There are two approaches towards ungrounded wiring, internationally. One, mostly used in Japan, is double isolation of appliances, i.e. no exposed metal parts that could become energized, even under fault conditions.
The other one is isolated rooms, i.e. rooms that don't provide any exposed grounded metal surfaces, thus even in case of a line to case fault in a metal cased appliance the ground path cannot be completed and humans or animals are not in danger. This allows for safely plugging appliances that should be grounded into ungrounded receptacles. Used to be most common in Germany prior to the advent of hot water central heating systems, taking exposed metal surfaces bonded to ground (pipes and radiators) into every room (hot water is the most common type of central heat all across Europe).
The third possibility is a system without ground reference, i.e. floating delta, where the ground path can't be completed either.
So, without knowing the exact details it's impossible to give a 100% safe answer.
However, considering the shape of most wiring in Brazil, most Brazilians couldn't care less about such issues I guess.
