CHAPTER 1 

INTRODUCTION 
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Chapter 1. Introduction 

1.1. Background 

The South Coast Air Basin (Basin), a highly urbanized area, is home to about 16 million people 

who own and operate about 11 million motor vehicles and contains some of the highest 

concentrations of industrial and commercial operations in the country. It also has the poorest air 

quality in the U.S. In 1986, SCAQMD conducted the first MATES Study to determine the 

Basin-wide risks associated with major airborne carcinogens. At the time, the state of 

technology was such that only ten known air toxic compounds could be analyzed. In 1998, a 

second MATES Study (MATES II) represented one of the most comprehensive air toxics 

measurement programs conducted in an urban environment. MATES II included a monitoring 

program of 40 known air toxic compounds, an updated emissions inventory of toxic air 

contaminants, and a modeling effort to characterize health risks from hazardous air pollutants. 

Since these studies were conducted, several emissions control programs have been implemented 

at the national, state, and local levels; and toxics emissions have been declining. However, at the 

community level, there is heightened awareness of toxic air contaminant exposures. There are 

also environmental justice concerns that programs designed to reduce emissions may not be 

effective in reducing risks from toxic air contaminants in certain areas, particularly in 

communities with lower income or multiple sources of air toxics. 

In September 2003, the SCAQMD Governing Board approved several enhancements to the 

District’s Environmental Justice Program. Initiative I-5 of these enhancements called for a oneyear sampling program for air toxics. Staff initiated the MATES III Study in April 2004, to 

provide current data on air toxic levels and exposures, address environmental justice issues, 

establish an updated baseline of toxic emissions, exposures, and risk levels. 

During the fall and winter of the study, there were unusual weather patterns that resulted in a 

near record rainfall in the Basin. To determine if these weather patterns affected the ambient 

levels of air toxics, the study was extended to two years through March, 2006. In this report the 

two years will be referred to as MATES III Year One (year 1) and MATES III Year Two (year 

2). 

1.2. Objective 

The objective of MATES III was to characterize the ambient air toxic concentrations and 

potential exposures in the Basin. This project included two years of ambient monitoring for air 

toxics. The project developed an updated toxics emissions inventory and conducted air 

dispersion modeling to estimate ambient levels and the potential health risks of air toxics. 

It is anticipated that the results of this study additionally would serve to inform an update of the 

District’s Air Toxics Control Plan. 

This study focuses on the carcinogenic risks from exposures to air toxics. It does not include an 

analysis of noncancer mortality from exposure to particulates. An analysis of mortality and other 

health effects from exposure to particulates was conducted as part of the 2007 AQMP. 

The results of this effort can determine the spatial concentration pattern of important hazardous 
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air pollutants in the Basin, assess the effectiveness of current air toxic control measures, provide 

trend data of air toxic levels, and be used to update and develop appropriate control strategies for 

reducing exposures to toxics associated with significant public health risks. 

There are three components to the study, as listed below: 

• Air Toxics Monitoring and Analyses 

• Emissions Inventory Enhancements 

• Air Toxic Modeling and Risk Assessments 

These components are further described in the chapters that follow. 

1.3. Estimates of Risks 

A health risk assessment evaluates the potential health impacts from exposures to substances 

released from a facility or found in the air. These assessments provide estimates of potential 

long-term cancer and noncancer health risks. The assessments do not collect information on 

specific individuals but are estimates of potential effects in a population at large. 

Potential health risks were estimated using methodology consistent with the procedures 

recommended in the 2003 OEHHA “Air Toxics Hot Spots Program Guidance Manual for 

Preparation of Health Risk Assessments” (Guidance Manual). As discussed in the Guidance 

Manual, the risk assessment process generally consists of four parts, namely hazard 

identification, exposure assessment, dose response assessment, and risk characterization. The 

risk assessment steps, as applied in this study, are briefly summarized below. 

Hazard Identification 

Hazard identification involves determination of whether a hazard exists; and, if so, if the 

substance of concern is a potential human carcinogen or is associated with other types of adverse 

health effects in humans. For this study, the list of air toxics in the OEHHA Guidelines was used 

in conjunction with information on ambient levels of air toxics from previous studies, as well as 

input from the Technical Advisory Group, to determine which substances on which to focus for 

this assessment. This list is provided in Appendix I. 

Exposure Assessment 

The purpose of an exposure assessment is to estimate the extent of public exposure for a 

substance. This can involve quantification of emissions from a source, modeling of 

environmental transport and fate, and estimation of exposure levels over some period of time. In 

this study, annual averages of the air toxics of concern were estimated in two ways. For the 

fixed site monitoring station data, annual averages were calculated and used as an estimate of 

exposure. For the modeling analysis, emissions over the Basin were estimated and allocated to 2 

kilometer geographic grids, and a regional dispersion model was used to estimate the annual 

average concentrations in each grid space. 
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Dose Response Assessment 

The dose response assessment characterizes the relationship between exposure to a substance and 

the incidence of an adverse health effect in an exposed population. For estimating cancer risk, 

the dose-response is expressed in terms of a potency slope that is used to calculate the probability 

of cancer associated with a given exposure. These cancer potency factors are expressed as the 

95th statistical upper confidence limit of the slope of the dose response curve assuming a 

continuous lifetime exposure to a substance at a dose of one milligram per kilogram of body 

weight. 

