Greta Jimenez
Portland's air pollution levels have been climbing since 2016, with the city's air quality index (AQI) rated a C in 2019. Researchers at Portland State University have been mapping the city's hottest and most polluted places, with the aim of identifying areas that are most vulnerable to heatwaves. The hottest places in the city are often the most polluted, and the combination of heat and pollution poses a serious risk to human health. Portland's historically redlined neighbourhoods, predominantly occupied by non-white Americans, are disproportionately affected by air pollution.
| Characteristics | Values |
|---|---|
| Cause of increased heat and pollution | Lots of pavement, lack of greenery |
| Impact of climate change | Higher risk of heart attacks, strokes and asthma attacks |
| Impact of increased heat and pollution | Higher rates of diabetes, high blood pressure, physical disabilities, cancer deaths, etc. |
| Areas with high pollution | Northern end of the city |
| Air pollution sources | Portland General Electric, Oregon's only coal-fired power plant, pulp and paper mills, natural gas-fired plants, motor vehicles, industrial complexes, factories, etc. |
| Areas with high heat | The airport |
| Areas with low heat | Forested parks |
| Strategies to reduce heat | Opening cooling centers, removing pavement, adding trees, investing in bioswales, tree planting and preservation, de-paving, etc. |
| Air Quality Index (as of July 22, 2025) | Overall AQI: 21, PM2.5 AQI: 21, NO2 AQI: 2, O3 AQI: 0, CO AQI: 0 |
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What You'll Learn
Portland's air pollution levels have been climbing since 2016
Portland's air pollution is characterised by a combination of PM2.5 and ozone pollution, which are among the most harmful pollutants in the US. PM2.5 pollution, or fine particulate matter, tends to increase during winter due to household wood burning and temperature inversions that trap pollution. Ozone, a secondary pollutant, forms when high temperatures, sunlight, and precursor pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) interact. The presence of motor vehicles, industrial complexes, power plants, and factories further contributes to ozone pollution.
The distribution of air pollution in Portland is not uniform, with certain areas bearing a disproportionate burden. Historically, high-polluting infrastructure, such as airports, major roadways, and industrial sites, has been located near disadvantaged communities. Racist redlining practices have played a role in this distribution, as 42% of historically redlined neighbourhoods are within one mile of the city's top polluters. Consequently, non-white residents experience higher exposure to air pollution, leading to adverse health outcomes, including higher infant mortality, low birth weights, and increased rates of chronic diseases.
To address this issue, researchers from Portland State University have developed heat maps that identify the hottest and most polluted neighbourhoods. By incorporating air quality, temperature, and census data, they aim to pinpoint vulnerable areas and populations. This information is crucial for city planners to implement effective strategies, such as investing in bioswales, tree planting, and reducing impervious surfaces like asphalt. By taking targeted actions, Portland can work towards mitigating the health risks associated with extreme heat and air pollution, ultimately improving the well-being of its residents.
As climate change continues to exacerbate the frequency and intensity of heat waves, it is essential for cities like Portland to adapt and find ways to cool down vulnerable neighbourhoods. The interactive map developed by Portland State University serves as a valuable tool for city planners to make informed decisions. By addressing the urban heat island effect and reducing air pollution, Portland can create a healthier and more resilient urban environment for its residents.
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Portland's ozone season
The urban heat island effect is more pronounced in city neighbourhoods with lots of pavement and little greenery. Portland State University researchers have developed heat maps of Portland's neighbourhood temperatures, finding a 15-degree difference between places like airports and forested parks. They have also added air quality and census data to their maps to identify areas with vulnerable populations, such as older adults with pre-existing health conditions and no air conditioning.
Portland's air pollution levels have been climbing since 2016 due to a growing population, an increasing number of vehicles, EPA regulatory rollbacks, rising global temperatures, and more frequent and severe wildfires. The American Lung Association (ALA) gave Portland a "C" grade for 24-hour PM2.5 and 24-hour ozone levels in their 2019 State of the Air report, a downgrade from the previous monitoring period.
To address these issues, the city of Portland is considering strategies such as opening more cooling centres during heatwaves, removing pavement, and adding trees and green spaces. Portland's Bureau of Planning and Sustainability aims to redesign hotter neighbourhoods to stay cooler during heat waves by investing in bioswales and tree planting and reducing impervious surfaces like asphalt. These efforts are crucial as the combination of heat and pollution poses a significant risk to human health, especially for vulnerable populations.
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Urban heat island effect
Urban heat islands are parts of a city that experience higher temperatures during heat waves. They are often the result of a lack of green spaces, which naturally cool down an area. Trees and other plants reflect sunlight and release moisture, preventing heat from building up. In contrast, urban materials like pavement and roofing tend to absorb and emit more heat, contributing to the urban heat island effect.
In Portland, researchers from Portland State University have been mapping the city's temperatures and air quality to identify the hottest and most polluted areas. They found that neighborhoods with more pavement and less greenery tend to be hotter and more polluted, and these areas pose a growing risk to human health. The city's airport, for example, is one of the hottest places in Portland due to its abundance of asphalt and lack of trees.
