MEMORANDUM

SUBJECT:	PM10-2.5 Point Source Analysis

Evaluation of Proposed Suitability Test Conditions 1 and 2.

FROM:	Lewis Weinstock

		Ambient Air Monitoring Group (C304-06)

		Air Quality Assessment Division

		Office of Air Quality Planning and Standards

TO:		Dockets

		EPA-HQ-OAR-2004-0018, EPA-HQ-OAR-2001-0017

Following the completion of the monitoring proposal, EPA performed
additional analyses to determine the relationship of industrial point
sources to certain criteria in the proposed PM10-2.5 monitoring network
design for siting of NAAQS-comparable monitoring sites (see 71 FR 2782,
Comparability of PM10-2.5 data, conditions 1 and 2).  The 2002 National
Emission Inventory (NEI) point source data for coarse particle emissions
(PM10 minus PM2.5 emissions) was used for this analysis.

The NEI contained 3,601 sources emitting over 10 tons per year of
primary PM10-2.5.  These data records were filtered for sources emitting
at least 100 tons per year and EPA noted 645 industrial point sources in
the inventory meeting this criteria. Of these 645 sources, EPA noted
that 74 sources (12 percent) were located inside the boundaries of
urbanized areas meeting the 100,000 person population requirement
(condition 1), and 571 sources (88 percent) were located outside of the
urbanized area boundary.  Of the total PM10-2.5 emissions associated
with these 645 sources (206,418 tons per year), 10 percent of the
emissions (19,703 tons per year) were from sources located inside the
boundaries of urbanized areas of 100,000 population or more, and 90
percent (186,715 tons per year) were from sources located outside of the
urbanized area boundary.  This analysis indicated a weak correlation
between the proposed urbanized area criterion and coarse particle
industrial point sources in that the majority of significant PM10-2.5
sources were not included by the first suitability test condition. 

Of the 74 sources located inside urbanized areas with population of at
least 100,000 persons, EPA noted that approximately half (38 of 74, 51
percent) were located in block groups of at least 500 people per square
mile (condition 2).  The presence of non-residential industrial zones
within the 36 block groups with sources that did not meet the 500 people
per square mile criterion is likely a factor, in some cases reducing the
population density of the whole block group below the proposed 500
person per square mile cutoff even though some parts of the block group
may be above this population density.  Combining the effects of
suitability conditions 1 and 2, only 38 out of 645 sources (6 percent)
with PM10-2.5 emissions of 100 tons per year or greater would be located
in areas potentially suitable for NAAQS-comparable PM10-2.5 ambient
monitors (still subject to the three remaining proposed conditions in
the suitability test).

EPA also considered the available information on how many people reside
near included and excluded sources of PM10-2.5.  Of 901,647 people
living in the same block group as any of the 100-ton sources of
PM10-2.5, only 5 percent live in a block group with one the 38 included
sources.  Of 8,877,317 people living in the same zip code area as any of
the 100-ton sources, only 11 percent live in zip codes with one of the
38 included sources.

EPA performed several individual-source analyses to investigate the
distribution of households and other indicators of
population-orientation, such as schools, in areas surrounding
significant point sources that were located outside of the boundaries of
urbanized areas of at least 100,000 persons or more.  In these case
studies, EPA noted dense clusters of households and the presence of
multiple schools within a 2.5 kilometer radius of these PM10-2.5
sources, ranging from 255 tons per year to 826 tons per year.  Maps of
these sources are attached.

Based on this analysis, EPA concludes that the first two conditions of
the proposed suitability test (urbanized area population, block group
population density) would not be effective enough in identifying the
areas within which populations could be exposed to ambient PM mixes
dominated by major industrial sources of coarse particles, because
people located around the majority of coarse particle industrial sources
would be in areas not meeting the first two parts of the suitability
test.  EPA notes that if sources with emissions of less than 100 tons
were also considered, the situation might be even more extreme.  Tables
of data relating to emission sources, urbanized areas, and MSAs are
attached.  

EPA considered reducing the 100,000 person urbanized area population
cut-off to 50,000 and using an MSA population cutoff of 50,000 instead
of a cutoff on urbanized area population.  In the former, about 100
additional smaller MSAs would be eligible to have monitors that could be
compared to the NAAQS, but 550 major industrial sources of PM10-2.5
would still lie outside the eligible areas.