For effects other than cancer, dose-response data are used to develop acute and chronic 

Reference Exposure Levels (RELs). The RELs are defined as the concentrations at or below 

which no adverse noncancer health effects would be found in the general population. The acute 

RELs are designed to be protective for infrequent 1 hour exposures. The chronic RELs are 

designed to be protective for continuous exposure for at least a significant fraction of a lifetime. 

For this study, the dose-response estimates developed by OEHHA are used to estimate the 

potential for adverse health effects. It may be pointed out that these estimates sometimes differ 

from those developed by the U.S. EPA. For example, OEHHA has developed a cancer potency 

factor for diesel exhaust, whereas the U.S. EPA has elected not to do so. The U.S. EPA does 

state, however, that diesel exhaust is likely to be carcinogenic to humans and has adopted 

extensive regulations designed to reduce diesel exhaust exposure. While some of the potency 

estimates OEHHA has developed for other air toxics produce different estimates of risks then 

those that would be calculated using the U.S. EPA values, the risk from diesel exhaust calculated 

using OEHHA’s cancer potency factor is the dominant contributor to the estimated air toxics 

cancer risk in this study. 

Risk Characterization 

In this step, the estimated concentration of a substance is combined with the potency factors and 

RELs to determine the potential for health effects. In this study, the estimated or measured 

annual average levels for potential carcinogens were multiplied by the potency factor expressed 

as unit risks. The unit risk is the probability associated with a lifetime exposure to a level of one

microgram per cubic meter of air of a given substance. The unit risk factors developed by 

OEHHA and used in this study are listed in Appendix I. 

The potential cancer risk for a given substance is expressed as the incremental number of 

potential cancer cases that could be developed per million people, assuming that the population 

is exposed to the substance at a constant annual average concentration over a presumed 70-year 

lifetime. These risks are usually presented in chances per million. For example, if the cancer 

risks were estimated to be 100 per million, the probability of an individual developing cancer 

from a lifetime exposure would be one in a million. This would predict an additional 100 cases 

of cancer in a population of a million people over a 70-year lifetime period. 

Perspectives of Risk 

It may be useful to compare risks estimated from assessments of environmental exposures to the 

overall rates of health effects in the general population. For example, it is often estimated that 
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the incidence of cancer over a lifetime in the U.S. population is about 1 in 4, to 1 in 3. This 

translates into a risk of about 300,000 in a million. It has been also estimated that the bulk of 

cancers from known risk factors are associated with lifestyle factors such as tobacco use, diet, 

and being overweight. One such study, the Harvard Report on Cancer Prevention, estimated that 

of cancers associated with known risk factors, about 30% were related to tobacco, about 30% 

were related to diet and obesity, and about 2% were associated with environmental pollution 

related exposures. 

Source of Uncertainty 

The estimates of health risks are based on the state of current knowledge, and the process has 

undergone extensive scientific and public review. However, there is uncertainty associated with 

the processes of risk assessment. This uncertainty stems from the lack of data in many areas 

necessitating the use of assumptions. The assumptions are consistent with current scientific 

knowledge, but are often designed to be conservative and on the side of health protection in 

order to avoid underestimation of public health risks. 

As noted in the OEHHA guidelines, sources of uncertainty, which may either overestimate or 

underestimate risk, include: (1) extrapolation of toxicity data in animals to humans, (2) 

uncertainty in the estimation of emissions, (3) uncertainty in the air dispersion models, and (4) 

uncertainty in the exposure estimates. Uncertainty may be defined as what is not known and may 

be reduced with further scientific studies. In addition to uncertainty, there is a natural range or 

variability in the human population in such properties as height, weight, and susceptibility to 

chemical toxicants. 

Thus, the risk estimates should not be interpreted as actual rates of disease in the exposed 

population, but rather as estimates of potential risk, based on current knowledge and a number of 

assumptions. However, a consistent approach to risk assessment is useful to compare different 

sources and different substances to prioritize public health concerns. 

1.4. References 

The Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk 

Assessments, Office of Environmental Health Hazard Assessment, California Environmental 

Protection Agency, 2003. 

Harvard Report on Cancer Prevention Volume 1: Causes of Human Cancer 

Cancer Causes & Control, Volume 7 Supplement November 1996 
CHAPTER 2 

AIR TOXICS MONITORING AND ANALYSES 
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Chapter 2. Air Toxics Monitoring and Analyses 

2.1. Substances Monitored 

The chemical compounds (Table 2-1) to be monitored in MATES III include the toxics posing 

the most significant contributors to health risks as found in previous studies in the Basin. 

Additional measurements include organic carbon, elemental carbon, and total carbon, as well as 

Particulate Matter (PM), including PM2.5. Acrolein was initially considered to be included. 

However, there was no suitable method available for routine analyses at the time the study 

began. Other compounds are also reported, since they are additionally captured in both the 

sampling and analytical protocols proposed. 

Table 2-1 Substances Monitored in MATES III 

Benzene 1,3-Butadiene Carbon Tetrachloride 

Chloroform Dichlorobenzene Methylene Chloride 

MTBE Perchloroethylene 

(Tetrachloroethylene) Dichloroethane 

Dibromoethane Ethyl Benzene Toluene 

Trichloroethylene Xylene Styrene 

Vinyl Chloride Acetaldehyde Formaldehyde 

Acetone Methyl ethyl ketone 

Arsenic Cadmium Hexavalent Chromium 

Copper Lead Manganese 

Nickel Selenium Zinc 

Elemental Carbon Organic Carbon Naphthalene 

PAHs PM10 PM2.5

Naphthalene and other polycyclic aromatic hydrocarbons (PAHs), components of both mobile 

source and stationary source emissions, were measured. Recent reports have shown that annual 

averages of naphthalene are at levels hundreds to thousands of times higher than that of other 

PAHs. The National Toxicology Program has listed naphthalene as a potential human 

carcinogen. Additionally, the California EPA’s Office of Environmental Health Hazard 

Assessment (OEHHA) recently evaluated the health risk of ambient naphthalene under 

California’s Air Toxics Program and developed a cancer potency factor. The International 

Agency for Research on Cancer considers naphthalene to be possibly carcinogenic to humans. 

Given the likely importance of naphthalene to public health, it is of value to obtain additional 

information on ambient levels and emissions of this compound. 

PAHs were measured at three of the MATES III monitoring stations using EPA method TO-13A 

as a guideline. The West Long Beach and Central Los Angeles sites were selected because of 

their proximity to mobile emissions sources. Also, Lu, et al. (2005) incorporated ambient data 

from the Southern California Children’s Health Study and showed the highest naphthalene 

emissions rate in those regions. The Rubidoux site was selected as a receptor site and also for its 

particle-bound PAH measurement history as part of the ARB toxics network. 

Details of the methodology are given in Appendix IV. 
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2.2. Siting of Monitoring Stations 

The MATES III project conducted air toxics monitoring at ten locations over a two-year period. 

In addition to the ten fixed sites, the movable monitoring platforms were deployed that focused 

on “microscale” studies at five locations for periods up to several months. 

The combination of fixed and microscale sites was done to ensure sufficient resolution to 

monitor representative concentrations of varying land use types and characterize spatial gradients 

in the Basin. 

2.3. Ambient Sampling Schedule 

Sampling for MATES III followed a one-in-three day, 24-hour integrated-sampling schedule, 

which is double the schedule utilized during the MATES II Study. In the microscale studies, a 

24-hour integrated-sampling schedule was maintained for carbonyls, PM, and volatile organic 

compound (VOC) measurements, but in addition, three eight-hour integrated canister samples for 

VOCs were collected for higher temporal resolution over a single day. All data will be 

submitted to the U.S. EPA’s Air Quality System (AQS) after review and validation. 

2.4. Monitoring Sites 

2.4.1. Fixed Sites 

The fixed monitoring sites are those used in the MATES II Study, other than for the West Long 

Beach site. These sites were selected to measure numerous air toxic compounds at different 

locations in the Basin in order to establish a baseline of existing air toxic ambient concentrations, 

as well as risk level data, and to assist in the assessment of modeling performance accuracy. The 

West Long Beach site for the MATES III Study is about 2.5 miles east of the MATES II site, as 

the previous site was no longer available. 

The locations for the ten fixed sites reflect key locations within the Basin and are geographically 

dispersed. Fixed site locations include areas varying in land-use types to obtain a good spatial 

representation of the Basin which includes expected areas of possible elevated toxics levels (e.g. 

industrial and commercial) and those areas that are not directly near source emissions 

(neighborhoods). The sites also reflect resource constraints and the leveraging of existing 

specialized equipment. In addition, using these sites utilized in MATES I and MATES II allows 

for trend analysis. The sites used in MATES III are shown in Figure 2-1. 

The ten sites were selected with the input from the MATES II Technical Review Group and the 

Environmental Justice Task Force, and locations are listed in Table 2-2. Five were selected to 

provide continuity with the ARB long-term trend sites (Los Angeles, Burbank, Long Beach, 

Rubidoux and Inland Valley San Bernardino). The Pico Rivera site was selected because 

monitoring equipment was available from the EPA-sponsored PAMS Program. Anaheim was 

chosen for geographic equity, such that at least one site existed in each of the four counties. 

West Long Beach, Compton, and Huntington Park were sites selected to examine environmental 

justice concerns. Because the fixed site locations are based on EPA guidelines for 
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“neighborhood scale” monitoring, each of these sites may also be representative of adjacent 

communities. 

Table 2-2 Mates II Fixed Site Locations 

Site Address 

Anaheim 1010 S. Harbor Blvd. 

Burbank 228 W. Palm Ave. 

Compton 720 N. Bullis Rd. 

Inland Valley San Bernardino 14360 Arrow Highway 

Huntington Park 6301 S. Santa Fe Ave. 

North Long Beach 3648 N. Long Beach Blvd. 

Central Los Angeles 1630 N. Main St. 

Pico Rivera 3713 B-San Gabriel River Parkway 

Rubidoux 5888 Mission Blvd. 

West Long Beach 1903 Santa Fe Ave. 

At each site, sampling equipment included particulate samplers, canisters, and carbonyl 

samplers, as well as equipment to measure key meteorological parameters. 

Figure 2-1 Location of MATES III Monitoring Locations 

2.4.2. Microscale Sites 

The purpose of the microscale sites is to monitor air contaminants on a neighborhood level at 

locations of concern within the Basin. This information is used to determine if communities may 

F

o

Rubidoux

Wilmington

Pico Rivera

Indio

Sun Valley

San Bernardino

Industry

Fixed Sites Temporary Sites

Compton

Burbank

Anaheim

Inland Valley S.B.

Rubidoux

W. Long Beach

N. Long Beach

Pico Rivera

Los Angeles

Huntington Park

Indio

Santa Ana 

Sun Valley

San Bernardino

Commerce

Fixed Sites Temporary Sites
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be experiencing localized gradients of air toxics not otherwise determined by modeling as related 

to issues of environmental justice. 

The microscale sites utilize the SCAQMD’s movable monitoring platforms. As in MATES II, 

each microscale site will be paired with a nearby fixed site for comparison to determine if toxic 

air emissions at these microscale sites statistically exceed a neighboring fixed site. Due to the 

limited number of mobile monitoring platforms, each microscale site study lasts only a few 

months. Other considerations for site selection include the following: (1) power availability; (2) 

security; (3) accessibility to SCAQMD staff; and (4) availability of the premises for a six-to tenweek period. 

Since the sampling periods for the microscale sites are limited, annual averages for measured 

substances cannot be calculated. However, comparing the levels from the microscale sites to 

those from the nearest fixed site during the timeframe that the microscale site was operating can 

yield insights on potential community gradients. 

Microscale sites were selected using the following criteria, in consultation with the MATES III 

Technical Advisory Group: 

• Proximity to emissions source(s); 

• Areas identified with environmental justice issues;

• Potential for neighborhood gradients; 

• Elevated risks from MATES II modeling analysis; 

• Community concerns; and 

• Geographic equity. 

Input on potential types of sites has come from several sources, including the following: 

• Community concerns from public outreach and Town Hall meetings; 

• Public complaints; 

• MATES II modeling data; 

• Data from existing studies; and 

• MATES Technical Advisory Group. 

The locations of the microscale monitoring sites are shown in Figure 2-1 and are listed below. 

• Commerce 

• Indio 

• San Bernardino 

• Santa Ana 

• Sun Valley 

2.5. Monitoring and Laboratory Analysis 

For MATES III, meteorological equipment and sampling equipment for canisters, PM10 and 

PM2.5 filters, and carbonyl cartridges from the existing air monitoring network were used to the 

extent possible. The SCAQMD laboratory provided the analytical equipment and conducted the 

routine analysis. The analytical methods to measure the ambient species are briefly described 
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below and in Table 2-3. Detailed protocols are described in Appendix III. 

Table 2-3 Sampling and Analysis Methods for MATES III 

Ambient 

Species 

Sampling 

Method Laboratory Analysis 

Volatile Organic 

Compounds 

(VOCs) 

Summa 

Polished/ SilicaLined Canisters 

Gas chromatograph – Mass spectrometer (GC-MS) with 

automated pre-concentration and cryo-focusing 

Carbonyls DNPH 

Cartridge 

Solvent recovery and subsequent analysis via high 

performance liquid chromatography (HPLC) 

Hexavalent 

Chromium 

Cellulose Fiber 

Filters 

Treatment with buffer solution to maintain proper pH for 

unwanted conversions and then subsequent analysis via 

ion chromatograph(IC) 

Elemental and 

Organic Carbon 

(EC/OC) 

PM Filters Section of PM filter removed and analyzed on a laser 

corrected carbon analyzer 

PM10 High-Volume 

Quartz Filters 

Mass determined by analytical balance; metals 

determined Energy Dispersive X-Ray Fluorescence 

Spectrometry; ions extracted with water from filter and 

then subsequently analyzed on IC 

PM2.5 MediumVolume Teflon 

Filters 

Mass determined by Micro-balance; metals determined

by Energy Dispersive X-Ray Fluorescence Spectrometry, 

ions extracted with water from filter and then 

subsequently analyzed on IC 

Volatile Organic Compounds (VOCs) are measured from air samples collected in either 

summa polished or silica-lined six-liter canisters using an automated canister sampler to fill at a 

constant rate over a 24-hour or eight-hour time period depending upon the site. The filled 

canisters are brought back to the laboratory for analysis within 48 hours of the sample being 

collected. VOCs are identified and measured using gas chromatograph mass spectrometry (GCMS). The SCAQMD currently has two GC-MS instruments that are based upon the U.S. EPA’s 

TO-14 and TO-15 methods. These instruments are equipped with automated canister preconcentrators attached to the GC to enable continuous analysis. 

Carbonyl Compounds are sampled by drawing a continuous amount of air through a DNPH 

(2,4-Dinitrophenylhedrazine) cartridge. The carbonyl compounds undergo derivatization with 

DNPH, and the derivatives are analyzed using High Performance Liquid Chromatography 

(HPLC) in conjunction with U.S. EPA method TO-11. 

Hexavalent Chromium (Chrome VI) is analyzed using ion chromatography (IC). Sample

collection involves drawing air at a prescribed rate for 24-hours through a cellulose fiber filter. 

The filter is treated with sodium bicarbonate to prevent conversion of Chrome VI to Chrome III. 

Chrome VI is extracted from the filter by sonication and subsequently analyzed using IC. 
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Particulate Matter less than 10 microns (PM10) and less than 2.5 microns (PM2.5) are collected 

separately over a 24-hour period using size selective inlet (SSI) samplers according to the 

method based on U.S. EPA’s Federal Reference Method 40CFR50. All PM10 and PM2.5 samples 

are collected upon quartz filters and are analyzed for total PM mass, metals, ions, organic carbon 

(OC) and elemental carbon (EC). Metal analysis for particulate samples are determined using 

Energy Dispersive X-Ray Fluorescence Spectrometry. Identification of ions within the PM 

samples is also done by IC. Carbon analysis is conducted by taking a small circular disk from 

sampled PM10 or PM2.5 filters. The small circular disk is placed into a carbon analyzer which 

utilizes either a thermal optical reflectance or thermal optical transmittance method (IMPROVE 

method) to measure the OC and EC content of the filter. As part of this effort, speciation air 

sampling system (SASS) samplers were deployed to characterize specific PM species. 

