Technical Support Document (TSD) for 2008 Ozone NAAQS Designations

Massachusetts

Area Designations for the 

2008 Ozone National Ambient Air Quality Standards

Dukes County, Massachusetts

The table below identifies the area and county in Massachusetts that EPA intends to designate as 

nonattainment for the 2008 ozone national ambient air quality standards (2008 ozone NAAQS). In 

accordance with section 107(d) of the Clean Air Act (CAA), EPA must designate an area (county or part 

of a county) “nonattainment” if it is violating the 2008 ozone NAAQS or if it is contributing to a 

violation of the 2008 ozone NAAQS in a nearby area. The technical analysis supporting the boundaries 

for the nonattainment area is shown below.

Intended Nonattainment Area in Massachusetts

Area

Massachusetts Recommended 

Nonattainment Counties

EPA’s Intended 

Nonattainment Counties

Dukes County, MA1

Dukes County, MA Dukes County, MA

EPA intends to designate the remaining counties in Massachusetts that are not listed in the table above 

as “unclassifiable/attainment” for the 2008 ozone NAAQS. 

The analysis below provides the basis for the Dukes County nonattainment area boundaries. It relies on 

our analysis of whether and which monitors are violating the 2008 ozone NAAQS, based on certified air 

quality monitoring data from 2009 and 2010 and preliminary 2011 data and an evaluation of whether 

nearby areas are contributing to such violations. The analysis excludes other areas in Massachusetts, 

since Massachusetts recommended all other areas of the state as attainment, and committed to certify the 

2011 ozone data by February 29, 2012. EPA has evaluated contributions from nearby areas based on a 

weight of evidence analysis considering the factors identified below. EPA issued guidance on

December 4, 2008 that identified these factors as ones EPA would consider in determining 

nonattainment area boundaries and recommended that states consider these factors in making their 

designations recommendations to EPA.

2

 

1. Air quality data (including the design value calculated for each FRM or FEM monitor in the 

area);

2. Emissions and emissions-related data (including location of sources and population, amount of 

emissions and emissions controls, and urban growth patterns);

3. Meteorology (weather/transport patterns);

4. Geography and topography (mountain ranges or other basin boundaries);

5. Jurisdictional boundaries (e.g., counties, air districts, existing nonattainment areas, Indian 

country, metropolitan planning organizations (MPOs))

 

1 Dukes County is a multijurisdictional nonattainment area that includes areas of Indian Country.

2 The December 4, 2008 guidance memorandum “Area Designations for the 2008 Revised Ozone National Ambient Air 

Quality Standards” refers to 9 factors. In this technical support document we have grouped the emissions-related factors 

together under the heading of “Emissions and Emissions-Related Data,” which results in 5 categories of factors.
2

Ground-level ozone is not emitted directly into the air, but is created by chemical reactions between 

oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Because 

NOx and VOC emissions from a broad range of sources over a wide area typically contribute to 

violations of the ozone standards, EPA believes it is important to consider whether there are contributing 

emissions from a broad geographic area. Accordingly, EPA chose to examine the 5 factors with respect 

to the larger of the Combined Statistical Area (CSA) or Core Based Statistical Area (CBSA) associated 

with the violating monitor(s).

3 All data and information used by EPA in this evaluation are the latest 

available to EPA and/or provided to EPA by Massachusetts.

In EPA’s designations guidance for the 2008 ozone NAAQS, EPA recommended examining 

CSA/CBSAs because certain factors used to establish CSAs and CBSAs are similar to the factors EPA is 

using in this technical analysis to determine if a nearby area is contributing to a violation of the 2008

ozone NAAQS. EPA used the same basic approach in the designation process for the 1997 ozone 

NAAQS. Where a violating monitor is not located in a CSA or CBSA, EPA’s guidance recommended

using the boundary of the county containing the violating monitor as the starting point for considering 

the nonattainment area’s boundary. 

Technical Analysis for Dukes County, MA

Figure 1 is a map of the Dukes County, MA intended nonattainment area. The map identifies the

locations and design values of air quality monitors, county and other jurisdictional boundaries.

For purposes of the 1997 8-hour ozone NAAQS, Dukes County was included as part of the Eastern 

Massachusetts nonattainment area and was designated nonattainment. The boundary for the Eastern 

Massachusetts nonattainment area for the 1997 ozone NAAQS, includes all counties in Massachusetts 

east of, and including Worcester County.

In November 2011, Massachusetts recommended that Dukes County, MA be designated as 

nonattainment for the 2008 ozone NAAQS based on certified air quality data from 2009 and 2010 and 

preliminary 2011 ozone data. Massachusetts recommended all other counties in Massachusetts be 

designated as attainment for the 2008 ozone NAAQS, based on these same ozone data. These ozone 

data are from Federal Reference Method monitors, sited and operated in accordance with 40 CFR Part 

58. (See letter from Massachusetts Department of Environmental Protection (MassDEP) dated

November 8, 2011.)

