Introduction

Lead (Pb) is a global environmental pollutant and neurotoxicant metal that can cause irreversible harm, particularly to children and developing fetuses [1]. It is sometimes intentionally added to alloys and materials to enhance their machinability, corrosion resistance, and service life. Lead-containing alloys, including leaded brass (Pb ranges 1–6% [2,3]) and leaded zinc coatings on galvanized steel (0.5-2% [4]), are commonly found in water supply systems and can leach Pb into drinking water at levels of human health concern [5,6]. The World Health Organization (WHO) has published a guideline value for water lead levels (WLL) at 10 µg/L [7], which was exceeded in 23% (95% CI 20–26%) of drinking water samples from low- and middle-income countries (LMICs) in a recent meta-analysis [8].

Pb release into drinking water occurs through complex electrochemical, geochemical, and hydraulic mechanisms, that are highly dependent on water chemistry [9]. Key water quality parameters that influence Pb corrosion include pH, alkalinity, hardness, conductivity, disinfectant residual, temperature, chloride-to-sulfate mass ratio and concentrations of certain other anions, and the presence of corrosion inhibitors [10]. Corrosion inhibitors such as orthophosphates and silicates can reduce dissolved Pb concentrations by precipitating the metal as stable Pb scales on pipe surfaces, but require continuous and appropriate dosing based on influent water chemistry [11]. Pb release from materials is also a function of contact time and wetted surface area [12]. Pb concentrations in “first draw” samples increase with stagnation time, with the largest rates of leaching observed during the first 24 hours, though leaching continues for as long as water remains in contact with leaded materials [13].

International standards exist to regulate toxic metals contained in or leached from water system components that carry drinking water. However, many LMICs likely face challenges with respect to the laboratory capacity, infrastructure, and/or human resources needed to effectively adopt and enforce these standards. Typically, these standards specify either a maximum Pb content in components (“composition standard,” e.g., 0.25% wt/wt under NSF/ANSI/CAN 372 and the International Plumbing Code) [14] or a maximum allowable Pb leaching concentration under a uniform testing protocol (“performance standard,” NSF/ANSI/CAN 61) [12]. Where plumbing products are tested and certified for conformity with such standards, Pb content and/or leaching performance can be assumed to meet the applicable certification criteria. However, for other products lacking such certifications, Pb content in plumbing components and/or leaching rates often are not reported by (or, often, even known to) manufacturers, and may not be regulated, by authorities in the country of manufacture. As a result, importers and consumers cannot readily assess the Pb content or leaching risks of such unregulated products. The lack of publicly available data on Pb content in and leaching from uncertified lead-bearing parts such as brass and galvanized steel (GS) sold in LMIC markets represents a critical evidence gap, as hundreds of millions of LMIC residents potentially consume water from systems containing such parts [15]. A recent field survey of 101 rural water systems installed in Ghana over the last five years found that 57% handpumps and 100% taps exceeded the NSF 372 standard of 0.25% Pb by weight [16].

Stainless steel (SS) has been validated as a suitable non-leaded (lead-free) alternative material for water distribution due to its high corrosion resistance and long service life, with successful use documented in the US [10], Ghana [16], and elsewhere. Pb is not intentionally added to SS products and is rarely reported at levels of concern in SS plumbing products manufactured for use in drinking water supply [17]. At least 12 lead-free alternative materials, including SS, are available for use in water distribution applications [3]. Polymers such as polyvinyl chloride (PVC) are another class of alternatives that are more economical than SS. However, metal additives (including Pb) are sometimes added as stabilizers and/or fillers to make both new and recycled PVC more durable and less prone to thermal degradation [18]. Such leaded PVC is presumably an unsuitable alternative, making it essential to verify PVC composition before use in drinking water systems.

