40 CFR § 58.61
Monitoring other pollutants
June 9, 2020
The Administrator may promulgate criteria similar to that referenced in subpart B of this part for monitoring a pollutant for which an NAAQS does not exist. Such an action would be taken whenever the Administrator determines that a nationwide monitoring program is necessary to monitor such a pollutant.
[71 FR 61303, Oct. 17, 2006]