Does X mangle prompt environment variables?

I'm starting it with startx. Before that I have PS1 in my environment:

$ cat /proc/self/environ | tr '\0' '\n' | egrep '^PS'
PS1=[\u@\H \w] 
PS3=> 
PS2=> 
PS4=+ 

From inside X I get:

$ cat /proc/self/environ | tr '\0' '\n' | egrep '^PS'
PS3=> 
PS4=+ 

I checked in both GNOME and awesome. Is it expected behavior? Can I do something about it?