The aim of this research study was to determine whether rural water supply system components routinely installed in Ghana and likely other LMICs contain Pb, whether they leach Pb into water at concentrations of health concern, and whether SS components could serve as suitable lead-free alternatives. This was assessed by determining whether the GS and brass components (and their SS alternatives) a) contained Pb in excess of 0.25% w/w (per NSF 372) and b) leached WLLs above the threshold defined by NSF 61 and drinking water standards, including the WHO guideline value (10 µg/L) and the American Academy of Pediatrics recommendation for schools and childcare facilities (1 µg/L).

Methods

Plumbing components

Triplicate samples of two types of understudied plumbing components used in rural drinking water supply (India Mark II handpump spouts and ¾” taps used in piped systems and communal drinking water access points) made from two types of potentially high-risk materials (GS and brass, respectively) and SS alternatives for each (spouts and taps) were obtained from two Ghanaian importers based in Accra and Tamale, Ghana. All handpump spouts had a single welded joint at 90 degrees and were in turn welded to a larger holding tank. In addition, triplicate samples of lead-free ¾”-diameter PVC pipe were obtained from an American hardware store in Chapel Hill, North Carolina for use as a control, since this PVC pipe is certified to meet both NSF 372 and NSF 61 standards. The tested components and their respective characteristics of material, dimensions, weight, volume, and source are listed in Fig 1.

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Fig 1. Water System Component Characteristics.

https://doi.org/10.1371/journal.pwat.0000402.g001

Lead leaching

The NSF 61 Section 9 test procedure was conducted using three replicate samples of each component to quantify Pb leaching and assess compliance with the NSF 61 standard [12]. Per NSF 61 test protocols, synthetic test water was created daily with a standard composition and chemistry as follows: pH 8 ± 0.5, alkalinity 500 ± 0.5 mg/L as CaCO₃, free chlorine 2 ± 0.2 mg/L, and dissolved inorganic carbon (DIC) 122 ± 5 mg/L [12,19]. Chlorine was added as 5% available chlorine sodium hypochlorite stock solution (Spectrum Chemical, New Brunswick, NJ) into 20 L of deionized water to achieve a final 2 ± 0.2 mg/L free chlorine concentration. Total chlorine was verified using a Hach DR300 pocket colorimeter (Hach, Loveland, CO). To maintain pH within the specified range (8 ± 0.5), research grade carbon dioxide gas (Airgas, Radnor, PA) and 98% sodium hydroxide pellets (Thermo Fisher, Waltham, MA) were used. The pH was verified using a handheld Hanna HI98129 low range Combo pH/conductivity meter (Hanna, Woonsocket, RI). Sodium bicarbonate (MCB Reagents, Cincinnati, Ohio) was added at approximately 1 mM to adjust alkalinity and DIC: specifically, 25 mL of 0.04 M NaHCO₃ was added per 1 L synthetic water solution.

Test components were filled with standard synthetic test water from a 20 L Nalgene polypropylene carboy (Nalgene, Rochester, NY) and incubated at room temperature. All carboys and sample bottles were acid-washed thoroughly with hydrochloric acid prior to use. No headspace was present when capping each orifice with a solid natural rubber stopper (Grainger, Lake Forest, IL). The NSF 61 protocol requires collecting first draw samples from overnight dump-and-fill rounds to capture water stagnation 16-hour overnight dwell times. To achieve these parameters, fresh test water was replaced in tested components at two-hour intervals from 8 AM until 4 PM from Monday to Friday for three weeks (Days 1–5, 8–12, and 15–19) to simulate water usage with stagnant water sitting overnight (4 PM-8 AM Monday-Friday), over the weekend (4 PM Friday-8 AM Monday), and at two-hour intervals (8 AM-4 PM Monday-Friday) as shown in S1 Fig. First draw samples –650-mL, 35-mL, 420-mL, 15-mL, and 75-mL volumes for GS spouts, brass taps, SS spouts, SS taps, and PVC pipes, respectively, were collected at the 8 AM dump-and-fill point and poured into 1 L Nalgene HDPE sample bottles (Nalgene, Rochester, NY) on Wednesday, Thursday, and Friday of each week over the test period (Days 3, 4, 5, 10, 11, 12, 17, 18, and 19).

