specific causes of alienation among police officer caused by police work

They become disillusioned with humanity
- the nastier ones become predatory

What sort of answer are you hoping for in exchange for $2? I mean, I
could probably go on about this forever.

Your question supposes first that alienation is "caused" by police
"work"; and to come extent it is but it isn't solely to blame. There
is also the complex societal factors (how they are viewed by the
public, trends, politics) that alienates them. These are issues over
which they have little or no control. In addition there is alienation
from, by, or within the family that is a very comlpicated study all
it's own. So when you say "alienation among police officers" do you
mean within their own ranks only or are you wondering about why they
tend to be alienated by various segments of society?