California Air Resources Board

Download the 2023 Annual Data Quality Report for CARB’s Primary Quality Assurance Organization (PQAO) using the link at the bottom of this webpage. To request reports from previous years, please email: qa@arb.ca.gov.

Overview

The 2023 Annual Data Quality Report for CARB's PQAO (2023 Annual Report) provides ambient air quality data producers and users with a centralized review of the data quality within CARB’s PQAO. The data are described in quantifiable terms in relation to measurement quality objectives (MQO) established by United States Environmental Protection Agency (U.S. EPA) and summarized for ambient air monitoring stations in the statewide network within CARB’s PQAO. CARB’s PQAO data are also compared to other PQAOs in California and the nationwide average, where appropriate. Any data quality assessments are solely based on certified data available in U.S. EPA’s Air Quality System (AQS).

Background

U.S. EPA designated CARB as one of seven PQAOs in California responsible for monitoring air pollutants and assessing data quality. The 2023 Annual Report focuses on four PQAOs in California, which encompass most of the geographic area and population in the State. Within CARB’s PQAO, there are 22 monitoring organizations with air monitoring sites.

Data Quality

Data quality is assessed using the following MQOs.

• Ambient data capture rate, which is the amount of ambient data reported.
• Precision, which is the degree of mutual agreement among individual measurements of the same property.
• Bias, which is the systematic or persistent distortion of a measurement process which causes error in one direction.
• The amount of precision and bias data collected and reported.

Data quality is presented for two types of pollutants: gaseous and particulate matter.

Data Quality Results

Explore the data quality results by geographic area and/or by year (2023 and the previous two years) using the interactive tables below. A geographic area refers to a region covered by a monitoring organization. Sites may be operated by the monitoring organization, CARB, or both. Table 1 presents data quality results from gaseous instruments, while Table 2 presents data quality results from PM samplers. 

Gaseous Instruments

Table 1. Gaseous Instruments - Composite Table of 2021-2023 Ambient Data and Data Quality Results for Geographic Areas within CARB's PQAO

• Y = met criteria; N = not all sites met criteria; N† = impacted site(s) operated by CARB; N†† = impacted site(s) operated by both the monitoring organization and CARB; NA = not applicable for that geographic area.
• Data quality results shown for 2023 reflect certified data available in AQS as of July 2024. Note that the 2021 and 2022 data quality results shown may not reflect current information in AQS due to potential data uploads to AQS occurring after the reports for these years were published.

Particulate Matter Samplers

Overall, MQOs associated with PM samplers were consistent with the previous year. CARB explored potential causes behind low PM_2.5 precision among some collocated PM_2.5 samplers; however, no definitive source of the issue was identified. U.S. EPA is aware of the systemic issue of PM imprecision (in California and nationwide). The agency adopted new statistics for calculating the coefficient of variation (CV) in its Reconsideration of the National Ambient Air Quality Standards for Particulate Matter in March 2024. CARB will continue exploring the potential causes behind low PM_2.5 precision among some of the collocated PM_2.5 samplers within CARB’s PQAO. For the remaining instances where PM samplers did not meet the MQOs (as indicated by an N, N†, or N†† in Table 2), monitoring organizations are to investigate why these objectives were not met for each sampler in their respective jurisdictions and develop corrective actions, if appropriate, to meet them in subsequent years.

Table 2. Particulate Matter Samplers - Composite Table of 2021-2023 Ambient Data and Data Quality Results for Geographic Areas within CARB's PQAO

• Y = met criteria; N = not all sites met criteria; N† = impacted site(s) operated by CARB; N†† = impacted site(s) operated by both the monitoring organization and CARB; NA = not applicable for that geographic area.
• Data quality results shown for 2023 reflect certified data available in AQS as of July 2024. Note that the 2021 and 2022 data quality results shown may not reflect current information in AQS due to potential data uploads to AQS occurring after the reports for these years were published.

Download the 2023 Annual Data Quality Report for CARB’s PQAO using the link below. To request reports from previous years, please email: qa@arb.ca.gov.