The air we breathe
A story of air quality in the United States for the past and present
In an ideal world, we would all breathe fresh, crisp air. And while our air is cleaner than it was 40 years ago, we breathe harmful particles every day that can impact our health.
Poor air quality impacts us all. For some, especially those with cardiovascular or respiratory issues, pollution causes serious health risks and complications. Harmful particles in the air we breathe can get into our lungs and even our bloodstream, which is why it is important to keep our air as clean as possible.
Poor air quality isn't always easy to see, and can even occur in places with the freshest air such as national parks and rural areas.
What causes poor air quality?
While many people think that pollution is only created by humans, it can actually be both man-made, or naturally occurring. The sources emit many different pollutants, and each one can impact your health in different ways. The U.S. Environmental Protection Agency ( EPA ) provides a few examples of sources:
In 1970, a Federal law was passed to regulate all sources of air emissions in order to achieve cleaner air for the population. This law is known as the Clean Air Act. The pollutants regulated by this act are:
- ground-level ozone
- particle pollution (also known as particulate matter)
- carbon monoxide
- sulfur dioxide
- nitrogen dioxide
How is the air quality near me?
There are many ways to visualize air quality that help us learn more about the air that we breathe.
We can observe things like visible smoke with geographical layers such as this Living Atlas layer containing the 48 hour smoke forecast from the National Weather Service (NWS):
The EPA also has a system of monitors which measure daily concentrations of air pollutants, known as the Air Quality System (AQS) monitors.
To view the metadata for this layer, click here
In order to communicate daily air quality, the EPA created the U.S. Air Quality Index (or AQI). This is one way to detect areas that are at risk. The index is broken into six categories which indicate if an area is of concern or not.
EPA's Air Quality Index (AQI) categories
The EPA partners with AirNow to provide ratings of air quality across the United States based on the EPA index shown above. Each point on the map is a station recording data about the air quality in different areas. The ArcGIS Living Atlas layer behind this map provides hourly information about the concentration of pollutants from the different stations.
Browse or search the map below to see if there is a monitoring station near you, and investigate the current air quality in your area and across the country.
Hourly Air Quality Index by AirNow and EPA
Using these monitors, the EPA's Air Quality Flag Program and its participants raise a flag to communicate the air quality to nearby residents. The color of the flag matches the different colors of the AQI seen in the map above.
To read more about the Flag Project, visit this story map created by the EPA.
PM 2.5 near me
One way to investigate air quality is by how much particulate matter is in the air. These particles are small enough to get into our lungs, and even our bloodstream. The particles can come from sources such as construction sites, unpaved roads, fields, smokestacks, or fires. They can be invisible, and pose a threat to our overall well-being, especially those at higher risk.
Two of the commonly measured particulate matter sizes are 2.5 or 10 micrograms per cubic meter; PM 2.5 and PM 10. The image below, from the EPA , shows us how small these particles are in comparison to extremely small items such as human hair or grains of sand.
One way of mapping air quality is by showing the concentration of PM 2.5 particles. The map below shows stations, from OpenAQ, providing us PM 2.5 measurements from around the country. The layer is updated every hour, with at least one value reported in the past 30 days.
The World Health Organization sets guidelines for 24-hour PM 2.5 values, which can be broken down into categories:
- Meets guideline - under 25 µg/m3
- Interim Target 3 - 25 - 37.5 µg/m3
- Interim Target 2 - 37.5 - 50 µg/m3
- Interim Target 1 - 50 - 70 µg/m3
- Meets no target (unsafe air) - over 75 µg/m3
Browse the map or search for your area to learn more about the current PM 2.5 values in the United States. In general, you'll notice that most of the country currently has acceptable air quality when looking at PM 2.5 alone.
What is PM 2.5 like in the US right now?
The human impact
According to the World Health Organization (WHO) , "Air pollution is a major environmental risk to health. By reducing air pollution levels, countries can reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma.
