POU water filters effectively reduce lead in drinking water: a demonstration field study in flint, Michigan

Removal of metals and assimilable organic carbon by activated carbon and reverse osmosis point-of-use water filtration systems

Activated carbon (AC) systems and reverse osmosis (RO) systems are commonly used point-of-use (POU) water filtration systems for removing trace-level contaminants in tap water to protect human health. However, limited research has been done to evaluate their effectiveness in removing heavy metals like manganese (Mn) and uranium (U), or to assess the potential for undesired microbial growth within POU systems, which can reduce their treatment efficiency. This study aimed to systematically evaluate the removal of metals and assimilable organic carbon (AOC) in POU systems. AC systems were operated to 200% of their designed treatment capacities and RO systems were run for three weeks. The results showed that AC systems were generally ineffective at removing metals from drinking water, while RO systems effectively removed them. Both Mn and U were poorly removed by AC systems. Calcium (Ca) and magnesium (Mg) were poorly removed by AC systems, with efficiencies of less than 1%. Iron (Fe) removal by AC systems varied between 61% and 84%. Copper (Fe), likely due to its low influent concentration (<30 μg L-1), was effectively removed by AC systems with efficiencies over 95%. In contrast, RO systems consistently removed all metals effectively. Mn and U removal in RO systems exceeded 95%, while Ca, Mn, Fe, and Cu were all removed with efficiencies greater than 98%. AOC was effectively removed from all AC and RO systems, but with high variability in removal efficiency, which is likely attributed to the heterogeneity of biofilm and microbial growth within the POU systems. The new knowledge generated from this study can improve our understanding of chemical contaminant removal in POU systems and inform the development of better strategies for designing and operating POU systems to remove chemical contaminants in drinking water and mitigate their associated health risks.

Household Water Lead and Hematologic Toxic Effects in Chronic Kidney Disease

Importance

The consequences of low levels of environmental lead exposure, as found commonly in US household water, have not been established.

Objective

To examine whether commonly encountered levels of lead in household water are associated with hematologic toxicity among individuals with advanced kidney disease, a group known to have disproportionate susceptibility to environmental toxicants.

Design, Setting, and Participants

Cross-sectional analysis of household water lead concentrations and hematologic outcomes was performed among patients beginning dialysis at a Fresenius Medical Care outpatient facility between January 1, 2017, and December 20, 2021. Data analysis was performed from April 1 to August 15, 2023.

Exposure

Concentrations of lead in household water were examined in categorical proportions of the Environmental Protection Agency's allowable threshold (15 μg/L) and continuously.

Main Outcomes and Measures

Hematologic toxic effects were defined by monthly erythropoiesis-stimulating agent (ESA) dosing during the first 90 days of incident kidney failure care and examined as 3 primary outcomes: a proportion receiving maximum or higher dosing, continuously, and by a resistance index that normalized to body weight and hemoglobin concentrations. Secondarily, hemoglobin concentrations for patients with data prior to kidney failure onset were examined, overall and among those with concurrent iron deficiency, thought to increase gastrointestinal absorption of ingested lead.

Results

Among 6404 patients with incident kidney failure (male, 4182 [65%]; mean [SD] age, 57 [14] years) followed up for the first 90 days of dialysis therapy, 12% (n = 742) had measurable lead in household drinking water. A higher category of household lead contamination was associated with 15% (odds ratio [OR], 1.15 [95% CI, 1.04-1.27]) higher risk of maximum monthly ESA dosing, 4.5 (95% CI, 0.8-8.2) μg higher monthly ESA dose, and a 0.48% (95% CI, 0.002%-0.96%) higher monthly resistance index. Among patients with pre-kidney failure hemoglobin measures (n = 2648), a higher household lead categorization was associated with a 0.12 (95% CI, -0.23 to -0.002) g/dL lower hemoglobin concentration, particularly among those with concurrent iron deficiency (multiplicative interaction, P = .07), among whom hemoglobin concentrations were 0.25 (95% CI, -0.47 to -0.04) g/dL lower.

Conclusion

The findings of this study suggest that levels of lead found commonly in US drinking water may be associated with lead poisoning among susceptible individuals.

