Railroad Pollution: A Historical Perspective

Railroads have played a significant role in transforming transportation and industry, particularly since the first steam-powered railway was built in the UK in 1830. However, the environmental impact of railroads has become a growing concern. While they are considered a greener mode of transport than road vehicles, railroads do contribute to pollution, particularly air, soil, and water pollution. The primary sources of railroad pollution are diesel exhaust emissions, track abrasion, freight leakages, and the transportation of petroleum products and other chemicals. The pollution generated by railroads has been linked to adverse health effects, particularly in communities located near freight routes, including low-income communities and communities of color, who are disproportionately affected by this pollution.

Diesel exhaust and dust from tracks pollute the air

The environmental impact of railways is a highly discussed topic, with diesel exhaust and dust from tracks being major contributors to air pollution. Diesel engines emit a mixture of gaseous and solid air pollutants, including volatile organic compounds, oxides of nitrogen (NOx), and diesel particulate matter (DPM). DPM, composed of carbon particles and organic compounds, poses significant health risks, including respiratory and cardiovascular issues, and is classified as ""carcinogenic to humans" by the International Agency for Research on Cancer.

Diesel exhaust is a significant source of air pollution, particularly in urban areas where major diesel emission sources, such as trains, are located near highly populated regions. The health consequences of elevated DPM levels are more severe in these urban communities. In the United States, locomotive pollution disproportionately affects communities of color and lower-income individuals, with over 13 million people directly impacted by poor air quality and associated health risks.

The impact of diesel exhaust on the environment extends beyond human health. Emissions from diesel engines contribute to the production of ground-level ozone, which damages crops, trees, and vegetation. Additionally, acid rain, a byproduct of diesel emissions, affects soil, lakes, and streams, entering the human food chain through water, produce, meat, and fish. These emissions also contribute to property damage and reduced visibility.

While efforts have been made to reduce DPM exposure, such as using cleaner-burning diesel fuel and implementing advanced emission control systems, the transition to newer and cleaner diesel engine vehicles takes time. As of 2022, diesel fuel consumption still accounted for a significant portion of total U.S. transportation sector CO2 emissions. Therefore, diesel exhaust and dust from tracks remain pressing concerns in the discussion of air pollution and its impact on both human health and the environment.

Soil and plant contamination from fuel combustion, track abrasion, and freight leakages

One of the primary sources of pollution in railway areas is polycyclic aromatic hydrocarbons (PAHs), which are introduced through the use of machine grease, fuel oils, and transformer oils. PAH contamination is particularly high in areas such as railway sidings and platform areas. For instance, in a study conducted in the railway junction of Iława Główna, Poland, PAH concentrations in the soil were found to be as high as 59,508 μg kg−1 in the railway siding and 49,670 μg kg−1 in the platform area. PAHs have high toxicity, significant stability, and a cumulative effect on the environment, and they also possess carcinogenic and mutagenic properties.

Heavy metal contamination is another significant issue in railway areas. Heavy metals such as Pb, Cd, Zn, Hg, Fe, Co, Cr, and Mo have been detected in soil and plant samples collected from various functional parts of railway junctions. The rail rolling stock construction material abrasion, fuel combustion in diesel-electric locomotives, and cargo leakage contribute to the emission of particles containing these heavy metals, which subsequently contaminate the soil and plants through dry and wet deposition.

Track abrasion also plays a role in soil and plant contamination. The mechanical behaviour and deformation mechanisms of track geometry can lead to the release of pollutants. Data-driven methods have been employed to estimate the occurrence of track geometry defects and their impact on the environment.

Additionally, freight leakages can result in soil and plant contamination. For example, in an incident involving a freight train transporting diesel and aviation fuel between Russia and China, an explosion destroyed a car, causing fuel leakages that damaged the rails and the surrounding environment.

Water pollution from heavy metals and petroleum products

Railways are considered to be one of the most fundamental modes of transportation. However, they can cause typical organic and inorganic contamination. Railway areas are sites of intensive heavy metal emission, and these emissions are neither chemically nor biologically degraded, which can affect the growth of plants and ecosystems.

Railway areas are thought to be sites of intensive heavy metal emission. High concentrations of heavy metals are often found in the vicinity of railways. For instance, the concentration of nickel, cadmium, cobalt, and lead in moss was found to be the same 30 meters from the railway as it was at points near the railways. In addition, high concentrations of polycyclic aromatic hydrocarbons (PAHs) were found in the aerial parts of plant species near the railway and up to distances of 30 meters from the railway.