Diesel PM. For MATES II, diesel PM was estimated using ambient measurements of EC and 

using EC emissions inventories to determine the contribution of diesel emissions to ambient PM 

levels. For MATES III, several methodologies to assess the levels of diesel PM were explored. 

These methods include the following: 

• Using ambient EC levels as in MATES II 

• Using ambient EC and the ratio of PM2.5, EC, and diesel PM emissions from the 2005 

emissions inventory 

• Using the EPA Chemical Mass Balance model (CMB) to apportion source emissions to 

PM2.5

• Using Positive Matrix Factorization (PMF) to apportion source emissions to PM2.5

The results of these analyses are presented in the monitoring results section below. 

2.5.1. Quality Assurance and Quality Control (QA/QC) 

The SCAQMD is committed to achieving the highest possible data quality level in the MATES 

III Program. To achieve this data quality level, the SCAQMD has an implemented QA/QC Plan 

which follows U.S. EPA’s Quality Assurance Project Plan for the Air Toxics Monitoring 

Network (EPA-454/R-01-007). The SCAQMD objectives, procedures, documentation, and data 

review techniques assure the MATES III Program will produce accurate and precise data. The 

technical procedures for QA/QC include annual system audits on all equipment in the laboratory 

and at the MATES III sampling sites. Quality control procedures include proper record keeping, 

standard checks, and routine calibrations of the sampling and analytical equipment. These 

procedures include operating collocated samples greater than 10% of samples collected. For 

example, the SCAQMD is currently conducting a collocated sampling of its Rubidioux station 

using multiple samplers. 

2.6. Findings 

The findings are presented in terms of the concentrations of air toxics and by the estimated 

cancer risks resulting from exposures to the average concentrations found. Data are presented by 

year of the study, and these time periods are referred to as MATES III Year One (April ‘4 – 

March ’05) and MATES III Year Two (April ’05 – March ’06). In the following charts, the data 

are presented as annual means, and the error bars denote the 95% confidence interval of the 

mean. 
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For the second year of the study, a complete data set was not available for the Huntington Park 

and the Pico Rivera sites, and summary data is not included. 

Summary results are presented below by site and are compared to levels found in the MATES II 

Study to assess trends in levels of air toxics in the Basin. In general, concentrations of most 

toxics substantially decreased compared to levels measured during MATES II. 

In the charts below, the data is presented as the annual average by site and as the overall sites 

average. The error bars represent the 95% confidence interval of the average. 

2.6.1. Volatile Compounds 

Figures 2-2 and 2-3 present levels for 1,3 butadiene and benzene, which are emitted 

predominantly from mobile sources. Both substances show a substantial reduction in annual 

levels compared to MATES II, with benzene lower by 50% and 1,3-butadiene down by 73%. As 

in the MATES II Study, Compton and Huntington Park sites had the highest average levels. 

These decreases are likely reflective of reduced emissions from vehicle turnover and use of 

reformulated gasoline. 

Levels of the chlorinated solvents perchloroethylene and methylene chloride are shown in 

Figures 2-4 and 2-5. Both of these substances also show decreases from the MATES II Study. 

The decreases reflect the reduced usage of these substances as industrial solvents and in dry 

cleaning. Perchloroethylene and methylene chloride were lower on average by 78% and 53%, 

respectively. For methylene chloride, the North Long Beach site shows an increased level for 

year 1. This was due to high levels measured over three sampling days in February, 2005. No 

known sources are nearby. These levels may reflect an unusual use of this solvent over this time 

period. 

Formaldehyde and acetaldehyde concentrations are shown in Figures 2-6 and 2-7. There was 

about a 9% reduction in the average levels between the MATES II and MATES III studies. 

Formaldehyde is emitted from mobile sources and is also formed as a secondary pollutant 

through chemical reactions in the atmosphere. 

2.6.2. Metals 

Levels of several metals are shown in Figures 2-8 to 2-12. 

Arsenic and cadmium levels are shown in Figures 2-8 and 2-9. Both metals show declines, but 

this may be more a result of lower reporting limits for MATES III compared to MATES II. 

Figures 2-10 and 2-11 show the levels of lead and nickel. Lead concentrations were reduced 

compared to MATES II, and the values are well below the Ambient Air Quality Standard for 

lead of 1,500 ng/m3

. Nickel concentrations were also lower, other than for the West Long Beach 

site. This may be a reflection of the increased shipping activity at the ports, as nickel is a 

component of bunker fuel used in ships. 

Hexavalent chromium concentrations are shown in Figure 2-12. It should be noted that from 

previous studies, localized increases can occur near facilities using hexavalent chromium, such 
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as metal platers or facilities using paints containing hexavalent chromium. The monitoring 

locations in this study, however, are focused on a regional look at air toxics levels. Emissions 

that could result in a localized area of increased exposure thus may not be picked up in the 

monitoring. 

For comparison purposes, only the data from the SCAQMD lab analyses from MATES II are 

shown. This is because in MATES II half of the samples were analyzed by ARB and showed a 

lower overall average than did the SCAQMD analyzed samples. The ARB laboratory also 

reported higher method detection limits, which may be part of the reason for the differences. 

