Bronte Wells
The United States has witnessed improvements in air quality over the past five decades, largely due to the Clean Air Act. However, air pollution remains a pressing issue, with climate change increasing the risk of wildfires and their subsequent smoke spreading dangerous particle pollution. While various factors contribute to a city's carbon footprint, wealth and consumption patterns are significant drivers of higher carbon emissions. Large and wealthy cities, particularly those with lower urban density and less developed public transportation systems, tend to have bigger carbon footprints. Additionally, the availability of renewable energy sources, building quality, dietary patterns, and transportation options can influence a city's carbon pollution levels.
| Characteristics | Values |
|---|---|
| Cities with the largest carbon footprints | Seoul, Guangzhou, New York, Hong Kong, and Los Angeles |
| Factors that affect a city's carbon footprint | Availability of renewable energy, quality of buildings, dietary patterns of residents, and transportation options |
| Factors that contribute to a higher carbon footprint | Wealth, consumption of goods, size of living and working spaces, travel, and meat consumption |
| Cities with smaller carbon footprints | Cities with higher urban density and more use of public transit |
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What You'll Learn
Wealthier cities have higher carbon footprints
The key to slowing down global warming may lie in targeting large and wealthy cities, which have the biggest carbon footprints. A study by the University of Michigan found that the homes of wealthy Americans generate about 25% more greenhouse gases than residences in lower-income neighborhoods, with emissions in the most affluent suburbs up to 15 times higher. This is due to a variety of factors, including larger living spaces, greater energy use, and higher consumption of goods and meat.
A small number of large and/or affluent cities contribute significantly to national total emissions. For example, in the United States, New York and Los Angeles are considered megacities with relatively small carbon footprints in relation to their population density. However, the surrounding suburbs of these cities have much larger carbon footprints, offsetting the benefits of low-carbon areas in city centers. This is partly due to the higher percentage of emissions from individual vehicles in suburban areas compared to big cities.
The carbon footprint of a city is influenced by various factors, including population density, income levels, availability of renewable energy, dietary patterns, and transportation options. Wealthier cities tend to have higher carbon footprints because residents generally consume more goods, live and work in larger buildings, travel more, and eat more meat. Additionally, suburban parts of cities, which often have higher-income residents, tend to have larger carbon footprints due to higher emissions from transportation and individual vehicle use.
While wealthier cities have higher carbon footprints per capita, it is important to note that more populous cities have higher overall emissions. This is because emissions are correlated with population size, and in large cities, emissions per person can be lower due to shared resources and infrastructure. However, the type of emissions can differ between cities; for example, transportation accounts for 50% of emissions in suburban areas, while food services are a major contributor in New York City.
To address the issue of high carbon emissions in wealthier cities, local governments can implement measures to reduce emissions, such as investing in low-carbon energy and transport systems, reducing urban sprawl, and adopting nature-based solutions for urban cooling. Additionally, emissions-based performance ratings can be used to promote rapid decarbonization and hold urban governments and businesses accountable for their environmental impact.
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Wildfires are a significant source of pollution
While it is challenging to compare the carbon footprints of cities consistently, researchers have found that large and wealthy cities have the biggest carbon footprints. In the United States, this means that cities like Los Angeles, New York, and the suburbs of Washington, D.C. are among the cities with the largest carbon footprints.
The relationship between wildfires and pollution is a vicious cycle. Human activities, such as burning fossil fuels, transportation, and industrial processes, release greenhouse gases and black carbon emissions, fueling climate change. These pollutants trap heat in the atmosphere, causing the Earth's temperature to rise and weather patterns to become more erratic, increasing the likelihood of wildfires. Climate change-induced droughts also make forests more vulnerable to fires.
The impact of wildfires on pollution is evident in the thick smoke they produce, which contains harmful airborne particles. These particles can have severe health impacts, especially if inhaled over long periods. Particulate matter can reduce crop yields by up to 15% in highly polluted areas, affecting agriculture and ecosystem health. The smoke from wildfires can travel great distances, affecting air quality across regions. For example, smoke from wildfires in Chile in 2023 reached as far as Western Europe, resulting in elevated levels of particulate matter and carbon emissions.
Addressing the pollutants released by wildfires is critical to combating both the climate crisis and the harmful effects of pollution on human health and the environment. Policymakers play a crucial role in implementing interventions with long-standing, sustainable impacts, shifting from a reactionary approach to prevention.
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Air quality impacts health
Air pollution is a serious health threat, and certain cities in the US are more affected than others. While good air quality days are common throughout the country, unhealthy air quality is concentrated in the western and southwestern US.
The Los Angeles-Long Beach area ranked worst for ozone pollution for the 25th time in the 26-year history of the "State of the Air" report. The area also ranked seventh for short-term particulate matter. Despite their ranking as the fifth worst for long-term particulate matter, the 2025 report contained their lowest levels on record. The Eugene-Springfield area ranked third for short-term air quality. The Fresno area in California’s Central Valley also scored fifth for both short-term air pollution and ozone pollution, an improvement from previous years.
