Incidence of EBL (blood lead > or =10 microg/dL) for children aged < or = 1.3 years in Washington, DC increased more than 4 times comparing 2001-2003 when lead in water was high versus 2000 when lead in water was low. The incidence of EBL was highly correlated (R2 = 0.81) to 90th percentile lead in water lead levels (WLLs) from 2000 to 2007 for children aged < or = 1.3 years. The risk of exposure to high water lead levels varied markedly in different neighborhoods of the city. For children aged < or =30 months there were not strong correlations between WLLs and EBL, when analyzed for the city as a whole. However, the incidence of EBL increased 2.4 times in high-risk neighborhoods, increased 1.12 times in moderate-risk neighborhoods, and decreased in low-risk neighborhoods comparing 2003 to 2000. The incidence of EBL for children aged < or =30 months also deviated from national trends in a manner that was highly correlated with 90th percentile lead in water levels from 2000 to 2007 (R2 = 0.83) in the high-risk neighborhoods. These effects are consistent with predictions based on biokinetic models and prior research.

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The occurrence of particulate lead in drinking water deserves increased scrutiny. This is especially true because models of human exposure to lead, sampling protocols, analytical methods, and environmental assessments are often based on the presumed dominance of soluble lead in drinking water. Recent cases of childhood lead poisoning were tied to solder particles that detached from the plumbing and contaminated the potable water supply. In cases such as these, common samplehandling procedures can “miss” particulate lead present in water samples. In some instances, the actual amount of lead present in drinking water samples may be five times higher than that obtained using approved protocols. The presence of chloride, warmer temperature, and lower pH in the human stomach may render a significant fraction of this “missed” particulate lead as bioavailable when ingested.

Experimental tests and utilities' practical experience highlighted the importance of chloride‐to‐sulfate mass ratio (CSMR) in the control of lead leaching to potable water. The effect of higher CSMR was demonstrated in bench‐scale experiments using brass coupons and lead solder‐copper pipe joints, with the amount of lead leaching to water increasing by factors of 1.2–2.7 and 2.3–40.0, respectively. Anion exchange treatment, a switch in coagulant type, and other seemingly innocuous treatment steps can result in significant changes in CSMR. Practical data collected at three US utilities confirmed that alterations in CSMR can trigger serious lead contamination incidents.

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Partial lead service line replacement with copper pipe creates a galvanic cell that can accelerate lead corrosion. Bench‐scale experiments under stagnant water conditions of high chloride‐to‐sulfate mass ratio (CSMR) demonstrated that galvanic connections between lead pipe (new or aged) and copper pipe increased lead release into the water by 1.1 to 16 times, compared with a full length of lead pipe alone. The extent of galvanic attack was dependent on drinking water quality. Exposure to water of high CSMR increased lead release in the lead–copper rigs by 3 to 12 times, compared with a lessaggressive low CSMR water. Galvanic current also increased by 1.5 to 2 times when switching from low to high CSMR. The small area of lead pipe adjacent to the copper joint (< 0.5 ft) dissipated 90–95% of the total galvanic current and accumulated a thick (1‐in.‐wide) layer of lead rust (i.e., a lead‐containing scale), which constituted a reservoir for semirandom particulate lead detachment into the water.

US corrosion control practice often assumes that the orthophosphate component of blended phosphate corrosion inhibitors causes the formation of low‐solubility lead–orthophosphate solids that control lead release into drinking water. This study identified the solids that formed on the interior surface of a lead service line and a galvanized steel pipe excavated from a system using a proprietary blended phosphate chemical. The scale was analyzed by X‐ray diffraction, X‐ray fluorescence, and scanning electron microscopy/energy dispersive spectroscopy. Instead of crystalline lead–orthophosphate solids, a porous amorphous layer rich in aluminum, calcium, phosphorus, and lead was observed at the lead pipe scale–water interface. Thus, the mechanism inhibiting lead release into the water was not a thermodynamically predictable passivating lead–orthophosphate scale, but rather an amorphous barrier deposit that was possibly vulnerable to disturbances. Galvanized pipe scales showed relatively crystalline iron and zinc compounds, with additional surface deposition of aluminum, phosphorus, calcium, and lead.

To determine if residential water sampling corroborates the expectation that formation of stable PbO2 coatings on lead service lines (LSLs) provides an effective lead release control strategy, lead profile sampling was evaluated for eight home kitchen taps in three U.S. cities with observed PbO2-coated LSLs (Newport, Rhode Island; Cincinnati and Oakwood, Ohio). After various water standing times, these LSLs typically released similar or lower peak lead levels (1 to 18 μg/L) than the lead levels from the respective kitchen faucets (1 to 130 μg/L), and frequently 50-80% lower than the lead levels typically reported from Pb(II)-coated LSLs in comparable published sampling studies. Prolonged stagnation (10-101 h) at the Cincinnati sites produced varying results. One site showed minimal (0-4 μg/L) increase in lead release from the PbO2-coated LSL, and persistence of free chlorine residual. However, the other site showed up to a 3-fold increase proportional to standing time, with essentially full depletion of the chlorine residual. Overall, lead release was consistently much lower than that reported in studies of Pb(II)-coated LSL scales, suggesting that natural formation of PbO2 in LSLs is an effective lead "corrosion" control strategy.