The collected samples were acidified using 2% v/v trace metal grade 67–70% nitric acid (Thermo Fisher, Waltham, MA). Acidified samples were capped, thoroughly mixed, and stored at room temperature for at least 24 hours to ensure dissolution and homogenization of particulate Pb in samples. Samples were then mixed again and duplicate 10 mL aliquots were then removed from each sample and decanted into 15 mL trace metal-free polypropylene centrifuge tubes (Labcon, Petaluma, CA) and analyzed for Pb and other selected elements using an Agilent 8900 Triple Quadrupole ICP-MS (Agilent, Santa Clara, CA) per Standard Method 3125-B [20].

The ICP-MS instrument’s LOD and limit of quantification (LOQ) for Pb were 0.02 and 0.08 µg/L, respectively, as validated using lead-free laboratory blanks and standard reference materials. The deionized water used to create the synthetic test water was analyzed by ICP-MS and the resulting Pb concentrations were found to be < LOD (<0.02 µg/L). However, in multiple trials using synthetic test water, the prepared test water was found to have a background Pb concentration on the order of 0.5-0.6 µg/L. Furthermore, when the laboratory deionized water was spiked with 1 mM sodium bicarbonate, the resulting solutions had Pb concentrations of approximately 0.5 µg/L, suggesting that the background Pb in synthetic test water samples could have originated from the reagent-grade sodium bicarbonate (which is certified by the manufacturer as having Pb at levels below 5 mg/L, and could therefore reasonably contribute sub-µg/L Pb concentrations when diluted to 1 mM in synthetic test water solutions). To account for this background Pb contribution, synthetic test water samples from each batch were analyzed in duplicate each day, and the resulting mean background Pb concentration obtained (varying from 0.2-0.7 µg/L) was subtracted from the resulting Pb concentration obtained from the test water incubated in each component over the experimental stagnation periods. Water quality parameters for each daily batch of synthetic test water are reported in Table A in S1 Appendix.

Because of this background Pb occurrence in finished test water, a revised method LOD of 0.5 µg/L and revised method LOQ of 1.7 µg/L were used for all trials including synthetic test water, to account for this added background noise effect. Calibration curves were created for each set of analyzed samples and linear regression equations were fitted to the curves and used to calculate Pb concentrations. Multi-element standard reference materials and laboratory blanks were analyzed every 10 samples for quality control.

Results were analyzed and the “Q” test statistic was calculated for each sample per NSF 61 protocol (Table 1, calculation in S2 Appendix). Briefly, the natural log of corrected (measurements were corrected by subtracting background test water Pb concentration) measured Pb concentration was taken (Equation 1) and the collected samples were averaged for each component (Equation 2). For each triplicate set of samples, the mean (Equation 3) and standard deviation (Equation 4) were calculated and along with k₁ (k₁ = 2.60281 for a sample size of 3) to calculate the Q test statistic (Equation 5).

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Table 1. Q Test Statistic Equations.

https://doi.org/10.1371/journal.pwat.0000402.t001

Results

Elemental composition of water system components by XRF

The mean elemental compositions of water system components are presented in Table 2 (and S1 Dataset). Scans of the GS spouts revealed undetectable (<LOD) levels of Cd, Cu, and Ni, trace amounts (<0.1%) of Cr and Fe, 88% Zn, and 0.64% Pb. Two of the GS spouts had 0.86% Pb while the third had 0.20%. Scans of the brass taps revealed undetectable Fe, trace amounts of Cd and Cr, 0.77% Ni, high amounts of Cu (50%) and Zn (45%), and 1.3% Pb. The SS spouts had undetectable Cd and Pb, minor amounts of Cr (5.2%), Cu (6.3%), and Zn (1.5%), and high amounts of Fe (14%) and Ni (70%). The SS taps had undetectable Cd, trace amounts of Pb (0.01%) and Zn, minor amounts of Cu (0.27%) and Ni (3.5%), and high amounts of Cr (17%) and Fe (44%). The PVC pipes had undetectable Cd, Cr, and Pb and trace amounts of Cu, Fe, Ni, and Zn.

