Human exposure, drinking water

The health effects resulting from short-term exposure of humans to drinking water containing specific levels of thorium are not known. 

Following inhalation exposure, about 20-35% of nickel deposited in the lungs of humans is absorbed into the bloodstream. Absorption from the respiratory tract is dependent on the solubility of the nickel compound, with higher urinary nickel observed in workers exposed to soluble nickel compounds (nickel chloride, nicke sulfate) than in those exposed to less-soluble nickel compounds (nickel oxide, nickel subsulfrde). Following oral exposure, about 27% of the nickel given to humans in drinking water was... 

Accurate estimates of fluoride intake are important in order to resolve potential problems of too low or too high exposure. Drinking water, beverages and fluoride-containing dentifrices are regarded as the main contributors to human fluoride intake. The contribution of inhaled airborne fluoride, or fluoride from soil, to total fluoride intake is, under normal conditions, small [17,143,144] and is beyond the scope of this paper. 

Nitrobenzene can enter your body easily and quickly through your lungs, through your skin, or if you eat or drink contaminated food or water. Nitrobenzene is easily absorbed through the skin and this is a frequent pathway of human exposure. Drinking alcoholic beverages may result in nitrobenzene entering your body at a faster rate, no matter how you are exposed. 

To estimate human exposure to water pollutants, the pollutant concentrations predicted by the model must be combined with demographic data on the population using the water body(ies) under consideration as a water source. It can be assumed that the average adult drinks 2 liters of water per day 80). Therefore, if the concentration of the pollutant of interest in the water supply is known, the direct dietary exposure can be estimated. 

Lead-containing environmental media ingestion or inhalation rates are presented here for ambient air, diverse human diets, drinking water, and dust and/or soil. Dermal contact and potential dermal uptake into the bloodstream for the inorganic forms of environmental Pb encountered by nonoccupational populations are very low compared to the other routes of exposure, and this route is not addressed. 

States have made substantial recent progress in the adoption, and EPA approval, of toxic pollutant water-quahty standards. Furthermore, virtually all states have at least proposed new toxics criteria for priority toxic pollutants since Section 303 (c) (2) (B) was added to the CWA in February of 1987. Unfortunately, not all such state proposals address, in a comprehensive manner, the requirements or Section 303 (c) (2) (B). For example, some states have proposed to adopt criteria to protect aquatic hfe, but not human health other states have proposed human health criteria that do not address major exposure pathways (such as the combination of both fish consumption and drinking water). In addition, in some cases final adoption or proposed state toxics criteria that would be approved by EPA has been substantially delayed due to controversial and difficult issues associated with the toxic pollutant criteria adoption process. 

Human health effects of operations. This requires assessment of such things as workplace exposures effects of exposure to air toxics, contaminated drinking water and soil and exposures during product use, misuse, and disposal. 

Humans may also be indirectly affected through exposure to increased levels of toxic metals in drinking water and food. Increased levels of toxic metal are a consequence of direct deposition of pollutants into water sources, increased leaching of metal from soils and lake sediments, and increased corrosion of water pipes. 

Overview. Humans living in areas surrounding hazardous waste sites may be exposed to endosulfan primarily via dermal contact with or ingestion of contaminated soils since this compound is found bound to soil particles. Although endosulfan can be found in water as colloidal suspensions adsorbed to particles, ingestion of contaminated finished drinking water is not expected to be a major route of exposure since endosulfan is not very water soluble. Likewise, inhalation exposure to endosulfan via volatilization from contaminated media is not a major route of exposure since endosulfan is not very... 

Monte Carlo simulation, an iterative technique which derives a range of risk estimates, was incorporated into a trichloroethylene risk assessment using the PBPK model developed by Fisher and Allen (1993). The results of this study (Cronin et al. 1995), which used the kinetics of TCA production and trichloroethylene elimination as the dose metrics relevant to carcinogenic risk, indicated that concentrations of 0.09-1.0 pg/L (men) and 0.29-5.3 pg/L (women) in drinking water correspond to a cancer risk in humans of 1 in 1 million. For inhalation exposure, a similar risk was obtained from intermittent exposure to 0.07-13.3 ppb (men) and 0.16-6.3 ppb (women), or continuous exposure to 0.01-2.6 ppb (men) and 0.03-6.3 ppb (women) (Cronin et al. 1995). 

Reproductive Effects. Operating room nurses exposed to trichloroethylene have been reported to have an increased incidence of miscarriages, but they were exposed to many other anesthetics as well (Corbett et al. 1974). Survey results of 1,926 women who had spontaneous abortions revealed a greater risk of abortion associated with trichloroethylene exposure (Windham et al. 1991). This study is limited by multiple chemical exposure. Humans exposed to trichloroethylene in the drinking water in certain areas of the country have not shown adverse reproductive effects (Byers et al. 1988 Freni and Bloomer 1988 Lagakos et al. 1986a). 

With the exception of studies examining reproductive outcome in people exposed to trichloroethylene in drinking water (ATSDR 1997 MDPH 1994), intermediate-duration studies in humans following oral exposure were not available. Intermediate-duration oral studies of trichloroethylene in animals (Barret et al. 1991, 1992 Buben and O Flaherty 1985 Constan et al. 1995 Dawson et al. 1993 Goel et al. 1992 Isaacson et al. 1990 Mason et al. 1984 Merrick et al. 1989 NCI 1976 NTP 1988, 1990 Stott et al. 1982 Tucker et al. 1982 Zenick et al. 1984) are available, but did not adequately provide exposure levels that could be... 

Klienfeld and Tabershaw 1954 Prout et al. 1985 Stephens 1945 Stevens et al. 1992 Templin et al. 1993 Withey et al. 1983), or dermal (Bogen et al. 1992 Jakobson et al. 1982 McCormick and Abdul-Rahman 1991 Sato and Nakajima 1978 Steward and Dodd 1964 Tsuruta 1978) exposure. All these routes of exposure may be of concern to humans because of the potential for trichloroethylene to contaminate the air, drinking water, food, and soil. More information on the absorption of trichloroethylene following ingestion of contaminated soil and plants grown in contaminated soil near hazardous waste sites are needed to determine bioavailability of the compound in these media. 

Other environmental properties of interest are those that govern movement of chemicals, for these properties can influence not only the possibility of human exposure but also the lifetime and fate of the chemical. Clearly, if a nitrosamine is formed in, or introduced into, the soil and stays there, it presents little threat to man, and its lifetime will depend on the chemical or microbiological properties of the soil. If it should move to the surface and volatilize into the atmosphere, on the other hand, there will exist the possibility of human exposure via inhalation and also the possibility of vapor-phase photodecomposition. If a nitrosamine were to leach from soil into water, it could perhaps be consumed in drinking water alternatively, exposure of the aqueous solution to sunlight could provide another opportunity for photodecomposition. 

---