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EPA-450/3-77-004a
POPULATION EXPOSURE
TO OXIDANTS AND NITROGEN DIOXIDE
IN LOS ANGELES
VOLUME I: EXECUTIVE SUMMARY
by
Yuji Horie and Anton S. Chaplin
Technology Service Corporation
2811 Wilshire Boulevard
Santa Monica, California 90403
and
Neil H. Frank and William F. Hunt, Jr.
Environmental Protection Agency
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
Contract No. 68-02-2318
Project No. DU-76-C190
Program Element No. 2AF643
EPA Project Officer: Neil H. Frank
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
January 1977
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations - in limited quantities - from the
Library Services Office (MD-35) , Research Triangle Park, North Carolina
27711; or, for a fee, from the National Technical Information Service,
5285 Port Royal Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by
Technology Service Corporation, 2811 Wilshire Boulevard, Santa Monica.
California 90403, in fulfillment of Contract No. 68-02-2318, Project No.
DU-76-C190, Program Element No. 2AF643. The contents of this report
are reproduced herein as received from Technology Service Corporation.
The opinions, findings, and conclusions expressed are those of the
author and not necessarily those of the Environmental Protection Agency.
Mention of company or product names is not to be considered as an endorse-
ment by the Environmental Protection Agency.
Publication No. EPA-450/3-77-004a
11
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TABLE OF CONTENTS
SECTION
6.2 TEN-YEAR TREND FOR N02
HIGHLIGHTS ............................. v
LIST OF FIGURES ........................... i*
XI
LIST OF TABLES ...........................
1. ~ INTRODUCTION ......................... !
2. DESCRIPTION OF THE STUDY AREA ................. 3
3. DEMOGRAPHIC DATA ....................... 5
4. SUMMARY OF AIR QUALITY DATA .................. 7
5. POPULATION EXPOSURE ANALYSIS FOR 1973 DATA .......... 9
5.1 WEEKDAY/WEEKEND DIFFERENCE IN AIR QUALITY AND IN
POPULATION EXPOSURE ................... 9
5.2 EFFECTS OF DAILY POPULATION MOBILITY ON POPULATION
EXPOSURE ........................ 11
6. TRENDS IN AIR QUALITY AND IN POPULATION EXPOSURE ....... 13
6.1 TEN-YEAR TREND FOR 0
7. REFERENCES .......................... 19
APPENDIX A SUMMARY OF AIR QUALITY DATA OBSERVED AT MONITORING
STATIONS ........................ A-l
m
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HIGHLIGHTS
Detailed analyses for a single year (1973) and trend analyses for
1965-1974 reveal the following results concerning population exposure to
oxidants (0 ) and nitrogen dioxide (N02) in the Los Angeles Basin:
A
ANALYSIS OF WEEKDAY/WEEKEND EFFECTS AND IMPACT OF POPULATION MOBILITY ON
POPULATION EXPOSURE USING 1973 DATA
1. On an annual basis the population as a whole is exposed to Ox
air pollution exceeding the NAAQS on a smaller percentage of
days and a smaller percentage of hours during the weekends
than the weekdays.
2. The population exposure to N02 above the California Standard is
less during the weekends than the weekdays in both the percentage
of days and the percentage of hours.
3. Because of daily population mobility between residence and work-
place, workers as a whole are exposed less to QX above the NAAOS
than nonworkers. In contrast workers experience a greater number
of hours of exposure to N02 above the California Standard than
nonworkers.
4. Although incorporation of daily population mobility into a popu-
lation exposure analysis is important for identifying the
population-at-risk distribution,which describes the percentage
of the population exposed to a concentration above the standard
for a given fraction of the time, the population mobility con-
sideration has turned out not to be critical in determining the
aggregated indices of population exposure.
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ANALYSIS OF TRENDS IN POPULATION EXPOSURE FOR THE PERIOD 1965-1974
1. There has been a regionwide downward trend in both 0 air
J\
pollution and population exposure to DX above the NAAQS during
the 10-year study period (Figure 15).
2. There has been a sharper reduction in population exposure to
the higher 0 concentrations and in the frequency of violations
/\
of two and three times the NAAQS (Figure 17).
• The percentage of the total population exposed to QX levels
above the NAAQS (160 yg/m3--one-hour average) more than 180
days per year dropped from 53% in 1965/66 to a mere 5% in
1973/74 (Figure 17).
t The percent of the total population exposed to QX above the
NAAQS more than 75 days per year was reduced from 100% in
1965/66 to 36% in 1973/74 (Figure 17).
3. Practically the entire population in the Southern half of
Los Angeles County has been exposed to N02 annual mean concen-
trations above the NAAQb (100 yg/m3) during the 10-year period
(Figures 19 and 20).
4. There is no clear trend in either N02 air quality or population
exposure to N02. However, the higher percent!le concentrations
and the population exposure to such concentrations have fallen
in recent years (Figures 21 and 23).
VI
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5. The percentage of the population exposed to one-hour NC^ concen-
trations above the California Standard at least 22 days per year
has been reduced from 65% in 1965/66 to 35% in 1973/74 (Figure 23)
VII
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LIST OF FIGURES
TITLE £A§E_
1 BOUNDARIES SHOWING TREND ANALYSIS AREA, 1973 ANALYSIS
AREA, AND LOS ANGELES AQCR ................. 19
2. LOCATION OF MONITORING STATIONS .............. 20
3. TOPOGRAPHICAL FEATURES OF THE LOS ANGELES BASIN ...... 21
4. POPULATION DENSITY IN PERSONS PER SQUARE MILE IN 1970 ... 22
5. NUMBER OF PERSONS EMPLOYED PER SQUARE MILE IN 1970 ..... 23
6. PERCENT CHANGE IN POPULATION 1965 TO 1975 ......... 24
7. PERCENT CHANGE IN EMPLOYMENT FROM 1965 TO 1975 ....... 25
8. ISOPLETHS OF PERCENT OF DAYS ON WHICH THE NAAQS FOR OXIDANT
WAS EXCEEDED IN 1973 .................... 26
9 ISOPLETHS OF AVERAGE DURATION (HOURS) ON DAYS WHEN THE
NAAQS FOR OXIDANT WAS EXCEEDED IN 1973 .......... 27
10 THE DIFFERENCE IN PERCENT OF THE NUMBER OF DAYS ON WHICH
THE NAAQS FOR OXIDANT WAS EXCEEDED IN 1973, WEEKDAY MINUS
WEEKEND .......................... Zb
11 ISOPLETHS OF PERCENT OF DAYS ON WHICH THE CALIFORNIA ONE
HOUR STANDARD FOR N02 WAS EXCEEDED IN 1973 ......... &
12 ISOPLETHS OF AVERAGE DURATION (HOURS) ON DAYS WHEN THE
CALIFORNIA ONE HOUR STANDARD FOR N02 WAS EXCEEDED IN 1973. . 30
13 THE DIFFERENCE IN PERCENT OF THE NUMBER OF DAYS ON WHICH
THE CALIFORNIA ONE HOUR STANDARD FOR N02 WAS EXCEEDED
IN 1973, WEEKDAY MINUS WEEKEND ............... -31
14. THE NET INFLUX OF POPULATION (WORKERS) DURING WORKING
TIME IN 1970
15 PERCENT OF DAYS ON WHICH THE NAAQS FOR OXIDANT WAS
EXCEEDED DURING FIVE 2-YEAR PERIODS
16 AVERAGE DURATION (HOURS) ON DAYS WHEN THE NAAQS FOR OXIDANT
WAS EXCEEDED DURING FIVE 2-YEAR PERIODS .......... 34
IX
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LIST OF FIGURES (Cont'd)
TITLE PAGE
17. CHANGES IN POPULATION EXPOSURE TO 03 DURING FIVE 2-YEAR
PERIODS 35
18. THE AVERAGE VALUE AND THE RANGE OF VALUES FOR EIGHT
MONITORING STATIONS SHOWING N0? TRENDS IN ANNUAL MEAN
CONCENTRATIONS 36
19. N02 ANNUAL MEAN CONCENTRATION 37
20. CHANGES IN THE TOTAL POPULATION EXPOSURE TO N0? DURING FIVE
2-YEAR PERIODS 38
21. PERCENT OF DAYS ON WHICH THE CALIFORNIA 1-HR STANDARD FOR
N02 WAS EXCEEDED DURING FIVE 2-YEAR PERIODS 39
22. AVERAGE DURATION (HOURS) ON DAYS WHEN THE CALIFORNIA ONE
HOUR STANDARD WAS EXCEEDED DURING FIVE 2-YEAR PERIODS .... 40
23. CHANGES IN POPULATION EXPOSURE TO N0? DURING FIVE 2-YEAR
PERIODS 41
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LIST OF TABLES
TITLE PAGE
1. Characteristics of Study Areas 5
2. Regionwide Impact of Weekday/Weekend Effect on
Population Exposure to 0 and N09 in 1973 10
/\ £
3. Effect of Population Mobility Consideration on the
Population-at-Risk Indices of All Workers and Total
Population (Percent of Hours Exceeded) 12
4. Regionwide Trend in Average No. of Days NAAQS for QX
was Exceeded and the Average Duration of Excess Air
Pollution in Hours per Day 14
5. Regionwide Trend in Average No. of Days Per Year the
California Standard for N02 was Exceeded and the
Average Duration of Violations in Hours per Day 17
XI
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1. INTRODUCTION
*
This report summarizes the major findings of two related reports
which present the salient results of studies on population exposure to
photochemical oxidants (Ox) and nitrogen dioxide (N02) in the Los Angeles
Basin. The emphasis of this executive summary report is centered on a
description of the results rather than interpretation. At the conclusion
of this project the final report will attempt to interpret the results of
our research with regard to what is known about emission sources, meteor-
ology, air quality, and population distributions in the Los Angeles Basin.
To determine population exposure to air pollution, air quality measure-
ments taken at widely separated monitoring stations were interpolated to
provide the spatial distribution of pollutant concentrations. Demographic
data were merged with the air monitoring data to estimate the short-term
and the long-term concentrations experienced by the Los Angeles population.
The first part of this report examines special features of population
exposure in the Los Angeles Basin using detailed data for 1973. These
features include weekday-weekend differences in air quality and the effec:
of diurnal population mobility on population exposure. The second part of
Horie, Y., A. Chaplin, and E. Helfenbein, "Population Exposure to
Oxidants and Nitrogen Dioxide in Los Angeles, Volume II. Week/Weekend
and Population Mobility Effects," U.S. EPA/OAQPS Publication #EPA-450/3-
77-004b, Technology Service Corporation, January, 1977.
Horie, Y. and A. Chaplin, "Population Exposure to Oxidants and
Nitrogen Dioxide in Los Angeles, Volume III. Long Term Trends, 1965-
1974," U.S. EPA/OAQPS Publication #EPA-450/3-77-004c, Technology Service
Corporation, January, 1977.
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this report describes the spatial change in air quality and the regionwide
trends in population exposure for the 10-year period from 1965 to 1974.
Hourly 0 air quality data and annual mean N02 air quality data are
examined in relation to the primary National Ambient Air Quality Standards
(NAAQS) which are designed to protect the public health. Hourly N02 air
quality data are also examined in relation to the California one-hour Air
Quality Standard.
The remainder of this report is divided into five sections which
describe the methodology and the results. The five sections are:
2.0 A description of the study area,
3.0 A summary of relevant demographic data,
4.0 A summary of the air quality data,
5.0 A detailed analysis of population exposure in 1973, and
6.0 An analysis of trends in air quality and in population ex-
posure over the ten-year period 1965-1974.
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2. DESCRIPTION OF THE STUDY AREA
The regions under study are three subsets of the Los Angeles AQCR. As
shown in Figure 1, the area for which the 1973 analyses were performed dif-
fers only slightly from that of the LA-AQCR. The area for which the QX
trend analyses were performed (as shown by the dark boundary line) is much
smaller than the AQCR, because only in this limited region is the data base
adequate for trend analyses. For a similar reason, the N02 trend analysis
area, denoted by the slanted lines, is even smaller.
Figure 2 shows the locations of the air monitoring stations. Data from
22 stations monitoring 0 and 26 stations monitoring N02 were used for the
/\
1973 analyses. For the 10-year trend study, ten stations monitoring QX and
eight stations monitoring N02 were included in the analyses. Because fewer
N02 stations were included in the trend analysis, the study area for N02
trend analysis is only the Los Angeles county portion of the QX trend anal-
ysis area. Figure 3 illustrates the topographical features of the study
reg i on.
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3. DEMOGRAPHIC DATA
The population and employment statistics prepared by the Southern
California Association of Government (SCAG) and the 1970 census data were
used to develop a demographic network. The demographic network consists
of a number of receptor points at which local population data and local
air quality data are merged to compute population exposure variables. The
air quality of each receptor point is estimated from the actual monitoring
data by spatial interpolation [2].
The SCAG data are reported according to Regional Statistical Areas
(RSA's). One receptor point is assigned to each RSA irrespective of its
population size and land area. An additional receptor point is assigned
for each increment of population by 200,000 or land area by 200 square
miles. A description of the study areas is given below in Table 1.
Table 1. Characteristics of Study Areas
Type of Analysis
1973 analysis
0 trend analysis
/\
N02 trend analysis
estimated population in 1973
estimated population in 1970
Figures 4 and 5 depict the spatial variation of population density and of
employment density over the study region. Figures 6 and 7 present the
Population Size
9,899,814
**
8,548,431
**
6,858,390
Land Area
(square miles)
8612
2316
1509
No. if
Receptors
99
58
45
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percent change that occurred in population and in employment in each RSA
during the 10-year period 1965 to 1974. It can be seen from Figures 4 and
5 that the population density and the employment density are spatially
correlated to each other but the latter is more concentrated around the
downtown Los Angeles area. A comparison between Figures 4 and 5 and Figures
6 and 7 shows that the growth in both population and number of employments
is higher in the fringe areas than the urban core areas of Los Angeles and
Long Beach cities.
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4. SUMMARY OF AIR QUALITY DATA
The national ambient air quality standard (NAAQS) for oxidants (Ox)
is a one-hour average of 160 yg/m3 (~8 pphm). The NAAQS for N02 is an
o
annual arithmetic mean concentration of 100 yg/m (~5 pphm). The California
one-hour standard for N02 is 470 yg/m3 (~25 pphm). The information described
in this report is interpreted with reference to these three standards.
For the 1973 detailed analysis of special features of population
exposure, all of the hourly average and daily maximum hourly average air
quality data available from each air monitoring station in the region were
used to compute percentile concentration statistics. The percentile statistics
of the daily concentrations were made for three time categories: all time,
weekdays, and weekends. In addition, the percentile statistics of the hourly
concentrations were made for two time categories: working time, and non-
working time. Tables Al and A2 give the percent of days per year exceeding
the NAAQS for 0¥ and the California standard for N0? along with the avtr ge
A ~
duration in hours for those days on which the standard was exceeded.
For the ten-year trend analysis, the "Ten-Year Summary of California
Air Quality Data 1963-1972" and its supplements for 1973 and 1974 [4], were
used to develop percentile concentration statistics for five two-year periods:
1965/66, 67/68, 69/70, 71/72, and 73/74. The data were grouped into two-year
periods so that historical continuity could be maintained at a maximum
number of sites. Tables A3 and A4 give the percent of days the standard was
exceeded and the average duration in hours that the violation occurred for
0 and N0?, respectively, during each of these two-year periods. Table A5
X £
lists the annual arithmetic mean concentration of N02 for each of the two-
•
year periods.
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5. POPULATION EXPOSURE ANALYSIS FOR 1973 DATA
Population exposure to air pollution is characterized by using two
variables: the percentage of the population exposed to a pollutant con-
centration above the standard, i.e., the population-at-risk, and the average
percent of time that people in a region are exposed to a pollutant concen-
tration above the standard. These quantities were determined for different
populations (workers and non-workers) and for different time periods (working
time, non-working time, weekday and weekend).
5.1 WEEKDAY/WEEKEND DIFFERENCE IN AIR QUALITY AND IN POPULATION EXPOSURE
Air quality data for 1973 were analyzed to quantify the weekday/weekend
differences [4] in air quality and population exposure. This time period
was selected because it offered the maximum number of monitoring stations
producing a complete year of data.
5.1.1 Weekday/Weekend Difference in QX
Isopleths describing the percentage of days the DX NAAQS is exceedei
are shown in Figure 8. The lowest percent (10% or less) of days exceedir.q
the standard is found in the coastal area and the highest percent (50% or
more) in the inland area. Figure 9 shows isopleths of average duration in
hours for those days on which the standard was exceeded. The average dura-
tion is also the shortest (4 hours per day or less) in the coastal area and
the longest (7 hours per day or more) in the inland area.