Impact of orthophosphate on the solubility and properties of lead orthophosphate nanoparticles

Orthophosphate (PO4) is a commonly used corrosion control treatment to reduce lead (Pb) concentrations in drinking water. PO4 reduces Pb concentrations by forming relatively insoluble lead phosphate (Pb-PO4) minerals. In some cases, however, Pb-PO4 minerals have been observed to form nanoparticles, and if suspended in water, these nanoparticles can be mobile and reach consumer taps. Although recent research on Pb-PO4 particles has been performed, there remains a need to improve our understanding of the nature of Pb-PO4 nanoparticles. For that reason, Pb precipitation experiments were conducted to generate Pb-PO4 nanoparticles in bench scale studies for analysis. The study objective was to observe how pH, dissolved inorganic carbon (DIC), and PO4 impacted the properties of Pb-PO4 particles. Specifically, particle size, surface charge, mineralogy, and solubility were analysed. Hydrocerussite was precipitated when no PO4 was present, hydroxypyromorphite (Pb5(PO4)3OH) nanoparticles (<100 nm diameter) were precipitated when excess PO4 relative to Pb necessary to completely precipitate the mineral was present, and a mixture of the two minerals was precipitated when an insufficient amount of PO4 was present. Hydroxypyromorphite particles were less soluble than hydrocerussite by up to two orders of magnitude. The estimated K sp,OH of 10-66.87 in this work closely aligned with previous K sp,OH estimates that ranged from 10-66.77 to 10-62.79. Hydroxypyromorphite particles would not settle in water which was likely due to their small size and high negative charge. The mobility and size of these particles indicates that there are potential implications for such particulate Pb to remain suspended in water and thus be present in the tap water.

An evaluation of properly operated NSF/ANSI-53 Pb certified drinking water filters in Benton Harbor, MI

Communities across the United States and particularly in the Midwest continue to grapple with the complications associated with aging infrastructure. This includes the presence of lead (Pb)-bearing plumbing components such as lead service lines, downstream galvanized iron pipes, and Pb/tin solder. The community of Benton Harbor, MI, experienced six Pb action level exceedances between 2018 and 2021, leading to increasing community concern and a request from the state of Michigan for the US Environmental Protection Agency involvement. Between 9 November and 17 December 2021, US EPA Region 5 and Office of Research and Development, along with the state of Michigan, conducted a water filter efficacy and Pb-nanoparticulate (<100 nm) study to evaluate the performance of NSF/ANSI-53 Pb-certified drinking water filters and the presence of nanoparticulate. In this study, a total of 199 properly installed and operated drinking water filters (combination of faucet mounted and pitcher) were tested in their residential locations. One hundred percent of the water filters were found to perform to the standard to which they were certified, with filtered drinking water Pb concentrations below 5 ppb (maximum observed was 2.5 ppb). In addition, Pb particulate was identified; however, discrete Pb-containing nanoparticles were not widely found or identified.

Faucet-mounted point-of-use drinking water filters to improve water quality in households served by private wells

Approximately 13 % of Americans rely on private wells for household potable water. As private wells are not regulated beyond initial construction and often employ limited or no treatment, source water from wells can be vulnerable to contamination. While several studies have assessed applications of point-of-use (POU) filters in improving municipal tap water quality, few have investigated their use with private well water. This effort aims to build on previous examinations of POU treatment as a strategy to reduce adverse household drinking water exposures by: 1) assessing the effectiveness of commercially available faucet-mounted POU filters for improving microbial and chemical water quality in homes with private wells; and 2) documenting household ease of use and satisfaction with the filters. Faucet-mounted POU filters were distributed to 21 homes reliant on private wells in southern West Virginia and southwestern Virginia. Study participants were asked to collect water samples from two taps in their homes pre-filter installation, and again two-weeks and four-weeks post-installation. Participants filled out surveys about perceptions of their drinking water and the filter. Concentrations of Total Coliform, Ba, Cd, Cr, U, Cu, Pb, Al, Fe, Mn, Zn, and Sr were significantly lower (p < 0.05, Wilcoxon Rank Sum) in filtered water samples compared to paired unfiltered samples (n = 42) for the study period. However, concentrations of certain contaminants in filtered samples from homes with high levels of source water contamination still exceeded drinking water standards. Less than half of study participants reported that they intended to keep using the filters, citing issues of flowrate. Our findings suggest that faucet-mounted POU filters, while effective in reducing contaminants, might not be an appropriate intervention to improve water quality for all homes on private well water. Future investigation is required to improve filter user satisfaction and better assess appropriate source water chemistries for implementation.