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Table 2. XRF results for Galvanized Spouts, Brass Taps, Stainless-steel Spouts and Taps, and PVC Pipes.

https://doi.org/10.1371/journal.pwat.0000402.t002

Water lead concentrations and Q test statistic values (per NSF 61 test protocol)

The first draw Pb concentrations for each component are presented (Fig 2 and Table 3). Fig 2 shows the WLLs for all five components and relevant sampling days with 95% confidence interval error bars. Since the data for SS spouts, SS taps, and PVC controls are near 0 µg/L, their trend lines are indistinguishable from the Y-axis as opposed to data for GS spouts and brass taps. A separate, re-scaled graph of the former three components is presented (S2 Fig) for clarity. The signal-to-noise ratios for the SS spout, the SS tap, and PVC pipe are 0.5, 0.7, and 0.7, respectively. The 16-hour stagnation sample data with the three replicates for each component are provided (S1 Dataset). The resulting Q test statistics for components, along with descriptive statistics, are also presented (Table 4). For statistical purposes, sample values below the method LOD (0.5 µg/L) were substituted with half the LOD (0.25 µg/L). Reported statistics may include substituted values and should be interpreted accordingly.

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Table 3. First draw Pb concentrations (µg/L) for components tested according to NSF 61 Protocols.

https://doi.org/10.1371/journal.pwat.0000402.t003

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Table 4. Descriptive Statistics of WLLs (µg/L) for components tested according to NSF 61 protocols.

https://doi.org/10.1371/journal.pwat.0000402.t004

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Fig 2. Samples of first draw lead concentrations obtained for components tested according to NSF 61 protocols with 95% CI error bars.

https://doi.org/10.1371/journal.pwat.0000402.g002

Pb concentrations for SS components did not exceed 1.2 µg/L in any sample. Brass taps produced the highest first draw aqueous Pb concentrations, which declined from a maximum of 315 µg/L on Day 4 to a minimum of 105 µg/L on Days 17 and 18. The first draw concentrations of Pb leached from GS spouts remained roughly consistent during the 3-week test period, with a maximum of 39 µg/L on Day 3 and a minimum of 27 µg/L on Day 11. The discontinuous reduction in Pb concentrations on Day 11 was observed for both GS spouts and brass taps. The SS spouts, SS taps, and PVC control produced negligible Pb leaching in comparison to the former two parts. Levene’s test for relative variance comparison between brass taps and GS spouts had an F statistic of 21 and a p-value of 0.0002. Linear regression determined that the Pb leached from the average of the three brass taps significantly declined over time (R² = 0.89; p < 0.0001).

The ratio of WLLs to the unit surface area as a function of time was calculated for each component with results graphed in S3 Fig. Brass taps had the highest averaged ratio at 2.5 µg/L/cm², followed by GS spouts at 0.05 µg/L/cm², SS taps at 0.006 µg/L/cm², PVC control at 0.002 µg/L/cm², and SS spouts at 0.0005 µg/L/cm². There is a strong positive correlation between the WLL leached per unit surface area and Pb composition (Spearman’s ρ = 0.97, p < 0.005).

Discussion

The PVC control pipes and SS spouts contained undetectable Pb, while the SS taps had 0.01% Pb, which signifies that all three component types met NSF 372/IPC standard for Pb composition (<0.25% w/w). The GS spouts and brass taps had average Pb contents of 0.64% and 1.3%, respectively, which signifies that both components did not meet the NSF 372/IPC standard. The pXRF device used had a Pb LOD of 0.01%. Published Pb LODs for comparable instruments are on the order of 0.001% [21,22]. These detection limits indicate that since the pXRF is capable of a LOD several orders of magnitudes below the 0.25% regulatory threshold, readings above 0.25% can be confidently considered to exceed the international standard. The brass taps had the highest average ratio of WLLs to unit surface area as a function of time (2.5 µg/L/cm²), followed by GS spouts (0.05 µg/L/cm²). Although the brass taps had much lower volume than the GS spouts, the former leached a significantly higher amount of Pb than the latter on a per-unit-surface-area basis by a factor of 50. While results may change when other plumbing components and materials are tested, this study suggests that increasing Pb content is related to an increase in WLLs leached from lead-containing products. The results further suggest that uncertified GS and brass drinking water system components may merit particular attention.

