Response to OMB – CO NFR

Issue #1 – Population threshold by which CO monitors are to be required

The EPA proposed the population threshold by which CO monitors would be required 

(collocated with near-road NO2 monitors) to be CBSAs with populations of 1 million or more 

persons. The Agency received public comment from public health and environmental groups to 

lower the threshold to 500,000 (matching NO2 requirements), effectively adding to the total 

number of required monitors, while a number of states suggested the threshold be raised to a 

threshold of 2.5 million, effectively reducing the total number of required monitors. The Agency 

also received comment from one industry commenter (API) who stated that the 1 million 

threshold “...appears appropriate, but EPA should not require that both [near-road NO2] sites in 

the largest CBSAs host CO monitors.”

As noted in the preamble text, the EPA believes that the population threshold of 1 million 

is an appropriate threshold by which to require CO monitors, as it will result in a sufficiently 

sized national network to meet monitoring objectives. In their public comments, ALA, ATS, and

EDF described the proposed threshold to be more akin to a ‘pilot project’ due to its lack of size. 

While EPA does not believe the network needs to be so large to include CBSAs with 500,000 

people or more, the Agency does view a network required only in CBSAs of 2.5 million or more 

persons to provide an insufficient level of geographic coverage to be considered a national 

network, as it would only cover 21 urban areas (based on recently released 2010 Census Bureau 

data). The use of the 1 million population threshold is an efficient design requiring what the 

Agency believes is a sufficient number of monitors over a broad geographic area, representing 

approximately 52 different urban areas which contain approximately 55% of the total US 

population (based on recently published 2010 Census Bureau data). Additionally, this threshold 

provides for monitoring of a wide range of diverse situations with regard to traffic volume, 

traffic patterns, roadway designs, terrain/topography, meteorology, climate, as well as

surrounding land use and population characteristics. This more robust network will better 

support the evaluation of compliance with the NAAQS and support future NAAQS reviews.

Additionally, the EPA notes that state and local air agencies will be in a position to move 

existing monitors or pull analyzers out of storage for insertion in the near-road NO2 monitoring 

infrastructure to satisfy the near-road CO monitoring requirements. Accordingly, the Agency

believes that the costs and burden associated with the implementation of the 1 million person 

threshold are minimal, only $815 per required monitor, based on ICR calculations (~$0.06 

million, network wide, for the relocation of approximately 77 CO monitors). Further, the EPA 

believes that state and local air agencies will likely be able to shut-down some existing single 

pollutant CO monitoring sites as they relocate their monitors. These shut-downs of single 

pollutant sites will reduce overall resource burden to any air agency by reducing the total number 

of monitoring sites they operate (across all NAAQS pollutants). In the final rule EPA has 

postponed the deadline for installation of CO monitors from the proposed deadline of January 1, 
2013 to January 1, 2015 in order to provide time for states to prepare the near road infrastructure 

for NO2 monitors and to allow time for EPA to approve the shutdown and transfer of monitors, 

as appropriate.

In summary, the EPA believes that the 1 million person threshold supports the 

establishment of a minimally sufficient national CO network near roads, as part of a multipollutant monitoring paradigm, at a near negligible cost.

Issue #2 – Safety in the near-road environment

The EPA recognizes safety as a top priority in the implementation of any near-road 

monitoring requirements. This is evident in the preamble to the final rule promulgating the 

requirements for near-road NO2 monitors. By requiring CO monitors to be collocated with nearroad NO2 monitors, network implementation issues such as safety will effectively be handled as 

the near-road NO2 network is installed. In an effort to support state and local air agencies in the 

implementation of near-road NO2 sites, the EPA is collaborating with US DOT – Federal 

Highways, several state DOTs (Florida & Texas), along with partner state and local air agencies, 

to provide technical assistance on near-road site implementation to the air monitoring 

community. Safety is a key subject in that assistance, with topics covering issues of right-of-way

access, the use of safety features such as guardrails or recognition of ‘clear zones’, and how to 

engage DOTs to ensure safety of the travelling public, air monitoring staff, and air monitoring 

infrastructure at near-road monitoring sites. Further, monitoring by roads for CO is not a new 

concept to states and local air agencies. They have been monitoring near roads, mainly in 

downtown areas and in urban street canyons, since the late 1970s. The EPA believes that state 

and local air agencies are very aware of safety issues, in part based on existing experience, and 

the Agency is confident that they will be able to successfully implement near-road monitoring 

sites safely through the use of the technical assistance to be provided and by working with their 

respective DOTs as necessary.