Reader monads have been used to implement dependency injection in Haskell and Scala libraries. A monad in general is the ability to compose two functions that have pure arguments and return values that encode some effect... in this case the effect is simply to pass along some read only environment.

Based on my understanding of above, passing an environment as a parameter is not the Reader monad, in fact passing the parameter explicitly through chains of function calls is what the Reader monad intends to avoid in typed, pure functional programming.