905D77002
DRAFT REGION V POLICY FOR UNUSUAL AMBIENT AIR QUALITY DATA
Issue 1: Should valid air quality data generated during an unusual event be
entered into a State data handling system and subsequently entered into the
National Air Data Bank?
Backgound: During the Fall of 1976 and Spring of 1977, Region V as well as
other Regions experienced an area-wide dust storm which brought dramatically
to our attention the need for a policy on unusual data (Attachment 1). "Un-
usual" data may be defined as data which is valid, but not necessarily suit-
able for attainment analysis purposes (40 CFR 51.12). In the Spring of 1977,
Region IV drafted a data policy and sent it out to its eight States for
comments. The policy requested that only data suitable for attainment analy-
sis be submitted for inclusion into the National EPA data bank (NADR). The
data not submitted to NADB was to be submitted once a year to EPA with an
explanation of why it was not suitable for attainment analysis. Since NADR
data were (and are) used most of the time as the starting point for most
attainment analyses, Region IV wanted the data to "stand alone" for EPA
Headquarters, Congressional, and public use; i.e., the data user would not
have to call the Region or State for an explanation of which data they could
use. Region IV staff would thoroughly review this unusual data, submitted
once a year, to see if it should be excluded. Moreover, the Region felt it
was impossible to analyze the data and recalculate geometric means in a
reasonable amount of time when called upon to do an analysis or trends.
Generally, it would also be difficult to continue to maintain a log of the
unusual data.
In 1979, Region IV felt their States were excluding too much data. After
soliciting State's comments, they revised the unusual data submission policy.
AH data were and are to be submitted to SAROAD. States are to identify all
data they wish to be excluded from attainment analysis. However, since the
Region still wished to recalculate, means, number of short term standard
exceedances, they requested that a flagging system be devised by NADR so that
such recalculation could be accomplished. The NAD8 chose to implement a user-
oriented comments file to document problems or events of general nature, i.e.,
all ozone data collected in California during 1977 to 1979 is 20% high. In-
dividual data values could not be flagged and, therefore, excluded from sta-
tistical analysis.
During the Spring, NADB staff visited each Region to discuss the new data
base management system, Air Information Retrieval System (AIRS). During a
recent brief poll of the Regions, concensus was that EPA needed access to all
valid data but that the new AIRS should be able to flag unusual data and
optionally exclude this data from summary. A proposal for implementing such
flagging technique has been sent to NADB for consideration in AIRS (Attachment
2). NADB expects that the air quality portion of AIRS will be available for
direct input and retrieval on a pilot basis by the end of the Fiscal Year
1984.
In the interim, Region V proposes to its reporting agencies a draft policy
similar to the Region IV policy. An issue paper on this topic is also expec-
ted from the Standing Air Monitoring Work Group (SAMWG) during FY 1984.
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- 2 -
REGION V DRAFT POLICY FOR SUBMITTAL OF
UNUSUAL AMBIENT AIR QUALITY DATA
This policy supersedes any previous guidance issued by Region V concerning
data deletion and invalidation. It does not revise any guidance on data
to be excluded from control strategy or attainment/maintenance analyses.
Reporting Requirements for Ambient Air Quality Data
The Ambient Air Quality Monitoring, Data Reporting, and Surveillance Provi-
sions (40 CFR Part 58) require that specific quality assurance, methodology,
and siting for NAMS and SLAMS he followed as of January 1, 1983. Further,
40 CFR 58.14 specifies that any ambient air quality monitoring stations other
than a SLAMS or a Prevention of Significant Deterioration (PSD) station from
which a State intends to use the data as part of a control strategy demon-
stration or as support for a plan revision must meet the same requirements as
SLAMS after January 1, 1983. Methods, procedures and siting have been review-
ed and agreed upon by EPA, State and, as appropriate, local agency represent-
atives. All data is considered valid if the EPA reference or equivalent moni-
tor is at an approved site and proper quality assurance procedures are used.
The senior air pollution control officer in the State, or his/her designee,
is required to certify that the data in the annual SLAMS summary report are
accurate to the best of his/her knowledge. Therefore, EPA considers all
designated NAMS and SLAMS data entered into the SAROAD system to be val id.