After considering these recommendations and based on EPA's technical analysis described below, EPA 

intends to designate Dukes County, MA as “nonattainment” for the 2008 ozone NAAQS.

 

3 Lists of CBSAs and CSAs and their geographic components are provided at 

www.census.gov/population/www/metroareas/metrodef.html . The lists are periodically updated by the Office of 

Management and Budget. EPA used the most recent update, based on 2008 population estimates, issued on December 1, 

2009 (OMB Bulletin No. 10-02).
3

Table 1. State's Recommended and EPA’s Intended Designated Nonattainment Counties

for Dukes County, MA

Area State-Recommended 

Nonattainment Counties

EPA Intended

Nonattainment Counties

Dukes County, MA Dukes County, MA Dukes County, MA

Factor Assessment

Factor 1: Air Quality Data 

For this factor, we considered 8-hour ozone design values (in parts per million (ppm)) for air quality 

monitors in the intended Dukes County, MA nonattainment area based on data for the 2009-2011 period 

(i.e., the 2011 design value, or DV). Massachusetts based their November 8, 2011 recommendation on 

2009-2011 data and we expect at the time of final designations this will be the most recent three years 

with fully-certified air quality data. A monitor’s DV is the metric or statistic that indicates whether that 

monitor attains a specified air quality standard. The 2008 ozone NAAQS are met when the annual 

fourth-highest daily maximum 8-hour average concentration, averaged over 3 years is 0.075 ppm or less. 

A DV is only valid if minimum data completeness criteria are met. See 40 CFR part 50 Appendix P. 

Where several monitors are located in a county (or a designated nonattainment area or maintenance 

area), the DV for the county or area is determined by the monitor with the highest level.

The 2011 DV for the ozone NAAQS for Dukes County, MA is 0.076 ppm, which is above the NAAQS.

Since Dukes County shows a violation of the 2008 ozone NAAQS, and is the only ozone monitor in 

Massachusetts that violates the 2008 standard based on 2009-2011 data, EPA agrees with the MassDEP

recommendation. The Dukes County monitor is on the Indian country of the Wampanoag Tribe. The 

ozone monitor is operated by Wampanoag Tribe, in cooperation with the Massachusetts Department of 

Environmental Protection. 

Table 2. Air Quality Data.

County State Recommended 

Nonattainment?

2009-2011 Design Value

(ppm)

Dukes County, MA Yes 0.076

Factor 2: Emissions and Emissions-Related Data

EPA evaluated emissions of ozone precursors (NOx and VOC) and other emissions-related data that 

provide information on areas contributing to violating monitors.
4

Emissions Data

EPA evaluated county-level emission data for NOx and VOC derived from the 2008 National Emissions 

Inventory (NEI), version 1.5. This is the most recently available NEI. (See

http://www.epa.gov/ttn/chief/net/2008inventory.html.) Significant emissions levels in a nearby area

would indicate the potential for the area to contribute to observed violations. We will also consider any 

additional information we receive on changes to emissions levels that are not reflected in recent 

inventories. These changes include emissions reductions due to permanent and enforceable emissions 

controls that will be in place before final designations are issued and emissions increases due to new 

sources.

Table 3 shows emissions of NOx and VOC (given in tons per year (tpy)) for Dukes County. 

Table 3. Total 2008 NOx and VOC Emissions.

County State Recommended

Nonattainment?

NOx (tpy) VOC (tpy)

Dukes, MA Yes 1,298 1,789

Population density and degree of urbanization

EPA evaluated the population and vehicle use characteristics and trends of the area as indicators of the 

probable location and magnitude of non-point source emissions. These include ozone-creating 

emissions from on-road and off-road vehicles and engines, consumer products, residential fuel 

combustion, and consumer services. Areas of dense population or commercial development are an 

indicator of area source and mobile source NOx and VOC emissions that may contribute to ozone 

formation. Rapid population or VMT growth (see below) in a county on the urban perimeter signifies 

increasing integration with the core urban area, and indicates that the associated area source and mobile 

source emissions may be appropriate to include in the nonattainment area. Table 4 shows the population, 

population density, and population growth information for Dukes County. Note, Dukes County is not 

part of any CSA or CBSA.

Table 4. Population and Growth.

County

State 

Recommended 

Nonattainment?