The rail rolling stock construction material abrasion, fuel combustion in diesel-electric locomotives, action of pantographs on trolley wires, and cargo leakage emit particles containing heavy metals into the air and subsequently deposit them into the water, plant, and soil through dry and wet deposition. The heavy metals found in the water bordering the tracks are often caused by leakages from petroleum products carried on the system.

The contamination in the railway siding exceeded the average control level by about 80 times. In the soil of all the investigated areas, four- and five-ring PAHs prevailed. The highest concentration was found in the aerial parts of Taraxacum officinale growing in the cleaning bay. The comparison of the soil contamination with PAHs in the investigated railway junction showed a very significant increase in the PAHs level since 1995. It was found that the heavy metal contamination was also very high.

Locomotive exhaust contains pollutants like particulate matter and nitrogen oxides

Locomotive exhaust contains pollutants like particulate matter (PM) and nitrogen oxides (NOx). Locomotive pollution has been linked to a slew of transportation pollution-related health issues. More than 13 million people in the US—predominantly people of colour and lower-income individuals—are directly impacted by locomotive pollution, living through poor air quality and dangerous health issues. Locomotive exhaust contains pollutants like PM, which burrow deep into the lungs to poison people, and nitrogen oxides, which create a lethal form of air pollution called smog that is directly linked to heart, lung, and cardiovascular disease and asthma.

Diesel exhaust is the gas produced by a diesel engine, plus any contained particulates. Its composition may vary with the fuel type, rate of consumption, or speed of engine operation. Diesel engines produce one-twenty-eighth the carbon monoxide that gasoline engines do, as they burn their fuel in excess air even at full load. However, the lean-burning nature of diesel engines and the high temperatures and pressures of the combustion process result in significant production of NOx, an air pollutant.

Primary railway-derived air pollutants include PM, NOx, carbon monoxide (CO), and hydrocarbons (HCs). Railway transportation is a source of non-road emissions, and when diesel locomotive engine emissions are not controlled, the exhaust emissions can negatively affect communities and eco-systems. Exposure to diesel exhaust and diesel particulate matter (DPM) is an occupational hazard to railroad workers, miners using diesel-powered equipment in underground mines, and occupants of residential homes in the vicinity of a rail yard.

The impact of diesel trucks is more harmful to public health than previously believed. A 2025 analysis predicts that through 2040, there could be 307,000 premature deaths, 217,000 new childhood asthma cases, 120 million lost workdays, and $1.4 trillion in economic costs linked to diesel truck emissions. In the case of PM and NOx, emission concentrations increased as engine output increased. High concentrations of CO were detected at engine start and acceleration, while hydrocarbons showed weakly increased concentrations regardless of engine power.

Railroads disproportionately affect low-income communities and communities of colour

Railroads have been a source of pollution since their inception, with steam-powered trains being replaced by diesel-electric trains in the 1940s. While railroads are still the most environmentally friendly means of transport, producing 80% less gas emissions than cars, they are a significant source of noise, vibrations, and carbon emissions, which disproportionately affect low-income communities and communities of colour.

Polluting freight trains and trucks often run through or alongside low-income communities and communities of colour. Over 13 million people in the US, predominantly people of colour and lower-income individuals, live and work near railyards, rail lines, and ports, bearing the brunt of transportation pollution. Locomotive exhaust contains particulate matter, which penetrates deep into the lungs, and nitrogen oxides, which create smog and are linked to serious health issues such as heart, lung, and cardiovascular disease, and asthma.

The negative impacts of railroads on these communities are further exacerbated by a lack of transportation investments in predominantly Black communities. This was evident during the evacuation responses after Hurricane Katrina in New Orleans, where the lack of transportation infrastructure contributed to disastrous outcomes in the Lower Ninth Ward, a primarily Black community. Similarly, dysfunctional transportation policies contributed to the disproportionate impact of COVID-19 on Black communities in 2020.

Exclusionary zoning practices and gentrification have also played a role in displacing low-income residents and communities of colour from their neighbourhoods. Transit-oriented developments, while bringing improvements in infrastructure, can reinforce residential segregation and gentrification, leading to the displacement of existing community members. Additionally, discriminatory planning and zoning have contributed to unequal development, limiting access to transportation and opportunities for communities of colour.

To address these disparities, racial equity impact studies can be conducted to analyse how racial groups will be affected by proposed infrastructure projects. By anticipating potential harms, interventions can be designed to ensure equitable outcomes and prevent further injustices.

Frequently asked questions