Some sites, such as Burbank and Huntington Park, show declines in average levels, whereas 

others show little change. The Rubidoux site actually showed an increase in average levels. If 

Rubidoux is not included, the average hexavalent chromium level is about 13% lower compared 

to MATES II. 

Subsequent efforts by staff to determine the source of the hexavalent chromium near the 

Rubidoux site led to a cement plant in the area. The results of the intensive monitoring and 

analyses are available from the District’s web site at 

http://www.aqmd.gov/RiversideCement/RiversideCement.html. 

It is recognized that there can be a measurable value for hexavalent chromium in blank filters. 

To determine the extent of this, trip blanks were periodically taken at Rubidoux; and the average 

values are also shown in Figure 2-12. One can note that the blank values are about a third of the 

sites average values. When estimating risk from exposure to hexavalent chromium, the average 

blank value is subtracted out from the sites average. 

2.6.3. Elemental Carbon 

In the MATES II Study, elemental carbon (EC) was measured in the PM10 samples. In addition, 

the MATES III Study measured the levels of EC in the PM2.5 samples. The results are shown in 

Figures 2-13 and 2-14. 

In the PM10 samples, EC showed a decrease (∼38%) between MATES II and MATES III. One 

source of the reduction is the use of updated analytical instruments. For MATES III, new 

instruments were used to analyze for carbon. When compared with the older instrument used in 

MATES II, the new instruments showed about 10% lower results, on average. Thus, about a 

28% reduction remains after correcting for difference in the analytical instruments. This may be 

a reflection of reduced carbon emissions and meteorological differences. The Huntington Park 

and West Long Beach sites showed the highest levels. West Long Beach and Compton did not 

have data for EC from MATES II, so a comparison over time at these sites cannot be made. 

For the PM2.5 samples, year 2 levels on average were somewhat higher than for year 1 for the 

sites with data for both years. This may reflect weather differences and/or an increase in 

emissions during the second year of the study. Huntington Park and West Long Beach showed 

the highest levels for year 1 where data were available for all sites. 

2.6.4. Diesel PM 

In the MATES II Study, EC was used as a surrogate for diesel particulate levels, as staff 
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determined that this was the best method available during the MATES II Study. For the present 

study, staff used the Chemical Mass Balance (CMB) source apportionment technique to estimate 

the contribution from diesel, as well as from other major source categories, to the measured 

particulate levels. The CMB model was used on the recommendation of the Technical Advisory 

Group. 

To compare different methods to estimate diesel particulate levels, the method used in MATES 

II , which was based on the emissions ratios of diesel particulate and elemental carbon from a 

study conducted in the South Coast in the 1980’s and a method based on the ratio of PM2.5

emissions from the 2005 emissions inventory were also calculated. For MATES II, the PM2.5

elemental carbon levels were multiplied by 1.04 to estimate diesel particulate. The 2005 

inventory finds a ratio of diesel particulate to elemental carbon emissions of 1.95. The emissions 

and ratio are shown in Table 2-4. Multiplying the PM2.5 elemental carbon levels by 1.95 gives 

another estimate of diesel particulate. 

Table 2-4 2005 Emissions of Diesel PM and EC, lbs./day 

PM2.5 Diesel 

PM 

PM2.5 EC DPM/EC 

Ratio 

55,983 28,761 1.95 

The estimates using these methods compared to using the CMB model are shown in Table 2-5. 

The CMB model used several species of substances from emissions source profiles to estimate 

the contribution of these sources to ambient PM levels. The details of this calculation are given 

in Appendix VII. 

Table 2-5 gives the sites average estimates for diesel PM using the CMB model and compares 

the level with the methods based on emissions inventory ratios. For the CMB model, the 

estimates were sensitive to the species profile used for gasoline vehicles. Table 2-5 shows the 

range of values using two different gasoline profiles. The estimates used for the risk calculations 

were the midpoint of the range. 

As shown in the table, both the CMB model and the PM2.5 emissions ratio method give higher 

estimates than the MATES II method. Thus the MATES II Study method may underestimate the 

levels of diesel particulate. 

Table 2-5 Estimates of Average Diesel PM, μg/m3 

Estimation 

Method 

MATES III 

Year One 

MATES III 

Year Two 

MATES II: 

PM10 EC x 1.04 

2.18 2.14 

2005 Inventory: 

PM2.5 EC x 1.95 

3.37 3.70 

CMB 2.87 – 3.13 3.52 – 3.84 

2.6.5. Naphthalene and Other PAH Compounds 

Limited measurements of naphthalene and other PAHs (Polycyclic Aromatic Hydrocarbons) 

were taken at three sites. Summary data for naphthalene are shown in Figure 2-15, and the other 
MATES III Final Report

2-10 

PAHs measured are shown in Figure 2-16. 

Naphthalene levels were on average much higher than that of other PAHs, in line with previous 

observations in the Basin. For the three sites, Central Los Angeles showed the highest average 

levels of naphthalene and Rubidoux the lowest. For the sum of the other PAHs, West Long 

Beach showed the highest levels. 

2.7. Cancer Risk Estimates 

In the MATES II Study, cancer risks were estimated for exposure to the measured ambient levels 

of air toxics. The estimates assumed that a lifetime exposure (70 years) occurs to these levels, 

consistent with guidance on risk assessment established by OEHHA. We use the same 

methodology to estimate risks for the levels of toxics measured during MATES III. 