Principle Purposes of Collection and Uses of Air Monitoring Data
A summary of some uses of air monitoring data are listed as follows:
1. Judge attainment/non-attainment of NAAQS
2. Evaluate progress in achieving/maintaining NAAOS or State standards
3. Develop or revise SIP's to attain/maintain NAAQS
4. New Source Review and Prevention of Significant Deterioration
5. Develop or revise national control policies (e.g., New Source Performance
Standards)
6. Model development and validation
7. Energy related issues
8. Support enforcement actions
9. Public information (e.g., air quality indices)
10. Health research/establish standards
11.
' 1C Q I Vr'T I C.O C U I W 1 / C. •.» I* U " I I J » I O U U I rvj U I VJ J
Develop or revise local control strategy
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- 3 -
12. Determine specific cause of pollution in an area
13. Determine nature of air pollution problem in an area
14. Document and analyze unusual meteorological events
For a number of the above monitoring data uses it may be desirable to under-
stand and evaluate any unusual occurrence. For example, it may be true that
the area in which the air monitoring site is located exceeds the NAAOS and
that people may be exposed to those hazardous levels. However, the course of
action necessary to correct the violation may be dependent upon the reason
for the violation.
For calibrating a dispersion model, monitored geometric and arithmetic means
should only reflect impacts from fugitive and point sources in the emission
inventory and from representative background sources. Any inclusion of un-
usual data will result in an unexplained high intercept or an erroneous slope
of the calibration curve.
The use of data in showing past trends and estimating future projections is a
common practice. Trends are used to show what has happened over a general
area and are not usually used for the purpose of demonstrating short-term pro-
blems or unusual occurrences. Quarterly or yearly averages are used to plot
trends. As a result, outlying values and weighted quarters must be carefully
considered.
Invalidation of Data
At a minimum, the State is required to edit, validate, and submit NAMS data
to EPA within sixty days after the end of a calendar quarter. The State is
required to edit, validate, certify and submit a summary of SLAMS data to EPA
by July 1 after the preceding calendar year. This is ample time for any
instrument malfunction to be identified.
The following is assumed of all air quality data reviewed in State or local
agency reports and in SAROAD:
1. Data is of acceptable quality and reliability, i.e., proper and frequent
calibration has been performed.
2. The site is properly located and free from any bias.
3. There are no transcription or keypunch errors in the data.
4. Common statistical analysis may be performed on the data.
5. The characteristics of the site have not changed, i.e., elevation of
sampler and exposure.
It is only after these five assumptions are satisfied that the data will be
further analyzed for determination of attainment and maintenance of NAAOS,
NSR, PSD, and trends, dispersion modelling, and public dissemination.
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Quality controls limits are generally used to determine whether an instrument
is malfunctioning or beginning to malfunction. If the instrument has ceased
to operate completely, of course, maintenance and a new calibration are re-
quired. If the instrument is "trending" toward a control limit, optimally
the operator will provide necessary maintenance to cease the trending and re-
calibrate. In summary, control limits are a compromise between available
resources and desired data quality. Use of control limits result in the
initiation of specific corrective actions necessary to maintain desired data
quality. The exceedance of control limits may indicate that:
0 an instrument has malfunctioned,
0 the control limits are too rigid, or
0 the service frequency of the instrument is too lenient.
Data collected from a malfunctioning instrument is declared invalid only
from the time the malfunction was identified back to the last satisfactory
instrument check, i.e., precision check, audit, or calibration. These data
are not to be entered into the SAROAD system. All other data is to be submit-
ted and considered valid.
Invalidation of data which have already been entered into the SAROAD system
will be handled by EPA on a case by case basis as necessary.
Data from a properly operating instrument are not to be invalidated because
of any act of nature or man; the contribution to the atmospheric burden of
fires, volcanoes, tornadoes, dust storms, construction, demolition, tec.,
affects the interpretation and use to be made of the data but does not render
the data invalid. These data are valuable for future reference and are not
to be invalidated.
Missing Data
Missing data refers to any data not entered into the SAROAD system. All
periods of missing data are to be accounted for in a central record keeping
system and are to be readily available for inspection. Ideally, these records
are used by the agency to minimize the future loss of air quality data. Miss-
ing data includes but is not limited to, periods missed because of calibration,
audits, precision checks, routine maintenance and malfunctions.