Figure 10 presents differences in daily Ox frequency of violation be-
tween weekdays and weekends. It is seen that, in the coastal area, weekends
exceeded the standard more frequently than weekdays while, in the inland
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10
area, the opposite is true. As reported earlier [5], the demarcation at
which weekdays and weekends are equally polluted runs from the north of
Santa Monica to the east of Anaheim via the Los Angeles CBD.
The regionwide weekday/weekend effect on population exposure to Ox
is summarized in Table 2. Indeed daily maximum concentration of QX were
higher on weekends at some coastal stations. However, Table 2 shows
that the population in the study region on the whole receives a fewer per-
cent of both days and hours exceeding the standard on weekends than week-
days .
Table 2. Regionwide Impact of Weekday/Weekend Effect
on Population Exposure to QX and N02 in 1973
Average
Percent of Days Exceeded
Average
Percent of Hours Exceeded
Weekday
Weekend
Weekday/Weekend
Difference
V
30.1
28.6
+1.5
N02
4.4
2.1
+2.3
°x
6.31
5.77
+0.54
N02
0.57
0.18
+0.39
5.1.2 Weekday/Weekend Difference in N02
Isopleths describing the percentage of days the N02 California one-
hour standard is exceeded are shown in Figure 11. Figure 12 shows iso-
pleths of the average duration in hours for those days on which the
standard was exceeded. The highest percent of days exceeding the stan-
dard is found in the areas around the Los Angeles CBD and the lowest
percent is found in the fringe areas.
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11
The spatial distribution of the frequency of N02 short-term violations
is quite similar to that of population density and of employment density
shown in Figures 4 and 5 respectively, in contrast to the spatial distri-
bution of the frequency of 0 short-term violations whose isopleths run
A
approximately parallel to the coast line. The longest average duration
for N02 is found in Orange County. The spatial distributions of the daily
frequency of violation and of average duration in hours for NO^ differ from
those for 0 .
A
Figure 13 presents differences in daily NOp frequency of violation
during weekdays and weekends. It shows that in most of the study region
the N02 air pollution is less intense on weekends than weekdays, although
in Orange county weekends are more polluted than weekdays. From Table 2,
we can see that regionwide N02 air pollution is definitely lower on week-
ends than weekdays.
5.2 EFFECTS OF DAILY POPULATION MOBILITY ON POPULATION EXPOSURE
Daily population mobility was incorporated into the analysis of pop-
ulation exposure to photochemical air pollution in the Los Angeles Basin.
The working population is considered to be the mobile portion of the total
population. The effects of population mobility are examined by accounting
for the difference in exposures for the working population while at their
residence compared with exposure at their place of employment during
working time (weekdays, 7 A.M. - 6 P.M.).
Figure 14 shows that during daytime workers move from their residence
areas (where the highest Ov concentrations as well as the lowest Ov concen-
A A
trations occur) to the business districts (where 0 concentrations are
A
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12
about average). As a result of this population mobility, workers incur
on the average 8% fewer violations above the Ox NAAQS at their place of
employment (Table 3). In contrast to this, workers primarily move from
residential areas of lower N02 concentrations to business districts of
higher NCL concentrations. This means that workers are located in areas
which experience 16% more frequent violations of the California NO,, stan-
dard. Thus, the mobility effect is more prounced for N02 (Table 3).
The regionwide impacts of considering mobility on population expo-
sure for 0 and N0? are summarized in Table 3. Table 3 presents the
/^ ^
average percentage of time that people in the region are exposed to a
concentration above the standard. The mobile population assumption yields
a lower percentage of hours exceeded for GX than the static population
assumption, while for N02 the opposite is true. Since workers constitute
only about 40 percent of the total population, the effects of population
mobility are less pronounced when considered for the total population.
Table 3.
Effect of Population Mobility Consideration on the
Population-at-Risk Indices of All Workers and Total
Population (Percent of Hours Exceeded)
Static Population
Dynamic Population
°x
All
Workers
6.03
5.57
Total
Population
6.16
5.96
N0?
All *•
Workers
0.48
0.57
Total
Population
0.46
0.50
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13
6. TRENDS IN AIR QUALITY AND IN POPULATION EXPOSURE
Trend analyses of the N09 and 0 exposure of the total population
L- X
are based on the static population assumption rather than the daily mo-
bile population analysis. The static population assumption should intro-
duce very little error while yielding great savings in computational
effort. It should be noted, however, that the data used for the trend
analysis do reflect the year-to-year changes in the population distribu-
tion.
6.1 TEN-YEAR TREND FOR 0
A
Isopleth maps depicting percent of days the NAAQS for QX is exceeded
during the five two-year periods, 1965/66, 67/68, 69/70, 71/72, and
73/74 are shown in Figure 15. In 1965/66 more than half of the study
region violated the standard on more than 50% of the days and the rest
of the region at least 20% of the days. In 1973/74, the area in vio'ie^.ion
at least 180 days per year decreased to a small area around Azusa, and an
area in which the standard was violated less than 20% of the days appealed
in the southern half of the region.
The isopleth maps of average number of hours per day above the NAAQS
on days in violation in the five two-year periods are shown in Figure 16.
In 1965/66, the inland areas had an average duration longer than six hours
per day and the coastal areas longer than three hours per day. In 1973/74,
the average durations decreased compared to those in 1965/66 but were
slightly above the average duration in 1971/1972.
Figure 17 depicts the improvements in population exposure to QX over
the 10-year period. Each vertical bar indicates the percentages of the
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14
population who were exposed to a concentration above the NAAQS for various
percentages of days. For example, in the first set of bars, about 53% of
the population were exposed to 1-hour 0 above the NAAQS more than 50% of
A
the days in 1965/1966. In 1973/74, the percentage of the population with
the same exposure dropped to less than 5%. The second group of vertical
bars is prepared for oxidant exceeding a level twice as high as the standard,
while the third group is for three times the NAAQS.
