Lead in synthetic and municipal drinking water varies by field versus laboratory analysis.

Water lead measurements by two field analyzers, relying on anodic stripping voltammetry (ASV) and fluorescence spectroscopy, were compared to reference laboratory measurements by inductively coupled plasma mass spectrometry (ICP-MS) in progressively complex datasets (phases A, B, C), to assess field analyzer performance. Under controlled laboratory quantitative tests of dissolved lead within the field analysis range and optimal temperature range, lead recoveries by ASV ranged within 85-106 % of reference laboratory values (corresponding linear model: y = 0.96x, r2 = 0.99), compared to lower lead recoveries of 60-80 % by fluorescence (y = 0.69x, r2 = 0.99) in phase A. Field analyzer performance deteriorated in three opportunistic laboratory datasets compiled for phase B that contained dissolved lead (ASV: y = 0.80x, r2 = 0.98; no fluorescence data). Further lead underestimations were observed in five field datasets compiled for phase C, some of which contained known particulate lead (ASV: y = 0.54x, r2 = 0.76; fluorescence: y = 0.06x, r2 = 0.38). Deteriorating performance between phases was presumably due to the increasingly complex water matrices and lead particulates present in some phase C subsets (phase A < phase B < phase C). Phase C field samples had lead concentrations that were out-of-range, including a 5 % and 31 % false negative rate by ASV and by fluorescence, respectively. The range of results relevant to the diverse nature of compiled datasets, suggests that unless ideal conditions are known to be present (i.e., the lead content of water is dissolved within the field analysis range and optimal water temperature range), these field lead analyses might only be used as a water screening tool. Given the unknown conditions in many field settings, combined with the lead concentration underestimations including the false negative rates reported herein for field datasets, caution is encouraged when employing ASV and particularly fluorescence field analysis.

Reduction in water consumption in premise plumbing systems: Impacts on lead concentration under different water qualities.

Water conservation measures are increasing in response to regulatory requirements addressing the need for lower environmental footprint and in response to water shortages. In households with lead service lines (LSLs), lowering consumption can adversely impact lead release as it will increase stagnation. Using a lead dissolution model and data from extensive pilot studies on excavated LSLs, the impact of adaptation to different water conservation strategies on dissolved lead contamination at the kitchen tap is assessed under three water qualities and three LSL lengths (3, 14 and 30 m) using hydraulic and water quality modelling. Consumers' behavioural variability is also assessed based on integration of EPANET and results of the stochastic water demand model SIMDEUM. Demand reduction increased the dissolved lead concentrations (Pbdiss) at the end of the LSL with mean values ranging from 28.4 to 63.3 µg/L (without corrosion control) and from 4.6 to 9.9 µg/L with corrosion control (addition of orthophosphate and pH adjustment). Adding orthophosphate (1 mg P/L) to the water reduces the mean Pbdiss values at the kitchen tap from 7.1 µg/L to 1.2 µg/L for a high water demand scenario and from 31.2 to 4.9 µg/L for a low water demand scenario. Finally, the Integrated Exposure Uptake Biokinetic (IEUBK) model is used to predict the potential blood lead levels (BLLs) for children aged 0-84 months. Results showed that the orthophosphate addition of only 1 mg P/L can significantly decrease the proportion of children with a BLL >5 µg/dL, from 82 % to 17 %, under the most extreme water conservation scenario studied, using the 90th percentile of Pbdiss concentrations during usage at kitchen tap. Wide variations of Pbdiss concentrations at the kitchen tap were calculated at times of use over a week (up to 155 µg/L in lower demand scenarios, without corrosion control) showing evident limitations of single random daytime sampling.

Impacts of orthophosphate-polyphosphate blends on the dissolution and transformation of lead (II) carbonate.

Orthophosphate-polyphosphate blends are commonly used to control lead release into drinking water, but little is known about how they interact with lead corrosion scale. Conventional corrosion control practice assumes that orthophosphate controls lead release by forming insoluble Pb-phosphate minerals, but this does not always occur, and under certain conditions, phosphate blends may increase lead release. Here, we used continuously-stirred tank reactors to compare orthophosphate-polyphosphate blends with orthophosphate on the basis of lead (II) carbonate dissolution and transformation at environmentally relevant phosphate concentrations. Three model polyphosphates-tripoly-, trimeta- and hexametaphosphate-were used. Hexametaphosphate was the strongest complexing agent (1.60-2.10 molPb/molPolyphosphate), followed by tripolyphosphate and trimetaphosphate (1.00 and 0.07 molPb/molPolyphosphate, respectively. At equivalent orthophosphate and polyphosphate concentrations (as P), orthophosphate-trimetaphosphate had minimal impact on lead release, while orthophosphate-tripolyphosphate increased dissolved lead. Orthophosphate-hexametaphosphate also increased dissolved lead, but only over a 24-h stagnation. Both orthophosphate-tripolyphosphate and orthophosphate-hexametaphosphate increased colloidal lead after 24-h. Increasing the concentrations of hexameta- and tripoly-phosphate increased dissolved lead release, while all three polyphosphates inhibited the formation of hydroxypyromorphite and reduced the phosphorus content of the resulting lead solids. We attributed the impacts of orthophosphate-polyphosphates to a combination of complexation, adsorption, colloidal dispersion, polyphosphate hydrolysis, and lead mineral precipitation.

