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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION III

1650 Arch Street

Philadelphia, Pennsylvania 19103

DATE: November 3, 2011

SUBJECT: Technical Support Document for Notice of Proposed Rulemaking – Approval and 

 Promulgation of Air Quality Implementation Plans; Maryland; Baltimore 

 Nonattainment Area Determinations of Attainment of the 1997 Annual Fine 

 Particulate Standard

 /s/

FROM: Ruth Knapp, Environmental Protection Specialist

Office of Air Program Planning 

TO: File

 /s/

THRU: Cristina Fernandez 

Director, Office of Air Program Planning 

A. BACKGROUND

On July 18, 1997 (62 FR 36852), EPA established a health-based fine particulate matter (PM2.5)

National Ambient Air Quality Standard (NAAQS) at 15.0 micrograms per cubic meter (μg/m3) 

based on a 3-year average of annual mean PM2.5 concentrations, and a 24-hour standard of 65 

μg/m3based on a 3-year average of the 98th percentile of 24-hour concentrations. EPA 

established the standards based on significant evidence and numerous health studies 

demonstrating that serious health effects are associated with exposures to particulate matter. The

process for designating areas following promulgation of a new or revised NAAQS is contained in 

107(d)(1) of the Clean Air Act (CAA). EPA and state air quality agencies initiated monitoring 

for the 1997 PM2.5 NAAQS in 1999. On January 5, 2005 (70 FR 944), EPA published its air 

quality designations and classifications for the 1997 PM2.5 NAAQS based upon air quality

monitoring data from those monitors for calendar years 2001-2003. These designations became 

effective on April 5, 2005. The Baltimore, Maryland area was designated nonattainment for the 

1997 annual PM2.5 NAAQS (see 40 CFR Part 81.321).
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B. EPA REQUIREMENTS

PM2.5 Attainment Requirements 

These designations triggered the CAA’s requirements under 172(c), which requires the 

submission of an attainment plan for each designated nonattainment area. EPA’s PM2.5

implementation rule, published on April 25, 2007 (72 FR 20586) specifies that states must 

submit attainment plans for their nonattainment areas to EPA by no later than three years from 

the effective date of designation, that is, by April 5, 2008. EPA’s PM2.5 implementation rule 

outlines the SIP requirements for the attainment plan, which includes among other things, the 

submission of an attainment demonstration showing the air quality improvements expected to 

result from national and local control measures, an analysis of reasonably available control 

measures (RACM), including all reasonably available control technology (RACT), reasonable 

further progress plan (RFP), and contingency measures. EPA’s implementation rule also sets the 

attainment date in these areas as April 5, 2010, and the determination would be based on data 

from 2007-2009 (72 FR 20600).

The state of Maryland is subject to these requirements since several counties are located in PM2.5

nonattainment areas. The Baltimore fine particulate matter (PM2.5) nonattainment area (hereafter 

referred to as “the Baltimore Area” or “Area”) is composed of Anne Arundel County, Baltimore 

County, Harford County, Howard County, and the City of Baltimore.

Determinations of Attainment

Under EPA regulations at 40 CFR 50.7, the annual primary and secondary PM2.5 standards are 

met when the annual arithmetic mean concentration, as determined in accordance with 40 CFR 

50, appendix N, is less than or equal to 15.0 ug/m3. Data handling conventions and computations 

necessary for determining whether areas have met the PM2.5 NAAQS, including requirements for 

data completeness, are listed in appendix N of 40 CFR 50. A year meets data completeness 

requirements when at least 75 percent of the scheduled sampling days for each quarter have valid 

data. The use of less than complete data is subject to the approval of EPA, which may consider

factors such as monitoring site closures/moves, monitoring diligence, and nearby concentrations 

in determining whether to use such data. 

If these proposed determinations of attainment are made final, the requirements for Maryland to 

submit an attainment demonstration and associated RACM, a RFP plan, contingency measures, 

and any other planning SIPs related to attainment of the 1997 annual PM2.5 NAAQS within the 

Baltimore Area would be suspended until such time as: a) the Area is redesignated to attainment, 

at which time the requirements would no longer apply; or, b) EPA determines that the Area has 

violated the annual PM2.5 NAAQS, at which time, the Area would be required to submit such 

plans. See, 40 CFR 51.1004(c). Additionally, EPA will have met its statutory obligation 
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pursuant to 179(c)(1) of the CAA to make a determination based on the Area’s air quality data as 

of the attainment date whether the Area attained the standard by that date. 