2010 Population

2010 Population 

Density

(1000 pop/sq mi))

Absolute change

in population

(2000-2010)

Population % 

change

(2000-2010)

Dukes, MA Yes 16,535 0.14 1,459 +10

Sources: U.S. Census Bureau population estimates for 2010 as of August 4, 2011 

Traffic and commuting patterns

EPA evaluated the total Vehicle Miles Traveled (VMT) for Dukes County. In combination with the 

population/population density data and the location of main transportation arteries (Figure 1), this 

information helps identify the probable location of non-point source emissions. A county with high 

VMT and/or a high number of commuters is generally an integral part of an urban area and indicates the 

presence of motor vehicle emissions that may contribute to ozone formation. Rapid population or VMT 

growth in a county on the urban perimeter signifies increasing integration with the core urban area, and 

indicates that the associated area source and mobile source emissions may be appropriate to include in 

the nonattainment area. Table 5 shows 2008 VMT. As noted above, Dukes County is not part of any 
5

CSA or CBSA. Dukes County consists of several islands the largest of which is Martha’s Vineyard. 

The county is only accessible by boat, ferry or plane. There are no bridges to the mainland.

Table 5. Vehicle Miles Traveled (VMT) for Dukes County

County State Recommended 

Nonattainment?

2008 VMT*

(million miles)

Dukes, MA Yes 79

* MOBILE model VMTs are those inputs into the NEI version 1.5. 

Factor 3: Meteorology (weather/transport patterns)

EPA evaluated meteorological data to help determine how meteorological conditions, such as weather, 

transport patterns and stagnation conditions, would affect the fate and transport of precursor emissions 

contributing to ozone formation. 

The prevailing winds during the ozone season have a strong southwesterly component, indicating that 

the ozone source region most likely Connecticut, New York and New Jersey, all of which are included 

in other proposed ozone nonattainment areas for the 2008 ozone NAAQS.

In addition, back trajectories on days with elevated ozone in Dukes County show the source region to 

likely be the New York City area. (See two examples, shown below as Figures 2 and 3.)

Factor 4: Geography/topography (mountain ranges or other air basin boundaries)

The geography/topography analysis evaluates the physical features of the land that might affect the 

airshed and, therefore, the distribution of ozone over the area.

The Dukes County, MA area does not have any geographical or topographical barriers significantly 

limiting air pollution transport within its air shed. Therefore, this factor did not play a significant role in 

this evaluation. As noted above, however, Dukes County consists of several islands.

Factor 5: Jurisdictional boundaries

Once the general areas to be included in the nonattainment area were determined, EPA considered

existing jurisdictional boundaries for the purposes of providing a clearly defined legal boundary and 

carrying out the air quality planning and enforcement functions for nonattainment areas. Examples of 

jurisdictional boundaries include existing/prior nonattainment areas for ozone or other urban-scale 

pollutants, counties, air districts, townships, metropolitan planning organizations, state lines, areas of 

Indian country, urban growth boundary, etc. Where existing jurisdictional boundaries are not adequate 

to describe the nonattainment area, other clearly defined and permanent landmarks or geographic 

coordinates were considered.

The Eastern Massachusetts area has previously established nonattainment boundaries associated with the 

1-hour, and 1997 8-hour ozone NAAQS. The state has recommended a different boundary for the 2008 

ozone NAAQS. The only county in either the 1-hour or 8-hour Eastern Massachusetts nonattainment 

area that is violating the 2008 ozone standard based on 2009-2011 data and will remain nonattainment is 

Dukes County.
6

The Dukes County, MA area also includes areas of Indian country. As defined at 18 U.S.C. 1151, 

“Indian country” refers to: “(a) all land within the limits of any Indian reservation under the jurisdiction 

of the United States Government, notwithstanding the issuance of any patent, and, including rights-ofway running through the reservation, (b) all dependent Indian communities within the borders of the 

United States whether within the original or subsequently acquired territory thereof, and whether within 

or without the limits of a state, and (c) all Indian allotments, the Indian titles to which have not been 

extinguished, including rights-of-way running through the same.” EPA recognizes the sovereignty of 

tribal governments, and has attempted to take the desires of the tribes into account in establishing 

appropriate nonattainment area boundaries. The Massachusetts Wampanoag Tribe of Gay Head is 

located in this nonattainment area. The tribe has not submitted a designation recommendation. EPA has 

preliminarily concluded that all of Dukes County, including the Indian country of the Massachusetts 

Wampanoag Tribe of Gay Head, are nonattainment for the 2008 ozone NAAQS.

Conclusion

Based on the assessment of factors described above, EPA has preliminarily concluded that only Dukes 

County meets the Clean Air Act criteria for inclusion in the intended Dukes County, MA nonattainment 

area. 
7

Figure 1. Map of the Dukes County Nonattainment area
8

Figure 2: Back Trajectory of Dukes County Ozone Monitor for July 22, 2011

8-hour ozone value at monitor was 113 ppb.
9

Figure 3: Back Trajectory of Dukes County Ozone Monitor for June 8, 2011

8-hour ozone value at monitor was 93 ppb.