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.

Field analyzers for lead quantification in drinking water samples.

Field analyzers for the measurement of lead in drinking water samples are gaining interest from states, water utilities and building managers as rapid, inexpensive and simple tools to quantify lead concentrations. This literature review compares data quality by field analyzers to established laboratory methods and provides practical information (e.g. costs, ease-of-use) on commercial lead analyzers that are based on: (1) Electrochemistry, (2) Colorimetry and (3) Fluorescence. Between and within these three general field analyzer categories, manufacturers specify a variety of protocols to prepare the samples, which differ from the standard acidification in laboratory methods. Review of the literature raised concerns that without adequate sample preparation, field analyzers may not always fully quantify the total lead concentration, including particulate lead, thereby resulting in underestimations. Nonetheless, field analyzers have been used to quickly obtain experimental results in the laboratory, or in the field when access to laboratory equipment was limited, expensive or otherwise impractical. Field analyzers were also successfully used to detect lead from service lines, by a water utility where lead was mostly in the dissolved form. Overall, intrinsic strengths and weaknesses of field analyzers are discussed, to better balance practical convenience and adequate data quality depending on the objective.

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.

Lead and copper release from full and partially replaced harvested lead service lines: Impact of stagnation time prior to sampling and water quality.

Partial lead service line replacement (PLSLR) results in the addition of a new galvanic connection and can increase lead concentrations at the tap. Focus has been given to minimizing lead release after PLSLR, but little information is available on the impact of lead remedial actions on copper concentrations, especially before passivation occurs. The impact of water quality (decreased chloride-to-sulfate mass ratio from 0.9 to 0.3; addition of orthoP; pH increase to 8.3) on lead and copper concentrations was investigated after stagnation (30 min-336 h) in a pipe rig comparing full lead service line (LSL), and two configurations of partial LSLs (Cu-Pb and Pb-Cu). Results show different trends for lead and copper: maximum lead concentrations were reached in 16 h while copper concentrations continued to increase over 336 h. Lead release rates were also the highest in the first 16 h of stagnation and were strongly impacted by water quality and the configuration of PLSLR (Cu-Pb vs Pb-Cu). Increasing the sampling flow rate from 5 to 15 LPM drastically increased the particulate lead release (78-fold) in Pb-Cu configurations; this effect was however not observed in 100% Pb or Cu-Pb configurations. High velocity flushing prior to 16 h stagnation decreased total Pb release by a factor of 12-fold for Cu-Pb, 1.6-fold for Pb-Cu and 2.0-fold for 100% Pb. Results support the definition of sampling protocols targeted for the detection of lead and copper sources and the proscription of flushing prior to sampling.

Study of the long-term impacts of treatments on lead release from full and partially replaced harvested lead service lines.

Long-term (155 weeks) Pb concentrations, following partial lead service lines replacements (PLSLR), were measured in a flow through pilot made of harvested lead service lines (LSL) from the distribution system of the City of Montreal. The present study also investigates how release of Pb from full and partial LSLs is influenced by: pipe diameter, decrease in chloride-to-sulfate mass ratio (CSMR) from 0.9 to 0.3, addition of orthophosphate (1 mg P/L), and increase in pH to 8.3. Pb concentrations were measured after 16 h of stagnation and under flow conditions. In this study, Pb concentrations did not decrease, in the long term, after partial LSL replacement. Moreover, the most effective corrosion control treatment in full LSLs was the addition of orthoP. In contrast, the decrease of the CSMR best reduced lead release from partial LSLs. The impact of pipe configuration therefore influenced the effectiveness of corrosion control treatments. It is noteworthy that the increase in Pb concentrations following PLSLR were attributed to particulate Pb release from the galvanic section of the pipe. The occurrence of galvanic corrosion, caused by the connection between Pb and copper pipes, adds a new source of Pb in the partial LSL. At least, this new source of lead has to be offset by the removal of a long enough section of LSL during PLSLR. Full LSL replacements may be warranted to minimize the exposure of consumers to elevated Pb levels caused by galvanic corrosion in LSLs.

