The ambient RF microwave radiation exposure for all passengers inside a train carriage can reach high levels. For users on a train who are putting the devices next to their heads or on their bodies, those levels are even higher.
Display is in milliwatts per meter squared -- mW/m². On this measurement device, a level of 0.100 would be consider safe.)
Measuring some of what we are exposed to in the urban environment, from cell phone antennas, array, phone users, public transport, and other sources. Mostly taken in San Francisco CA. (For 'smart'-meter-specific information, please see that playlist.)