The State of the Air 2017
The ”State of the Air 2017” found continued improvement in air quality in 2013—2015 in ozone and year-round particle pollution, but an unrelenting increase in dangerous spikes in particle pollution. The number of people exposed to unhealthy levels of air pollution dropped to more than 125 million people, from 166 million in the years covered in the 2016 report (2012—2014).
The “State of the Air 2017” report shows that cleaning up pollution continues successfully in much of the nation. In the 25 cities with the worst ozone and year-round particle pollution, the majority saw improvements from last year. Many again reached their lowest levels ever of these widespread air pollutants.
"State of the Air" 2017 shows that more than four in 10 people had unhealthy air quality in their communities.
Yet, even as most cities experienced strong improvement, too many cities suffered worse episodes of unhealthy air. While most of the nation has much cleaner air quality than even a decade ago, many cities reported their highest number of unhealthy days since the report began, including some that experienced extreme weather events.
The “State of the Air 2017” report shows that, even with continued improvement, too many people in the United States live where the air is unhealthy for them to breathe. Despite that continued need and the nation’s progress, some people seek to weaken the Clean Air Act, the public health law that has driven the cuts in pollution since 1970, and to undermine the ability of the nation to fight for healthy air.
The “State of the Air 2017” report looks at levels of ozone and particle pollution found in official monitoring sites across the United States in 2013, 2014 and 2015. The report uses the most current quality-assured nationwide data available for these analyses.
The report examines particle pollution (PM2.5) in two different ways: averaged year-round (annual average) and over short-term levels (24-hour). For both ozone and short-term particle pollution, the analysis uses a weighted average number of days that allows recognition of places with higher levels of pollution. For the year-round particle pollution rankings, the report uses averages calculated and reported by the U.S. Environmental Protection Agency (EPA). For comparison, the “State of the Air 2016” report covered data from 2012, 2013, and 2014.1
The "State of the Air 2017" found continued improvement in air quality in 2013—2015 in ozone and year-round particle pollution, but an unrelenting increase in dangerous spikes in particle pollution. The number of people exposed to unhealthy levels of air pollution dropped to more than 125 million people, from 166 million in the years covered in the 2016 report (2012—2014).
Overall, the best progress came in the continued reduction of ozone and year-round particle pollution, thanks to cleaner power plants and increased use of cleaner vehicles and engines. Continued progress to cleaner air remains crucial to reduce the risk of premature death, asthma attacks and lung cancer. However, a changing climate is making it harder to protect human health.
Nearly 4 in 10 people (38.9 percent) in the United States live in counties that have unhealthful levels of either ozone or particle pollution. More than 125 million Americans live in 204 counties where they are exposed to unhealthful levels of air pollution in the form of either ozone or short-term or year-round levels of particles.
Still, this represents a major improvement: One-quarter fewer people now live where the air quality hit unhealthy levels in 2013—2015 than in the 2016 report. In last year’s report, covering 2012-2014, more than 166 million Americans lived in counties with unhealthful levels of air pollution.
More than 18 million people (5.6 percent) live in 12 counties with unhealthful levels of all three: ozone and short-term and year-round particle pollution. This is nearly 1.9 million fewer people than in the 2016 report when approximately 6.3 percent were exposed. However, we continue to lack data on particle pollution in all or parts of two states.
Still, this represents a major improvement: One-quarter fewer people now live where the air quality hit unhealthy levels
Los Angeles remains the city with the worst ozone pollution as it has for nearly the entire history of the report. Bakersfield, CA, maintains its rank as the city with the worst short-term particle pollution, while Visalia-Porterville-Hanford, CA, moved for the first time to rank as the most-polluted city for year-round particle pollution.
The "State of the Air 2017" report shows the sustained success of the Clean Air Act, continuing to clean up pollution in much of the nation, as it nearly completes its fifth decade of service. Many cities reported fewer days of high ozone and lower levels of year-round particle pollution. Several cities again reported their cleanest years ever during this period, while others had their worst periods of air pollution.
Thanks to the provisions in the Clean Air Act, the United States has continued to reduce ozone and particle pollution as well as other pollutants for decades. Figure 1 from EPA shows that since 1970, the air has gotten cleaner while the population, the economy, energy use and miles driven increased greatly. As the economy continues to grow, overall air emissions that create the six most-widespread pollutants continue to drop.
Figure 1: Air pollution emissions continue to drop steadily since 1970 thanks to the Clean Air Act. As the economy continues to grow, emissions that cause ozone and particle pollution continue to drop. Source: U.S. EPA, Air Trends: Air Quality National Summary, 2017.
The Clean Air Act must remain intact and enforced to enable the nation to continue to protect all Americans from the dangers of air pollution. This law has driven improvements in air quality for 47 years, as shown in Figure 1. Since first issued in 2000, the "State of the Air" reports have also documented these improvements, as shown in trend charts for counties and cities available by zip code. The nation must ensure that the Clean Air Act’s tools remain in place, funded, and followed.
The "State of the Air 2017" report adds to the evidence that a changing climate in making it harder to protect human health. While most of the nation has much cleaner air quality than even a decade ago, a few cities reported their worst number of unhealthy days since the report began, including many that experienced wildfire smoke.
As climate change continues, cleaning up these pollutants will become ever more challenging. Climate change poses many threats to human health, including worsened air quality and extreme weather events. The nation must continue to reduce emissions that worsen climate.
- A complete discussion of the sources of data and the methodology is included in Methodology.