MAD Water: Integrating Modular, Adaptive, and Decentralized Approaches for Water Security in the Climate Change Era

Centralized water infrastructure has, over the last century, brought safe and reliable drinking water to much of the world. But climate change, combined with aging and underfunding, is increasingly testing the limits of-and reversing gains made by-these large-scale water systems. To address these growing strains and gaps, we must assess and advance alternatives to centralized water provision and sanitation. The water literature is rife with examples of systems that are neither centralized nor networked, but still meet water needs of local communities in important ways, including: informal and hybrid water systems, decentralized water provision, community-based water management, small drinking water systems, point-of-use treatment, small-scale water vendors, and packaged water. Our work builds on these literatures by proposing a convergence approach that can integrate and explore the benefits and challenges of modular, adaptive, and decentralized ("MAD") water provision and sanitation, often foregrounding important advances in engineering technology. We further provide frameworks to evaluate justice, economic feasibility, governance, human health, and environmental sustainability as key parameters of MAD water system performance.

Reductions in Children's Blood Lead Levels from a Drinking-Water Intervention in Madagascar, Sub-Saharan Africa

One in three children globally is estimated to have blood lead levels (BLL) at or above the BLL reference value of 5 μg/dL with increased burden falling on low- and middle-income countries (LMIC). Within developed countries, aqueous lead is the predominant exposure route. However, aqueous lead exposure is rarely examined in the LMIC, leaving a gap in the literature that ignores a potentially significant route of exposure. Furthermore, limited lead-based remediation efforts around consumer products have been examined. This study investigates the importance of lead exposure from the water supply through a case study in Toamasina, Madagascar. The project measured aqueous lead and BLL of children pre- and postremediation efforts (i.e., removal of leaded pump components in hand pumps) to verify the impact of aqueous lead exposure within this community. Removal of the leaded pump components (i.e., piston and foot valves) and replacement with nonleaded components decreased aqueous lead levels below the World Health Organization provisional guideline of 10 μg/L in all but 4% of pumps tested. Measured BLL concentrations indicated a statistically significant decrease in BLL from pre- to postremediation. Furthermore, the remediation resulted in a decrease in BLL for 87% of children with the greatest changes in BLL observed for children with the highest preremediation concentrations. These findings point to a need for greater consideration of lead in drinking and cooking waters as an important exposure route in LMIC.

Reviewing performance of NSF/ANSI 53 certified water filters for lead removal

Properly certified NSF/ANSI 53 water filters are distributed as a temporary measure to protect residents from risk of exposure to elevated lead (Pb) levels resulting from water system changes and various activities. Water consumers and other stakeholders have raised questions on the performance of these filters in field settings, particularly in cases where water Pb levels exceeded the NSF/ANSI 53 challenge water level of 150 µg/L and when Pb phosphate nanoparticles (≤ 200 nm) were present in drinking water. This literature review summarizes findings from 23 studies that evaluated the ability of NSF/ANSI 53 post-2007 certified filters to reduce soluble and/or particulate Pb from water. The studies in total examined 1,486 faucet-mounted, 25 under-the-sink, and 167 pitcher filters, with 1,528 filters used in field studies and 150 filters in laboratory studies. This review found that filter performance varied with different filter type, test water source, and initial unfiltered total Pb concentration. 99% (1,512/1,528) of the filters used in field studies removed Pb to at or below the certification benchmark of pre-2019, 10 µg/L or post-2019, 5 µg/L. In contrast, 61% (91/150) of the filters used in laboratory studies reduced Pb to the benchmark. Laboratory filters were often tested under conditions beyond what they were certified to handle. Pb concentration, particle form and size, improper operation and maintenance of certified water filters were attributed to reported filter failures. This information is intended to help water utilities, regulators, and others make decisions regarding the deployment of water filters to the public when drinking water Pb exposure concerns have been raised.