Data Flagging
EPA recommends that all "unusual" data and all data concentrations which ap-
proach or exceed the primary or secondary national ambient air quality stand-
ard be thoroughly and objectively investigated and documented. Calculations,
and instrument performances should be verified. Local emission sources and
meteorology should be investigated. Data generators should consider the
value of investigating and documenting, all exceedances of the national am-
bient air quality standards (NAAQS), any other outstanding values, and/or the
ten highest values at each site each year; microscopic analysis should be
performed on hi-vol filters for the days with exceedances of the NAAQS. In
this way, elevated valid data can be objectively evaluated and flagged for
future interpretation.
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It is incumbent on the data generator to flag "unusual" data; any limitations
or restrictions on the data should be entered into the flag system (comments
file). It is incumbent on the data generator to keep thorough and accurate
records of the data investigation and the data flagged. The data generator
should report to the EPA Regional Office so that the NADB comments file is
updated to ensure the proper use of all data.
Currently, the flag system is independent of the SAROAD system and is main-
tained on State files. EPA is working towards consolidating these systems
and estimates completion by the end of 1984.
To flag data, the data generator needs to submit the following information to
the Environmental Monitoring Branch, Environmental Services Division, EPA
Region V, Chicago, Illinois:
0 SAROAD site number
0 Pollutant
0 Sample time(s) (year, month, day, hour)
0 Sample concentration and units
0 Explanation
Data may be flagged at any time, but should be flagged as soon as possible to
minimize the potential for its misuse.
Consideration of Unusual Data
In addition to flagging unusual data in the NADB, the data generator should
notify the Air Management Division, Environmental Protection Agency, Region
V, Chicago, Illinois of the existence of this data. This may be accomplished
by submitting a report containing the following:
0 Information submitted to the flag system.
0 Explanation for "unusual" data accompanied by some certification, such
as a newspaper article or letter of the unusual circumstances.
0 Meteorological data, maps, modelling results, etc., which support the
influence of the unusual circumstances on the monitor.
0 Microscopic analysis of hi-vol filters to determine source impact.
For industrial source pollution control malfunctions, the following informa-
tion should also be submitted:
0 Meteorological data, maps showing the impact on the monitor, and
modeling demonstration.
0 Summaries of past malfunctions or similar accidents for the previous
two years from the involved source.
0 Estimate of total actual emissions (type and amount).
0 Enforcement actions to be taken.
0 Procedures to minimize any future recurrence.
The Air Management Division may request additional background information.
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Issue 2: TSP Sampling Schedule and Completeness Criteria
Should 10 samples per calendar quarter (i.e., 75% of samples collected on a
six day schedule) instead of the EPA minimum of 5 he required to consider the
annual geometric mean for a TSP site for comparison against the air quality
standard?
Background: On April 19, 1983, Mr. Harry Williams, Director of the Indiana
Air Pollution Control Division, sent a letter to Larry Purdue, IISEPA, EMSL,
to request that USEPA require site data completeness of 75%, based on a six-
day sampling schedule, or 10 samples. The existing requirement of 5 samples
per quarter was based on the old National Air Surveillance Network (NASN)
biweekly sampling modified when EPA minimum recommended sampling schedule was
increased to once every six days.
Mr. Williams stated in his letter that Indiana had thrown out data for many
years and some of that data was not utilized for modelling purposes because
it did not meet six day criteria for completeness, i.e., 10 samples. Indiana
contended that if a site did not meet the six day schedule, EPA should not
utilize the data. Indiana, therefore, recommended that USEPA make adjustment
to 10 samples to take into account the more frequent sampling schedule.
Mr. Neil Frank, Office of Air Quality Planning and Standards, Monitoring and
Reports Branch, responded to Mr. Williams letter, that the U.S. EPA Task
Force Report on Air Quality Indicators "essentially acknowledged that an ad-
justment to the current EPA data completeness policy would be one way to
handle the heavier, every 6-day sampling schedule". He pointed out that EPA
Monitoring and Data Analysis Division has initiated a study to re-examine
validity criteria for all criteria pollutants and is expected to publish re-
commendations for revisions to these criteria in the fall of 1983. With the
use of every fi-day or more frequent TSP monitoring, the current NADB criteria
is certainly minimal. However, reasonable estimates of the geometric mean for
TSP can be obtained from a small number of samples. EPA does not suggest
throwing out a data set merely because the number of observations is less than
40 per year. The completeness criteria is still EPA guidance, but sampling
on a six schedule j_s_ mandated under 40 CFR 59.13 (b).
