Illinois' Air Quality: A Pollution Crisis?

Illinois has a long history of air pollution, with electricity generation and transportation being the two most polluting sectors. Chicago, the state's largest city, has been ranked as one of the most polluted cities in the United States, with a particular issue of ozone pollution. The state's Air Quality Index (AQI) has been fluctuating, but as of March 2025, it was reported to be 'good' or 'satisfactory'. However, air pollution in Illinois still poses a risk to residents' health and quality of life, with potential issues including lung irritation, respiratory problems, and cardiovascular disease.

Chicago's air quality

Chicago has a long history of poor air quality, dating back to the city's industrialization in the late 19th century. During this period, the city relied on dirty coal, which produced soot that blanketed Chicago in a toxic cloud. This led to increased instances of pneumonia, asthma, and heart and lung diseases.

While Chicago was among the first cities to implement regulations to combat air pollution as early as 1881, the city continues to struggle with unhealthy air quality levels. In 2019, Chicago averaged an annual PM2.5 level of 12.8 μg/m3, exceeding both World Health Organization (WHO) and US Environmental Protection Agency (EPA) targets. PM2.5 refers to fine particle pollution with a diameter of 2.5 microns or less, which can penetrate deep into the lungs and is associated with increased risks of respiratory and cardiovascular issues, as well as cancer and premature death. Chicago's PM2.5 pollution ranks worst in Illinois and 79th nationally out of 1517 metropolitan areas.

Ozone is another significant contributor to Chicago's poor air quality, particularly during the summer months when higher temperatures facilitate its formation. In 2019, Chicago exceeded the number of allowed unhealthy air pollution days by more than five times, with an average of 19.2 unhealthy ozone days per year.

Transportation emissions, especially from motor vehicles, have been identified as a major source of air pollution in Chicago in recent years. To address this issue, the city has promoted initiatives such as increasing the accessibility of biking through the development of on-street bike lanes. Additionally, the City of Chicago, the State of Illinois, and the federal government have implemented various regulations and legislation over the last three decades to improve air quality. As a result, there has been a significant reduction in unhealthy ozone and PM2.5 days.

Despite these efforts, Chicago's air pollution levels remain "unhealthy" by EPA standards, and the city continues to address the ever-changing pollution levels through real-time data monitoring and forecasting. Sensitive groups, including children, the elderly, and people with pre-existing health conditions, are particularly vulnerable to the health risks associated with Chicago's air pollution.

Sources of pollution

Illinois has a long history of air pollution, with Chicago, in particular, facing significant air quality issues. The state's air pollution is caused by a range of sources, which have impacted the health and quality of life of Illinois residents.

One of the major sources of air pollution in Illinois is transportation. Cars, trucks, and buses contribute significantly to the state's air pollution, with Chicago's transportation sector being among the worst in the nation. The increase in the number of vehicles on the roads has led to higher levels of ozone and particulate matter in the air. This problem is further exacerbated by the state's electricity generation, which relies on fossil fuels, contributing to the overall poor air quality.

In addition to transportation, Illinois has historically relied on burning coal for power and heat, particularly during its industrialization in the late 19th century. This resulted in the ubiquitous presence of soot and smoke, spoiling the city's architecture and increasing health issues such as pneumonia, asthma, and heart and lung diseases. While Chicago took steps to curb the use of dirty coal as early as 1881, the problem of coal-related air pollution persisted.

Another factor contributing to Illinois' air pollution is the increase in temperature and the impact of global warming. Higher temperatures lead to more ozone production, and the resulting hotter weather can worsen air quality. Additionally, global warming contributes to more severe wildfires, which further increase air pollution and pose a growing threat to human health.

To address these issues, Illinois has implemented various measures. The state has legislated for cleaner air, resulting in a decrease in unhealthy ozone and PM2.5 days over the last three decades. Chicago has also taken initiatives such as increasing the accessibility of biking and maintaining on-street bike lanes to reduce vehicle emissions. However, despite these efforts, air pollution remains a concern, particularly in Cook County and Chicago, where levels are still considered ""unhealthy" by EPA standards.

It is important for individuals to monitor local air quality and take necessary precautions, such as limiting outdoor activities on poor air quality days and using air purifiers indoors. Additionally, reducing fossil fuel consumption and transitioning to renewable energy sources, such as wind and solar power, are crucial steps towards improving Illinois' air quality and protecting the health of its residents.

Health risks

Air pollution in Illinois is a serious issue, with the state ranking 8th in the bottom states for air pollution in the US. The air quality in Chicago, Illinois's largest city, has a long history of being unhealthy, dating back to the city's industrialization in the late 19th century. While the air quality has improved over the last three decades, with the frequency of unhealthy ozone days falling by 33% between 1996-1998 and 2006-2008, it still remains "unhealthy" by EPA standards.

The health risks associated with air pollution in Illinois are significant. Exposure to pollutants such as ozone and PM2.5 is linked to an increased risk of lung irritation, respiratory problems, cardiovascular disease, asthma, cancer, and even premature death. PM2.5 pollution, which can penetrate deep into the lungs, is particularly harmful. Studies suggest that 5% of early deaths in Chicago each year can be attributed to exposure to PM2.5. Fine particulate matter (PM2.5) and ozone are two of the most common "main pollutants" responsible for a city's AQI due to their potential for harm and prevalence at high levels.