Ambient (outdoor air pollution) in both cities and rural areas was estimated to cause 4.2 million premature deaths worldwide in 2016."
To visualize the impact of air quality, the map below shows where the most densely populated areas are in the US. Counties with darker shading have more people living there per square mile. Do you see any areas where there are alot of people being impacted by poor air quality?
What is PM 2.5 like in the US right now?
Another tool for visualizing the human impact of current air quality is through the Air Quality Aware app, which uses the EPA AirNow data shown earlier. When you click on any of the EPA stations, you are provided with the current breakdown of air quality, and you also learn more about the population living in that area. For example, the seniors, school age children, and a breakdown by racial/ethnic groups. Click on a station near you to learn more:
Air Quality Aware
Has air pollution decreased?
In the United States, our air is vastly cleaner than it was in the early 1900s because of policies such as the Clean Air Act. But are we still seeing improvement? Are we continuing to help the population breathe cleaner air? Are policies actually working?
To investigate, let's look at historical patterns derived from NASA's Socioeconomic Data and Applications Center (SEDAC). SEDAC's annual PM 2.5 grids provide surface concentrations of PM 2.5 down to a detailed level from 1998 to 2016. By analyzing 19 years of estimated PM 2.5 values, we are able to see trends overtime across the United States.
How is the air in the US?
Annually, the WHO guideline for PM 2.5 concentrations is aimed to be lower than 10 µg/m3.
When looking at the average concentration across the country, many areas are meeting the goal, and we can see which areas are not meeting the goal.
The area commonly known as the "rust belt" still shows signs of the many years of manufacturing, but if you click on one of these counties and see the chart of annual averages, you'll see that the PM 2.5 trends generally are going down.
When looking at a more detailed view, by 50km hex bins, you can see some areas have clustering of air pollution.
This area in southwest Texas might be attributed to the longstanding oil and gas industry presence in this part of the country.
The good news
Many policies exist in order to help clean the air we breathe. The accomplishments of the Clean Air Act and policies such as the Diesel Emissions Reduction Act can be seen across the country in the map we see here. Most of the country has seen downward trends in PM 2.5 since 1998, with only a few areas showing an increase in PM 2.5 since 1998.
In fact, the EPA shows an overall decrease in all of the major pollutants recorded.
Browse this map to see how you state trend is doing over time. Zoom in to investigate your county, congressional district, or local area.
Looking at the same pattern, but compared with where the population lives, you can see just how many people are impacted by the overall improvement in air quality. Areas with large blue circles represent the largest populations.
This map shows us that millions of Americans breathe cleaner air than they did in the 90's.
Are some people more impacted than others?
Looking at another map, we see that some parts of the country have both high counts of minority population and high PM 2.5 values.
Maps such as this make us ask if everyone is getting the equal opportunity to have cleaner air, and could help generate new policies in areas of concern.
These historical maps are just a few of many others that can help answer more questions about how air quality has changed in the past 19 years. Explore and interact with the collection of maps seen below, or go through a guided tour of some of the maps to learn more about the patterns we are seeing.
Conclusions
In general, the United States has seen a great deal of improvement in our overall air quality over the years. This is helping us breathe cleaner air than ever, but as long as pollutants exist, we are still facing health risks every day.
Informed policy is our greatest tool toward reaching better air quality. The EPA and local governments have enacted many new policies along local governments to help improve the air we breathe. Continuing to support and generate these policies will help not only us, but future generations to come.
The data behind the maps
The maps seen in this story can be used to map the air quality in your area.
A collaboration effort of different agencies such the EPA have made accessing authoritative data easier than ever. This collaboration comes together in a collection called ArcGIS Living Atlas of the World where trustworthy sources contribute their data as ready to use layers for others to use in their maps and analysis. The layers are hosted online and documented so that anyone with an internet connection can access and use them.
The metadata and ArcGIS Online layers for the maps seen in this story map can be found in the following places: