Characterization of the emissions of trichloroethylene, chloroform, and 1,2-dibromo-3-chloropropane in a full-size, experimental shower.

We have characterized emissions of trichoroethylene and chloroform (two highly volatile organic chemicals), as well as 1,2-dibromo-3-chloropropane (DBCP) (a moderately volatile organic chemical) from a full-size (1.5 m3), experimental shower. For typically hot showers (approximately 40 degrees C), the present volatilization was found to be approximately 80% for trichoroethylene (TCE), 60% for chloroform, and 20% for DBCP. Among the factors studied, the temperature of the water typically had a dominant effect on the total release of each of the three chemicals from the shower water to the air, such that the extent of volatilization increased as influent water temperature increased. For TCE, water flow rate was found to be negatively correlated with fractional volatilization, while airflow through the chamber had a small effect, although it did affect the ensuing air concentrations in the shower chamber.

Modeling the effects of water usage and co-behavior on inhalation exposures to contaminants volatilized from household water.

The volatilization of volatile organic chemicals during domestic water usage can result in significant indoor air concentrations, and the subsequent inhalation of these contaminants is an important route of exposure. The magnitude of these exposures is highly dependent on the activities undertaken by the exposed individual, as well as the activities of other occupants of the home. The indoor air quality-exposure Model for the Analysis of Volatiles and Residential Indoor Air Quality (MARVIQ) was used to ascertain the impact of water-use activities on the potential contaminant dose to household members. Human time-activity patterns of various population groups were sampled from the California Air Resources Board database, applying distributions of water-use occurrence and water-use duration to each activity based on survey results. Indoor air concentrations in a sample house and the resulting potential inhalation dose to the occupants were computed for different individuals and pairs of individuals to test for exposure and coexposure effects. The simulated daily exposure is well described by a simplified equation that is a function of the amount of time the individual spends in the shower, the bath, and the bathroom; the total water usage in the home; and the fraction of time the individual is at home. These results can be used to identify high-risk populations, individuals, and households. The study also demonstrates the importance of further research on joint time-activity patterns in multiperson households for assessment of exposure and coexposure effects.

Determining health risks associated with disinfectants and disinfection by-products: research needs.

In order to minimize the levels of potentially toxic disinfectants and disinfection by-products in treated water while maintaining adequate protection against microbiological contamination, the total risks associated with disinfection have to be measured and compared with the risks from microbial agents. Because much work has already been carried out on chlorination and its by-products, it is recommended that research focus on major disinfection alternatives, i.e., ozonation, chloramination, carbon dioxidation, and the most practical combinations of these options. The primary research needs are (1) assessment of the relative toxicological hazards of the disinfectants and their by-products and (2) development of biologically based models for the dose-response relationships of these chemicals.

Inhalation exposure in the home to volatile organic contaminants of drinking water.

Our field studies show that indoor air concentrations of volatilized trichloroethylene (TCE) can be substantial when TCE-contaminated water is used domestically. Using a model shower, increases in TCE water concentrations, water temperature and drop path (time) increased the steady-state air TCE concentrations. Volatilization was incomplete and the rates were comparable to predicted ones. Indoor air models show that the inhalation route of exposure for such chemicals has the potential for being much greater than by direct ingestion. This should be considered in developing regulations to limit adverse health impacts from contaminants of potable water.

Human exposures to volatile halogenated organic chemicals in indoor and outdoor air.

Volatile halogenated organic chemicals are found in indoor and outdoor air, often at concentrations substantially above those in remote, unpopulated areas. The outdoor ambient concentrations vary considerably among sampling stations throughout the United States, as well as diurnally and daily. The vapor pressures and air-water equilibrium (Henry's Law) constants of these chemicals influence considerably the likely relative human exposures for the air and water routes. Volatilization of chemicals from indoor uses of water can be a substantial source of exposure, as shown for radon-222. Measurements of air concentrations of trichloroethylene (TCE) in showers using TCE contaminated groundwater show increases with time to as high as one-third of occupational threshold limit values. Using a scaled down experimental shower, such volatilization and subsequent decay in air was also demonstrated. Using a simplified indoor air model and assuming complete volatilization from a full range of typical water uses within the home, calculations indicate that the expected air inhalation exposures can be substantially higher than those from ingestion of these chemicals in drinking water. Although the regulation of toxic chemicals in potable water supplies has focused traditionally on direct ingestion, the volatilization and inhalation from other much greater volume indoor uses of water should be considered as well.

Polynuclear aromatic hydrocarbons in the water environment.

Many polynuclear aromatic hydrocarbons (PAH) are known to be carcinogenic to animals and probably to man. This review is concerned with carcinogenic and non-carcinogenic PAH in the water environment, with emphasis on 3,4-benzpyrene (BP) because it is ubiquitous, is one of the most potent of the carcinogenic PAH and has been widely studied. Although PAH are formed in combustion and other high-temperature processes, there is also evidence for their endogenous formation in plants, which may explain their ubiquity therein. Although the solubility of these compounds in pure water is very low, they may be solubilized by such materials as detergents, or they may otherwise occur in aqueous solution associated with or adsorbed on to a variety of colloidal materials or biota, and thereby be transported through the water environment. A notable characteristic of PAH is their sensitivity to light.PAH have been found in industrial and municipal waste effluents, and occur in soils, ground waters and surface waters, and their sediments and biota. With the exception of filtration or sorption by activated carbon, conventional water treatment processes do not efficiently remove them, and they have been found in domestic water supplies. Because of the ubiquity of PAH in the environment, it is impossible to prevent completely man's exposure to them; nevertheless their surveillance should be continued and their concentrations in the environment should be reduced where practicable.