Microplastic Removal from Drinking Water Using Point-of-Use Devices

The occurrence of microplastics in drinking water has drawn increasing attention due to their ubiquity and unresolved implications regarding human health. Despite achieving high reduction efficiencies (70 to >90%) at conventional drinking water treatment plants (DWTPs), microplastics remain. Since human consumption represents a small portion of typical household water use, point-of-use (POU) water treatment devices may provide the additional removal of microplastics (MPs) prior to consumption. The primary objective of this study was to evaluate the performance of commonly used pour-through POU devices, including those that utilize combinations of granular activated carbon (GAC), ion exchange (IX), and microfiltration (MF), with respect to MP removal. Treated drinking water was spiked with polyethylene terephthalate (PET) and polyvinyl chloride (PVC) fragments, along with nylon fibers representing a range of particle sizes (30–1000 µm) at concentrations of 36–64 particles/L. Samples were collected from each POU device following 25, 50, 75, 100 and 125% increases in the manufacturer’s rated treatment capacity, and subsequently analyzed via microscopy to determine their removal efficiency. Two POU devices that incorporate MF technologies exhibited 78–86% and 94–100% removal values for PVC and PET fragments, respectively, whereas one device that only incorporates GAC and IX resulted in a greater number of particles in its effluent when compared to the influent. When comparing the two devices that incorporate membranes, the device with the smaller nominal pore size (0.2 µm vs. ≥1 µm) exhibited the best performance. These findings suggest that POU devices that incorporate physical treatment barriers, including membrane filtration, may be optimal for MP removal (if desired) from drinking water.

Recent advances and remaining barriers to the development of electrospun nanofiber and nanofiber composites for point-of-use and point-of-entry water treatment systems

In this review, we focus on electrospun nanofibers as a promising material alternative for the niche application of decentralized, point-of-use (POU) and point-of-entry (POE) water treatment systems. We focus our review on prior work with various formulations of electrospun materials, including nanofibers of carbon, pure metal oxides, functionalized polymers, and polymer-metal oxide composites, that exhibit analogous performance to media (e.g., activated carbon, ion exchange resins) commonly used in commercially available, certified POU/POE devices for contaminants including organic pollutants, metals (e.g., lead) and persistent oxyanions (e.g., nitrate). We then analyze the relevant strengths and remaining research and development opportunities of the relevant literature based on an evaluation framework that considers (i) performance comparison to commercial analogs; (ii) appropriate pollutant targets for POU/POE applications; (iii) testing in flow-through systems consistent with POU/POE applications; (iv) consideration of water quality effects; and (v) evaluation of material strength and longevity. We also identify several emerging issues in decentralized water treatment where nanofiber-based POU/POE devices could help meet existing needs including their use for treatment of uranium, disinfection, and in electrochemical treatment systems. To date, research has demonstrated promising material performance toward relevant targets for POU/POE applications, using appropriate aquatic matrices and considering material stability. To fully realize their promise as an emerging treatment technology, our analysis of the available literature reveals the need for more work that benchmarks nanofiber performance against established commercial analogs, as well as fabrication and performance validation at scales and under conditions simulating POU/POE water treatment.

Blood Lead Levels among Non-Occupationally Exposed Pregnant Women in Southern Thailand

Lead (Pb) is a heavy metal that is toxic to humans, especially children and pregnant women. In Thailand, guidelines exist to minimize lead exposure in pregnant women working in lead-related occupations. However, no guidelines exist for pregnant women who are not employed in these economic sectors. This cross-sectional study aimed to examine blood lead levels (BLLs) and related risk factors among 80 non-occupationally exposed pregnant women from the general population living in Nakhon Si Thammarat province, Southern Thailand. BLLs were determined by graphite furnace atomic absorption spectrophotometry. A validated questionnaire was adopted to interview participants which included demographic, consumer goods, supplement intake, and health factors. The mean BLL was 4.68 ± 1.55 µg/dL (95% CI 4.33-5.02) and 42.50% had BLLs ≥ 5 µg/dL. Higher education was the only demographic factor associated with BLLs ≥ 5 µg/dL (aOR 0.16, 95% CI 0.03-0.80, p = 0.027). Systolic blood pressure was also associated with BLLs ≥ 5 µg/dL (aOR 5.00, 95% CI 1.23-17.16, p = 0.023). However, consumer goods and supplement intake were not associated with BLLs. Our results indicate that pregnant women from the general population who were not in the risk exposure group had lead in their bodies. Except for education, demographics were not associated with pregnant women with BLLs. However, with health factors, even low BLLs had a small effect on systolic blood pressure. These data suggest a need for promoting health education and health interventions to prevent the dangers of lead exposure, especially for pregnant women and children.

