This research data supports the publication "Neurological and Respiratory Outcomes of the HIPTox Controlled Double-Blind Air Pollution Exposure Trial", published in npj clean air, April 2026. The dataset contains demographic information, raw health data, raw cognitive data, processed cognitive data, and estimated marginal means and SDs following analysis. Also included are hourly average concentrations of Particulate Matter and Nitrogen Oxides during air pollution (or clean air) exposure sessions.