Apparatus, systems, and methods for measuring environmental exposure and physiological response thereto are provided. A monitoring apparatus worn by a subject includes a physiological sensor that detects physiological information from the subject, an environmental exposure sensor that detects at least one airborne analyte in a vicinity of the subject, and a processor. The processor processes signals produced by the environmental exposure sensor and calculates a volumetric concentration of the least one airborne analyte. In addition, the processor process signals produced by the at least one physiological sensor to determine a physiological response of the subject to the at least one airborne analyte. The apparatus also includes a motion sensor and the processor calculates a distance traveled by the subject via signals produced by the motion sensor and calculates a volume of air to which the subject has been exposed using the distance traveled by the subject.