Time-resolved exposure to volatile organic compounds in two California residences

Knowledge of human exposures to volatile organic compounds (VOCs) is critical for understanding their impact on human health. We measured time-resolved concentrations in combination with collecting occupancy data for a wide range of VOCs in two residences in northern California. We report exposures to hundreds of volatile organic compounds present indoors, spanning orders of magnitude in abundance, toxicity and reactivity. We show that concentrations of most VOCs were considerably higher indoors than outdoors, with the sum of measured VOCs being of an order of magnitude higher, in each season and each residence. Occupant's activities were the largest source of short-term episodic exposures, while VOCs from wood degradation were prominent contributors to chronic exposures. We show a comprehensive account of known and newly observed air toxics, their sources, and quantify time-resolved and daily-integrated exposures. We found that daily-integrated measurements could underestimate total exposure to VOCs and point to the need for time-resolved concentration measurements to accurately assess exposures.