Brian Barton
Millions of people who use the subway every day may be unknowingly exposing themselves to harmful air pollution. Studies have found that subway stations have high levels of indoor air pollution, with particulate concentrations two to seven times higher than the 24-hour exposure limits set by organisations like the US Environmental Protection Agency and the World Health Organization. This poor air quality may disproportionately affect minority and low-income riders, particularly those from Black and Hispanic communities, who often have longer commutes and transfer through more polluted stations. The health effects of exposure to these pollutants are still being studied, but research suggests that it may increase the risk of adverse health effects such as heart issues, aggravated asthma, decreased lung function, and even death for those with pre-existing heart or lung disease.
| Characteristics | Values |
|---|---|
| Air pollution in subway stations | High levels of harmful air pollution |
| Sources of pollution | Dust from friction on rails and wheels, diesel maintenance locomotives, fossil fuels |
| Health risks | Increased risk of heart and lung disease, aggravated asthma, decreased lung function |
| Vulnerable populations | Lower-income, minority, and Hispanic and Black passengers |
| Locations with high pollution | 168th Street, 181st Street, 72nd Street, High Street, Borough Hall, Fulton Street, Bowling Green |
| Pollution measurements | PM2.5 concentrations, iron content, WHO guidelines, EPA standards |
| Solutions | Improved ventilation, vacuum trains, power-washing platforms |
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What You'll Learn
- Air pollution in subway stations is worse in some cities than others
- Particles in the air can enter the bloodstream and lead to health issues
- Poor ventilation in underground stations can increase pollution levels
- Marginalised communities are disproportionately affected by subway pollution
- The health effects of long-term exposure to subway pollution are unknown
Air pollution in subway stations is worse in some cities than others
Air pollution in subway stations is a serious issue, with potential health risks for commuters and transit workers. While subway systems are promoted as a means to reduce traffic congestion and improve air quality, studies have found that the air quality inside subway stations can be significantly worse than outdoors. This is particularly true in certain cities, with some stations having air pollution levels far above the recommended guidelines.
A study by researchers from New York University found that the air in New York City subway stations contained high levels of tiny, invisible particles of iron. These particles are a result of friction between brakes, train wheels, and tracks. The study revealed that concentrations in some stations were 15 times higher than the World Health Organization (WHO) guidelines, with the average concentration across stations ranging from 150 to 200 units, far exceeding the WHO limit of 15. Notably, the 168th Street and 181st Street stations on the No. 1 line were identified as the most polluted, with levels between 550 and 600 units.
Another study, led by Terry Gordon from New York University's Langone School of Medicine, investigated 71 subway stations during rush hour in five US cities: New York City, Jersey City, Boston, Philadelphia, and Washington, DC. This study found that the concentrations of airborne particles smaller than 2.5 µm in diameter (PM2.5) were much higher than those in the ambient outdoor air. On average, the PM2.5 levels were two to seven times higher than the 24-hour exposure limits set by the US Environmental Protection Agency. Among these cities, New York City consistently scored worse for air pollution in its subway stations.
The high levels of air pollution in subway stations can be attributed to various factors, including limited access to outside air, the frequency of trains, large passenger numbers, and the age of the subway system. Additionally, the use of graphite lubricants on brake pads, poor ventilation, station depth, and the wear on wheels and rails can contribute to the problem. Improving ventilation, utilizing platform screen doors, and increasing cleaning frequency to minimize dust are potential strategies to enhance air quality in subway stations.
While the presence of air pollution in subway stations is a concern, it's important to note that the health effects of these pollutants may vary across different locations and populations. The impact on individuals with existing health conditions, particularly lung-related issues, could be more significant. As a precautionary measure, wearing masks, such as N95 or surgical masks, can provide excellent protection against inhaling harmful particles while using the subway.
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Particles in the air can enter the bloodstream and lead to health issues
Air pollution is a mix of tiny solid and liquid particles, also known as particulate matter or soot. These particles are so small that they can bypass our body's natural defenses, making their way deep into the lungs. Some particles are even small enough to pass through the lungs and enter the bloodstream, just like essential oxygen molecules.
The size of particles is directly linked to their potential for causing health problems. Smaller particles less than 10 micrometers in diameter can get deep into the lungs, and some may even enter the bloodstream. Exposure to such particles can affect both the lungs and the heart, increasing the risk of heart and lung disease. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including premature death in people with heart or lung disease, and increased respiratory symptoms such as irritation of the airways, coughing, or difficulty breathing.
Subway stations, particularly those in large cities, have been found to have surprisingly high levels of indoor air pollution. This is due to a variety of factors, including poor ventilation, diesel-powered maintenance locomotives, and dust created by friction on the rails and between train wheels and tracks. This dust has a high iron content and can remain suspended in the air for long periods. When inhaled, these particles can easily enter the bloodstream.
While everyone is at risk from the health impacts of particle pollution, those who live near emission sources, such as subway stations, are at a higher risk. Other vulnerable subpopulations include people of color, children, older adults, and people from minority and low socioeconomic status populations.
The good news is that air quality has improved in recent decades due to stricter emissions standards and cleaner power plants, industrial sites, and vehicles. Additionally, the construction of subway systems in highly polluted cities can help reduce overall air pollution and provide external mortality benefits. However, it is important to address the high levels of air pollution in subway stations, especially through improved ventilation, to protect the health of commuters and transit workers.
