of transportation, diesel trains that operate in enclosed stations emit large quantities of pollutants, threatening the well-being of frequent travellers and workers. Locomotive exhaust contains harmful pollutants like nitrogen oxides and particulate matter.

Nitrogen oxides are produced in significant amounts due to the lean-burning nature of diesel engines and the high temperatures and pressures of the combustion process. These oxides constitute a unique challenge regarding their reduction, as they create a lethal form of air pollution called smog, which is directly linked to heart, lung, and cardiovascular disease and asthma. While petrol cars have reduced nitrogen oxide emissions by around 96% through the use of catalytic converters, diesel cars still emit similar levels of nitrogen oxides as they did 15 years ago.

Particulate matter, such as soot, is another pollutant found in locomotive exhaust. This matter burrows deep into the lungs, causing harmful health effects. The mass of particulate matter increases with engine output, and it can remain in the air even after the locomotive has passed.

The health impacts of exposure to diesel exhaust have been studied, with research showing that combustion-derived air pollutants are considerably higher in the passenger carriages of diesel trains compared to electric trains. These pollutants include black carbon, ultrafine particles, and nitrogen oxides. The adverse health effects of diesel exhaust exposure include lung cancer, asthma, and premature deaths.

To mitigate the harmful effects of locomotive exhaust, various methods have been developed to reduce nitrogen oxides and particulate matter. Selective catalytic reduction (SCR) systems, for example, inject ammonia or urea into the exhaust to convert nitrogen oxides into gaseous nitrogen and water. Additionally, changing the fuel composition by mixing in bio ether or other fuels like hydrogen can also reduce pollutant emissions.

The rail industry is fighting to keep trains polluting

Despite the rail industry's positive track record, it is facing scrutiny for its contribution to air pollution, particularly from diesel trains. Diesel engines are the primary source of train pollution, and an independent study by the University of Cambridge and other institutions found that emissions from diesel trains at London's Paddington Station exceeded European recommendations, with levels of nitrogen dioxide (NO2) breaching outdoor air quality standards.

The rail industry, particularly in the United States, is under fire for its resistance to change and efforts to maintain the status quo of polluting practices. Environmental justice leaders and communities are demanding action, highlighting the health consequences of locomotive pollution, which disproportionately affect people of color and low-income communities living near freight railroad infrastructure.

In response to mounting pressures, California has taken a leading role in driving change. The state's Air Resources Board has passed rules to fund cleaner, zero-emission locomotives, reduce rail idling near residential areas, and promote the turnover of older, polluting trains. These efforts are significant in triggering industry-wide decarbonization and providing a model for national regulations.

However, the rail industry in the US is fighting to maintain its polluting practices, employing aggressive legal strategies to challenge these progressive rules. This resistance has dire implications for the health and well-being of millions of people, especially those from marginalized communities who are already bearing the brunt of transportation pollution.

To truly address this issue, policy changes at the national level are necessary. The EPA must remove arcane rail preemption regulations that shield large rail companies from taking responsibility for reducing their environmental impact. Additionally, upgrading diesel engines to meet the Stage IIIB standard can help mitigate the effects of exhaust emissions, focusing on particulate matter, nitrogen oxides, hydrocarbons (HC), and carbon monoxide (CO).

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