Sampling in schools and large institutional buildings: Implications for regulations, exposure and management of lead and copper.

Legacy lead and copper components are ubiquitous in plumbing of large buildings including schools that serve children most vulnerable to lead exposure. Lead and copper samples must be collected after varying stagnation times and interpreted in reference to different thresholds. A total of 130 outlets (fountains, bathroom and kitchen taps) were sampled for dissolved and particulate lead as well as copper. Sampling was conducted at 8 schools and 3 institutional (non-residential) buildings served by municipal water of varying corrosivity, with and without corrosion control (CC), and without a lead service line. Samples included first draw following overnight stagnation (>8h), partial (30 s) and fully (5 min) flushed, and first draw after 30 min of stagnation. Total lead concentrations in first draw samples after overnight stagnation varied widely from 0.07 to 19.9 µg Pb/L (median: 1.7 µg Pb/L) for large buildings served with non-corrosive water. Higher concentrations were observed in schools with corrosive water without CC (0.9-201 µg Pb/L, median: 14.3 µg Pb/L), while levels in schools with CC ranged from 0.2 to 45.1 µg Pb/L (median: 2.1 µg Pb/L). Partial flushing (30 s) and full flushing (5 min) reduced concentrations by 88% and 92% respectively for corrosive waters without CC. Lead concentrations were <10 µg Pb/L in all samples following 5 min of flushing. However, after only 30 min of stagnation, first draw concentrations increased back to >45% than values in 1st draw samples collected after overnight stagnation. Concentrations of particulate Pb varied widely (≥0.02-846 µg Pb/L) and was found to be the cause of very high total Pb concentrations in the 2% of samples exceeding 50 µg Pb/L. Pb levels across outlets within the same building varied widely (up to 1000X) especially in corrosive water (0.85-851 µg Pb/L after 30MS) confirming the need to sample at each outlet to identify high risk taps. Based on the much higher concentrations observed in first draw samples, even after a short stagnation, the first 250mL should be discarded unless no sources of lead are present. Results question the cost-benefit of daily or weekly flushing as a remediation strategy. As such, current regulatory requirements may fail to protect children as they may not identify problematic taps and effective mitigation measures.

Evaluation of exposure to lead from drinking water in large buildings.

Lead results from 78,971 water samples collected in four Canadian provinces from elementary schools, daycares, and other large buildings using regulatory and investigative sampling protocols were analyzed to provide lead concentration distributions. Maximum concentrations reached 13,200 and 3890 µg/L following long and short stagnation periods respectively. High lead levels were persistent in some large buildings, reflected by high median values considering all taps, or specific to a few taps in the building. Simulations using the Integrated Uptake Biokinetic (IEUBK) model and lead concentrations after 30 min of stagnation in the dataset showed that, for most buildings, exposure to lead at the tap does not increase children's blood lead levels (BLLs). However, buildings or taps with extreme concentrations represent a significant health risk to young children attending school or daycare, as the estimated BLL far exceeded the 5 µg/dL threshold. Ingestion of water from specific taps could lead to acute exposure. Finally, for a few taps, the total daily lead intake reached the former World Health Organization (WHO) tolerable level for adults, suggesting potential health risks.

Impact of treatment on Pb release from full and partially replaced harvested Lead Service Lines (LSLs).

Release of lead from 80% partially replaced service lines was compared to full lead service lines using harvested-stabilized lead pipes and field brass connectors. After more than a year of stabilization, lead release was consistent with field samples. Over the relatively short duration partial replacement of lead pipe by copper pipe (3 months), generated high lead release, attributed to galvanic corrosion, resulting in a final outcome for lead release that was even worse than for a full lead pipe. Increased lead release was especially evident at higher flow rates. Orthophosphate reduced lead release from full lead pipes by 64%. For partially replaced samples with copper, lead concentrations were unchanged by phosphate dosing at moderate flow (103 ± 265 vs 169 ± 349 µg/L) and were increased to very high levels when sampled at high flow rates (1001 ± 1808 vs 257 ± 224 µg/L). The increase lead release was in the form of particulate lead (>90%). In comparison to the condition without treatment, increased sulfate treatment had little impact on lead release from 100%-Pb rigs but reduced lead release from partially replaced lead pipes with copper. Our results also raise questions concerning protocols based on short 30 min stagnation (as those used in Canada) due to their incapacity to consider particulate lead release generated mostly after longer stagnation.