Developing Toxic Metal Environmental Justice Indices (TM-EJIs) for Arsenic, Cadmium, Lead, and Manganese Contamination in Private Drinking Wells in North Carolina

Toxic metal exposure via private drinking wells is an environmental health challenge in North Carolina (NC). Policies tainted by environmental racism shape who has access to public water supplies, with Black People, Indigenous People, and People of Color (BIPOC) often excluded from municipal services. Thus, toxic metal exposure via private wells is an environmental justice (EJ) issue, and it is under-studied in NC. In this study, we developed four Toxic Metal Environmental Justice Indices (TM-EJIs) for inorganic arsenic (iAs), cadmium (Cd), lead (Pb), and manganese (Mn) to quantitatively identify areas of environmental injustice in NC. TM-EJIs were calculated at the census tract level (n = 2038) as the product of the following: (1) number of well water tests with concentrations exceeding national standards, (2) percentage of the low-income and minority population, and (3) population density. Mn had the greatest proportion (25.17%) of positive TM-EJIs, which are indicative of socioeconomically disadvantaged groups exposed to toxic metals. Positive TM-EJIs, particularly for Pb and Mn, were primarily located in eastern NC. These results highlight several new counties of concern and can be used by public health professionals and state environmental agencies to prioritize remediation efforts and efforts to reduce environmental injustices.

Influence of point-of-use filters and stagnation on water quality at a preschool and under laboratory conditions

A local preschool installed NSF/ANSI 42 and 53 certified point-of-use (POU) filters in its classroom sinks and drinking fountains to protect children from the possibility of elevated lead (Pb) levels in drinking water. We examined the effects of these filters during flowing water and immediately following stagnation periods on Pb, chlorine, and bacterial concentrations in the field and the laboratory. Before and after typical school stagnation periods, we collected samples from filtered classroom sinks, a filtered drinking fountain and nearby unfiltered sinks for a year. No unfiltered samples exceeded Illinois State limits of 5 µg/L for Pb in pre-K through 5th grade schools. However, following stagnation periods as short as overnight (14.5 h), over half of post-stagnation filtered samples from classroom sinks exceeded 5 µg/L while post-stagnation unfiltered samples remained below 5 µg/L. Laboratory testing showed no significant increases in Pb with stagnation, suggesting that the preschool classrooms may have had Pb-bearing plumbing downstream of the filters which released Pb into the filtered drinking water. The filters effectively removed free chlorine (99% decrease) in both the preschool and laboratory. Installing the filters had the unintended consequence of significantly increasing the bacterial concentrations (as measured by qPCR) in the preschool's drinking water and in laboratory filter effluent. Legionella pneumophila, Pseudomonas aeruginosa, and Mycobacterium spp. were not detected in pre-stagnation unfiltered and post-stagnation filtered samples. These results suggest that the installation of POU filters be considered as one component of an overall strategy to decrease Pb concentrations in school drinking water that holistically considers the premise plumbing system. A 5-minute flush significantly decreased concentrations of Pb and bacteria in filtered sinks. Replacing Pb-bearing plumbing components downstream of a POU filter may also be needed to combat Pb levels in drinking water.

Effectiveness of point-of-use and pitcher filters at removing lead phosphate nanoparticles from drinking water

Orthophosphate (PO₄) addition is a common corrosion control treatment used to lower lead (Pb) concentrations at the consumer's tap by forming relatively insoluble Pb-phosphate (Pb-PO₄) minerals. However, some Pb-PO₄ particles that can form in drinking water are mobile nanoparticles (i.e., 0.001-0.1 µm) that have the potential to reach the tap. Point-of-use (POU) or pitcher filters are often used to manage risks during distribution system upsets, when corrosion control treatment is not optimized, or following Pb service line replacements. To abide by industry convention, POU and pitcher filters must be NSF/ANSI-certified for Pb reduction (NSF/ANSI-53) using a test water containing dissolved Pb and large Pb particles. Certification for particulates reduction (NSF/ANSI-42) is done using a test water that contains particles, but not leaded particles. To address the lack of testing for Pb nanoparticles, this study challenged six certified commercially available faucet-mounted POU (3) and pitcher (3) filters with aqueous suspensions of Pb-PO₄ nanoparticle. For the water quality investigated, the Pb particles formed ranged between 0.016 and 0.098 µm, based on scanning electron microscopy, transmission electron microscopy, and dynamic light scattering analysis. These particles represented 98.5% of total Pb in suspension. The total Pb removals were between 44.6 and 65.1% for the POU filters, and between 10.9 and 92.9% for the pitcher filters. The electron microscopy results confirm that Pb-PO₄ nanoparticles passed through the filters. The findings can inform future efforts to re-examine the test waters used in the certification challenge tests.

