Benzene drinking water contamination

Our experiment showed that formation rate of phenol from the reaction of OH with benzene was reduced by the addition of BPA. The reciprocal phenol formation rates are linearly correlated to the concentration of BPA (Fig. 1). From the slope and intercept of the regression line, the rate constant for reaction of OH with BPA was calculated to be 1.55 X 10 M This value is close to diffusion-controlled limits for bimolecular reactions ( 10 M Brezonik and Fulkerson-Brekken (1998)). Haag and Yao (1992) estimated rate constants for reactions of OH with several drinking water contaminants using the relative rate method. The rate constants for the reactions of OH with PAHs and methoxychlor were found to have values of 1 X 10 and 2 X 10 s respectively, close to the value obtained for BPA in... 

The question arose whether contaminants in the fairly dirty city air could pollute the drinking water by air-water exchange. You remember the two-box model shown in Fig. 21.9 and decide to make a first assessment by using the steady-state solution of this model. As an example you use the case of benzene, which can reach a partial pressure in air of up to p = 10 ppbv in polluted areas. You use a water temperature of 10°C and the corresponding Henry s law constant K, H = 3.1 L bar mol-1. The air-water exchange velocity of benzene under these conditions is estimated as vi a/w = 5 x 10 4 cm s 1. 

Benzene can enter your body through your lungs when you breathe contaminated air. It can also enter through your stomach and intestines when your eat food or drink water that contains benzene. Benzene can enter your body through skin contact with benzene-containing products such as gasoline. 

Inhalation exposure to high concentrations of benzene in the occupational setting may lead to death from pancytopenia and leukemia. However, environmental exposure to benzene in the air, drinking water, soil, or food is unlikely to be fatal. People living near hazardous waste sites who are chronically exposed to contaminated air, water, or soil may be at a higher risk of death due to adverse health conditions, including leukemia and other types of cancer. 

These data indicate that exposure to high levels of benzene in air, direct contact of the skin with benzene, and ingestion of high doses may result in dermal effects, but it is unlikely that levels of benzene in ambient air, in contaminated drinking water, or at hazardous waste sites are high enough to be of concern. 

Based on the above information, it is reasonable to assume that benzene could cause cancer in humans if inhaled or ingested in sufficient quantities. The increased risk that individuals may have by living near waste sites through contaminated air, drinking water, or soil cannot be ascertained until exposure estimates of benzene at these locations become better defined. 

Composite data from the Comprehensive Emergency Response, Compensation, and Liability Act (CERCLA) monitoring program indicate that benzene was detected at a frequency of 11.2% in groundwater in the vicinity of 178 inactive hazardous waste disposal sites (Plumb 1987). Data from a 1980 national survey by the Council on Environmental Quality on groundwater and surface water contamination showed benzene concentrations in contaminated drinking water wells in New York, New... 

Today a great variety of chemicals can contaminate sources of drinking-water. By far the most frequent contaminants in this category are trichloroethylene and tetrachloroethylene because of their large production volumes and widespread use in industry. Other chemicals that occur less frequently or at lower concentrations include dichloromethane, carbon, tetrachloride, chloroethylene (i.e. vinyl chloride), the 3 possible isomers of dichloroethylene, dichloroethane, 1,2,-dibromoethane, l,2-dibromo-3-chloropropane, and benzene. 

In 1990 there were 3 reports of the low level occurrence of benzene in beverages. Bottled mineral water was contaminated with benzene originated from an underground source of carbon dioxide which was inadequately carbon treated [23]. Two manufacturers found benzene in fmit flavoured mineral waters at levels greater than 5.0 pg/kg [24], The US EPA maximum contaminant level (MAE) for benzene is 0.005 mg/L [25] which is also the Canadian guideline as maximum acceptable concentration (MAC) in drinking water [26]. The manufacturers attributed the benzene to the presence of ascorbic acid and sodium benzoate in combination in their drink formations [27], omitting either of these additives eliminated the benzene. 

European Union Directive 98/83 underlines the importance of determining the quality of drinking water in order to protect human health. In particular, a number of chemical compounds are listed, such as benzene, 1,2-dichloroethane, tetrachloroeth-ylene, chloroform, and trihalomethanes, whose concentration in drinking water must be kept under well-defined thresholds. In Italy, laws DL 31/01, DM 152/99, and DM 471/99 set the norms for the concentrations of these, and of many other compounds in drinking water, wastewater, and contaminated sites, respectively. 

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