Evaluating the U.S. Air Quality Index as a risk communication tool: Comparing associations of index values with respiratory morbidity among adults in California.

BACKGROUND: The Air Quality Index (AQI) in the United States is widely used to communicate daily air quality information to the public. While use of the AQI has led to reported changes in individual behaviors, such behavior modifications will only mitigate adverse health effects if AQI values are indicative of public health risks. Few studies have assessed the capability of the AQI to accurately predict respiratory morbidity risks. METHODS AND FINDINGS: In three major regions of California, Poisson generalized linear models were used to assess seasonal associations between 1,373,165 respiratory emergency department visits and short-term exposure to multiple metrics between 2012-2014, including: daily concentrations of NO2, O3, and PM2.5; the daily reported AQI; and a newly constructed health-based air quality index. AQI values were positively associated (average risk ratio = 1.03, 95% CI 1.02-1.04) during the cooler months of the year (November-February) in all three regions when the AQI was very highly correlated with PM2.5 (R2 ≥ 0.89). During the warm season (March-October) in the San Joaquin Valley region, neither AQI values nor the individual underlying air pollutants were associated with respiratory morbidity. Additionally, AQI values were not positively associated with respiratory morbidity in the Southern California region during the warm season, despite strong associations of the individual underlying air pollutants with respiratory morbidity; in contrast, health-based index values were observed to be significantly associated with respiratory morbidity as part of an applied policy analysis in this region, with a combined risk ratio of 1.02 (95% CI: 1.01-1.03). CONCLUSIONS: In regions where individual air pollutants are associated with respiratory morbidity, and during seasons with relatively simple air mixtures, the AQI can effectively serve as a risk communication tool for respiratory health risks. However, the predictive ability of the AQI and any other index is contingent upon the monitored values being representative of actual population exposures. Other approaches, such as health-based indices, may be needed in order to effectively communicate health risks of air pollution in regions and seasons with more complex air mixtures.

Accuracy of quantification of risk using a single-pollutant Air Quality Index.

Health risks associated with short-term exposure to ambient air pollution are communicated to the public by the US EPA through the Air Quality Index (AQI), but it remains unclear whether the current regulatory-based, single-pollutant AQI fully represents the actual risks of air pollution-related illness. The objective of this study is to quantify cardiovascular hospital admissions attributable to PM2.5 at each AQI category. Based on National Ambient Air Quality Standards (NAAQS), the highest AQI value among criteria pollutants (driver pollutant) is reported daily. We investigated excess cardiovascular hospital admissions attributable to fine particulate matter (PM2.5) exposure from 2000 to 2010 in Bronx, Erie, Queens, and Suffolk counties of New York. Daily total, unscheduled cardiovascular hospital admissions (principal diagnosis) for individuals aged 20-99 years, concentration-response functions for PM2.5, and estimated quarterly effective daily concentrations were used to calculate excess cardiovascular hospital admissions when PM2.5 was reported as the driver pollutant and when PM2.5 was not reported as the driver pollutant at each AQI category. A higher proportion of excess hospital admissions attributable to PM2.5 occurred when PM2.5 was the driver pollutant (i.e., ~70% in Bronx County). The majority of excess hospital admissions (i.e., >90% in Bronx County) occurred when the AQI was <100 ("good" or "moderate" level of health concern) regardless of whether PM2.5 was the driver pollutant. During the warm season (April-September), greater excess admissions in Suffolk County occurred when PM2.5 was not the AQI driver pollutant. These results indicate that a single-pollutant index may inadequately communicate the adverse health risks associated with air pollution.

American Thoracic Society and Marron Institute Report. Estimated Excess Morbidity and Mortality Caused by Air Pollution above American Thoracic Society-Recommended Standards, 2011-2013.

Estimates of the health impacts of air pollution are needed to make informed air quality management decisions at both the national and local levels. Using design values of ambient pollution concentrations from 2011-2013 as a baseline, the American Thoracic Society (ATS) and the Marron Institute of Urban Management estimated excess morbidity and mortality in the United States attributable to exposure to ambient ozone (O3) and fine particulate matter (PM2.5) at levels above the American Thoracic Society-recommended standards. Within the subset of counties with valid design values for each pollutant, 14% had PM2.5 concentrations greater than the ATS recommendation, whereas 91% had O3 concentrations greater than the ATS recommendation. Approximately 9,320 excess deaths (69% from O3; 31% from PM2.5), 21,400 excess morbidities (74% from O3; 26% from PM2.5), and 19,300,000 adversely impacted days (88% from O3; 12% from PM2.5) in the United States each year are attributable to pollution exceeding the ATS-recommended standards. California alone is responsible for 37% of the total estimated health impacts, and the next three states (Pennsylvania, Texas, and Ohio) together contributed to 20% of the total estimates. City-specific health estimates are provided in this report and through an accompanying online tool to help inform air quality management decisions made at the local level. Riverside and Los Angeles, California have the most to gain by attaining the ATS recommendations for O3 and PM2.5. This report will be revised and updated regularly to help cities track their progress.