Difference between the desktop PATH and switchd user PATH

I have user who gets "word too long" error when trying to start the
application from his desktop (as a user). the tcsh PATH when using
the env command from the desktop terminal, is too long.

However, he has no problem starting the application when he logs in as
a root, start the terminal session, and switches the user using su -
jeff. Also, the PATH is lot shorter when I use "env" command.

I will really appreciate if someone can explain why there is a
difference in PATH variable between desktop user env and switched user

Thanks in advance.