A determination of attainment does not shield an area from other required actions such as New 

Source Review (NSR), conformity and emission inventory requirements, and provisions to 

address pollution transport, which would require emission reductions at sources or other types of 

emission activities contributing significantly to nonattainment in other areas or states, or 

interfering with maintenance in those areas.

Determinations as to whether individual areas have attained the PM2.5 standards and thus qualify

for the application of a determination of attainment are being made in the context of rulemakings 

for individual areas. This Technical Support Document (TSD) provides an explanation of EPA’s 

analysis used to determine whether the Baltimore Area has attained the annual PM2.5 standard 

and whether it attained the standard by the applicable attainment date. 

C. MONITORING NETWORK

The Baltimore Area currently has seven monitors which can be used for comparison to the 1997 

PM2.5 annual NAAQS. The data from these monitors is discussed below in section D. One 

monitor located in the Area with site ID 24-510-0040 does not meet the criteria (40 CFR 58 

subpart D 58.30) to be used for comparison to the annual standard and is therefore not included 

in this assessment. This area also has some collocated monitors which also are not comparable to 

the annual standard, but their data may be used to substitute for missing data at a primary monitor

in some situations (See, 40 CFR 50 appendix N). Finally, the monitor with site ID 24-510-0035 

which was sometimes referred to as the FMC monitor had to be shut down in August 2008 due to 

demolition occurring at the monitoring site. Based upon information provided by the Maryland 

Department of the Environment (MDE), EPA agreed with MDE that the remaining monitoring 

network adequately reflects air quality in the Area. The monitoring site that was demolished was 

not the site of the maximum design value for the Area. Additional technical support explaining 

why data from this site is not needed to assess the attainment status of this area can be found in 

two documents provided by MDE to EPA. See the attached e-mail correspondence to this TSD

for this information. 

D. EPA’S ANALYSIS OF MONITORED DATA

Monitoring Data 2008-2010 

In order to demonstrate that the Area is attaining the annual 1997 PM2.5 NAAQS and has clean 

data for purposes of 40 CFR 51.1004(c), air quality data from EPA’s Air Quality System (AQS) 

from calendar years 2008-2010 was reviewed. EPA’s determination that the Baltimore 

nonattainment area attains the annual 1997 PM2.5 NAAQS is based upon quality-assured, qualitycontrolled and state certified ambient air monitoring data for the 2008–2010 period, as measured 
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by Federal Reference Method (FRM), Federal Equivalent Method (FEM), or Approved Regional 

Method (ARM) monitors described in 40 CFR Part 50 Appendix N. The primary monitors used 

to determine the design value for the Baltimore, MD nonattainment area are listed in Table 1. 

The design value (DV) for each monitor is the 3-year average of annual mean PM2.5

concentrations at the monitor, and is the value that would be compared to the 1997 PM2.5 annual 

NAAQS. The DV for the area is the highest 3-year average of the annual means measured at all 

the monitors in the Area that meet the criteria to be used for comparison to the NAAQS. 

Table 1. Baltimore Area 2008-2010 PM2.5 Data (in μg/m3)

City Site ID

2008 Annual 

Mean

2009 Annual 

Mean

2010 Annual 

Mean

2008-2010

Design Value 

Glen Burnie 24-003-1003 12.6 11.1 11.0 11.6

Padonia 24-005-1007 11.9 10.2 10.4 10.8

Essex 24-005-3001 12.6 11.0 11.6 11.7

Edgewood 24-025-1001 11.3 9.6 9.5 10.1

Baltimore 24-510-0006 12.2 10.1 10.1 10.8

Baltimore 24-510-0007 12.4 10.3 10.3 11.0

Baltimore 24-510-0008 12.7 11.1 11.0 11.6

According to AQS, monitoring site ID 24-003-0008 had some missing data for one quarter of 

2010. However, data from a collocated monitor was substituted for the missing data in 

accordance with 40 CFR 50 appendix N (Interpretation of National Ambient Air Quality

Standards For PM2.5). See, section 3.0 of the “Guideline on Data Handling Conventions for the 

PM NAAQS”, EPA-454/R-99-008 (April 1999). A copy of this guideline is included as one of 

the attachments to this TSD along with the AQS data report. The values from the collocated 

monitor are reflected in the annual 2010 mean value provided in AQS. 