There are inherent uncertainties in risk assessment, as discussed in the Introduction of this report 

and in the OEHHA Air Toxics Hot Spots Program Risk Assessment Guidelines (August 2003)1

. 

Despite these uncertainties, risk assessment remains the most useful tool to estimate the potential 

health risks due to low level environmental exposures. This tool is also useful as a yardstick to 

measure progress in attaining healthful air quality. 

Figures 2-17 and 2-18 show the estimated cancer risks for the toxics measured by site summed 

by substance for each year of the MATES III Study. The second year includes the levels for 

naphthalene and other PAHs for which there are adopted cancer potency values for the three sites 

where measurements were collected. The sites average also includes the PAHs using the 

available three-site average. The PAHs are relatively small contributors to the overall average 

risk. The average level of naphthalene was 180 ng/m

3

 over the three sites. This equates to a 70-

year risk of about six per million. 

As shown in the charts, diesel particulate is the major contributor to air toxics risk. The average 

risk over the two years is about 1,200 per million. This compares to about 1,400 per million in 

the MATES II Study. It should be noted that different methods were used to estimate diesel 

particulate levels in the MATES III Study, so the results are not strictly comparable. Based on 

the discussion above, the MATES II Study method may have underestimated the levels of diesel 

particulate. 

On average, diesel particulate contributes about 84% of the total air toxics risk. This is a larger 

portion of risk compared to the MATES II estimate of about 70%. In addition to the differences 

in methods for estimating diesel particulate, this may reflect a larger relative decrease in ambient 

levels of other toxic air contaminants compared to diesel exhaust. 

 

1

 California Environmental Protection Agency Office of Environmental Health Hazard Assessment, Air Toxics Hot 

Spots Program Risk Assessment Guidelines. The Air Toxics Hot Spots Program Guidance Manual for Preparation 

of Health Risk Assessments. August 2003. 
MATES III Final Report

2-11 

1,3 Butadiene 

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Sites

Average

ppb

MATES II MATES III Year 1 MATES III Year 2

Figure 2-2 Average Concentrations of 1,3-Butadiene

Benzene 

0.0

0.5

1.0

1.5

2.0

2.5

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Sites

Average

ppb

MATES II MATES III Year 1 MATES III Year 2

Figure 2-3 Average Concentrations of Benzene 
MATES III Final Report

2-12 

Perchloroethylene 

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Sites

Average

ppb

MATES II MATES III Year 1 MATES III Year 2

Figure 2-4 Average Concentrations of Perchloroethylene 

Methylene Chloride 

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West. Long

Beach

Sites

Average

ppb

MATES II MATES III Year 1 MATES III Year 2

*Extremely higher concentrations measured for three samples over a 15-day period. 

Figure 2-5 Average Concentrations of Methylene Chloride 
MATES III Final Report

2-13 

Formaldehyde 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Sites

Average

ppb

MATES II MATES III Year 1 MATES III Year 2

Figure 2-6 Average Concentrations of Formaldehyde 

Acetaldehyde 

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Sites

Average

ppb

MATES II MATES III Year 1 MATES III Year 2

Figure 2-7 Average Concentrations of Acetaldehyde 
MATES III Final Report

2-14 

 Arsenic

0.0

0.5

1.0

1.5

2.0

2.5

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Average

ng/m3

MATES II MATES III Year 1 MATES III Year 2

Figure 2-8 Average Concentrations of Arsenic in Total Suspended Particulate (TSP) 

 Cadmium

0

5

10

15

20

25

30

35

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Average

ng/m3

MATES II MATES III Year 1 MATES III Year 2

Figure 2-9 Average Concentrations of Cadmium in Total Suspended Particulate (TSP) 
MATES III Final Report

2-15 

 Lead

0

10

20

30

40

50

60

70

80

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Average

ng/m3

MATES II MATES III Year 1 MATES III Year 2

Figure 2-10 Average Concentrations of Lead in Total Suspended Particulate (TSP) 

 Nickel

0

5

10

15

20

25

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Average

ng/m3

MATES II MATES III Year 1 MATES III Year 2

Figure 2-11 Average Concentrations of Nickel in Total Suspended Particulate (TSP) 
MATES III Final Report

2-16 

Hexavalent Chromium

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Average Rubidoux

Filter Blank

ng/m3 MATES II AQMD Lab data MATES III Year 1 MATES III Year 2

Figure 2-12 Average Concentrations of Hexavalent Chromium in Total Suspended 

Particulate (TSP) 

Elemental Carbon - PM10

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Sites

Average

ug/m3

MATES II MATES III Year 1 MATES III Year 2

Figure 2-13 Average Concentrations of PM10 Elemental Carbon (EC) 
MATES III Final Report

2-17 

 EC PM2.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Anaheim Burbank Central LA Compton Inland

Valley S.B.

