Not just picture taking, video shooting or data collection: drones are now also used for air analisys. Through sophisticated sensors, it is possible to detect presence of a large number of substances, with a live analytics data feedback from the drone itself, or by sending the raw data to a base station to perfom its magic. There are obviously constraints, mainly dictated by the sensor technology that still is not as accurate as it should be (hopefully a revolution will be brought by recently developed graphene sensors).
The turbulence created by the propellers it’s another issue that impose some limits, that will be overcome with time.
An interesting experiment was carried out in Poland: http://fpv.tv/mobile-platform-for-monitoring-selected-parameters-of-low-emissions/
and in Italy by the FlyingNose project: