In-home formation of halogenated volatile organic compounds (VOCS): implications for human exposure and indoor air quality
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Recent studies have shown that drinking water can be an important source of indoor air pollution. For many chemicals a much greater risk is posed when these chemicals are emitted from residential water sources and then inhaled, compared to risks by ingestion. The overall goal of this research was to better characterize emissions and subsequent exposures of building occupants to chlorinated organic compounds. A series of 14 preliminary flask experiments and 16 laboratory experiments were completed to quantify formation and emission of disinfection byproducts (DBPs) from the use of chlorine-containing detergents in residential dishwashers. Flask experiments involved mixing food and dishwasher detergent in water and were intended to identify chemicals that may form from dishwasher usage. Liquid concentrations of chloroform ranged from 1-41 mg/L. Laboratory experiments involved collection of liquid and gas samples over the course of a dishwasher operating cycle. Background concentrations of chloroform in the water supply were generally between 0 and 10 mg/L; liquid chloroform levels in the wash cycle were typically at least 50 mg/L. The other trihalomethanes (THMs) were detected less frequently, though this result was likely a result of low bromide ion levels in the water supply. Gas chloroform concentrations were generally between 0 and 5 mg/L in the dishwasher headspace. Concentrations of the other THMs were lower than chloroform but consistent with corresponding liquid samples. A computational model was used to complete a detailed assessment of the contribution of dishwashers to chloroform inhalation exposure. Overall exposure to chloroform was found to be highly dependent on activity patterns. Inhalation was predicted to be a more important exposure pathway than ingestion for chloroform exposure. A series of field experiments was completed in three homes to measure chloroform concentrations during periods of residential water usage. Field experiments involved operating a shower and dishwasher at each test house and a washing machine in one home, then measuring gas chloroform concentrations in two different rooms. Room chloroform concentrations were typically between 0 and 5 mg/m3 . The highest concentrations were generally measured immediately after dishwashing and showering events.