The realistic assessment of the Electromagnetic Field exposure due to wireless telecommunication base stations is critical to protect the population from harm due to excessive exposure, and allow wireless service providers to use the available technology in the most rational way. The classic approach based on the worst-case scenario used in 2G to 4G leads to over conservative results in the 5G base stations, due to the use of massive MIMO and dynamic pattern beamforming. A statistical approach is required to obtain a more realistic assessment. In this contribution, we propose first results obtained using a Monte Carlo simulation method to assess electromagnetic field exposure levels for different scenarios.