Annual Report 

on the 

Air Resources Board’s 

 

Fine Particulate Matter Monitoring Program 

January 2015 

California Environmental Protection Agency 

 Air Resources Board 
PM2.5 Air Quality Monitoring Program

State of California 

California Environmental Protection Agency 

Air Resources Board 

Annual Report on the Air Resources Board’s 

Fine Particulate Matter Monitoring Program 

January 2015 

This report has been reviewed by the staff of the California Air Resources Board and 

approved for publication. Approval does not signify that the contents necessarily reflect 

the views and policies of the Air Resources Board, nor does the mention of trade names 

or commercial products constitute endorsement or recommendation for use. 
8

1 

PM2.5 Air Quality Monitoring Program

Health and Safety Code, Section 39619.5(g) requires the 

Air Resources Board (ARB or Board) to provide an update 

each year on the status and results of the fine particulate 

matter (PM2.5) monitoring program. This report provides 

a summary of PM2.5 monitoring activities in 2014 and how 

the data are being used to support ARB programs. 

California’s PM2.5 air quality monitoring program provides 

information used for determining which areas violate 

standards, characterizing the sources that contribute to 

PM2.5 pollution, determining background concentrations, 

assessing pollution transport, and supporting health 

studies and other research. Monitoring data also provide 

information to develop and evaluate programs for 

improving air quality. 

California’s PM2.5 monitoring network began collecting 

data in 1998. A number of different types of PM2.5

monitors are operated to provide information on PM2.5 

mass and chemical composition which are summarized 

below. Figure 1 displays the locations of PM2.5 monitors 

throughout the State. Additional information on PM2.5 

monitoring can be found at: 

http://www.arb.ca.gov/aaqm/partic.htm 

Federal Reference Method Monitors 

The installation of federally-approved PM2.5 mass 

monitors throughout California began in 1998. In 2014, 

Federal Reference Method (FRM) monitors were operated 

at 63 sites. These monitors collect particulate samples on 

filters, which are later weighed and analyzed in a 

laboratory. Because of this two-step process, PM2.5 air 

quality data collected with these monitors are not 

immediately available. To provide “real-time” PM2.5 air 

quality information, we added continuous PM2.5 mass

monitors to our network. 

Continuous Mass Monitors 

Continuous PM2.5 mass monitors provide valuable 

information for public reporting, temporal representation, 

health studies, transport studies, and background 

monitoring. PM2.5 mass can be measured continuously 

with several different commercially available technologies. 

California’s 

PM2.5 monitoring 

network includes:

• Federally-approved 

monitors that measure 

PM2.5 mass over a 

24-hour period at 

63 sites; 

Federal reference method 

monitor 
8

2 

PM2.5 Air Quality Monitoring Program

We chose the Beta Attenuation Monitor (BAM) for use in 

California and have installed monitors at 97 sites. The 

U.S. Environmental Protection Agency (U.S. EPA) 

designated certain models of the continuous monitors as 

Federal Equivalent Method (FEM) monitors. They are 

considered equivalent to the FRM monitors and can 

therefore be used to determine compliance with federal 

standards. California has deployed 61 of these FEM 

monitors. 

Speciation Monitors 

Another major stage of network implementation is the 

deployment of PM2.5 speciation monitors. Speciation 

monitoring provides valuable information about the 

composition (and ultimately sources) of PM2.5 pollution. 

However, monitoring of the individual species that make up 

PM is still an emerging field, with continuous speciation 

measurements the greatest challenge. We continue to 

evaluate newly emerging methods not currently used in 

routine monitoring for potential incorporation in California’s 

PM2.5 monitoring network. 

In 2014, along with states, U.S. EPA conducted a 

nationwide assessment of the PM2.5 speciation network to 

determine whether the sites were meeting the objectives 

and still needed. The review determined that all of the 

sites in California were needed and should continue to 

operate. 

Federally-Required Speciation Monitors 

There are two components to the PM2.5 speciation 

network in California. The first component, mandated by 

the U.S. EPA, required filter-based PM2.5 speciation 

monitoring at eight California sites that are now part of a 

national trends network for PM2.5 speciation. These 

monitors are the National Air Monitoring Stations (NAMS) 

monitors for the speciation network. The eight PM2.5 

speciation monitors are located in Bakersfield, El Cajon, 

Fresno, Sacramento, San Jose, Los Angeles, Riverside, 

and Simi Valley. 

• Samplers that 

quantify PM2.5 mass 

continuously at 97 sites; 

Beta attenuation monitor

and 

• Monitors that collect 

PM2.5 samples for 

analysis of chemical 

components at 20 sites. 

Speciation monitor
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3 

PM2.5 Air Quality Monitoring Program

Additional Speciation Monitors 

The second component of California’s PM2.5 speciation 

network is the selection and deployment of samplers at 

selected State and Local Air Monitoring Stations (SLAMS). 

Data from these sites provide additional information 

needed for developing effective air quality attainment 

plans. The focus of the SLAMS PM2.5 speciation network 

is to enhance the spatial coverage of the NAMS sites in 

areas with a diversity of PM problems. 