Six of the top seven cities with the worst air quality are in California, and four are in the state's Central Valley, a 450-mile flat valley that runs parallel to the Pacific coast. Bakersfield, Visalia, and Fresno are located at the drier and hotter southern end of the valley, which is worse for air quality. The top three local sources of PM2.5 emissions in 2023 were farms (20%), forest management/agricultural waste burning (20%), and road dust (14%).
The Detroit metro area is a new addition to the Top 10 list in long-term particle pollution, marking the first appearance of a non-West Coast region. The area ranks 22nd for short-term particle pollution and was impacted by the Canadian wildfires.
The air quality of a city can have a direct impact on the health of its residents. Exposure to unhealthy air is detrimental to an individual's health, leading to an increased risk of stroke, ischemic heart disease, heightened risk of cancer, increased severity in asthma attacks, chronic obstructive pulmonary disease, lung cancer, and pneumonia. It is also linked to increased fetal and infant mortality and pregnancy complications.
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Public transport reduces emissions
The American Lung Association's "State of the Air" report for 2025 found that nearly half of Americans live in areas where the air quality is poor. More than 42 million people live in counties that received an F for all three air pollution measures. Air pollution is a serious health threat, increasing the risk of adverse health effects such as premature birth, low birth weight, asthma attacks, and harm to lung development in children.
Public transportation has a proven record of reducing congestion and emissions. In 2011, US public transportation use saved 865 million hours in travel time and 37 million metric tons of carbon dioxide emissions. This is equivalent to the emissions from the electricity generated for use by nearly 5 million households or all the households in Washington DC, New York City, Atlanta, Denver, and Los Angeles combined. Public transportation use also saves the US the equivalent of 4.2 billion gallons of gasoline annually and more than 11 million gallons per day.
The use of public transportation can help reduce emissions by taking passenger cars off the road. For example, KCATA's move from diesel to compressed natural gas (CNG) fuel for its RideKC buses has resulted in cost savings and environmental benefits, reducing greenhouse gas emissions by 1,870 metric tons, the equivalent of removing 395 passenger cars from the road for a year.
Other factors that influence a city's carbon footprint include the availability of renewable energy, the quality of buildings, dietary patterns of residents, and transportation options. Wealth is also correlated with higher carbon footprints, as wealthier people tend to consume more goods, live and work in larger buildings, travel more, and eat more meat.
Concerted action by local governments, therefore, has the potential to significantly reduce national carbon footprints, especially in large and wealthy cities, which tend to drive a significant share of total emissions.
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California has the most polluted national parks
California is home to some of the most famous national parks in the United States, including Yosemite, Sequoia, Kings Canyon, and Joshua Tree. Unfortunately, these parks are also known for their poor air quality, with four out of the ten most polluted sites in the country located in California. The state's national parks have not seen the same improvements in air quality as the rest of the nation.
There are several factors contributing to the poor air quality in California's national parks. One significant factor is their proximity to large cities, busy highways, and industrial and agricultural operations. For example, Sequoia and Kings Canyon National Parks, which top the list of parks with the unhealthiest air, are located downwind from the state's largest cities and busy highways. Vehicle emissions, industrial operations, and agricultural activities in regions like the San Joaquin Valley of California, which is one of the most polluted areas in the nation, contribute to the high levels of air pollution in these parks.
Wildfires also play a significant role in degrading air quality in California's national parks. The state has experienced more intense wildfires in recent years, which have had devastating effects on the parks. The smoke from these fires can cause yellow haze thousands of miles away, and the fine particles released into the air can infiltrate the heart and lungs, causing serious health issues. The combination of vehicle emissions, industrial operations, agricultural activities, and wildfires has made it challenging to improve air quality in these parks.
Climate change and other human activities further exacerbate the problem. California's national parks are facing unique and devastating consequences from human-caused air pollution and climate change. Drought, invasive species, and extreme heat have weakened the health of plants and animals, permanently harming ecosystems and negatively affecting the visitor experience. The state's reliance on car-dependent population centers, such as Los Angeles, and industrial and agricultural operations in certain regions, has made it difficult to reduce air pollution levels significantly.
While the Environmental Protection Agency has been working to reduce "visibility impairments" in national parks since 1999, California's national parks continue to struggle with unhealthy air quality. The state's parks foundation has advocated for increased budget allocations to address these issues, proposing the spending of tens of millions of dollars to tackle wildfires, sea-level rise, and other climate change-related challenges.
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Frequently asked questions
According to a 2018 report by the Norwegian University of Science and Technology, New York City, Los Angeles, Chicago, and New Orleans are among the US cities with the biggest carbon footprints.
A city's carbon footprint is influenced by various factors, including population density, transportation options, dietary patterns, energy consumption, and building infrastructure. Wealth also correlates with higher carbon emissions as it is associated with increased consumption, larger living and working spaces, frequent travel, and higher meat consumption.
Cities can reduce carbon emissions by encouraging the use of public transportation, investing in renewable energy sources, improving building energy efficiency, promoting sustainable dietary choices, and implementing targeted measures to reduce consumption in high-income areas.
