1It isn't possible to modify the env vars 
2of a running process. This isn't unique to 
3NodeJS processes. It's just how env vars 
4work on UNIX like operating systems.
5The vars live within the address space of 
6the process. And while they are, typically,
7initially placed at a well known location
8near the top of the stack the current vars are 
9likely to be at an arbitrary address in the heap. 
10Env vars are intentionally private to each process. 
11So unless the program provides an API for 
12changing its env vars you can't
13modify them once the program is running.