In-home formation of halogenated volatile organic compounds (VOCS): implications for human exposure and indoor air quality
Abstract
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.
Description
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