The SS spouts, SS taps, and PVC pipes met NSF 61 (Pb leaching) standards and produced lower WLLs (<2.7 µg/L) that predominantly were indistinguishable from background Pb concentrations in freshly prepared NSF 61 standard synthetic test water. Specifically, signal-to-noise ratios for Pb concentrations leached from SS spouts, SS taps, and PVC pipes were below 1, indicating that WLLs were indistinguishable from background concentrations in freshly prepared synthetic test water, and therefore cannot reliably be quantified. In contrast, GS handpump spouts and brass taps exceeded NSF 372 limits and leached Pb well above the 10 µg/L WHO guideline value (67% of spouts and 100% of taps). Additionally, 100% brass tap, 100% GS spout, 4% PVC, 4% SS tap, and 0% SS spout WLLs exceeded the 1 µg/L American Academy of Pediatrics recommended WLL threshold for schools and daycares, confirming prior findings that lead-free components occasionally fail to meet this strict threshold [19].

The SS spouts, SS taps, and PVC control pipes met the NSF 61 certification standard (Q ≤ 1 µg/L), while brass taps (Q = 225 µg/L) and GS spouts (Q = 577 µg/L) did not. The Q statistic indicates, with 90% confidence, the highest first draw WLL leached from 75% of leaded brass taps and GS handpump spouts are 225 µg/L and 577 µg/L, respectively. If an estimated four million India Mark II galvanized hand spouts are in use globally [15] and are exposed to water as aggressive as the NSF 61 standard test water, nearly one million systems may leach Pb above 577 µg/L during initial commissioning and may potentially continue leaching Pb at levels of high concern throughout their design life. India Mark II handpumps may also contain other leaded GS and brass parts capable of leaching Pb at concerning levels, consistent with high WLLs observed in field samples from such systems in Ghana, Mali, and Niger [23].

Since the Q test statistic calculation exponentiates the standard deviation, large variation among triplicate samples can inflate Q statistic estimates, especially for the GS spouts in this study. When the outlier GS spout is removed from the results, the Q test statistic is reduced from 577 to 53 µg/L and the average WLL increases from 34 to 48 µg/L. The magnitude reduction of the Q test statistic is still above the 1 µg/L compliance threshold and the average WLL is still above the WHO guideline value of 10 µg/L.

Taken together with prior research, our findings provide compelling evidence that leaded brass taps and GS fittings of the types tested here fail NSF 61 and NSF 372 standards, can leach unsafe levels of Pb, and are therefore unsuitable for use in drinking water systems. A previous study [23] found 72% of brass components in three West African countries failed to meet the NSF 372 standard, with systems containing brass parts recording WLLs 3.8 times higher than those without.

With an estimated 0.6-1 billion persons in LMICs relying on India Mark II handpumps [15] and another 300 million (or 55% of urban population in Sub-Saharan Africa without piped water) relying on standpipes with brass taps [24,25] as their primary water source, this study’s findings have serious implications for water safety. As LMICs without monitoring capabilities to measure and verify Pb content in plumbing products progress rapidly in their efforts to expand safely managed drinking water services, they may be at the mercy of contaminated supply chains, in which lead-leaching and safe plumbing products may not be readily distinguishable. At a minimum, these results highlight the urgent need for clear and enforceable national policies to avoid installing leaded components that fail NSF 372 and NSF 61 standards, and the corresponding need to prioritize availability of (preferably certified) lead-free alternatives such as products and fittings made from lead-free SS. While implementing engineering solutions such as corrosion control treatment could help reduce Pb leaching in existing piped systems, its implementation in some rural LMIC settings and in many small or point-source water systems may be slow or infeasible due to the need for consistent and precise chemical dosing and water chemistry monitoring, added costs of implementation and training, and/or other logistical and human resources requirements and challenges.

