In What Ways Does an Air Quality Index Value of 500 Affect Human Health? At one point this week, the smoky air in New York City registered a 407 on the EPA’s Air Quality Index, meaning that pollution levels were “hazardous” and historically unsafe.
However, the air quality isn’t the worst the U.S. has ever experienced. About 40 times in the past decade, the index has soared above 500, into territory the Environmental Protection Agency (EPA) refers to as “Beyond the A.Q.I.” The E.P.A. said in an email that most of these incidents have occurred in the Western states, including California, Oregon, and Washington due to the smoke from wildfires.
The E.P.A. produced the current six-tier index in 1999 to inform the public about the concentrations of five contaminants. If the air quality index is between 301 and 500, it is termed “hazardous,” and alerts are issued to the public. Everyone should stay inside and minimize their activity levels if the temperature rises to that level or above. The E.P.A. suggests using the exact data for the “hazardous” classification.
Robert Rohde, the head scientist of Berkeley Earth, an organization specializing in environmental data research, noted that while the A.Q.I. measurement employed in the United States does not support numbers above 500, such values occur so infrequently that the issue rarely comes up.
Dr. Rohde has observed that “such levels occur more often in some foreign countries,” including India. He also noted that third-party air quality tracking tools go beyond the U.S. A.Q.I. scale to monitor AQI values above 500.
According to Harshal Salve, a professor at the All India Institute Of Medical Sciences in New Delhi, people over the age of 65 and children under the age of five are at the most significant risk for respiratory illness when air quality reaches hazardous levels close to or above 500 on the U.S. A.Q.I. scale.
Since pollution particles can cause inflammation of lung tissue and increase vulnerability to infections, the detrimental effects can persist even after air quality levels have improved.
AirNow, a data source on air quality, reports that the air quality in the United States has improved since Thursday morning, with the highest A.Q.I. recorded in the Susquehanna Valley in Pennsylvania on Thursday at 448 and dropping to 150 on Friday. Generally, levels below 100 are not harmful to human health.
The A.Q.I. has been proposed for revision by the E.P.A. to represent better the results of recent scientific studies on the relationship between particle pollution and human health and to increase the reliability of monitoring data. Even if climate change is making wildfires more frequent and severe, the government said air quality in the United States is improving overall.
NASA Goddard Institute for Space Studies atmospheric scientist Olivia Clifton said this week that the E.P.A. should define what A.Q.I. levels above 500 mean for air quality if they become more common.
“Has this become even more dangerous, or is it still dangerous?” Dr. Clifton said. Asking, “What is the qualitative description of the air quality that would need to be described for a higher A.Q.I.?”