It is evident that the mobile connected to the pure active system consistently maintains an output power below 0.01 W, and the mobile connected to a passive system can easily reach 1 or even 2 W (as shown in Figure 4.51). Using a traditional passive distributed antenna system will to some extent help with radiation from mobiles, especially mobiles being serviced by antennas with relatively low loss, close to the base station room. However, the fact is that, due to the losses in the passive system, the mobile has to compensate for the losses in the passive cable dB for dB, resulting in higher transmit power from the mobile and thus higher EMR exposure of the users.
Even if you often need to install an uplink attenuator between the active DAS and the base station to minimize the noise load of the base station, it is clear that the active DAS will keep radiation from the mobiles to the lowest possible power.
Both passive and active DAS will help bring down the transmit power from the mobiles, if the alternative is to rely on coverage via the outdoor macro net. All mobiles have to apply a certain radiation limit (SAR value), so even when operating on the highest power level, no mobile is dangerous.