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STATE OF CALIFORNIA 

SUPPLEMENTAL INFORMATION FOR 

RECOMMENDED LEAD NONATTAINMENT AREA 

SOUTH COAST AIR BASIN PORTION OF LOS ANGELES COUNTY

EIGHT FACTOR ANALYSIS 

INTRODUCTION 

This document provides additional justification for recommending only the South 

Coast Air Basin portion of Los Angeles County be designated as nonattainment 

for the 2008 lead national ambient air quality standard. Specifically, the following 

sections address the eight factors U.S. EPA recommends for evaluating lead 

area designations. 

ANALYSIS 

 Jurisdictional Boundaries

As shown in Figure 1, Los Angeles County is divided between two air basins. 

The southern two-thirds of the County is located in the South Coast Air Basin 

(South Coast) and falls under the jurisdiction of the South Coast Air Quality 

Management District (South Coast AQMD or District). The northern third of the 

County is located in the Mojave Desert Air Basin (Mojave Desert) and falls under 

the jurisdiction of the Mojave Desert Air Quality Management District. Pollutant 

concentrations are substantially higher in the South Coast portion of the County 

because several significant lead-related stationary sources are located there, in 

the City of Commerce, the City of Industry, Santa Fe Springs, and Vernon. As a 

result, the South Coast AQMD has implemented rigorous, source-specific, 

emissions control requirements. The jurisdictional differences, along with the 

disparity among emissions sources and other factors, justify limiting the lead 

nonattainment area to the South Coast portion of Los Angeles County. 
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FIGURE 1 

LOS ANGELES COUNTY 

 Air Quality Data

Mobile sources were once the major source of lead emissions in California, 

contributing over 90 percent of ambient lead concentrations. Since the 1970s, 

federal and State regulations have virtually eliminated lead from gasoline sold in 

the State, except for very limited use in general aviation applications. Figure 2 

shows the dramatic decrease in ambient lead concentrations since 1975. Values 

plotted in Figure 2 are representative of the South Coast, which generally has the 

highest lead concentrations in the State. Although lead from gasoline no longer 

poses an air quality problem, lead emissions from remaining industrial sources, 

and potentially from general aviation airports, may still pose “hot spot” problems 

at isolated South Coast locations. Such sources are not reflected in Figure 2. 

Figure 3 compares maximum 24-hour measured lead concentrations in the South 

Coast portion of Los Angeles County with those in the Mojave Desert portion. 

Although the 24-hour concentrations are not comparable with the federal lead 

standard, they provide an indication of the differences in ambient concentrations. 

Data for the Mojave Desert portion of the County are available only through 

1986, when lead sampling was discontinued at the Lancaster site because 

concentrations were very low. Data in Figure 3 represent neighborhood scale 

sites, and concentrations in the South Coast were, on average, four and a half 

times the level of concentrations in the Mojave Desert. In terms of the current 

0.15 micrograms per cubic meter (μg/m3

) federal standard, the highest 

three-month average concentration at Lancaster during 1986 was 0.126 μg/m3, 
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which is below the federal standard. In contrast, the highest three-month 

average for the South Coast portion of the County was 0.443 μg/m3

, a value that 

exceeds the standard and is three and a half times the value for Lancaster. 

Based on data for 2005 through 2007, the most recent complete three-year 

period for which data area available, design values for the continuing network of 

FIGURE 2 

MAXIMUM 30-DAY AVERAGE LEAD CONCENTRATIONS IN CALIFORNIA 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

1976197819801982198419861988199019921994199619982000200220042006

Year

30-Day Average Lead (ug/m3)

FIGURE 3 

MAXIMUM 24-HOUR LEAD CONCENTRATIONS IN THE SOUTH COAST AND 

MOJAVE DESERT PORTIONS OF LOS ANGELES COUNTY 

0

2

4

6

8

10

12

14

16

1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986

Year

Lead Concentration (ug/m3)

South Coast Mojave Desert
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neighborhood scale sites in the South Coast portion of the County are now all 

below the federal standard, ranging from less than 0.01 μg/m3

 to 0.03 μg/m3. 

Based on the continuing large differences in emissions, we expect the 

discrepancy in ambient concentrations in the South Coast and Mojave Desert 

portions of Los Angeles County still exists. 

Although concentrations at all of the South Coast neighborhood scale sites meet 

the standard, concentrations measured near lead-related stationary sources do 

not. To address this hot spot problem, the South Coast AQMD established a 

network of source-specific lead sampling sites in the early 1990s and has 

expanded the network over the years. A number of these source-oriented sites 

were established as part of the District’s Rule 1420 -- Emissions Standard for 

Lead. The samplers are located at or beyond the property line of lead-related 

facilities, and they comply with U.S. EPA siting and operating criteria. Lead 

samples are generally collected on a 1-in-6 day schedule, although samples are 

collected more frequently at sites with the highest concentrations. 

Design values for the affected facilities are summarized in Table 1. Based on 

these data, the design value for the South Coast portion of Los Angeles County 

is 2.49 μg/m3

, which exceeds the 0.15 μg/m3 federal lead standard. Although the 

design value is much higher than the 2008 federal lead standard, values for the 

District’s other source-oriented sites surrounding the Exide facility are lower, with 

maximum 3-month averages ranging from 0.03 μg/m3

 to 0.55 μg/m3. Although 

one of these values also exceeds the standard, both values are significantly 

lower than the high concentration. In addition, concentrations at these other sites 

decrease with distance from the Exide facility, confirming the rapid drop in lead 

concentrations with distance from a source. This relationship provides additional 

support for limiting the size of the nonattainment area. 

 

TABLE 1 

LEAD DESIGN VALUES FOR 

SOUTH COAST SOURCE-ORIENTED MONITORS 

Facility 

Name City Monitor 3-Month Period 

Lead 

Design 

Value* 

Exide 

Technologies

City of 

Commerce 

LA Paper Box, 

61st Street 

Jan-Mar 

2006 

0.14 

μg/m3* 

Quemetco, 

Inc. City of Industry Closet World, 500 S. 7th Street 

Jan-Mar 

2006 

0.09 

μg/m3

Trojan 

Battery Co. Santa Fe Springs Uddeholm,9331 Santa Fe Springs Road 

May-Jul 

2007 

0.18 

μg/m3

Exide 

Technologies Vernon Rehrig-Pacific Street Jan-Mar 

2008 

2.49 

μg/m3

* 

* Data available for LA Paper Box monitor from January 2006 through May 2006 only. Data available for Closet World 

monitor from January through December 2006 and October through December 2008. Data available for Rehrig-Pacific 

Street monitor from mid-November 2007 through mid-July 2009. 
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Emissions Data and Level of Emissions Control

As shown in Table 2, there are significant differences between lead emissions in 

the South Coast and Mojave Desert portions of Los Angeles County. In 

combination, sources in the South Coast portion of the County emit nearly 

three times more lead than sources in the Mojave Desert portion of the County. 

When looking only at stationary sources, emissions in the Mojave Desert portion 

of the County are less than 1 percent of the South Coast value. In addition, the 

Air Resources Board’s emissions inventory indicates there are no stationary 

sources or general aviation airports located in the Mojave Desert portion that 

come close to meeting the 0.5 ton per year threshold of concern established by 

U.S. EPA. While the Exide facility and several general aviation airports in the 

South Coast portion of the County exceed the 0.5 ton per year threshold 

U.S. EPA is currently considering (only Exide Technologies and Van Nuys Airport 

exceed 1 ton/year), the closest one is more than 20 miles from the South CoastMojave Desert air basin boundary. Given the rapid drop in lead concentration 

with distance, the South Coast facilities do not have any measurable impact on 

concentrations in the Mojave Desert portion of the County. 

 

TABLE 2 

LEAD EMISSIONS IN THE SOUTH COAST AND MOJAVE DESERT

PORTIONS OF LOS ANGELES COUNTY 

Emissions 

Category 

Los Angeles County 

South Coast Portion 

(tons / day ) 

Los Angeles County 

Mojave Desert Portion 

 (tons / day) 

Stationary 4.45 0.03 

Area-wide 13.63 6.59 

On-Road Mobile 0.20 0.01 

Other Mobile 0.09 0.34 

TOTAL 18.37 6.97 

In September 1992, the South Coast District adopted Rule 1420, which is 

specifically aimed at reducing lead emissions from non-vehicular sources. 

Rule 1420 (Emissions Standard for Lead) applies to all facilities that use or 

process materials containing lead, including primary or secondary lead smelters, 

foundries, lead-acid battery manufacturers or recyclers, as well as facilities that 

produce lead-oxide, brass, and bronze. The Rule has been, and will continue to 

be, very effective in dealing with high, facility-related lead concentrations, and 

forms the basis of the District’s lead attainment strategy. This type of rule is not 

warranted in the Mojave Desert portion of the County because of the lack of lead 

sources and measurable impact. 
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Population Density, Degree of Urbanization, and Expected Growth 

Similar to air quality and emissions, there are vast differences between the 

population and degree of urbanization in the two portions of Los Angeles County. 

Based on estimates for 2010, the highly urbanized South Coast portion of the 

County has a population of more than 10 million, compared with a population of 

328,000 in the Mojave Desert portion. This means that nearly 97 percent of the 

County population lives in the South Coast portion, compared with only 3 percent 

in the Mojave Desert portion of the County. In terms of urbanization, the South 

Coast portion of Los Angeles County is part of the largest metropolitan area in 

California. In contrast, the Lancaster-Palmdale area is the only urbanized area in 

the Mojave Desert portion of the County. In terms of size, the South Coast 

portion of Los Angeles County is a little more than one and a half times larger 

than the Mojave Desert portion (2538 square miles versus 1522 square miles). 

However, the population density is 3,992 people per square mile, compared with 

only 216 people per square mile in the Mojave Desert portion. 

Over the last decade, the South Coast and Mojave Desert portions of 

Los Angeles County have realized similar growth rates, with population in both 

areas showing a seven percent increase from 2000 to 2005 and a two percent 

increase from 2005 to 2010. These trends are expected to continue, thereby 

maintaining the significant differences in population between the two sub-county 

areas. 

Geography and Meteorology

Meteorological conditions in the South Coast and Mojave Desert portions of 

Los Angeles County are substantially different. The South Coast portion is 

bounded by the Pacific Ocean, which makes for a more temperate climate with 

cooler temperatures and a diurnal pattern of on-shore / off-shore air flow. 

Temperatures generally average in the 70s during the summertime and the 50s 

during the wintertime. Average annual precipitation is about 15 inches per year. 

In contrast to the coastal area, the Mojave Desert portion of Los Angeles County 

is a high desert area with average temperatures in the 80s during summer and 

the 40s during the winter. This desert portion of the County receives half as 

much rainfall, averaging about 7 inches per year. 

The South Coast portion of Los Angeles, where the major lead emissions 

sources are located, is surrounded by mountains which act as barriers to airflow 

between the South Coast and Mojave Desert (refer to Figure 1). Although there 

are a limited number of gaps in these mountains where transport has been 

documented, transport of lead emissions from the South Coast into the Mojave 

Desert is highly unlikely, given the weight of lead particles and the rapid 

decrease in concentration with distance from a source. As a result, emissions 

sources in the South Coast are not expected to have an impact on lead 

concentrations in the Mojave Desert portion of the County. 
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SUMMARY AND RECOMMENDATION 

The South Coast and Mojave Desert portions of Los Angeles County are two 

distinct areas. The highly urbanized South Coast portion is primarily a coastal 

area with a high population density and a concentration of several lead-related 

processing facilities that have the potential to violate the federal lead standard. 

In contrast, the Mojave Desert portion of the County is a sparsely populated high 

desert area that lacks any notable lead emissions sources. 

Because of these differences, the lead air quality problem in the South Coast 

portion of the County is much more significant than in the Mojave Desert portion. 

Even so, lead concentrations exceeding the federal standard are found only near 

the lead-related facilities that are generally located in the coastal plain area of the 

South Coast. Lead measurements show these concentrations decrease rapidly 

with distance from the source, and transport of lead particles or pollutants from 

the South Coast to the Mojave Desert is not expected to occur. The two areas 

are separated by mountains, and although there are some documented transport 

routes, the heavy weight of lead particles and the quick decrease in 

concentration with distance from the source make any measurable transport 

impact extremely unlikely. 

In terms of air quality regulation, the two County portions fall under the 

jurisdiction of two separate air pollution control districts. The primary strategy for 

dealing with the high concentrations in the South Coast portion of Los Angeles 

County is the South Coast District’s Rule 1420, which has been effective in 

reducing source-specific emissions and resulting high concentrations. This 

strategy will continue to address violations of the federal lead standard. 

Rule 1420 has no application in the Mojave Desert portion of the County because 

there are no sources. 

Based on the previous analyses, the Air Resources Board recommends that 

U.S. EPA limit the extent of the federal lead nonattainment area to the portion of 

Los Angeles County located in the South Coast Air Basin.