NO2 Monitoring - Susceptible and Vulnerable Populations

As part of the final rule revising the nitrogen dioxide (NO2) NAAQS in 2010 (75 FR 6474), EPA required the Regional Administrators to identify an additional 40 monitors that would be located in areas representing susceptible and vulnerable (S/V) populations.  As noted in the preamble, “EPA recognizes that susceptible and vulnerable populations, which include asthmatics and disproportionately exposed groups, are at particular risk of NO2-related health effects, both because of increased exposure and because these groups have a higher prevalence of asthma and higher hospitalization rates for asthma.  EPA is requiring the Regional Administrators, under their discretionary authority, to work with States to site an additional forty monitors across the nation to focus primarily on communities where susceptible and vulnerable populations are located. To address the risks of increased exposure to these populations, the Administrator has determined that it is appropriate and necessary, under this provision, to ensure these additional forty monitors are sited primarily in communities where susceptible and vulnerable populations are exposed to NO2 concentrations that have the potential to exceed the NAAQS (due to emissions from motor vehicles, point sources, or area sources).”

These monitors were required to be operational no later than January 1, 2013. Siting and detailed monitor information is required for inclusion in annual monitoring network plans that are submitted by the monitoring agencies to EPA by July 1st of each year.

During 2012, EPA worked to identify candidate NO2 sites that were being operated in addition to the already required area-wide and near-road monitors required by the 2010 NAAQS rule.  Although the pertinent monitoring regulations did not specify a preferred regional allocation of S/V sites, EPA worked on the premise that a broad regional distribution of sites would be a desirable attribute of the network of sites intended to characterize susceptible and vulnerable populations.

Additionally, the monitoring regulation did not specify a metric to be used to identify candidate locations. EPA therefore utilized available analytical capabilities and local knowledge to prioritize locations of interest.

A minimum of 40 NO2 sites have been identified to meet the specific rule requirement. EPA has worked with state and local monitoring agencies to ensure that identified sites are documented in annual monitoring network plans as meeting the requirement for characterizing susceptible and vulnerable populations and that such sites are listed as State and Local Air Monitoring sites (SLAMS) in the Air Quality System (AQS) database.

Since AQS does not have specific metadata field to denote those sites identified as meeting the above described requirement, EPA is providing a supplementary table to document that the specific requirement as described in 40 CFR Part 58, Appendix D, section 4.3.4(a) is being met.¹

S/V NO2 monitors representing susceptible and vulnerable populations – Listed by EPA Region and AQS ID
Click the hyperlink to obtain a Google Maps view of the area surrounding each site

Table Revised July 12, 2013