May 2015: Different Methodology and Different Grades
Reports covering ozone and fine particulate data for the period 2011 – 2013 are out and, once again, the grades vary widely. Hoosiers need accurate information about the quality of Indiana’s ambient air. It is important to look at the methodology behind reports.
The American Lung Association (ALA) released its State of the Air 2015 report in April. Short term grades for the ALA are based upon its own grading system. This system relies on how many days were above the standard in each county and by how much. What they fail to cover is that each monitor is allowed a number of exceedances before it is considered a violation.
So for example, Marion County has four ozone monitors. The highest ozone design value for these monitors is 0.074 ppb, so technically, by the U.S. Environmental Protection Agency’s (U.S. EPA’s) definition, this county is attainment (it meets the standard). However the ALA determined that during the three year period there were 15 different days where the ozone standard was exceeded. Each of these days is considered Unhealthy for Sensitive Groups using U.S. EPA’s Air Quality Index scale. ALA took the 15 value and divided it by 3 years to get a value of 5.0. Based upon ALA’s grading scale, any county with a value of 3.3 or greater is graded as an F. The ALA methodology is not consistent with how U.S. EPA interprets the National Ambient Air Quality Standards (NAAQS).
In April, IDEM published the States’ View of the Air 2015 Report. The IDEM method of grading uses the U.S. EPA guidance of how to calculate design values and then compares these values to the NAAQS. If the values are between the standard and 10 percent better than the standard, the county is given a C. If the value is between 10 and 20 percent better than the standard, the county is rated as a B. If the design value is more than 20 percent better than the NAAQS, the county is rated as an A. If the design value is up to 10 percent worse than the standard, the county is rated as a D. Finally, if the design value is more than 10 percent worse than the NAAQS, the county is rated as an F. We have used this grading scale for the past four years. The key is that the IDEM grading system is consistent with the way that the NAAQS are applied.
The following table shows design values for ozone and PM-2.5 for each Indiana County, the U.S. EPA standard (NAAQS), and the IDEM and ALA grades. For the annual PM-2.5 standard, ALA gives a Pass or Fail grade based upon whether the design value for a county meets the NAAQS or not. In this case, the grades are fairly consistent.
Based upon the ALA grading scale, 14 Indiana counties are above the standard for ozone. Based upon U.S. EPA’s methodology, there are only two (Clark and La Porte). Based upon the ALA grading system, three Indiana counties exceed the short term PM-2.5 standard. Based upon a comparison with the NAAQS, no counties exceed the 24-hour PM-2.5 standard. The ALA identifies Clark as exceeding the PM-2.5 standard. At that time it did. However, newer data for the period 2012 – 2014 shows that it now meets the standard.
The ALA methodology rewards areas for doing the minimum monitoring and penalizes areas that go above and beyond. The message that ALA seems to be sending is do less monitoring. Is this really what they want to be telling the public?
|A Comparison of IDEM and ALA Grades for Indiana Counties|
|Ozone||24-Hour PM-2.5||Annual PM-2.5|
|County||Daily Value||No. Monitors||NAAQS||IDEM Grade||ALA Grade||Daily Value||No. Monitors||NAAQS||IDEM Grade||ALA Grade||Daily Value||NAAQS||IDEM Grade||ALA Grade|