In plain English
FAR 52.223-19, Compliance with Environmental Management Systems, is a contract clause prescribed at FAR 23.406(b), most recently dated May 2011. The complete official text is reproduced below, verbatim, from GSA's published FAR source files.
Its text contains no sentence requiring insertion into subcontracts; see the flowdown section below for what that does and does not mean.
Does it flow down to subcontracts?
No flowdown mandate found in the clause text
We scanned the full clause text and found no sentence directing the contractor to insert this clause into subcontracts. That is a statement about the text, not legal advice: a prime contractor may still flow terms down contractually, an agency supplement (DFARS, VAAR, …) may add requirements, and clauses listed below (if any) may order this clause into subcontracts from the outside.
Where it's prescribed
As prescribed in 23.406(b), insert the following clause:
Prescribing reference: FAR 23.406(b).
The official text, verbatim
As prescribed in 23.406(b), insert the following clause:
Compliance with Environmental Management Systems (May 2011)
The Contractor’s work under this contract shall conform with all operational controls identified in the applicable agency or facility Environmental Management Systems and provide monitoring and measurement information necessary for the Government to address environmental performance relative to the goals of the Environmental Management Systems.
(End of clause)