The regionwide trends in population exposure to 0 are summarized in
J\
Table 4. On the average, people in the study region were exposed to a
1-hour concentration above the NAAQS 176 days in 1965/66, 144 days per
year in 1969/70, and 105 days per year in 1973/74. The average duration of
such exposure also decreased from 5.1 hours per day in 1965/66 to 4.6 hours
per day in 1969/70, and to 4.3 hours per day in 1973/74. The trends are
similar for concentrations exceeding twice the standard.
Table 4. Regionwide Trend in Average No. of Days NAAQS for 0 was
Exceeded and the Average Duration of Excess Air Pollution
in Hours per De
Threshold
0 NAAQS
160 yg/m3
(8 pphm)
2X Ox NAAQS
320 pg/m3
(16 pphm)
Average # Bays
Per Year
Avg. Duration
Average # Days
Per Year
Avg. Duration
1965/66
176
5.1
70
3.1
1967/68
162
4.8
59
3.1
1969/70
144
4.6
45
2.8
1971/72
109
3.8
26
2.1
1973/74
105
4.3
26
2.9
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15
6.2 TEN-YEAR TREND FOR NOg
The N02 trends in both the annual mean concentrations and the 99th
percentile concentrations are shown in Figure 18. The vertical bar indicates
the range of values about the average and 99th percentile of one hour concen-
trations observed at the 8 monitoring stations. Although there is no obvious
trend in both the annual mean concentrations and the 99th percentile concen-
trations, the range of individual station values decreases steadily after
1967/68.
Isopleth maps of annual mean N02 concentration are shown in Figure 19.
Almost everywhere over the study region the national air quality standard
o
(100 yg/m ) was violated during the entire 10-year period. However, an air
quality improvement during the later part of the study period can be detected.
For example, during the 1967/68, 69/70, and 71/72 periods, N02 concentration
3
levels higher than 130 yg/m covered the majority of the heavily populated
areas, while in 1973/74 those levels were confined to the San Fernando Valley.
Figure 20 depicts the percentages of the population exposed to var ous
levels of annual mean N02 concentration. For example, the percent of the pop-
o
ulation exposed to 130 yg/m or higher changed from 19% in 1965/66 to 65% in
1969/70, and then back to 33% in 1973/74, indicating a mixed trend in popula-
tion exposure to NO,,. There is a slight degradation at low levels of exposure.
Virtually everyone in the study area was exposed to annual average N02 over
the national standard after 1969.
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16
Isopleth maps of the percentage of days exceeding the California one-
2
hour standard (470 yg/m ), as shown in Figure 21, again indicate a mixed
trend. The area exceeding the standard more frequently than 6% of the days
was approximately matched with the area of Los Angeles city in 1965/66, ex-
tended to almost the entire study region in 1967/68, 69/70, and 71/72, and
was drastically reduced in 1973/74.
The isopleth maps of the average number of hours exceeding the California
one-hour standard per day on days in violation are shown in Figure 22. The
area with an average duration longer than three hours per day was confined to
the north-central part of the San Fernando Valley in 1965/66, extended to the
majority of the study region in 1967/68, 69/70, and 71/72, and shrank to the
Los Angeles downtown area in 1973/74.
Figure 23 shows the percentages of the population exposed to N02 con-
centrations above the California one-hour standard. For example, in 1965/66
9% of the total population was exposed to excessive concentrations on more than
44 days C\z% x 365) per year, while in 1973/74 none of the population was ex-
posed that often.
The regionwide trends in population exposure to N02 are summarized in
Table 5. On the average people in the study region were exposed to a 1-hour
NOp concentration above the California standard 25 days per year in 1965/66,
27 days per year in 1969/70, and 18 days per year in 19/3/74. The average
duration of such exposure changed from 2.6 hours per day in 1965/66 to 3.0
hours per day in 1969/70, and to 2.5 hours per day in 1973/74.
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17
Table 5. Regionwide Trend in Average No. of Days Per Year the California
Standard for NO- was Exceeded and the Average Duration of Viola-
tions in Hours per Day
Threshold
CA. N02 STD
470 yg/m3
(25 pphm)
Index
Average # Days
E-xeeeded/Year
Avg. Duration
1965/66
25
2.6
1967/68
40
3.3
1969/70
27
3.0
T97T/72"
33
3.0
1973/74
18
2.5
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18
7. REFERENCES
1. Zupan, J. M., "The Distribution of Air Quality in the New York
Region," Resources for the Future, Inc., Wash. D.C., 1973.
2. Horie, Y. and A. C. Stern, "Analysis of Population Exposure to
Air Pollution in the New York-New Jersey-Connecticut Tri-State
Region," U.S. EPA Publication No. EPA-450/3-76-027, March 1976.
3. California Air Resources Board, "Ten-Year Summary of California
Air Quality Data 1963-1972," State ot California, The Resources
Agency, January 1974.
4. Elkus, B., and K. R. Wilson, "Air Basin Pollution Response Func-
tion: The Weekend Effect," University of Calif., San Diego, 1976.
5. California Air Resources Board, "Weekend Oxidant Concentrations,"
in California Air Quality Data, 6(2) p. 5, July-Sept., 1974.
-------
17
Table 5. Regionwide Trend in Average No. of Days Per Year the California
Standard for NOp was Exceeded and the Average Duration of Viola-
tions in Hours per Day
Threshold
CA. N02 STD
470 yg/m3
(25 pphtn)
Index
Average # Days
E-xceeded/Year
Avg. Duration
1965/66
25
2.6
1967/68
40
3.3
1969/70
27
3.0
1971/72
33
3.0
1973/74
18
2.5
-------
18
7. REFERENCES
1. Zupan, J. M., "The Distribution of Air Quality in the New York
Region," Resources for the Future, Inc., Wash. D.C., 1973.