The health effects of air pollution are not limited to respiratory issues. Air pollution has been linked to increased risk for adverse pregnancy outcomes, such as low birth weight and pre-term birth, other cancers, diabetes, cognitive impairment, and neurological diseases. Exposure to high levels of particulate matter can also lead to reduced lung function, respiratory infections, and aggravated asthma from short-term exposure. Long-term exposure can increase the risk of stroke, heart disease, chronic obstructive pulmonary disease, and cancer.

Certain populations are more susceptible to the health risks of air pollution. These include individuals with pre-existing heart and respiratory conditions, older adults, children, infants, and pregnant women. Additionally, low-income communities, urban residents, and Black, Asian, and Hispanic populations are more likely to be exposed to air pollution and face higher health risks. People of color are more likely to be living with chronic conditions that make them more vulnerable to the effects of air pollution, such as asthma and diabetes. Psychosocial stressors, such as poverty, racial/ethnic discrimination, and residency status, can also amplify the harmful effects of air pollution.

To reduce their exposure to air pollution, individuals can monitor local air quality, limit their time outdoors on days with poor air quality, and use air purifiers indoors. However, it is important to address the systemic issues that contribute to air pollution and health disparities. This includes transitioning to clean, renewable energy sources, promoting the use of electric vehicles, and implementing policies to reduce emissions and protect vulnerable communities.

Historical trends

Illinois, and particularly Chicago, has a history of poor air quality. As the city became more industrialised, it relied on poor-quality, cheap coal from Southern Illinois for power and heat. This coal was burned in boiler rooms, locomotives, steel mills, and domestic furnaces, creating an ever-present smoke. As far back as 1881, Chicago introduced legislation to curb the use of dirty coal. In 1959, the city established the Department of Air Pollution Control to investigate and regulate emission sources.

Subsequent regulations, including the federal Clean Air Act of 1970, and more recent city and state legislation, have helped further mitigate emissions. Over the last three decades, the United States federal government, State of Illinois, and City of Chicago have legislated for cleaner air. During this time, the frequency of unhealthy ozone days fell 33% from 28.5 days annually between 1996-1998 to 19.2 days between 2006-2008. The frequency of unhealthy PM2.5 days also fell 97% from 25.3 days annually between 2000-2002 to 0.7 days between 2006-2008.

Despite this long-term trend of improving air quality, recent years show a worsening trend. Particle pollution nearly doubled between 2017 and 2019, rising from 6.7 μg/m3 in 2017 to 12.8 μg/m3 in 2019. While these year-over-year gains can’t be attributed to any specific pollution events, the suburbanisation of the city and its dependence on motor vehicles have been blamed for the increase in transport emissions. In 2019, Chicago averaged an annual PM2.5 level of 12.8 μg/m3, breaching both World Health Organization (WHO) and US EPA targets. Chicago PM2.5 pollution is the worst in the state of Illinois for particle pollution.

The American Lung Association's 2019 "State of the Air" report found that Chicago ranked as the 18th most polluted city in the nation for ozone pollution, which was a worsening of its position compared to the previous year's report. The report also revealed that Chicago had a weighted average of 14 unhealthy ozone days between 2015-2017, significantly higher than the average of 9.8 unhealthy days from the previous year’s report.

The highest pollution levels in Illinois are in the Chicago area, though these levels have notably decreased over the past two decades. If recent progress continues, Illinois can expect significant increases in life expectancy and quality of life.

Solutions and initiatives

Air pollution in Illinois is a pressing issue, with the state ranking 8th for the worst air pollution in the US. The state's air quality has been affected by a range of factors, including electricity generation, transportation, and the increase in vehicles on the road. The good news is that there are several solutions and initiatives in place to address this problem.

Government Action

The United States federal government, the State of Illinois, and the City of Chicago have all implemented legislation to improve air quality over the last three decades. The federal Clean Air Act of 1970 and more recent city and state legislation have helped to reduce emissions. The Illinois Environmental Protection Agency (IEPA) and the Partners for Clean Air Act are also playing a crucial role by monitoring air quality during the summer months and alerting the public when pollution levels increase.

Transition to Clean Energy

There is a growing recognition of the need to transition to clean, renewable power sources such as wind and solar. This includes encouraging the use of electric vehicles to reduce transport emissions, which are a significant contributor to air pollution in Illinois.

Individual Action

Individuals can play a part by reducing their fossil fuel consumption and participating in local energy conservation programs. People can also limit their exposure to air pollution by monitoring local air quality and staying indoors on days with poor air quality. Using air purifiers in enclosed spaces can also help filter out pollutants.

Biking Initiatives

The City of Chicago is promoting biking as a mode of commuting by increasing the accessibility and attractiveness of biking through the development of on-street bike lanes.

Air Quality Monitoring

Companies like Prana Air provide air quality monitoring solutions for various spaces, including schools, workplaces, retail stores, and hospitals, to ensure that people are breathing clean air.

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