Consistent with World Health Organization guidelines [26], this study should not necessarily be used to justify decommissioning existing drinking water systems with leaded brass or GS components in rural LMIC settings. Reducing access to safely managed drinking water could increase risks from fecal contamination and other microbial hazards and is therefore not justified [27]. Rather, the results underscore the importance of using lead-free components in new systems, and undertaking progressive mitigation, remediation, and/or corrosion control in existing systems as safe and feasible to do so without disrupting or diminishing access to safely managed and improved drinking water services. Lead-containing components are sometimes erroneously sold or imported as “lead-free” without documentation of any third-party certification or verification, and can thus go undetected in procurement or installation processes, even when lead-free parts or materials are specified in written requirements for water system parts, components, and materials. In such cases, implementers may unknowingly install these parts, increasing risks of Pb exposure [16]. To reduce this risk, uncertified brass taps and leaded galvanized components that have not been subjected to third-party testing, and/or that fail NSF 372 or 61 standards in such testing, should generally be avoided when new drinking water systems are being constructed. Results from this and future studies can further inform policy to prevent the importation, sale, and/or installation of such components for use in LMIC drinking water systems. Strengthening regulatory frameworks and protecting supply chains [16] may also help achieve this objective. Harmonization among different countries and regions seeking to strengthen certification, regulation, testing, and verification schemes may further facilitate and accelerate such efforts, where feasible [28].

This study has several limitations. To meet the NSF 61 Section 9 alkalinity requirements, sodium bicarbonate (MCB Reagents, Cincinnati, Ohio) was used, which may have introduced trace Pb in the test water, as the chemical bottle label noted “Heavy Metals (as Pb) – 5 ppm.” The small sample size (n = 3) per component may have skewed results for GS spouts due to manufacturing variability, as one had a quarter of the Pb content of the other two. Testing more components from different batches or ensuring greater uniformity among replicates could reduce this variability.

While the NSF 61 standard (and the resulting Q test statistic) offers a useful benchmark for the safety of drinking water system components and a preliminary assessment, conformity assessment of such products with respect to this standard is resource-intensive, often requiring costly instrumentation and substantive laboratory capacity. Field conditions may also not be accurately reflected due to variability in manufacturing, water chemistry, temperature, exposure time, and installation practices (e.g., heating of brass components, which affects Pb lability and mobilization) which can influence Pb release in ways unlikely to be captured by a standard laboratory test protocol. A simplified performance standard and testing approach for determining Pb leaching potential could be beneficial for a wider range of conditions. Though lower-cost methods exist capable of facilitating conformity assessment with respect to composition standards such as NSF 372, it is not widely used for such assessment to the best of our knowledge. Both Pb leaching and Pb composition assessments are rarely conducted in LMIC settings, where water system components, including handpump parts and faucets, remain understudied. An enhanced test method combining the rigor of the NSF 61 Pb leaching standard, with the wider accessibility of utilizing the NSF 372 Pb composition standard would aid in progressing towards a more feasible application in LMICs where resources may not be available for conducting the original test methods, without compromising on the robustness of either standard.

The strengths of this study include the evaluation of commonly used water system components in a controlled environment using replicable conditions under NSF 61 protocols. This provides a baseline for assessing product safety in rural water systems. Though useful for preliminary compliance results, the study also highlights that NSF 61 may need to be used alongside other standards or experimental tests, as variability in material composition understandably affects Pb release.