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Poor ventilation in underground stations can increase pollution levels
The air quality in underground stations is affected by various factors, including the type of trains, the depth of the station, and the ventilation system. For example, electric and hybrid-style trains generally have lower emissions than diesel-powered trains. Deeper stations, such as those on the Northern Line in London, tend to have higher pollution levels than those on higher-level lines. Stations with poor ventilation have been found to have higher pollution readings.
The primary source of particulate matter in underground stations is iron oxide, which comes from the mechanical wear of train components, brake blocks, and rail wear. These particles are created by the friction between the brakes, train wheels, and tracks and have a high iron content. Other sources of pollution in underground stations include the external atmosphere, underground tunnels, cleaning chemicals, and equipment. The movement of trains creates air turbulence, suspending these particles in the confined air and exposing staff and passengers to inhalation.
The health effects of particulate matter in underground stations are a concern. These particles are small enough to enter the bloodstream and may increase the risk of heart and lung disease. However, it is important to note that the overall risk to public health from underground stations is not considered serious or substantial. Additionally, the use of public transport, such as subways, can help reduce traffic congestion and improve air quality in cities.
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Marginalised communities are disproportionately affected by subway pollution
Several studies have found that subway stations have high levels of air pollution that are harmful to human health. These subterranean emissions may increase the risk of heart and lung disease in commuters and transit workers.
While subways are touted as a solution to traffic congestion and a way to improve air quality, the air quality inside subway systems can be poor. This is due to the high levels of particulate matter (PM2.5) in the air, which is caused by friction between brakes, train wheels, and subway tracks.
Marginalised communities, particularly racial minorities and lower-income groups, are disproportionately affected by subway pollution. This is due to various factors, including longer commutes and the unequal distribution of environmental hazards.
Firstly, Black and Hispanic workers tend to live farther from their workplaces and have longer commutes, often requiring transfers at more polluted stations. This results in higher exposure to air pollution, with studies finding that these workers were exposed to 20 to 35% more particles than their Asian and white counterparts.
Secondly, people of colour often suffer from environmental injustices, with air pollution being distributed unevenly among different racial groups. This is a form of environmental racism, where marginalised communities bear the brunt of environmental impacts and hazards.
Additionally, low-income communities are more exposed to pollution compared to affluent communities. This is further exacerbated by the fact that marginalised groups often have weaker adaptive capacities to react to climate changes, making them more vulnerable to the adverse effects of pollution.
Furthermore, some stations with poor ventilation tend to be located in marginalised communities, leading to higher pollution levels.
It is important to address these disparities and ensure that sustainability investments and environmental policies benefit disadvantaged communities.
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The health effects of long-term exposure to subway pollution are unknown
While subway stations are known to have high levels of air pollution, the health effects of long-term exposure to subway pollution are unknown. Subway stations in five US cities, namely New York City, Jersey City, Boston, Philadelphia, and Washington, DC, have been found to have surprisingly high levels of indoor air pollution. These emissions may increase the risk of heart and lung disease in commuters and transit workers. However, the specific health consequences of long-term exposure to these pollutants are yet to be determined.
The air in subway stations contains tiny, almost invisible particles of iron, resulting from the friction between brakes, train wheels, and subway tracks. These particles have higher iron content than those found outdoors. The concentrations of these particles in some stations were found to be significantly above the World Health Organization's guidelines. Stations in upper Manhattan, including Washington Heights and Inwood, have the highest per capita levels of subway pollutant commuting exposure due to a large number of commuters and longer commute times.
The impact of subway pollution disproportionately affects minority and low-income commuters, particularly Black and Hispanic passengers. These individuals often have longer commutes, requiring more transfers between trains, resulting in higher exposure to pollutants. The stations outside of Manhattan are mostly above ground and generally less polluted. However, Black and Hispanic communities tend to live near these stations and still experience higher overall exposure due to their longer commutes and transfers through more polluted stations.
While the health effects of long-term exposure are not fully understood, the high levels of air pollution in subway stations are concerning. More research is needed to determine the exact sources of the pollutants and the specific health consequences for individuals with underlying health conditions and transit workers who are regularly exposed to these pollutants for extended periods. The long-term health impact of subway pollution remains a subject of ongoing investigation.
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Frequently asked questions
Studies have found that the air in subway stations is highly polluted, with particulate matter concentrations at least 10 times higher than air above ground. This can lead to a range of adverse health effects, including an increased risk of heart issues, aggravated asthma, decreased lung function, and even death for those with heart or lung disease. Therefore, living next to a subway station may also be unhealthy.
The sources of pollution in subways include dust created by friction on the rails and train wheels, maintenance locomotives that run on diesel, and particles that may derive from fossil fuels.
Yes, studies have found that subway pollution disproportionately impacts minority and low-income commuters, particularly Black and Hispanic communities. This is due to a combination of longer commute times, transferring through more polluted stations, and residing in areas with higher per capita levels of subway pollutant exposure.
To mitigate subway pollution, improvements in ventilation and air quality are necessary. Additionally, researchers suggest the need for further characterization of the chemical composition and toxicity of particulate matter in subways. Policy changes that prioritize cleaner air for all, especially in vulnerable neighborhoods, are also essential to address this environmental justice issue.
