Near Road Air Monitoring Network


On February 9, 2010, U.S. EPA promulgated new minimum monitoring requirements for the NO2 monitoring network in support of newly revised 1-hour NO2 National Ambient Air Quality Standard (NAAQS) and the retained annual NAAQS. To implement the new monitoring requirements, SCAQMD is installing near-road NO2 monitoring stations at locations where peak hourly NO2 concentrations are expected to occur within the near-road environment in larger urban areas with consideration to traffic volumes, fleet mix, roadway design, traffic congestion patterns, local terrain or topography, and meteorology in determining where a required near-road NO2 monitor should be placed. Information on how sites are selected was presented at the Near Road Workshop and also the Annual Network Plan Workshop (PDF, 5.3MB).

Below are summaries and the data from the Near Road Monitoring:

It should be noted that an exceedance of the concentration level of a federal standard does not necessarily mean that the NAAQS was violated or that it would cause a nonattainment designation. The 1-hour NO2 NAAQS (100 ppb) is the 3-year average of the annual 98th percentile of the daily maximum 1-hour average concentrations. The annual NO2 NAAQS (53 ppb) is the annual average concentration, averaged over three years.

Time Series Graphs: Graphs showing the daily value of the 24 hour average and the hourly maximum average for the near road monitoring, nearby air monitoring station and from the entire SCAQMD monitoring network. 

Anaheim: 2014, Q1 (PDF, 141kb)

Bar Graph Averages: Graphs showing the average, 24 hour maximum and hourly maximum value for near road monitoring, closest air monitoring station, and from the entire SCAQMD air monitoring network. 

Anaheim: 2014, Q1 (PDF, 125kb)

Hourly Data: Table of hourly NO2 (ppb) concentrations

Anaheim: 2014 (PDF, 795kb)  -  2014 (XLS, 210kb)


Use of SCAQMD’s Near Road NO2 air quality data is at the user’s discretion and should be done with caution. The intent of the monitoring data is to provide air quality information that is supplemental to the existing SCAQMD air quality monitoring regional coverage. This monitor is intended to represent Near Road NO2 concentrations, in which the objective is to determine the air quality impact of NO2 in locations adjacent to the highway source of pollution (motor vehicles). Measurements from this monitor alone cannot determine the relative contributions of regional or source-specific origins to NO2. Local conditions for pollutants can vary widely based on meteorological conditions and proximity to sources of NO2.

This monitor measures Oxides of Nitrogen (NO, NO2, and NOx). NO2 is one of several routinely monitored “criteria” pollutants that the US EPA links to human health impacts, and also is a key ingredient in the production of the secondary criteria pollutant, Ozone (O3). 

Data provided on this website has been reviewed but not yet finalized for EPA submission, and is therefore subject to change. Gaseous analyzers such as this instrument require a daily automated calibration sequence, which disrupts measurements every morning for 1-2 hours. Measurements may also be disrupted for periodic weekly maintenance and quality checks, as well as unforeseen power failures and instrument malfunctions. Data provided is representative only of valid hourly averages, whereby hourly averages with less than 75% valid minute averages were omitted per EPA Quality Assurance guidelines. Finalized data is cross checked against for daily calibration specifications and Quality Assurance Audit thresholds. Until data is finalized for EPA submission, portions of the reviewed quarterly data presented on the SCAQMD website may not meet quality assurance criteria, and therefore not be submitted for review of NAAQS attainment.

SCAQMD provides no guarantee, either express or implied, as to the accuracy, reliability or completeness of data furnished via the website, maps, or of the forecasts provided in the SCAQMD website. Further, SCAQMD shall not be liable under any circumstances for any direct, special, incidental or consequential damages with respect to any claim by any user or third party as a result of, or arising from, the use of the data, forecasts or maps.