2. Horie, Y. and A. C. Stern, "Analysis of Population Exposure to
Air Pollution in the New York-New Jersey-Connecticut Tri-State
Region," U.S. EPA Publication No. EPA-450/3-76-027, March 1976.
3. California Air Resources Board, "Ten-Year Summary of California
Air Quality Data 1963-1972," State ot California, The Resources
Agency, January 1974.
4. Elkus, B., and K. R. Wilson, "Air Basin Pollution Response Func-
tion: The Weekend Effect," University of Calif., San Diego. 1976.
5. California Air Resources Board, "Weekend Oxidant Concentrations,"
in California Air Quality Data. 6(2) p. 5, July-Sept., 1974.
-------
San Bernardino
County
Miles
Trend Analysis for Ov
1973 Analysis x
County Boundary
AQCR
/////// Trend Analysis for NO
i .
Figure 1. BOUNDARIES SHOWING TREND ANALYSIS AREA, 1973
r- AREA> nND LOS ANGELES AQCR.
-------
I—
• TREND ANALYSIS
o+« 1973 ANALYSIS
\
\ LOS ANGELES COUNTY
\
VENTURA COUNTY
4
\ O
\
'i
r1 i
10
o
1. Ojai
2. Camarillo
3. Point Mugu
4. Newhall
5. Reseda
6. West L.A.
7. Lennox
8. Burbank
9. Los Angeles
10. Pasadena
11. Long Beach
12. Azusa
13. Whittier
14. La Habra
15. Anaheim
16. Costa Mesa
17. Pomona
18. Chino
19. El Toro
20. Upland-ARB
21. Upland
22. Norco
23. Riverside
24. Riverside
25. San Bernardino
26. Redlands
u
SAN BERNARDINO COUNTY
25
.020 * 26
' 1 i
O23
T 22 O24
_.i o
ro
O
•
ORANGE COUNTY
v
RIVERSIDE COUNTY
Figure 2. LOCATION OF MONITORING STATIONS
-------
K>
Figure 3. TOPOGRAPHICAL FEATURES OF THE LOS ANGELES BASIN.
-------
100-1 ,000
1,000 - 10,000
> 10,000
LOS ANGELES AIR BASIN
Figure 4. POPULATION DENSITY IN PERSONS PER SQUARE MILE IN 1970.
-------
1
CD
CD
m
o
Tl
-a
OO
c/
-o
i—
O
m
o
on
XD
c:
—I
O
-------
LOS ANGELES AIR BASIN
Figure 6. PERCENT CHANGE IN POPULATION 1965 TO 1975.
-------
< 0
0 5 10
miles
LOS ANGELES AIR BASIN
Figure 7. PERCENT CHANGE IN EMPLOYMENT FROM 1965 TO 1975.
-------
ro
CT1
Figure 8. ISOPLETHS OF PERCENT OF DAYS ON WHICH THE NAAQS FOR OXIDANT WAS EXCEEDED IN 1973.
-------
Figure 9. ISOPLETHS OF AVERAGE DURATION (HOURS) ON DAYS WHEN THE NAAQS FOR OXIDANT
WAS EXCEEDED IN 1973.
-------
ro
lea
Fiaure 10 THE DIFFERENCE IN PERCENT OF THE NUMBER OF DAYS ON WHICH THE NAAQS FOR OXIDANT
FngurelO. ™t j"'":™ ^ Ig73> WEEKDAy MINU$ WEEKEND. (DARK LINE EQUALS ZERO PERCENT.)
-------
Figure 11 . ISOPLETHS OF PERCENT OF DAYS ON WHICH THE CALIFORNIA ONE HOUR STANDARD FOR N02
WAS EXCEEDED IN 1973.
-------
co
o
Figure 12. ISOPLETHS OF AVERAGE DURATION (HOURS) ON DAYS WHEN THE CALIFORNIA ONE HOUR STANDARD
FOR N02 WAS EXCEEDED IN 1973.
-------
Figure 13. THE DIFITRENCE IN PERCENT OF THE NUMBER OF DAYS ON WHICH THE CALIFORNIA ONE HOUR
STANDARD FOR NO, WAS EXCEEDED IN 1973, WEEKDAY MINUS WEEKEND. (DARK LINE EQUALS
ZLRO PERCENT.) L
-------
WORKERS PER SQUARE MILE
Ficmre 14 THE NET INFLUX OF POPULATION (WORKERS) DURING WORKING TIME IN
' PERSONS PER SQUARE MILE IN 1970
-------
1965/1966
1967/1968
1969/1970
1971/1972
1973/1974
Fiqure 15 PERCENT OF DAYS ON WHICH THE NAAQS
' FOR OXIDANT WAS EXCEEDED DURING
FIVE 2-YEAR PERIODS.
< 20%
20 - 50%
> 50%
-------
1965/1966
1967/1968
1971/1972
1973/1974
Figure 16. AVERAGE DURATION (HOURS) ON DAYS
WHEN THE NAAQS FOR OXIDANT WAS
EXCEEDED DURING FIVE 2-YEAR PERIODS,
< 3 HRS
3 - 5 HRS
> 5 HRS
-------
VD 00 O
P IN PERCENT
P < 5
5 £ P < 10
10 £ P < 20
20 <_ P < 50
50 < P
Example: In 1965/1966 about 53% of the
total population was exposed to U3
leves above the NAAQS (8 pphm for one
hour) more than 50% of the days per year
In the same period about 44* of the total
population was exposed to 03 levels at
twice the NAAQS for at least 20^ of the
days per year, but less than 50/0 of the
days per year.
OJ
CJ1
3 x standard
1 x standard 2 x standard
Figure 17. CHANGES IN POPULATION EXPOSURE TO ^ DURING FIVE 2-YEAR PERIODS.
