LTE+Wifi FaceTime on a BT headset, while roaming on another network that is not your home network, while air playing the session to a portable LCD TV via AppleTV, and buying some gum at best buy using applepay and viewing the bestbuy app on the screen so it is using your location .
Because interrogation mode for your home service provider is still performed, and if you are roaming on a competing GSM /GSM or CDMA /CDMA scenario, the frequency spectrums are not common.
So it is possible for you to be splitting the upper and lower spectrums of the roamed network on 1.8Ghz and 850Mhz, on GSM, on AT&T, or GSM 850Mhz on Verizon (thought Alltel ) and in aggressive mode looking for UMTS and LTE on 1.7Ghz , 2.1Ghz AWS and 1.9Ghz PCS if you are a TMO subscriber.
The total PowerOut won’t aggregate above the 1.8W but the level of electromagnetic RF saturation would be elevated .
Just because the wattage for any frequency doesn’t elevate abive a safe threshold, you could be transmitting 10x the broadcast RF across the spectrum and that would mean vastly increased microwave radiation.