Mr. Williams contended in a reply to Neil Frank on June 13, 1983, that the
present USEPA data completeness policy "allows anyone who reports data to the
National Aerometric Data Bank (NAHB) to manipulate the numbers in a way that
best suits their purpose. For instance, if an industry shows non-attainment
via a six-day, three day or daily sampling network, what would keep that
industry from reporting only those numbers from a twelve-day schedule and
still meet EPA's criteria for data completeness and possibly show attainment?
The answer is contained under Section 113(c)(?)» "Federal Enforcement", of
the Clean Air Act as amended August 1977: Any person who knowingly makes any
false statement, representation, or certification in any application, record,
report, plan, or other document filed or required to be maintained under this
Act or who falsifies, tampers with, or knowingly renders inaccurate any
monitoring device or method required to be maintained under this Act, shall
upon conviction, be punished by a fine of not more than $10,000 or by inpri-
sonment for not more than six months, or by both.
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ATTACHMENT J_
EPA-450/1-77-002
DECEMBER 1977
NATIONAL AIR QUALITY
AND EMISSIONS TRENDS REPORT,
1976
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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3. NATIONAL AND REGIONAL TRENDS
IN CRITERIA POLLUTANTS
Trends in ambient levels of total suspended paniculate, sulfur dioxide, carbon monoxide,
oxidants, and nitrogen dioxide are reported in this section. Each of these criteria pollutants is
discussed individually; the extent of the analysis varies according to the amount of available historical
data. In contrast to Section 2, which dealt with specific urban areas, this section focuses upon national
trends and trends over broad geographic regions. (Section 4 of this report presents maps illustrating
the concentration ranges of several pollutants in various parts of the country.)
Considerable thought has been given to various ways to improve the nation's ambient air quality
monitoring programs. The recent activities of the Standing Air Monitoring Work Group (SAMWG)
have served as a focal point for new ideas. This work group, composed of representatives from EPA and
State and local air monitoring agencies, has developed a comprehensive strategy document for ambient
air quality monitoring.1 Because many elements of the SAMWG strategy document will affect future
trend analyses, some of these points are mentioned here so that interested readers will be made aware
of anticipated improvements in the nation's air monitoring programs.
The most obvious change will be the designation of specific National Air Quality Stations (NAQTS)
for the criteria pollutants. These NAQTS sites would primarily be determined by the population of
the area. For total suspended particulate and sulfur dioxide, the allocation would be on the basis of
population and pollutant concentration. Selected for the primary purpose of long-term trends.
analyses, these measuring stations will provide more consistent data bases from one year to the next
and also ensure adequate geographical coverage. Obviously, these NAQTS sites would not be the onK
component of an air monitoring program. There are a variety of purposes for ambient monitoring
programs, and, therefore, it will be necessary to supplement these NAQTS sites with other types of
monitoring stations. Other items of note in the SAMWG strategy document relate to qua!it\
assurance, increased continuous monitoring, and adherence to standardized siting criteria, all of
which will improve the ambient air quality data bases and thereby serve to improve subsequent trend
analyses. Readers interested in the details of the SAMWG recommendations are referred to the
strategy document.
3.1 TRENDS IN TOTAL SUSPENDED PARTICULATE
The general long-term improvement in ambient air quality with respect to total suspended
particulate (TSP) has been discussed in previous reports. *'• During the 1970's, there has been
nationwide improvement in TSP concentrations, but many areas experienced increases between 1975
and 1976. This section discusses national and regional TSP trends during the 1970-1976 time period
with particular attention given to comparisons between 1975 and 1976.
The data used in these analyses were obtained from EPA's National Aerometric Data Bank. The
vast majority of the data were collected by State and local agencies through their air monitoring
programs and then submitted to EPA. All sites having four consecutive quarters of data from 1970-
1973 and also from 1974 through 1976 were included in these analyses. This selection criterion was used
to ensure balanced seasonally and a comparable data base from the beginning to the end of the time
period. Sufficient data to satisfy this selection criterion were available from 2,350 sites. Although a site
would need only a minimum of 2 years of data to qualify for selection, 70 percent of these 2,350 sites
had at least 4 complete years of data during the 1970-1976 time period.
