A new AQI?

One final thing can complicate citizens’ understanding of AQI: The ranges that reflect different levels of health concern vary dramatically over time and space.

A single AQI value means different things in different countries. The same PM2.5 gets an AQI score of 75 in India, but 124 in the US. This is because India’s air pollution regulations are a bit laxer than in the US. What is “unhealthy” in the US is merely “moderate” in India.

As the EPA changes its pollution standards over time, the scales shift as well. A PM2.5 concentration of 15 micrograms per cubic meter used to be equal to an AQI of 50, but in 1997 the EPA changed it to 12.5 micrograms. It’s good the EPA updates standards to reflect the science, but it changes how citizens interpret and compare AQI scores across time.

Image for article titled The Air Quality Index is in need of an update
Image: AirNow.gov

Some air pollution experts suggest we simply look directly at the air pollution concentration numbers themselves, rather than creating an index. Specifically, Apte thinks we would be better off promoting an understanding of PM2.5 concentration numbers, the most deadly pollutant and the sixth leading cause of death in the world. A snapshot from the AQI technical guidance below shows hazardous concentrations of various criteria pollutants as scientists measure them in μg/m3, parts per million, and parts per billion over one, eight, and 24-hour periods.

That might be too much for some. Another solution will be to update AQI based on a better understanding of just how multiple air pollutants affect our health. Breeze Technologies, an air quality sensor and analytics company, proposes evaluating 10 pollutants and evaluating them across all relevant time scales, to give a better picture of the risk of air pollution.

It may be time for the EPA to update the AQI once again.

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