Concentration from drinking water

Dietary fluoride supplements, available in the form of tablets, drops, lozenges and rinse supplements, are recommended for caries prevention by medical societies in some countries, especially if the fluoride concentration from drinking water is low. These supplements contain different quantities of fluoride, usually 0.25, 0.50 and 1.00 mg of fluoride per unit, in the form of NaF [60]. Fluoride supplements are rarely prescribed for adults. 

Essentially, there are two distinct practical alternatives to the testing of complex mixtures. These are (1) the testing of material concentrated from drinking water and (2) the testing of a synthetic mixture of chemicals that have been identified in drinking water. 

In a recent study, which analyzed influent and effluent concentrations from drinking water treatment plants, it was concluded that only the treatment plants with membrane filtration removed PFCs efficiently [90]. However, PFCs analyzed did not include compounds with carbon chain lengths shorter than C6, thus not revealing the removal capacity for, e.g., PFBA and PFBS at process scale [90]. The generation of a concentrated waste stream when membrane filtration is used and the relatively high operation costs make this treatment method not widely used yet in the drinking water treatment process. 

The odor perception threshold for benzene in water is 2 ing/L. The benzene drinking water unit risk is 8.3 x lO L/pg. Calculate the potential benzene intake rate (mg benzene/kg-d) and the cumulative cancer risk from drinking water with benzene concentrations at half of its odor threshold for a 30 year exposure duration. 

Le Bel GL, Williams DT, Griffith G, et al. 1979. Isolation and concentration of organophosphorus pesticides from drinking water at the ng/L level, using macroreticular resin. J AOAC 62 241-249. 

Granular activated carbon (GAC) is commonly used to remove contaminants from drinking water. It has the ability to remove contaminants to very low concentrations. Brunotts and colleagues66 have studied 11 chemical spills and 18 groundwater contamination cases, which have shown that most... 

Sherlock JC, Ashby D, Delves HT, et al. 1984. Reduction in exposure to lead from drinking water and its effect on blood lead concentrations. Human Toxicol 3 383-392. 

Allergic conjunctivitis was most intensely aggravated at 1 ppm chloroform. At higher doses (10 and 100 ppm) the aggravation was still noticeable, yet less significant. At 1,000 ppm chloroform, the aggravating effect was not present. Blood chloroform concentrations increased as the concentration in drinking water increased from 0.01 to 1,000 ppm. 

Also reported are drinking water equivalent levels (DWELs). The DWEL is defined by the U.S. EPA as a lifetime exposure concentration protective of adverse, noncancer health effects that assumes all exposure to a contaminant is derived from drinking water. 

In a recent study in Australia, Thompson et al. [121] assessed the exposure to PFCs via potable water in Austraha. Sixty-two samples of potable water were collected from 34 locations across Austraha, including capital cities and regional centre. PFOS and PFOA were the most commonly detected compounds, and quantifiable levels were found in 49% and 44% of all samples, respectively. The maximum concentration in any sample was seen for PFOS with a concentration of 16 ng/L, second highest maximums were for PFHxS and PFOA at 13 and 9.7 ng/L. Assuming a daily intake of 1.4 and 0.8 ng/kg b.w. for PFOS and PFOA the average contribution from drinking water was 2-3% with a maximum of 22% and 24%, respectively. 

Macroreticular resins, particularly the Amberlite XAD series, have been used extensively to isolate and concentrate trace organic compounds from drinking water (1-8). We have previously reported the use of an XAD cartridge for this purpose and have evaluated the system for the analysis of organophosphorus pesticides (OPs) (4), polynuclear aromatic hydrocarbons (PAHs) (5), phosphate triesters (TAAPs) (6), or-... 

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