As in last year's Trends Report,* a modified version of the graphical technique known as a box-plot7
is used to display trends. This plotting technique depicts several characteristics of the data
simultaneously. Figure 3-1 is a sample illustration of the plotting conventions used for the box-plots in
3-1
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A~
C
-*«
I
90TH PERCENTILE
75TH PERCENTILE
COMPOSITE AVERAGE
MEDIAN
25TH PERCENTILE
10TH PERCENTILE
Figure 3-1. Sample illustration
of plotting conventions for
box plots.
this report. For each year, various percentiles and the composite averages are indicated so that the
general trend in the average levels may be seen as well as the trends for the higher and lower
concentration ranges.
3.1.1 Long-Term TSP Trends: 1970-1976
During the I9701s, there has been general improvement nationally in ambient TSP concentrations.
Figure 3-2 shows a box-plot presentation of trends in geometric mean TSP levels during the 1970-1976
time period for the 2,350 sites used in this analysis. This plot is consistent with results discussed in
previous reports.2'6 The general pattern shows stability for the lower concentration sites and more
pronounced improvement for the higher concentration ranges. The median and composite average
also indicate fairly consistent improvement through 1975. During this time period, the overall rate of
improvement was slightly less than 4 percent per year, with more marked improvement in the
Northeast and Great Lakes regions. Figure 3-3 displays trends in peak values at these same sites and
shows a similar pattern during this time period. It should be noted that sampling frequencies at many
of these sites were increased during this time period. While increasing sampling frequencies would
not alter trends in annual means, it could be expected to result in an artificial increase on the order of
2 to 3 percent per year for the peak values during this time period. Even with this contribution,
however, the general pattern in Figure 3-3 shows improvement through 1975. Also apparent in both
graphs is the trend reversal in 1976, which is discussed in more detail in the following section dealing
with short-term changes. Knowledge of geographical differences in long-term TSP trends provides
background information that is useful in considering the short-term changes.
Figure 3-4 displays 1970-1976 trends for each EPA Region and provides a convenient presentation
of trends by geographical area. Although all areas had improved TSP levels in the 1970-1976 time
period, trends in the western areas of the country were generally less pronounced. In many cases, this
geographical variation is attributable to a difference in the nature of TSP problems from one area to
another. In some locations, wind-blown dust is an important component of TSP levels and is more
difficult to control than emissions from traditional sources.
As would be expected from these graphs, improvement was fairly consistent from 1970 to 1976, with
72 percent of the sites having decreases in ambient TSP levels. Because air pollution control strategies
are designed to reduce levels at locations exceeding the National Ambient Air Quality Standards,
more pronounced improvement would be expected for the sites with higher concentrations. For those
sites with 1970-1973 averages above the annual primary standard, 81 percent showed improvement.
For sites in this category, improvements outnumbered increases by at least a 2 to 1 margin in all
3-2
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110
100
•0
70
CO
A
•»•
SO
«0
30
20
10
I I I
T
1970
1971
1972
1973
YEAR
1974
1976
197E
Figure 3-2. Trends of annual mean total suspended paniculate
concentrations from 1970 to 1976 at 2,350 sampling sites.
regions of the country. Using nonparametric regression, 27 percent of these higher concentration sites
show statistically significant improvement while only 1 percent of these sites had statistical!)
significant increases.
3.1.2 Short-Term TSP Trends: 1975-1976
In many areas of the country, the general downward trend in TSP levels in the early 1970's was
followed by a reversal in 1976. This was apparent in Figure 3-2 and 3-3 for the nation, but is more
obvious in some of the regional graphs in Figure 3-4. Based upon changes between comparable
quarters in 1975 and 1976 for these TSP trend sites, 53 percent of those comparisons showed increases.
Over half the States had more increases than decreases between 1975 and 1976. The Southeast,
Midwest, and West generally recorded increases.
