The Environmental Protection Agency finalized new air pollution rules on Wednesday, strengthening standards that had not been updated in over a decade. Somewhat counterintuitively, the change could mean that even as the air gets cleaner, you might get more air quality alerts.
As part of the rule change, the EPA updated its Air Quality Index, that colorful scale that many Americans grew intimately familiar with last summer, as wildfire smoke went from being a West Coast problem to a hazard for almost the entire country, seemingly overnight.
The AQI is both easy to interpret, with a color code that goes from a healthy green to a perilous purple, and esoteric. The colors correspond with numbers from zero to upwards of 300, and those numbers correspond with measures of five different pollutants — particulate matter, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide.
The Clean Air Act tasks the EPA with setting standards for each of these pollutants. If local concentrations of any one of them tick up above those protective standards, the AQI will jump from green to a more alarming color. The higher the level of pollution is, the higher the AQI and the darker the color will be.
Previously, the EPA’s annual standard for concentrations of particulate matter was 12 micrograms per cubic meter (µg/m3). Based on epidemiological research showing that this standard did not adequately protect public health, the agency has now lowered the standard to 9 µg/m3.
Air quality has improved immensely since the 1970s when the Clean Air Act was passed, preventing hundreds of thousands of premature deaths. But thousands of people still die early, are rushed to the emergency room, develop asthma, or miss work due to air pollution.
The new AQI scale doesn’t mean you need to rethink how you make decisions about when to spend time outdoors or whether to wear a mask. But it does mean that if and when people make decisions based on the AQI, they will be more informed by the science and, in aggregate, contribute to lower all of these public health costs. The rules are expected to prevent 4,500 premature deaths per year by 2032.
All AQI scores above 300 are considered hazardous, but identifying a top value for the scale helps the EPA determine the actual score.Environmental Protection Agency
Some parts of the country could start to see more days with “moderate air quality,” the yellow category. “People who live in places that have frequent flips over nine — those will be people who have environmental justice issues or live near traffic and industries and big cities and so forth — they are going to get warned a little more,” John Bachmann, a former associate director in EPA’s Office of Air and Radiation told me. “Which is a positive thing.” The agency considers moderate air quality to be “acceptable,” but there may still be a risk for people who are particularly sensitive to pollution.
Also, during major air quality events like wildfires or chemical fires, impacted areas could now be deemed “hazardous” when previously they may have been “very unhealthy,” or deemed “very unhealthy” when before they would have been simply “unhealthy.” This will affect when and how public health officials respond to these kinds of events.
“This is for everybody, not just the most exposed or the most sensitive people. So on both ends of it, this is a step in the right direction,” Bachmann said.
As part of the changes, the agency will also now require cities with more than 350,000 people to report the AQI seven days a week, up from five — a rule that’s been in place since 1999. However, the agency said that most states and cities are already doing this.
The new AQI scale will take effect in 60 days, in early April.
All AQI scores above 300 are considered hazardous, but identifying a top value for the scale helps the EPA determine the actual score.Environmental Protection Agency