Future work will be conducted to quantify population-level Pb exposure from unsuitable components using improved leaching data and biokinetic modeling. Studies will address current limitations by testing more samples (e.g., at least five per component), using components from the same manufacturing batches, and exploring varied conditions (e.g., water chemistry, component type, heat pretreatment, and sampling frequency), and assessing and addressing the risks of galvanic corrosion when lead-free materials are directly connected to legacy components of dissimilar metallic composition within existing infrastructure. Despite limitations, our findings strongly support the guidance of avoiding uncertified or known-leaded brass and GS components that have not been subject to third-party conformity testing, or that fail to conform to NSF 372 and/or NSF 61 standards in such testing, for use in new drinking water systems. In LMIC settings, where testing for Pb leaching is sometimes challenging, sourcing components certified by independent third parties to conform to NSF 372 and NSF 61 standards is likely to be a practical and health-protective first step. Where suitable certified products meeting implementer specifications may not be readily available, verification of conformity with NSF 372 or a comparable composition standard may be easier and more cost effective to undertake independently or with third-party services, as compared to verifying conformity with more involved performance standards, such as NSF 61. Additional measures, such as random XRF screening of drinking water plumbing products at ports of entry, may likewise be feasible to undertake for some implementers. However, without robust monitoring, conformity assessment, and enforcement [26], regulatory standards alone are unlikely to be impactful. Where leaded components persist, our study provides compelling evidence of their potential to leach harmful levels of Pb into potable water, posing a clear and present public health threat. Given the global nature of many relevant supply chains, such threats are likely to be of global concern.

Conclusion

This study demonstrates that leaded brass taps and galvanized steel handpump tank spouts procured from retailers and implementing partners in Ghana, and representative of components commonly used in rural community water systems in LMICs, fail to meet NSF 372 and NSF 61 standards for Pb content and leaching. With average Pb contents of 1.3% and 0.64% by weight, respectively, these components significantly exceeded the 0.25% w/w threshold for the NSF 372/IPC standards. The experimental leaching data underscore the public health risk: over a three-week period, average water Pb levels leached from brass taps and galvanized steel spouts were 192 µg/L (SD = 89) and 34 µg/L (SD = 3), respectively. These levels far exceed the WHO guideline value of 10 µg/L demonstrating that these components leach Pb at concentrations of significant health concern.

In contrast, the stainless-steel alternatives proved to be safer than their lead-bearing counterparts. These components leached significantly lower Pb concentrations (0.4 µg/L (SD = 0.1) for taps and below the limit of detection for spouts) and met both NSF standards. The trace Pb detected in the leaching tests of stainless-steel components were below the limit of quantification, and may have originated from the sodium bicarbonate used in the synthetic test water, rather than the materials themselves.

Study limitations included testing three replicates and use of a specific test water chemistry (NSF 61 Section 9). Future research should expand the scope of testing to include additional replicates, other lead-bearing materials currently in use, representative field water quality conditions, including “worst case” corrosive scenarios, and managing the risks of galvanic corrosion when integrating lead-free materials into existing infrastructure. Studies that integrate best available leaching and field data with biokinetic modeling could help better estimate the health benefits of switching from leaded to lead-free alternatives.

The findings demonstrate that lead-bearing plumbing components exceeding NSF 372 and/or NSF 61 standards, such as leaded brass and galvanized steel, are unsuitable for use. Consequently, this study supports a strong recommendation to prohibit their use in drinking water supply systems. It also underscores the importance of prioritizing safer materials, such as stainless steel, especially in the absence of effective corrosion control treatment. Implementers and decision-makers should prioritize enforceable regulation, conformity verification, and procurement efforts that align with NSF 372 and NSF 61 standards to effectively mitigate the risks of Pb exposure from drinking water.

Supporting information

Acknowledgments

The authors would like to thank Joe Brown, Kaida Liang, Ryan Cronk, and Kevin Zhu at the UNC Water Institute, those at IAPMO and NSF, as well as Jeff Parks, Douglas Hill, Lily Eubanks, and Grace Lower for their help in conducting and advising the laboratory experiments. Much gratitude to those at World Vision Ghana and Clarissa Brocklehurst for assisting in procuring materials to be tested in the laboratory.