Modified bone char with C-MgO as a green antibacterial household water treatment filter: Comparing the microbial quality with refrigerator cartridge filters

The present study examines the efficiency of modified bone char (BC) with C-MgO nanoparticles (MBC-C-MgO) as media in a cartridge filter as an antibacterial agent to produce a new filter. The filters were operated in a continuous mode using a pre-static pump. MBC-C-MgO were produced and modified with sucrose through the co-precipitation method. The microbial quality of effluent water samples was compared with commercial refrigerator cartridge filters using a heterotrophic plate count (HPC) test and SEM analysis. The results showed that the effluent water from the filter with MBC-C-MgO media had the lowest HPC (177 CFU/mL) compared to bioceramic (271 CFU/mL) and carbon (500 CFU/mL) under similar experimental conditions after 4 months of operation. Maximum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests were determined using the broth dilution method on Escherichia coli (ATCC 25922) and Enterococcus faecalis (ACC 29212). The MIC results for E. faecalis and E. coli were 156.25 and 312.5 µg/mL, respectively. Furthermore, the MBC results for E. faecalis and E. coli were 312.5 and 625 µg/mL. The experimental results obviously showed the antibacterial properties of C-MgO nanoparticles and the MBC-C-MgO.

Lead service line identification: A review of strategies and approaches

Lead service lines (LSLs) represent the greatest source of lead in drinking water. Identifying the locations of LSLs can be challenging, and recent service line (SL) material surveys in Michigan, Illinois, Wisconsin, and Indiana found that on average the materials making up 16% of SLs in these states are unknown and may be lead. Given the large number of possible LSLs in the United States, new and pending regulatory requirements, LSL replacement costs, associated lead exposure risks, and the public's desire to reduce lead exposure, there is a need to rapidly and cost-effectively identify where LSLs are located, on public and private property. This review summarizes current industry LSL identification methods, including records screening, basic visual examination of indoor plumbing, water sampling, excavation, and predictive data analyses. A qualitative comparison of method cost, accuracy, disturbance, and other impacts is provided as a starting point for utilities that are developing a feasible approach for their specific needs/constraints. Lastly, an example stepwise approach to identify unknown SL materials is proposed.

Diet: A Source of Endocrine Disruptors

BACKGROUND

Food is indispensable for human life and determines the health and wellbeing of the consumer. As food is the source of energy for humans, it also emerges as one of the most important sources of exposure to deleterious chemicals both natural and synthetic. The food exposed chemicals cause a number of detrimental health effects in humans, with endocrine disruption being of serious concern amongst these effects. Such chemicals disrupting the health of endocrine system are known as endocrine-disrupting chemicals (EDCs). The food exposed EDCs need to be identified and classified to effectuate a cautious consumption of food by all and especially by vulnerable groups.

AIM

The aim of the present review was to discuss food as a source of exposure to common endocrine disruptors in humans. This review presents the occurrence and levels of some of the critical endocrine disruptors exposed through frequently consumed diets.

METHODS

The major source of data was PubMed, besides other relevant publications. The focus was laid on data from the last five years, however significant earlier data was also considered.

CONCLUSION

The food as a source of endocrine disruptors to humans cannot be neglected. It is highly imperative for the consumer to recognize food as a source of EDCs and make informed choices in the consumption of food items.

Under-Sink Activated Carbon Water Filters Effectively Remove Lead from Private Well Water for over Six Months

Children who rely on private well water in the United States have been shown to be at greater risk of having elevated blood lead levels. Evidence-based solutions are needed to prevent drinking water lead exposure among private well users, but minimal data are available regarding the real-world effectiveness of available interventions like point-of-use water treatment for well water. In this study, under-sink activated carbon block water filters were tested for lead and other heavy metals removal in an eight-month longitudinal study in 17 homes relying on private wells. The device removed 98% of all influent lead for the entirety of the study, with all effluent lead levels less than 1 µg/L. Profile sampling in a subset of homes showed that the faucet fixture is a significant source of lead leaching where well water is corrosive. Flushing alone was not capable of reducing first-draw lead to levels below 1 µg/L, but the under-sink filter was found to increase the safety and effectiveness of faucet flushing. The results of this study can be used by individual well users and policymakers alike to improve decision-making around the use of under-sink point-of-use devices to prevent disproportionate lead exposures among private well users.

