Benzene contamination

TABLE 1 Comparison of Projected Capital Costs for Major Bioreactor Components and of Operating Costs for Three Treatment Alternatives for Benzene-Contaminated Water (Costs in U.S. Dollars, 1995)... 

Monochlorobenzene is widely used as a solvent and industrial intermediate it can also be formed upon chlorination of benzene-contaminated water, a possible explanation of the higher incidence in treated water than in raw water (3). Levels detected in this limited survey, however, were all <5 /xg/L. 

Exposure to benzene-contaminated water can also provide an opportunity for both inhalation and dermal absorption. In a series of experiments conducted in a single-family residence from June 11 to 13, 1991,... 

Several in vivo and in vitro studies conclusively demonstrate that benzene can be absorbed through human skin (Blank and McAuliffe 1985 Franz 1984 Susten et al. 1985 Tsuruta 1989). In general, skin absorption is considered a minor source of concern in the occupational environment as it occurs at a much lower rate and extent compared with benzene absorption through the respiratory system (OSHA 1989). However, benzene absorption through the skin as a result of benzene contamination in rubber solvents is a major route of exposure in tire building operations (Susten et al. 1985). Benzene is an irritant to the skin and, by defatting the keratin layer, may cause erythema, vesiculation, and dry and scaly dermatitis... 

Figure 5-1. Frequency of NPL Sites With Benzene Contamination... 

CEH. 1983. Centers for Environmental Health. Benzene contamination in well water, Perdido, Alabama. Public Health Service-CDC-Atlanta EPI-82-90-2. 

The current allowable airborne exposure level for benzene as an impurity in solvent mixtures is 0.1 %. Benzene is also readily absorbed through the skin and those having dermal contact with solvents used for cleaning that contain 0.1% benzene contamination (the current allowable level) can be subjected to significant benzene absorption. In a study of workers who cleaned their hands with such solvents, the risk for leukemia was increased by 42%J161 This example points out the need for a more stringent regulation for the allowable concentration of benzene in solvent mixtures. The authors of the study cited recommend that the allowable level be reduced from 0.1 % to 0.01%. Other studies have made similar recommendations. 1171... 

Fortunately, several factors, including dilution, specific inactivation by chorine, ozone or other disinfectants, nonspecific inactivation by natural factors such as sunlight and microbes, filtration, and the small quantity of water individuals consume reduce the risk of disease from intentional contamination of water supplies (45). A few water treatment facilities add activated carbon to filter media to control taste, odor, and other chemical problems. These filters may provide additional protection against some of the organic toxins (45). The international recall of Perrier bottled water due to concerns abont benzene contamination is evidence that bottled water is susceptible to contamination (45). 

Kudla, I. (1997). Exposure to benzene-contaminated toluene and bone marrow disorders—A retrospective exposure assessment Appl Occup Environ Hyg 12, 11-14. 

It is rather interesting to note that the impurity values determined by static methods are systematically lower than those determined on the same sample by dynamic methods (3,4). However, an extremely careful study by Glasgow et al. (18) on a sample of very pure benzene contaminated by known amounts of n-heptane showed that the divergence between the two methods of determination was not so large as was formerly obtained. The results of this study are given in Table 10.2. It is suggested that the difference in values may be due to chemisorbed water as a source of contamination. 

Leakage from underground storage tanks or from hazardous waste sites containing benzene can result in benzene contamination of well water. 

Carbon disulfide from a number of sources was analyzed for benzene contamination. The results are given in the following table. The benzene contaminant can be removed with the procedures given in section 4.1. 

Lead is a toxic metal that affects the central nervous system. A Pb-contaminated water sample contains 0.0011% Pb by mass. What volume of the water in milliliters contains 115 mg of Pb (Assume that the density of the solution is 1.0 g/mL.) 58. Benzene is a carcinogenic (cancer-causing) compound. A benzene-contaminated water sample contains 0.000037% benzene by mass. What volume of the water in liters contains 175 mg of benzene (Assume that the density of the solution is 1.0 g/mL.)... 

Benzene has a significant contamination effect on fuel cell performance. For example, with 50 ppm benzene in the air, cell voltage can drop by 160 mV within 15 min at 0.2 A cm [9]. The severity of benzene contamination was found to be a function of operating current density When a fuel cell was fed with 50 ppm benzene in the air for 30 min, rather than pure air feed, the power output dropped 5% at 50 mA cm , and 28% at 200 mA cm . In addition, cell performance did not fully recover until after the benzene-containing air was replaced with neat air. 

The effect of benzene contamination on the PEMFC performance is a function of operating current density (Moore et al., 2000) as the cell performance loss was more marked at higher current densities. 

The role of equilibrium in these processes is summarized in Figure 1.3. This shows that we want to go from where we are to somewhere else (e.g., make ammonia or remove the benzene contaminant), but that equilibrium acts like a brick wall between here and there, allowing us to get only part way. We use separation and recycle (Figure 1.1) or large amounts of one stream (Figure 1.2) to overcome this difficulty. To know the dimensions of our problem, we... 

Benzene-contaminated water is pumped from a remediation well to a storage lagoon. In the lagoon, benzene is present at a concentration of 10 mol/liter. Given a density of benzene-degrading bacteria of 10 cells/ml, a Vmax of 10 mol/(cell sec), and a Ks of 7.8 x 10 M, estimate the rate of benzene biodegradation. 

The unknown spectrum is that of a sample of benzene contaminated by Af-methyl hexamide. 

---