The urban heat island effect in Portland is exacerbated by the city's layout, with narrow streets and tall buildings blocking natural wind flow that could otherwise provide a cooling effect. Additionally, industrial complexes, power plants, and factories located near disadvantaged communities contribute to higher temperatures and air pollution in these areas. Portland's growing population, increasing vehicle emissions, regulatory rollbacks, and frequent wildfires have also contributed to climbing air pollution levels since 2016.
To address these issues, the City and Metro-area government are working to mitigate the impact of urban heat islands through targeted tree-planting efforts. They are also developing strategies to help vulnerable populations, such as the sick, elderly, and those without air conditioning, stay cool during heat waves. Portland's new interactive map, which combines heat, pollution, and population data, will aid in identifying the neighborhoods most in need of intervention.
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Portland's air pollution is a combination of PM2.5 and ozone pollution
Ozone, on the other hand, is a secondary pollutant that occurs in the atmosphere when high temperatures (over 84°F) and sunlight (UV radiation) cause pollutants, nitrogen oxides (NOx), and volatile organic compounds (VOCs) to react. Precursor pollutants are largely emitted by vehicles and smoke stacks, but they can also travel hundreds of miles from neighbouring cities when carried by wind. For instance, Portland's air quality can be adversely affected by the air quality in nearby cities like Seattle, Bend, or Eugene.
Portland's ozone season typically runs from May through September, when the city experiences an average of 51 days over 80 degrees Fahrenheit. As temperatures continue to rise due to climate change, the formation of ozone becomes more favourable. Fine particle pollution, on the other hand, tends to rise during the winter months due to increased household wood burning and pollution-trapping temperature inversions.
The sources of Portland's air pollution are diverse and include motor vehicles, fossil fuel combustion at industrial complexes, power plants, and factories. Portland General Electric, Oregon's only coal-fired power plant, pulp and paper mills, and natural gas-fired plants are among the stationary emission sources contributing to the city's air pollution. Additionally, historical redlining practices have resulted in high-polluting features such as airports, major roadways, and industrial complexes being placed near disadvantaged communities, further burdening them with higher air pollution levels.
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Portland's redlined neighbourhoods
Portland's air pollution levels have been climbing since 2016, with a concerning trend of a growing population, an increasing number of vehicles, EPA regulatory rollbacks, warming global temperatures, and more frequent and severe wildfires. The city's air pollution is a combination of PM2.5 and ozone pollution, which share sources such as motor vehicles, industrial complexes, power plants, and factories.
Portland's historically redlined neighbourhoods, predominantly inhabited by African Americans and other people of colour, have been disproportionately affected by air pollution. Racist redlining practices dating back to the 1930s have had a lasting impact on the distribution of air pollution in the city. High-polluting city features such as airports, major roadways, factories, industrial complexes, and power plants have been placed near these disadvantaged communities, further driving down property values and burdening residents with unhealthy air. A study by Portland State University found that 42% of historically redlined neighbourhoods are within 1 mile of the city's top 10 polluters.
The legacy of redlining has resulted in non-white residents suffering from adverse health effects due to air pollution. They experience higher infant mortality, low birth weights, and higher rates of diabetes, high blood pressure, physical disabilities, stroke, heart disease, and cancer deaths.
To address this environmental injustice, researchers from Portland State University have developed heat maps of Portland's neighbourhood temperatures, integrating air quality and census data. This allows for the identification of vulnerable areas and the implementation of strategies to mitigate the health risks associated with extreme heat. Suggested strategies include opening cooling centres, removing pavement, and increasing green spaces.
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Frequently asked questions
In general, city neighborhoods with lots of pavement and fewer trees tend to be hotter and more polluted. This phenomenon is called the urban heat island effect. Portland State University researchers have developed heat maps of Portland's neighborhood temperatures, and the airport seems to be one of the hottest places in the city.
Portland's unhealthy air pollution is a combination of PM2.5 and ozone pollution, two of the most prevalent and dangerous pollutants in the US. The main sources of these pollutants include motor vehicles, industrial complexes, power plants, and factories. Portland General Electric, Oregon's only coal-fired power plant, is one of the stationary emission sources, along with pulp and paper mills, and natural gas-fired plants.
The negative health effects of air pollution are well-documented, and Portland is no exception. The city has seen an increase in adverse health outcomes such as higher infant mortality, low birth weights, and higher rates of diabetes, high blood pressure, physical disabilities, stroke, heart disease, and cancer deaths, particularly in historically disadvantaged communities.
Researchers at Portland State University have developed an interactive map that combines heat, pollution, and population data. This map will help local officials identify the most vulnerable areas and plan strategies to mitigate the heat island effect, such as opening more cooling centers, removing pavement, and adding trees and shade.
Yes, Portland has several sites designated as Superfund Sites by the Environmental Protection Agency due to their high levels of pollution. These include the former Arkema plant, the Harbor Oil property near Heron Lakes Golf Course, the McCormick and Baxter Superfund Site, and the Triangle Park sub-site within the Portland Harbor Superfund Site. These sites have been contaminated with various industrial toxins, pesticides, and other hazardous materials.