The widespread pattern of these increases suggests that some common factor was involved. Because
Jio general increases in particulate emissions throughout these areas occurred in 1976 and there were
3-3
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350
300
5250
3200
= 150
too
I T V
T
T
T T-
1970
1971
1972
1973
YEAR
1974
1975
1976
Figure 3-3. Trends of peak daily total suspended paniculate
concentrations from 1970 to 1976 at 2,350 sampling sites.
not widespread changes in sampling methodology, meteorological conditions would be the likely
candidate for explaining these increases. In fact, many State agencies ranging from the Midwest to
Washington and California have cited meteorology as the main reason for these TSP increases in
1976.8*14 Large areas of the country experienced drought during 1976, and these extremely dry soil
conditions increased the likelihood of wind-blown dust contributing to ambient TSP levels.
Figure 3-5 illustrates the geographical areas affected by drought in 1976. This map was constructed
by integrating the Palmer Index* throughout 1976. The Palmer Index, a reasonable indicator of
overall soil moisture conditions, reflects both rainfall and evapotranspiration. This map shows that
dry soil conditions existed in those general areas that had TSP increases. Specific days that had high
TSP concentrations may also be examined to see whether the dry conditions contributed to these
values.
* Obtained from the Weekly Weather and Crop Bulletin, 1976.
3-4
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o
c.
O)
u
o
u
CO
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a
re
*-
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(0
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ro
a>
a>
CC
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k-
I!
3-5
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NEAR OR ABOVE
NORMAL
SLIGHTLY BELOW
NORMAL
SEVERE
DROUGHT
EXTREME
DROUGHT
MODERATE
DROUGHT
Figure 3-5. Index of drought from monthly Palmer Indices for period April - October 1976.
Such an analysis was done in the Midwest by EPA's Region V with the cooperation of the State
agencies in Region V and also Iowa.15 Figure 3-6 illustrates TSP isopleths in this area for October 15,
1976. Elevated TSP levels were recorded throughout this area. On this particular day, dry soil
conditions and strong winds combined to increase the likelihood of wind-blown dust. These
meteorological factors also coincided with fall harvesting, which increased the likelihood of
wind-blown soil particles. This explanation of these high levels was also supported by microscopic
examination of the high-volume filters for this day.15
An even more dramatic example of the impact of wind-blown dust over a broad geographic area
occurred in February 1977 in the Southeast. Although this incident took place in 1977 rather than
1976, it illustrates the potential impact that dust storms can have. Extremely high TSP values were
recorded on February 24, 1977, throughout this area, and an analysis was conducted by personnel of
EPA's Region IV office with the cooperation of State and local air pollution agencies in the Southeast
as well as the National Weather Service Forecast Office (NO AA) in Birmingham, Alabama. '* Figure 3-7
shows TSP concentration isopleths in EPA Region IV for February 24, and is indicative of the
3-6
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100
100
150
Figure 3-6. Isopleths of total suspended particulate concentrations
(/jg/m3) in EPA Region V and Iowa for October 15, 1976.
extremely high values in this area for that day. The basic cause was wind erosion of the soil. Figure 3-8
graphically depicts a satellite view of the dust storm at successive points in time from February 23-25,
1977. Extremely dry soil conditions in the Central Plains and the development of a strong frontal
system resulted in dust being stirred up and eventually transported east. Meteorological conditions
that were likely to cause dust storms coincided with widespread cultivation for farming, and the end
result was widespread transport of wind-blown dust throughout a broad geographical area. It should
be noted that the concentration levels reported during this storm were extremely unusual for this area
and represent historically high values that are not at all typical of the normal TSP ranges in the region.
In discussing the 1975-1976 increases, it should be noted that some areas continued to improve in
