Was the brick ever sand-blasted or anything? Was it painted BEFORE at some point? Was the brick re-pointed recently? Water, itself, shouldn't be a problem on brick. It's a fired material and somewhat breathable (by defacto design.)
Yes, I'd say you'd want a Brick (or Stone) Mason to look at it. I don't think in and of itself the powder is a problem because that could be Efflorescence from the 'pointing' (the cement BETWEEN the bricks) that's leaching out and probably 'running down' on the brick face. But, as for the brick, itself, doing some acting up, have a pro look at it. If you can't find one in the Phone Book, visit or call a local Stone Quarry or Gravel Yard for references.