Huntington

Park

North Long

Beach

Pico Rivera Rubidoux West Long

Beach

Sites

Average

ug/m3

MATES III Year 1 MATES III Year 2

Figure 2-14 Average Concentrations of PM2.5 Elemental Carbon (EC) 

Figure 2-15 Average Monitored Naphthalene Concentrations for MATES III Year 2 

Naphthalene

0

50

100

150

200

250

Central LA Rubidoux West Long 

Beach

Sites Avg

ng/m3
MATES III Final Report

2-18 

PAHs - MATES Year 2

0

5

10

15

20

25

30

35

40

45

50

Central LA Rubidoux W. Long

Beach

Sites Avg

ng/m3

Benz(a)Anthracene

Benzo(a)pyrene

Indeno(1,2,3-cd)pyrene

Benzo(ghi)perylene

Dibenz(a,h)anthracene

Chrysene

Benzo(b+j+k)Fluoranthene

Anthracene

Pyrene

Fluoranthene

Acenaphthylene

Acenaphthene

Fluorene

Phenanthrene

Figure 2-16 Average Concentration of PAHs for MATES III Year 2 
MATES III Final Report

2-19 

Air Toxics Risk - MATES Year 1

0

200

400

600

800

1000

1200

1400

1600

Anaheim

Burbank

Central LA

Compton

Inland Valley S.B.

Huntington Park

North Long Beach

Pico Rivera

Rubidoux

West Long Beach

Sites Average

Risk per Million

Chloroethene (Vinyl Chloride)

Trichloroethylene, 1,1,2- (TCE)

Lead

Chloroform

Methylene Chloride

Nickel

Dichlorobenzene, pEthylbenzene

Perchloroethylene

Arsenic

Cadmium

Acetaldehyde

Cr+6

Carbon Tetrachloride

Formaldehyde

Butadiene, 1,3-

Benzene

Diesel PM

Figure 2-17 Estimated 70-Year Risk from MATES III Year 1 Monitoring Data 

Air Toxics Risk - MATES Year 2

0

200

400

600

800

1000

1200

1400

1600

Anaheim

Burbank

Central LA

Compton

Inland Valley S.B.

North Long Beach

Rubidoux

West Long Beach

Sites Average

Risk per Million

Chrysene

Benz(a)Anthracene

Dichloro ethane, 1,2- (EDC)

Indeno(123-cd)pyrene

Dibromo ethane,1,2- (EDB)

Chloroethene (Vinyl Chloride)

Benzo(b+j+k)fluoranthene

Dibenz(ah)anthracene

Trichloroethylene, 1,1,2- (TCE)

Benzo(a)pyrene

Lead

Chloroform

Methylene Chloride

Nickel

Dichlorobenzene, pEthylbenzene

Perchloroethylene

Arsenic

Naphthalene

Cadmium

Acetaldehyde

Cr+6

Carbon Tetrachloride

Formaldehyde

Butadiene, 1,3-

Benzene

Diesel PM

Figure 2-18 Estimated 70-Year Risk from MATES III Year 2 Monitoring Data 
MATES III Final Report

2-20 

2.8. Other Data Sources 

Measurements of PM2.5 mass and limited analyses of some PM2.5 components are available for 

several other sources and studies. For example, charts and averages of PM2.5 mass and EC were 

provided to staff by the ports in comments to the January 2008 draft MATES III report. While 

useful for geographic comparisons, these data are of limited use for comparing to the MATES III 

data, as the time periods of sample collection were different, and the sampling periods did not 

completely overlap the MATES III study period. 

In visually comparing the port monitoring data with the MATES III data on a daily basis during 

the times of sampling overlap, there was a concordance in the reported values. Although the 

different monitoring sites showed different values, as might be expected, the correlation of the 

values appeared to be high. 

In terms of source apportionment, these data are also limited in that organic components and 

other species needed for the source apportionment methods are not available. 

In terms of comparable data, the EPA Speciation Trends Network (STN) provides data from two 

of the MATES III monitoring sites, namely Central Los Angeles and Rubidoux. The PM2.5

sampling methods are equivalent, as the MATES III sampling protocol is based on the method 

used by EPA. Comparisons of the daily values and averages from data taken over the MATES 

III monitoring period from these locations are shown in the charts below. The MATES III 

samples give similar results as the collocated EPA samplers. 

















	

Apr-04

May-04

Jun-04

Jul-04

Aug-04Sep-04

Oct-04

Nov-04

Dec-04

Jan-05

Feb-05Mar-05

Apr-05

May-05

Jun-05

Jul-05

Aug-05Sep-05

Oct-05

Nov-05

Dec-05

Jan-06

Feb-06Mar-06

ug/m3

PM2.5 Mass - Central LA

MATES III EPA Speciation Trend Network (STN)



 

  

 	 

  

 

Figure 2-19 PM2.5 Mass from MATES III and EPA Collocated Samplers at Los Angeles 
MATES III Final Report

2-21 

0

20

40

60

80

100

120

Apr-04

May-04

Jun-04

Jul-04

Aug-04Sep-04

Oct-04

Nov-04Dec-04

Jan-05

Feb-05

Mar-05

Apr-05

May-05

Jun-05

Jul-05

Aug-05Sep-05

Oct-05

Nov-05Dec-05

Jan-06

Feb-06

Mar-06

ug/m3

PM2.5 Mass - Rubidoux

MATES III EPA Speciation Trends Network (STN)



 

  

  

  

  

Figure 2-20 PM2.5 Mass from MATES III and EPA Collocated Samplers at Rubidoux 

Commenters on the draft report also provided annual average PM2.5 mass comparisons from the 

ambient monitoring data available from the ARB air quality database. These measurements, 

however, use a different sampler (also referred to as RASS or FRM samplers) that has a different 

design and higher flow rates than the samplers used in MATES III and the EPA STN network 

(also referred to as SASS samplers). It is known that the speciation samplers (SASS) give 

somewhat higher mass values than the samplers (FRM) used in the network designed to assess 

compliance with ambient air quality standards.