UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

Office of Air Quality Planning and Standards (OAQPS) 

Research Triangle Park, North Carolina 27711 

December 14, 2012 

MEMORANDUM 

SUBJECT: Evaluation of the PM2.5'Collocated PM10' Data Substitution Routine, 

 2009-2011. 

FROM: Mark Schmidt, Air Quality Analysis Group, OAQPS/OAR /s/ 

TO: PM NAAQS Review Docket (EPA-HQ-OAR-2007-0492) 

This memorandum describes an evaluation of the PM2.5“collocated PM10” data and 

“maximum quarterly value” substitution tests. Specifically, the goal of this analysis is to 

quantify the utility of both tests and to determine if both are needed. The most recent design 

value period (2009-2011) is used for this evaluation. 

The EPA proposed both tests for inclusion into 40 CFR Part 50, appendix N, which 

contains the codified data handling rules for making comparisons between reported ambient 

PM2.5data and the PM2.5 NAAQS (77 FR 39001 - 39002, June 29, 2012). As proposed, both data 

substitution tests were to be used for validating “otherwise incomplete” annual standard and 24-

hour standard design values that were equal or below their respective NAAQS levels. Both tests 

are described in the 1999 PM2.5data handling guideline (U.S. EPA, 1999) and have been 

implemented as standard operating procedure for EPA design value computations. 

 In this assessment of 2009-2011 PM2.5 design values which did not meet the nominal data 

completeness requirements, the EPA found that collocated PM10 test was almost entirely 
redundant with the maximum quarterly value test and therefore very infrequently needed as a 

separate test. The results presented in Table 1 for each of the two PM2.5standards shows the 

number (and percentage) of sites that passed one, both, or neither of the two noted data 

substitution tests. 

For the annual NAAQS, the maximum quarter value test in 100 cases resulted in a test 

design value (TDVmax) less than or equal to 12.0 μg/m3

. There were only two other cases (2 

percent) when TDVmax was greater than 12.0 μg/m3

 but the TDV associated with the collocated 

PM10 test was less than 12.0 μg/m3. Similarly for the 24-hour NAAQS, the maximum quarter 

value test in 116 cases resulted in a test design value (TDVmax) less than or equal to 35 μg/m3

and again only 2 other sites (less than 2 percent) passed the collocated PM10 test but not the 

maximum quarterly value test. Furthermore, the maximum quarterly value tests allowed the 

annual and 24-hour design value to be validated approximately 5 times more often than through 

the use of the collocated PM10 test. Accordingly, the EPA has decided to not include the 

collocated PM10 data substitution tests in Appendix N, and thereby further simplifying the data 

handling procedures for making comparisons to the annual and daily NAAQS. 
Data substitution for the PM2.5 annual standard, 2009-2011 Data substitution for the PM2.5 24-hour standard, 2009-201

Category Number 

Percent of total number 

of nominally 

incomplete sites for the 

annual standard for 

which the DV was 

validated with one or 

both data substitution 

tests

Category 

Number of sites with nominally incomplete annual design values that passed the "maximum quarterly value" data substitution test 100 98.0%

Number of sites with nominally incomplete 24-hour design values that passed the "maximum quarterly value" data substitution test 

Number of sites with nominally incomplete annual design values that passed the "collocated PM10" data substitution test 21 20.6%

Number of sites with nominally incomplete 24-hour design values that passed the "collocated PM10" data substitution test 

Number of sites with nominally incomplete annual design values that passed both data substitution tests 19 18.6%

Number of sites with nominally incomplete 24-hour design values that passed both data substitution tests 

Number of sites with nominally incomplete annual design values that passed the "maximum quarterly value" data substitution test b t t th " ll t d PM10" d t b tit ti t t 81 79 4%

Number of sites with nominally incomplete 24-hour design values that passed the "maximum quarterly value" data substitution test but not the "collocated PM10" data substitution t t 

Table 1. Site counts for 2009-2011 with respect to design values and data substitution testsbut not the "collocated PM10" data substitution test 81 79.4% test 

Number of sites with nominally incomplete annual design values that passed the "collocated PM10" data substitution test" but not the "maximum quarterly value" data substitution test 2 2.0%

Number of sites with nominally incomplete 24-hour design values that passed the "collocated PM10" data substitution testbut not the "maximum quarterly value" data substitution test 

Number of sites with nominally incomplete annual design values that passed either data substitution test 102 100.0%

Number of sites with nominally incomplete 24-hour design values that passed either data substitution test 

Number of sites with nominally incomplete 24-hour design values that passed the "collocated PM10" data substitution testTotal number of sites that could use the "collocated PM10" data substitution test to validate an otherwise incomplete PM2.5 design valueRatio of: Total number of sites that could use the "maximum quarterly value" data substitution test to validate an otherwise incomplete PM2.5 design value / Total Number of sites with nominally incomplete annual design values that passed the "maximum quarterly value" data substitution test

Category

Data substitution for the both the PM2.5 annual standard and the PM2.5 24-hour standard, 2009-2011

Number of sites with nominally incomplete 24-hour design values that passed the "maximum quarterly value" data substitution test

Total number of sites that could use the "maximum quarterly value" data substitution test to validate an otherwise incomplete PM2.5 design valueNumber of sites with nominally incomplete annual design values that passed the "collocated PM10" data substitution test