Method for determining an exposure indication as a continuous cumulated exposure of a user to toxic substances in the air over a relatively long period of time, having the following steps: - providing a time motion profile as an indication over the course of time of a geographical position of the user during a journey, wherein the provision of the time motion profile is carried out by continuously acquiring geographical positions using one or more position localization units in a main device which is embodied as a mobile device, and an additional device which can be secured in a motor vehicle, wherein the additional device makes possible recording of a motion profile of the user which is independent of the vehicle system, and the additional device communicates with the mobile device via a communication interface, wherein the provision of the time motion profile is carried out (S4, S5) by checking plausibility and adding to time motion profiles which are acquired by the main device and the additional device; wherein the plausibility of the motion profile which is recorded in the mobile device is checked if the user is carrying the mobile device on his person during a journey, and in order to check the plausibility a last acquired geographical position can be compared with a current geographical position, wherein if the geographical distance is too large to be covered with a vehicle in the time which has passed, an acquisition gap is diagnosed, which can be closed manually by the user, and wherein the motion profile which is recorded in the mobile device is added to and a completed time motion profile is produced if the user is not carrying the mobile device on his person during a journey and is used to add to the motion profile of the additional device, - retrieving time-related and location-related air quality information items from an information source as a function of the provided time motion profile, wherein the air quality information items indicate one or more temporal progressions of dimension indications for toxic substances in the air of one or more toxic substance categories for a plurality of locations; - cumulating the dimension indications for the one or more toxic substance categories in accordance with a time grid and as a function of the respective location of the user; and - providing the one or more cumulated dimension indications as an exposure indication of a user to toxic substances in the air, wherein the exposure indication rates the effect of a preceding load, wherein the exposure indication is correspondingly updated by retrieving the air quality information items from the information source for the past if a motion profile which the mobile device has not acquired is subsequently received by the mobile device, wherein the motion profile is retrieved by the additional device. - providing a time motion profile as an indication over the course of time of a geographical position of the user during a journey, wherein the provision of the time motion profile is carried out by continuously acquiring geographical positions using one or more position localization units in a main device which is embodied as a mobile device, and an additional device which can be secured in a motor vehicle, wherein the additional device makes possible recording of a motion profile of the user which is independent of the vehicle system, and the additional device communicates with the mobile device via a communication interface, wherein the provision of the time motion profile is carried out (S4, S5) by checking plausibility and adding to time motion profiles which are acquired by the main device and the additional device; wherein the plausibility of the motion profile which is recorded in the mobile device is checked if the user is carrying the mobile device on his person during a journey, and in order to check the plausibility a last acquired geographical position can be compared with a current geographical position, wherein if the geographical distance is too large to be covered with a vehicle in the time which has passed, an acquisition gap is diagnosed, which can be closed manually by the user, and wherein the motion profile which is recorded in the mobile device is added to and a completed time motion profile is produced if the user is not carrying the mobile device on his person during a journey and is used to add to the motion profile of the additional device, - retrieving time-related and location-related air quality information items from an information source as a function of the provided time motion profile, wherein the air quality information items indicate one or more temporal progressions of dimension indications for toxic substances in the air of one or more toxic substance categories for a plurality of locations; - cumulating the dimension indications for the one or more toxic substance categories in accordance with a time grid and as a function of the respective location of the user; and - providing the one or more cumulated dimension indications as an exposure indication of a user to toxic substances in the air, wherein the exposure indication rates the effect of a preceding load, wherein the exposure indication is correspondingly updated by retrieving the air quality information items from the information source for the past if a motion profile which the mobile device has not acquired is subsequently received by the mobile device, wherein the motion profile is retrieved by the additional device.