1976. For example, the continued progress in the New York area was presented in Section 2.
Nationally, for those trend sites with complete 1975 and 1976 data, 54 percent of the sites above the
primary standard in 1975 showed improvement in 1976. In general, the short-term 1975-1976 increases
did not appreciably affect status with respect to the primary standards. For those sites located in
highly populated areas (SMSA's), 5 percent went from above 75 ug/mj (the primary standard) to below,
while another 5 percent crossed in the opposite direction for a net change of zero. For those sites
located outside these populated areas, however, 8 percent crossed in the increasing direction while
only 3 percent dropped below the standard so that there was a net increase. This seems consistent with
the meteorological contribution to these increases in that the urbanized areas showed a lesser impact
3-7
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oEPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/2-78-052
December 1978
Air
National Air Quality,
Monitoring, and
Emissions Trends Report,
1977
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3. NATIONAL AND REGIONAL TRENDS IN CRITERIA
POLLUTANTS
Trends in ambient levels of total suspended paniculate (TSP), sulfur dioxide (SO2), carbon monoxide
(NOJ, oxidants/ozone (O3), and nitrogen dioxide (NO2> are reported in this section. Each of these
criteria pollutants is discussed individually; the extent of the analysis varies according to the amount
of available historical data. The major emphasis is upon national trends and trends over broad
geographical regions. As in previous reports.1 6 California is emphasized in the subsections dealing
with the automotive-related pollutants -CO, O3, and NO2 - because of extensive historical monitoring
of these pollutants.
3.I TRENDS IN TOTAL SUSPENDED PARTICULATE
Total Suspended Particulate (TSP) levels throughout the nation have improved during the 1970's
These trends have been discussed in previous reports.1"6This section examines long-term TSP trends
from 1972 through 1977 and the short-term changes from 1976 to 1977. The general trend shows
long-term improvement with a gradual leveling off in the past few years.
Data for describing these trends were obtained from EPA's National Aerometric Data Bank, which
stores air quality data submitted by State and local agencies and by federal monitoring programs To
ensure seasonal balance, trend sites were selected only if they had four consecutive quarters of TSP
data in both the 1972-74 and the 1975-77 time periods. Accordingly, 2,707 sites that met this selection
criterion were included in the analysis. Over 70% of these sites had at least 4 years of data and over
90% had at least 3 years.
Throughout this section, as in previous reports,5'6 trends are depicted using a modified box-plot7 to
display simultaneously several features of the data Figure 3-1 illustrates the use of this technique in
presenting the composite average, the median, and selected percentiles corresponding to the lower
and higher concentration levels.
3.1.1 Long-Term TSP Trends: 1972-77
Figure 3-2 is a box-plot presentation of national trends in geometric mean TSP levels from 1972 to
1977. During this period, the nationwide average decreased by 8%, an improvement of almost 2% per
year. While all parameters show improvement, the decrease in TSP levels is most pronounced in the
90th percentile values of the box-plots.
Figure 3-3 summarizes TSP trends for each of the 10 EPA Regions. The overall trend in improve-
ment from 1972 through 1975 was followed by a reversal in some regions in 1976; this reversal is
discussed in more detail in the following section on short-term changes.
160
90TH PERCENTILE
r
-75TH PERCENTILE
-COMPOSITE AVERAGE
-MEDIAN
25TH PERCENTILE
ICIX PLOT ANNUAL VALUES
1972
1971
10TH PERCENTILE
1174 U75
YEAR
1S76
Figure 3-1. Sample illustration
of plotting conventions for
box plots.
Figure 3-2. Nationwide trends in annual mean total suspended
particulate concentrations from 1972 to 1977 at 2,707 sampling
sites.
3-1
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U.S. EPA REGIONS, EASTERN STATES
fe
F-
160
140
120
^E 100
5 80
a.' 60
w ou
*~ 40
20
0
l
REGION 1
J_
1972 1973 1974 1975 1976 1977
REGION 2
i I
I I
l
1972 1973 1974 1975 1976 1977
REGION 3
1972 1973 1974 1975 1976 1977
160
140
120
5 80
ft 60
*~ 40
20-
REGION 4 _
l
l
i
1972 1973 1974 1975 1976 1977
REGION 5 _
I
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1972 1973 1974 1975 1976 1977
Figure 3-3. Regional trends of annual mean total suspended particulate concentrations,
1972- 1977.
32
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U.S. EPA REGIONS, WESTERN STATES
160
140
120
"E100
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60
40
20
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B
REGIONS
1972 1973 1974 1975 1976 1977
REGION 7 -
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REGIONS -
1972 1973 1974 1975 1976 1977
1972 1973 1974 1975 1976 1977
160
140
120
«E 100
^ 60
£ 40
20-
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REGION 9
1972 1973 1974 1975 1976 1977
REGION 10 -
i i i
1972 1973 1974 1975 1976 1977
YEAR
Figure 3-3 (continued). Regional trends of annual mean total suspended paniculate
concentrations, 1972- 1977.
3-3
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Despite the short-term reversal in 1976, 60% of the sites showed long-term improvement from
1972-1977. For those sites with TSP concentrations exceeding the annual standard, 77% showed
long-term improvement. Approximately 25% of the sites reported their lowest annual values in 1977.
Although there has been a nationwide decrease in levels of total suspended paniculate matter,
there is evidence that levels of some types of particulates may be increasing. This is indicated by in-
creasing trends in secondary particulates, such as sulfates8 and deterioration of visibility in the
Southwest and nonurban areas of the East.910 The patterns are consistent with growth of emission
sources outside of large metropolitan areas.
3.1.2 Short-Term TSP Changes: 1976-77
The short-term increase in TSP levels in 1976 was discussed in detail in last year's report.6 Many
areas experienced unusually dry weather in 1976; the resulting wind-blown dust may have con-
tributed to elevated TSP levels. On February 24, 1977, the extremely dry soil conditions in the Central
Plains and a strong frontal system resulted in dust being stirred up and transported east. The resulting
high TSP levels measured throughout the Southeast were discussed previously.6 Figure 3-4 shows
peak value TSP levels in Region VI (Central Plains) by quarter from 1972 through 1977. The dramatic
increase in the first quarter of 1977 is obvious from this graph. Monitoring sites throughout Texas,
Oklahoma, and Arkansas reported high TSP levels during this February dust-storm. Several sites
recorded daily values in excess of 1000 ^g/m3, a single value of this magnitude would increase the an-
nual geometric mean at a site by 10%.
The short-term increases associated with unusually dry conditions had relatively little effect on the
percentage of sites nationwide exceeding the TSP standard. In fact, those sites exceeding the annual
mean standard continue to show improvement by a two to one margin.
3.2 TRENDS IN SULFUR DIOXIDE
Sulfur dioxide
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ATTACH MEN
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION V
DATE Sfcp 1 \ 1983
SUBJECT Suggested Method for Flagging Anomalous Data in the Future AIRS System
FROM Stephen K. Goranson, Chief
Environmental Monitoring Branch
TO: John C. Bosch, Acting Chief
National Air Data Bank
MDAD, OAQPS (MD-14)
Our State agency and Regional Office participants appreciated your staffs'
visit in May to discuss AIRS. We welcome your return at least annually to
keep our staff and the States abreast of changes in the national air qual-
ity/emissions data base management systems as well as listening to our
concerns.
One important discussion topic raised at the meeting was the ability to
flag individual data points which were valid but which should be excluded
for specific purposes such as attainment analysis. An example might be a
single documented dust storm which affected most monitors over a large
geographic area. AIRS will utilize ADABAS, a data base management system,
offering the ability to select on a single or multiple parameter basis and
then to perform statistical analysis of the selected data. The data base
management system also allows tables and coordinated files, which could
prove to be useful in tracking unusual data through the following scheme.
Obviously, maintaining a flag for each data value would be a tremendous
overhead of disk space. However, if AIRS data records ard constructed on a
SAROAD site/pollutant/year/data value(s) basis, as I believe the current
system is for intermittent data, a one character flag could indicate whether
the record contains at least one anomalous concentration value.
If the record indicates, for example, a flag ?*0, then a coordinated file
could be scanned to determine which value or values could be excluded from
statistical analysis (e.g., arithmetic mean, maximums, etc.).
The coordinated file would consist of the site/parameter/year key and the
associated date(s) and unusual value(s). A one character code could be
assigned to the data value to indicate the type of event which occurred to
exclude it from the statistical analysis. Since the expected number of
these data would be small, the coordinated file could contain a free format
comments field like the current NADB*AERO-MESSAGE file. If a summary file
of statistics is also maintained, NADB has the choice to include or exclude
such data upon update.
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- 2 -
Depending on the structure of the raw data transaction record, the unusual
data file could be updated either manually or automatically. A schematic of
the flagging structure is attached.
As I am certain you have already been planning on such a request from the
Regions, I hope this information maybe useful to you. If your have further
questions or suggestions, please contact me at 353-2306.
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