Tracking exposure to air pollution

An apparatus for tracking a user's exposure to air pollutants, the apparatus comprising:

• a receiver configured to receive pollutant information from a plurality of data sources at one or more user locations;
• a processor;
• and
• a tangible non-transitory computer-readable medium that stores instructions,
• which when executed by the processor, cause the processor to:
• to determine a weighting for each of the plurality of data sources, the weighting representing quality of the pollutant information from the respective data source;
• select data sources from the plurality of data sources based on the weighting, wherein the selected data sources have a weight that is greater than a predetermined threshold;
• and aggregate pollutant information from pollutant information from the selected data sources to determine the user's exposure over a predetermined period of time.