-------
36
30 -
CALIFORNIA 1-HR
STANDARD ,
25pphm = 470yg/m':
20 ~
-
600
-500
-1- o
-400
-300
o.
D.
00
O
10 -
EPA STANDARD
ANNUAL AVERAGE
100yg/ni3 = 5.3pphm
•>
I t *
I
.200
-150
•TOO
. 50
en
3.
CM
O
! , , 1 i
65/66 67/68 69/70 71/72 73/74
Figure 18., THE AVERAGE VALUE AND THE RANGE OF VALUES FOR EIGHT MONITORING
STATIONS SHOWING N02 TRENDS IN ANNUAL MEAN CONCENTRATIONS (LOWER
SEGMENT) AND IN 99th PERCENTILE CONCENTRATIONS'(UPPER SEGMENT).
-------
1965/1966
r~
1967/1968
1973/1974
Figure 19. N02 ANNUAL MEAN CONCENTRATION
(yg/rri ) FOR FIVE 2-YEAR PERIODS.
_3
1969/1970
< TOO yg/m"
100 - 130 yg/m'
> 130 yg/rrT
1971/1972
I
-------
i.o r
N02 ANNUAL MEAN I
in yg/nr
ONCENTRATION
[N02] < TOO
100 <_ [N02] < 130
130 < [N02]
Example: During 1965/66 about 91% of the population
was exposed to N0£ concentration between 100 and
130 yg/iA About 19% were exposed to N02 concen-
trations above 130 ug/m3. The NAAQS is 100 yg/nr3
annual average.
00
Figure 20. CHANGES IN THE TOTAL POPULATION EXPOSURE TO N02 DURING FIVE 2-YEAR PERIODS.
-------
1965/1966
1971/1972
1969/1970
L
1973/1974
Figure 21 PERCENT OF DAYS ON WHICH THE
' CALIFORNIA 1-HR STANDARD FOR N02
WAS EXCEEDED DURING FIVE 2-YEAR
PERIODS.
< 6%
6-12%
> 12%
-------
1965/1966
1967/1968
1971/1972
1973/1974
Figure 22. AVERAGE DURATION (HOURS) ON DAYS
STANDARD WAS EXCEEDED DURING
FIVE 2-YEAR PERIODS.
< 2 MRS
2 - 3 HRS
> 3 HRS
•P-
O
1969/1970
-------
PERCENT OF TOTAL POPULATION
ro
GO
o
X
-o
o
oo
o
z
o
o
c:
ro
i
m
70
-o
m
70
*-H
o
o
o
f*
•73
O
m
x
o
-------
A-l
APPENDIX A . SUMMARY OF AIR QUALITY DATA OBSERVED
AT MONITORING STATIONS
Table Al. Percent of Days the NAAQS for 0 was Exceeded and the
X
Average Duration in Hours (x.x) in 1973.
Table A2. Percent of Days the California Standard for N02 was
Exceeded and the Average Duration in Hours (x.x) in
1973.
Table A3. Percent of Days the NAAQS for 0 was Exceeded and the
A
Average Duration in Hours (x.x) for Each of the Five
2-Year Periods.
Table A4. Percent of Days the California Standard for N02 was
Exceeded and the Average Duration in Hours (x.x) for
Each of the Five 2-Year Periods.
Table A5. Annual Arithmetic Mean Concentrations for N02 in Each
of the Five 2-Year Periods.
-------
CVJ
•a:
(17*9
u'e
(9*9
(9'f
(S'fr
(1*9
(£'17
C9*<7
(8*t7
(l-9
(9*9
(S'S
(f7|S
(9*f7
C6'2
0*6?
9»S
S'frfr
&§S£
0'£
l*Z?
£*££
o's?
0»q?
0*17 f?
0*t7t7
SM£
9ȣT
«*ST
O'S?
OM?
fO'9
(1*8
Cfr!£
(9*5
(5*9
(S*f7
(i*9
(£'f7
(f!*5
(0*9
(5*4
U'9
(0*i
(5*9
(0*9
(O'f
(O't;
(0*£
2*t?q
J*I7»
I'A?
S'S
O'Ofi
S fr b
6'£
O'i?
^•8f
? * S" C
»7%£
S* IT
<3* I?
17*99
£* rt *_
T V
0*05
i 4 t. ^~
Ci O I*
b*/.
8%t
/.*6e
t7*et
if
11 V M f , "--I M
I SIM
•v'l
i vru
7
I?
61
/ t
T
0
b
P
Z
n
i
V I S
SVM
M
xn
(X*X) SrtOfjM Nil
jo
t*
-------
UtfLE A*.
*AS t
1
d
3
a
b
to
7
6
9
10
1 I
12
li
15
lo
17
18
20
•T IJF OAV5 THE CALIFORNIA STANDARD F OK N02
A\f, T^t AVERAGE DURATION IN HOOPS (X.X) IN 197,
S 1 A i TH-M
A-~4 An£ JM
LA HA^RA
CU&TA MESA
Ei, (nun
SAN REHNAGIrv.)
RfcULANOS
c' H i N Q
UPLAND,CIV 1C CT*
UPt-AND-AKij
UJAI
MUGU
AZUbA
BU^BANK-RALM
^ts r L»A,»^s"
LUW* BEACH
w H i r T i E H
PASADENA-WALNUT
AE.iK*PAY
2,a f 5,0)
3,a ( a.fe)
1,1 ( 1,1)
.7 ( 1,9)
0,0 ( 0,0)
0,0 ( 0,0)
.6 ( 1,6)
0,0 ( 0.0)
0.0 f 0,0)
.7 f 1,9)
,9 f 4.0)
«,0 ( 0,0)
( 0,0)
( 0,0)
C 1,7)
( 3.3)
( 1.3)
( 3.1)
( 2 ^)
f 2!*)
f 34)
( 2)2)
0,0
0,0
t.l
5,7
«,3
9,2
«.5
6.7
3 4
2J3
6,4
3,4 ( 3.8)
0,0 ( 0,0)
2.8 ( 2.2)
WEEK-END
• «••*
6,0
( 1,9)
( 1,7)
( 0,0)
( 0,0)
( 0,0)
( 2.7)
f 0,0)
( 0,0)
( 0,0)
( 0,0)
C 0,0)
( 0,0)
( 0,0)
( 0,0)
1.6
0,0
0,0
0,0
1 ,"5
0,0
0,0
0,0
0,0
o.o
0,0
0,0
0,0
1.0 ( l.«)
0,0 ( 0,0)
1.3 C 2,6)
3,3 ( 1.5)
3,5 ( 3,1)
0,0 C 0,0)
0,0 ( 0,0)
0,0 ( 0,0)
4,7 ( 1,9)
0,0
I
CO
0,0
0,0)
0,0)
-------
TABLE A3, PERCENT o DAYS THE NAAQS FOR ox WAS EXCEEDED AND THE AV
DURATION IN huu«S (X,*) f-'UR EACH OF THE Fivt 2-VEAR PERIODS.
NO, STATION 1965/66 lt6|/68 If6*/70
1
8
4
5
6
7
8
9
10
ANAHEJM
A2USA
BURBANK.PAIM
LENNOX
LQNli BEAGH
I, A, DOWNTOWN
PQM1JKIA
RESEDA
SAN BERNADINO
WEST L.A.-WSTWOOD
69U
61.0
27 ,9
22^3
62,1
65,4
4} J
53!3
(7.6)
(6. a)
(3.f)
(3.6)
(6^6)
(6!o)
(5.1 )
IS. 4 (3,8) 25,0
68,7 (7
64.0 (6
25.0 (3
17,0 (2
55.1 (5
6
-------
TA8U A«. PCRCfeNT OF DAYS 1 Ht CALIFORNIA 8T
T>fc AVFRAGE DURATIPN IN HIJUWS fX.X) FOR
NO,
1
2
i
4
5
6
STATION
AZUSA
BURBANK-PALM
LENNOX
LONG BEACH
l,A, DOWNTOWN
POMONA
RESEo A
WEST L.A.-WSTWOQD
196S/66
;a (?
7,4 (3
5*0 (2
5.0 C?
U;6 (2
1.3 (1
242 (2
e.d (2
.0)
.&)
.1)
.9)
• $)
.1)
.1)
.7)
ANDARD I
EACH UF
1967/68
«. a
19.8
14.4
14.4
fO.9
4 7
5 4
10.*0
(l.T)
(4,5)
(4,3)
(3.4)
(2,1)
(3.0)
(3.6)
(2,4)
!'OR Noa
THE FI
WAS kXCEEDED AND
V£ 2-YEAR PfcRIQDS,
1*69/70
2.3
16.9
5,5
10.7
7*6
4.6
3.0
7.1
(3.2)
(3.9)
(2.3)
(3.2)
(3,0)
(3,4)
(2.9)
(2.3)
19T1/7J
3.9
11. e
6.1
8.?
14.6
5.9
5.%
10.0
(8.7)
(3.2)
(1,0)
(3,f2)
(1.4)
(2,9)
(2.4)
1973/74
5J
6.1
4.2
5.6
* •
6.1
2.1
8.*3
(2.1)
(2.0)
(2.1)
(1 .6)
(3.3)
(2.4)
( 1 ,8)
(2,4)
-------
TABLE A5. ANNUAL ARITHMETIC MEAN CONCENTRATIONS FOR N02
IN EACH OF THE FIVE 2-YEAR
NO.
STATION
1965/66
1967/69
1969/70
1971/72
1973/74
1
I
I
4
*
6
7
8
AZUSA
BURBANK*PAlM
LENNOX
LONG BEACH
L.A, OOrtNTQWN
POMONA
RESEDA
WEST L.A,«*WSTWOOD
«.«5
6,90
6. IS
5.90
7. as
6. SO
5,00
6.10
a. so
9.80
7.50
7.90
6.65
7,45
6.15
6.65
*,70
9,40
6.75
7,70
7,00
8,05
6.95
6.55
6,eo
8.5b
6.65
6,«5
8,45
7.75
7.00
6.90
6,2k
7,25
6.19
6,75
7,05
7,05
6.05
7,05
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/3-77-004a
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Population Exposure to Oxidants and Nitrogen Dioxide
in Los Angeles Volume I: Executive Summary
5. REPORT DATE
January 1977
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Yuji Horie, Anton S. Chaplin, Neil H. Frank, and
William F. Hunt, Jr.
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
10. PROGRAM ELEMENT NO.
2AF643
11. CONTRACT/GRANT NO.
68-02-2318
12. SPONSORING AGENCY NAME AND ADDRESS
Technology Service Corporation
2811 Wilshire Boulevard
Santa Monica, California 90403
13. TYPE OF REPORT AND PERIOD COVERED
contract, re
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A new methodology was developed to characterize population exposure to air
pollution and was applied to the analyses of two photochemical pollutants in the
Los Angeles Basin -- Ox and NO?.
An analysis was made on the 1973 air quality and population data to examine
the weekend effect and the population mobility effect on population exposure to
these two pollutants.
The methodology was applied to the air quality and population data for the
five 2-year periods from 1965/66 to 1973/74 to determine the trends in air quality
and in population exposure to Ox and N0£.
The important results of the study are described in the section called
"Highlights" presented as a preface to this report.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Photochemical Air Pollution
Air Quality Monitoring
Population Exposure
Data Analysis
Air Quality Trend
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
61
Unlimited
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
------- |