Adsorptive performance of activated carbon reused from household drinking water filter for hexavalent chromium-contaminated water

Powdered activated carbon blocks (PACBs) are waste products obtained from household drinking water purification systems. In this study, we demonstrate that they can be used as adsorbents for the cost-effective and environmentally benign removal of hexavalent chromium (Cr(VI)) from contaminated-water and rinse electroplating wastewater. To evaluate Cr(VI) sorption onto the PACB, studies on equilibrium, kinetics, and thermodynamics were performed using batch mode experiments. The experimental results indicated that Cr(VI) ions were efficiently adsorbed under acidic conditions (i.e., at initial pH below 3) and low initial Cr(VI) concentrations. The adsorptive behaviors of the PACB for Cr(VI) were well explained by the Langmuir isotherm, as well as pseudo-second-order kinetic models, suggesting that a Cr(VI) monolayer was adsorbed onto the PACB surface via chemisorption. The maximum adsorption capacity of Cr(VI) onto the PACB was determined to be 6.207 mg/g. The results of thermodynamic studies revealed that the adsorption process of Cr(VI) onto PACB was endothermic and non-spontaneous. Additionally, analysis of the PACB after Cr(VI) adsorption at an initial pH of 2 using scanning electron microscopy, energy dispersive spectrometry, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) revealed that the interaction between the surface oxygenic functional groups on the PACB and Cr(VI) was primarily responsible for Cr(VI) sorption via surface complexation and electrostatic interactions. Based on the result of XPS analysis, the presence of trivalent chromium on the PACB surfaces indicated that some synergistic redox reactions involving Cr(VI) could have occurred during the sorption process. Although a commercially available powdered activated carbon outperformed the PACB adsorbent with respect to Cr(VI) removal from wastewater, complete Cr(VI) adsorption could be achieved using relatively large quantities of the PACB. These findings indicate that the PACB adsorbent could be used as a cheap and efficient material for the removal of Cr(VI) from wastewater.

Synthesis and characterization of stable lead (II) orthophosphate nanoparticle suspensions

There is great interest in producing nanoparticles for various applications. The objective of this work was to develop a procedure for reproducibly creating stable lead (Pb) phosphate nanoparticle aqueous suspensions. A stable 5 mg/L Pb-phosphate nanoparticle "stock" suspension was synthesized via chemical precipitation of Pb and orthophosphate in water at pH 7.5 with 4.4 mg soluble PO₄/L and 7 mg C/L dissolved inorganic carbon. The stock suspension was subsequently diluted to produce stable 0.10 mg/L Pb "challenge" water suspensions without compromising the nanoparticle size, structure, mineralogy and solubility. Specifically, the hexagonal hydroxypyromorphite nanoparticles had an average diameter of 38 nm based on transmission electron microscopy analysis and an associated Pb solubility of 0.001 mg/L. The properties of the stock suspensions were not impacted by further dilutions, and the challenge water suspensions remained stable for 24 hours. In the context of drinking water, a protocol to produce such a stable Pb nanoparticle challenge water suspension would be very useful in evaluating Pb bioavailability, identifying Pb remediation strategies, and testing filter effectiveness to remove Pb from water.

Social factors shaping the adoption of lead-filtering point-of-use systems: an observational study of an MTurk sample

Some municipalities are promoting lead-filtering point-of-use (POU) systems to minimize the risk of lead exposure through drinking water, often targeting use at racial minorities and low-income households. However, links among social inequality markers and adoption of these systems are not well understood. Survey data on adoption and use of POU systems were collected from a U.S. Mechanical Turk (MTurk) sample (N = 2,867) in March 2018. We use logistic regression to assess the association of race/ethnicity, socioeconomic status (SES), and lead-filtering POU adoption. We also examined key health behaviors related to POU systems. We found that race and SES are indirectly predictive of lead-filtering POU adoption through the propensity of some respondents to report a residence with a lead service line and levels of concern and knowledge about lead exposure. In addition, individuals with similar levels of concern about lead in water have lower odds of adopting a POU system if they have lower, rather than higher, incomes. Among POU adopters, while confidence in correct use of these devices was relatively high, the frequency of filtered water use for cooking was lower than drinking frequency. Overall, these findings inform health policies aimed at mitigating risk of lead exposure through water.