ARB and the air districts have deployed filter-based 

speciation monitors at twelve sites - Anaheim, Calexico, 

Chico, Fontana, Escondido, Modesto, Portola, Visalia, 

Sacramento, Vallejo, Livermore, and Oakland. 

In 2007, ARB began monitoring for specific wood smoke 

tracers to determine the contribution of wood burning 

sources to PM2.5 ambient levels. Wood smoke tracers 

are being monitored at seven of the speciation SLAMS 

sites - Calexico, Chico, Escondido, Modesto, Portola, 

Sacramento, and Visalia during the winter season. 

Accessing PM2.5 Data 

Data collected as part of California’s PM2.5 monitoring 

program can be obtained through a number of means. 

Daily PM2.5 values as well as summary statistics can be 

accessed through the interactive query program on ARB’s 

web page at: 

http://www.arb.ca.gov/adam/welcome.html

Real-time hourly PM2.5 data from California’s continuous 

monitors can also be found at: 

http://www.arb.ca.gov/aqmis2/aqdselect.php

PM2.5 Designations 

The Clean Air Act requires the U.S. EPA to set national 

24-hour and annual PM2.5 ambient air quality standards, 

and to designate nonattainment area for the national 

standards. ARB established a more health protective 

State and National PM2.5 

Ambient Air Quality Standards 

(micrograms per cubic meter) 

 California National 

Annual 12 12

24-hour --- 35

Designations for 

State PM2.5 Standard
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4 

PM2.5 Air Quality Monitoring Program

National 2006 24-hour 

PM2.5 Std. 

Nonattainment Areas

National 2012 annual 

PM2.5 Std. 

Nonattainment Areas

State PM2.5 ambient air quality standard as required by 

California State Law. California State Law also requires 

ARB to designate each area as attainment, nonattainment, 

or unclassified for the State standard. 

Based on data collected as part of California’s PM2.5 

monitoring network, the ARB designates the attainment 

status of areas with respect to the State annual average 

PM2.5 ambient air quality standard of 12 μg/m3. Based on 

2010-2013 air quality data, there were no changes to any 

area’s PM2.5 attainment status. Most urban areas of 

California exceed the State PM2.5 standard, as well as 

several more isolated sub-areas. However, as air quality 

has improved more areas now meet the State PM2.5 

ambient air quality standard. 

In 2006, U.S. EPA strengthened the national 24-hour

PM2.5 standard from 65 μg/m3 to 35 μg/m3. The U.S. EPA 

issued final designations for this standard which became 

effective in December 2009. Seven areas in California 

were designated as not meeting the strengthened federal 

24-hour PM2.5 standard – the South Coast Air Basin, San 

Joaquin Valley Air Basin, Bay Area Air Basin, Sacramento 

Metropolitan area, a portion of the Feather River Air 

Pollution Control District, a portion of Butte County, and a 

portion of Imperial County. In 2013, based on recent data, 

U.S. EPA determined that the Bay Area Air Basin, the 

Feather River Air Pollution Control District, Sacramento 

Metropolitan area, and Butte County attained the standard. 

Information on the final determinations can be found at: 

http://www.epa.gov/region9/air/actions/ca.html

In 2012, U.S. EPA lowered the annual PM2.5 standard

from 15 μg/m3 to 12 μg/m3

. The U.S. EPA issued final 

designations for this standard in December 2014 based on 

2011-2013 air quality data. Four areas in California were 

designated as not meeting the lowered annual PM2.5 

standard – South Coast Air Basin, San Joaquin Valley Air 

Basin, and portions of Imperial and Plumas Counties. 

Information on the State and federal designations can be 

found at: 

http://www.arb.ca.gov/desig/pm25desig/pm25desig.htm
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5 

PM2.5 Air Quality Monitoring Program

PM2.5 Attainment Plans 

To meet the requirements of the revised 24-hour PM2.5 

standard, the South Coast Air Quality Management District 

and the San Joaquin Valley Air Pollution Control District 

prepared State Implementation Plans in 2012. ARB 

adopted the plans and submitted them to U.S. EPA in

2013. Imperial County Air Pollution Control District also 

prepared a State Implementation Plan for the Imperial 

County nonattainment area. This plan was adopted by 

ARB in December 2014 and submitted to U.S. EPA. 

Information on the South Coast Plan, the San Joaquin 

Valley Plan, and the Imperial County Plan are available, 

respectively, at: 

http://www.arb.ca.gov/planning/sip/planarea/scabsip.htm

http://www.arb.ca.gov/planning/sip/planarea/sanjqnvllysip.h

tm

http://www.arb.ca.gov/planning/sip/planarea/imperial/imperi

alsip.htm

New PM2.5 attainment plans for the revised annual PM2.5 

standard of 12 μg/m3

 will be due to U.S. EPA in 2016. 
6 

Fine Particulate Matter Program

Figure 1: PM2.5 Monitoring Stations in California