The DV for the Baltimore Area for 2008-2010 is 11.7 ug/m3 and is below 15.0 ug/m3. Therefore, 

the Area is attaining the annual PM2.5 NAAQS based on the most recent complete, qualityassured and state certified data available. 

Monitoring Data 2007-2009

In order to determine that the Baltimore Area attained the annual 1997 PM2.5 NAAQS by its 

attainment date of April 5, 2010, quality-assured, quality-controlled and state certified ambient 

air monitoring data for the 2007–2009 period, as measured by FRM, FEM, or ARM monitors 

described in 40 CFR 50 appendix N was reviewed. This data is in Table 2. 

Table 2. Baltimore Area 2007-2009 PM2.5 Data (in μg/m3)

City Site ID

2007 Annual 

Mean

2008 Annual 

Mean

2009 Annual 

Mean

2007-2009

Design Value 

Glen Burnie 24-003-1003 13.4 12.6 11.1 12.4
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Padonia 24-005-1007 13.3 11.9 10.2 11.8

Essex 24-005-3001 14.0 12.6 11.0 12.6

Edgewood 24-025-1001 12.2 11.3 9.6 11.0

Baltimore 24-510-0035 14.1 * * *

Baltimore 24-510-0006 13.1 12.2 10.1 11.8

Baltimore 24-510-0007 13.4 12.4 10.3 12.0

Baltimore 24-510-0008 15.0 12.7 11.1 12.9

*Monitor Site ID 24-510-0035 shut down in August 2008 due to demolition of the monitoring site.

Air Quality Data from site ID 24-003-1003 had some missing data for one quarter in 2007. In

order to assess if this monitor attained the standard, the maximum quarter substitution test as 

explained in the “Guideline on Data Handling Conventions for the PM NAAQS”, EPA-454/R99-008 (April 1999) was applied. Basically, the test requires replacing the missing data with the 

maximum concentration recorded at the site during the same quarter over the 3-year period in 

question, provided that the following criteria are met. The site must have valid data for at least 

50 percent of the scheduled number of samples for each quarter for all three years, and the 

emissions and meteorology for the quarters to be substituted must be comparable to the 

emissions and meteorology for the quarters in question. Air quality data from site ID 24-003-

1003 met the criteria and the site also attained the standard for 2007-2009 using this test. 

The DV for the Baltimore Area for 2007-2009 is 12.9 ug/m3 and is below 15.0 ug/m

3.

 Therefore, 

the Area attained the annual PM2.5 NAAQS by its applicable attainment date based on qualityassured and state certified data. 

Preliminary Monitoring Data for 2011

Preliminary data available to date for 2011 when considered in conjunction with data from 2009 

and 2010 indicates that the Baltimore Area continues to attain the standard. The 2011 data is not 

complete and has not yet been quality-assured or certified but is provided below. 

Table 3. Baltimore Area Preliminary 2011 PM2.5 Data (in μg/m3)

City Site ID 2011 Preliminary Annual Mean

Glen Burnie 24-003-1003 10.5

Padonia 24-005-1007 9.9

Essex 24-005-3001 10.6

Edgewood 24-025-1001 9.3

Baltimore 24-510-0006 9.9

Baltimore 24-510-0007 9.5

Baltimore 24-510-0008 10.8
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RECOMMENDED AGENCY ACTION

Based on quality-assured, quality-controlled, and state certified ambient air monitoring data from 

2008-2010 from the Baltimore Area, EPA is making the determination that the Area attains the 

annual 1997 PM2.5 NAAQS. Preliminary data from 2011 indicates that the Area continues to 

attain the NAAQS. Therefore, EPA is suspending the attainment-related SIP requirements for 

the annual 1997 PM2.5 NAAQS pursuant to 40 CFR 51.1004(c). Also, based on the qualityassured, quality-controlled, and state certified ambient air monitoring data from 2007-2009 for 

the Baltimore Area, EPA is making the determination that the Area attained the annual 1997 

PM2.5 standard by its attainment date of April 5, 2010. 

The following four attachments are included with this TSD:

EPA AQS Quick Look Report (AMP480) dated October 20, 2011

Guideline on Data Handling Conventions for the PM NAAQS, EPA-454/R-99-008 (April 1999)

E-mail Correspondence from MDE to EPA dated 8/14/2008 Notification of Closing of FMC Site

E-mail Correspondence from MDE to EPA dated 8/18/2008 Network Analysis of FMC Closure