California cities claimed seven of the top 10 spots in the American Lung Association State of the Air report.
Imperial County received an “F” from the organization and El Centro ranked #8 of U.S. cities by year-round particle pollution. The county had 56 “orange” days considered unhealthy for sensitive populations.
American Lung Association (ALA) officials said local air quality has been declining over the past five years. To compile the "State of the Air" report each year, the ALA relies on publicly available, quality-assured data from monitors operated by states, counties, federal agencies, and tribes across the nation. This year's report examines monitoring data collected during 2015, 2016, and 2017.
However, according to the ALA charts, the ozone high days have continued to steadily fall in the Imperial County for 24 years. Smog is created when carbon emissions, typically from cars and trucks, mix with nitrogen oxides and is then heated by the sun. Pollution damages the lungs and can make it hard to breathe.
The Imperial County's greatest challenge to improving air quality is sharing a border with Mexico, whose metropolitan area has more than five times the population of the entire county, Monica Bugarin Soucier, air pollution control division manager explained during a 2017 workshop. Imperial County has elevated pollution concentrations because emissions from Mexico blow into the Valley.
Soucier also said the county's ozone levels demonstrate Imperial County could attain the ozone standard, except for emissions emanating across the international border.
"If we shut down the Imperial County completely, we basically would not move the needle,” said Reyes Romero, the county’s assistant air pollution control officer, about pollution levels. "Mexicali has five times the residents of the Valley, all are located right on the border, [and] they have more vehicles, factories, and a backed-up border crossing."
According to the ALA, Los Angeles, Visalia, and Bakersfield are the top three polluted cities in the United States.