Point-of-use Treatment Research Articles

Temporal Variability in Drinking Water and Toenail Arsenic Exposure Measurements

P-616 Abstract: Health effects associated with chronic, low-level exposures to arsenic in drinking water (<100 μg/L) remain unclear, in part due to uncertainties in assessing exposure. Drinking water and toenail arsenic concentrations have been used to assess past exposure to arsenic in epidemiological studies, under the assumption that a single measurement can be used to estimate historical exposure. Using data from a population-based case-control study of arsenic exposure and bladder cancer in Michigan, this study aims to better understand variability in drinking water and toenail arsenic concentrations. Drinking water samples were collected an average of fourteen months apart for 261 participants whose drinking water sources included private wells (n= 215), public water supply systems (n=33), and bottled water supplies (n = 13). Samples were collected from the primary drinking water source, which often included a point-of-use (POU) treatment system such as a home water softener or filter. Untreated samples were also collected from participants on private wells. Up to three toenail samples were obtained from participants. The first and second sample were clipped an average of fourteen months apart, while the second and third samples were collected an average of one month apart. All samples were analyzed for total arsenic using an Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Pearson correlation coefficients reveal strong relationships between the two drinking water measurements collected from untreated private wells (r= 0.91, p<0.0001, n=197). The correlation was also high for samples collected from the primary source of drinking water (r=0.88, p<0.0001, n=196), suggesting that a single measurement may be effective in estimating past exposure. While POU treatment devices did not differentially affect measurement reproducibility, use of these systems affected arsenic concentrations. Toenail samples collected an average of fourteen months apart were positively correlated (r=0.43, p<0.0001, n=236); less variability is apparent for samples clipped consecutively (r=0.77, p<0.0001, n=189). The influence of arsenic concentration, drinking water source, and other variables on reproducibility of the toenail arsenic measurement will be discussed. In conclusion, both exposure measurements may be effective in monitoring past exposures in a stable population; exposure misclassification may be reduced by accounting for consistency of drinking water source, POU treatments, and drinking water concentration over time.

Effects of time and point-of-use devices on arsenic levels in Southeastern Michigan drinking water, USA

Health effects associated with chronic, low-level exposures to arsenic in drinking water (<100 μg/L) remain unclear, in part due to uncertainties in assessing exposure. Drinking water concentrations have been used to assess past exposure to arsenic in epidemiological studies, under the assumption that a single measurement can be used to estimate historical exposure. This study aims to better understand (1) temporal variability in arsenic concentrations in drinking water and (2) the impact of point-of-use (POU) treatment devices on arsenic exposure measurements, and on reliability of the exposure measurement for population-level studies. Multiple drinking water samples were collected at two points in time (an average of fourteen months apart) for 261 individuals enrolled in a case-control study of arsenic exposure and bladder cancer in Michigan. Sources of drinking water included private wells (n=221), public water supplies (n=33), and bottled water (n=7); mean arsenic concentration was highest in private wells (7.28 μg/L) and lowest in bottled water samples (0.28 μg/L). Arsenic concentrations in primary drinking water samples were highly correlated (r=0.88, p<0.0001, n=196), with 3% of the water sources exceeding the United States Environmental Protection Agency's Maximum Contaminant Level (MCL) in one sample but not in the other sample. Measurement reproducibility did not vary by type of POU device (e.g., softener, filter, reverse osmosis system). Arsenic concentrations did differ, however, between samples treated with POU devices and untreated samples taken on the same day. Substantial differences in arsenic concentrations were consistently observed for reverse osmosis systems; other POU devices had variable effects on arsenic concentrations. These results indicate that while a single residential arsenic measurement may be used to represent exposure in this region, researchers must obtain information on changes in water source and POU treatment devices to better characterize population exposures over time.

Small Systems Is POU the Right Choice for Your System?

Point‐of‐use (POU) treatment often looks attractive to small community water systems, especially when compared to the difficulty and cost of installing centralized treatment or finding a new drinking water source. However, appearances can be deceiving. POU treatment may not be the right solution for everyone. This article explains the drawbacks and advantages of installing POU devices as an alternative to centralized treatment.

Point‐of‐use treatment and the revised arsenic MCL

Community water systems (CWSs) may comply with the US Environmental Protection Agency's new 10‐μg/L arsenic (As) standard using point‐of‐use (POU) treatment by reverse osmosis; however, current regulations do not specify exactly how a CWS should implement POU treatment. This article describes three scenarios for implementing a POU program and provides cost estimates for each scenario. These costs vary significantly depending on the amount of monitoring and maintenance assistance provided for each POU unit. The scenario with less‐frequent (triannual) As monitoring and annual maintenance assistance to the customer could be substantially less expensive than centralized treatment for many small CWSs. The triannual As monitoring is supplemented by more frequent conductivity measurements to ensure proper operation of the individual POU treatment units. The higher‐cost scenario, which includes a quarterly As monitoring schedule more typical of recent POU applications, is likely to be more expensive than centralized treatment for most CWSs. Although most CWSs would probably not adopt POU treatment as the preferred method of compliance with a stricter As standard under the current regulations, a POU treatment program may be a less‐costly variance option for CWSs for which centralized treatment is not economically feasible.

Reducing fluoride by managed POU treatment

Reducing fluoride at the point of use may be a solution for some small systems.Through the cooperative efforts of regulatory agencies, utility management, and equipment manufacturers, a small systems demonstration study involving reverse osmosis point‐of‐use (POU) drinking water units for fluoride reduction has been successfully concluded in Suffolk, Va. This three‐year study offers evidence for the regulatory consideration of individual POU treatment units for fluoride reduction in small public water systems if more conventional measures are unavailable.

Field Experience With Point‐of‐Use Treatment Systems for Arsenic Removal

Point‐of‐use (POU) treatment devices can be effective for removing inorganic contaminants. This article describes the investigation of POU treatment systems used for arsenic removal in four homes in Alaska and Oregon. Small systems utilizing activated alumina, ion exchange, and reverse osmosis techniques were field‐tested on waters naturally contaminated with arsenic. The waters contained arsenic in concentrations ranging from 0.1 to 1.0 mg/L, which were successfully lowered to below the 0.05‐mg/L maximum contaminant level.