Evaluating the Effects of Full and Partial Lead Service Line

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Evaluating the effects of full and partial lead service line replacement on drinking water lead levels Benjamin F Trueman, Eliman Camara, and Graham A. Gagnon Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b01912 • Publication Date (Web): 23 Jun 2016 Downloaded from http://pubs.acs.org on June 24, 2016

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Environmental Science & Technology

EVALUATING THE EFFECTS OF FULL AND PARTIAL LEAD SERVICE LINE REPLACEMENT ON DRINKING WATER LEAD LEVELS Benjamin F. Trueman1, Eliman Camara1, and Graham A. Gagnon1,* 1

Civil & Resource Engineering Dalhousie University 1360 Barrington St. Halifax, NS, CAN B3H 4R2 *Corresponding Author: G.A. Gagnon, e-mail [email protected], Tel: 902.494.3268, Fax 902.494.3108 Submitted to Environmental Science & Technology in revised form for review and possible publication, June 2016 KEYWORDS: lead service line replacement; drinking water; distribution system; lead and copper rule

ACS Paragon Plus Environment


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ABSTRACT

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lead exposure via drinking water, but jurisdictional issues can sometimes

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interfere with full replacement of the lead line. The effects of full and partial

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LSLR on lead levels were assessed using 5 × 1L sample profiles collected at

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more than 100 single-unit residences. Profiles comprised four sequential

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standing samples (L1-4) and a free-flowing sample (L5) drawn after a 5-

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minute flush of the outlet. At 45 sites with full LSLs, 90th percentile lead

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levels in standing samples ranged from 16.4 to 44.5 µg L-1 (L1 and L4,

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respectively). In the free-flowing sample (L5), 90th percentile lead was 9.8

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µg L-1. Within 3 days, full LSLR had reduced L3-5 lead levels by more than

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50%, and within 1 month, lead levels were significantly lower in every litre

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of the sample profile. Conversely, partial LSLR more than doubled premise

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plumbing (L1-2) lead release in the short term and did not reduce L1-2 lead

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release in the long term. Even 6 months after partial LSLR, 27% of first-

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draw lead levels were greater than 15 µg L-1 (the U.S. EPA action level),

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compared with 13% pre-replacement.

Lead service line replacement (LSLR) is an important strategy for reducing

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INTRODUCTION

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Lead service lines (LSLs)—pipes connecting distribution mains to premise

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plumbing—were installed widely throughout the first half of the twentieth

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century in North America and even occasionally up until the U.S.

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congressional ban in 1986.1 In Canada, the National Plumbing Code

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permitted installation of LSLs until 1975.2 At sites where they were

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installed, 50-75% of drinking water lead may be attributable to the LSL.3

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Elevated lead in drinking water is a significant public health concern

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because water lead levels have been shown to correlate positively with blood

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lead levels.4-7 Childhood blood lead levels below 10 µg dL-1—and early

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childhood levels as low as 2 µg dL-1—are linked with deficits in cognitive

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and academic skills.8-10 Chronic lead exposure in adults is associated with

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renal dysfunction11 and hypertension12 and lead is a known abortifacient.13

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Lead in U.S. drinking water is regulated under the Lead and Copper Rule,14

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which specifies an action level of 15 µg L-1 for the 90th percentile first-draw

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lead level. In Canada, the maximum acceptable concentration in a free-

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flowing sample is 10 µg L-1, a benchmark that serves as the current Nova

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Scotia regulation.15 Health Canada also recommends corrective action when



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the 90th percentile first-draw lead level exceeds 15 µg L-1.2,16

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Lead service line replacement (LSLR) is an important strategy for reducing

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lead exposure via drinking water, but joint (public-private) ownership can

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interfere with full replacement of the LSL. Typically, partial LSLR occurs

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when the public LSL is replaced with copper and joined to the private LSL

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left in place.1 Partial LSLR can cause elevated lead in drinking water—

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disturbance of LSL corrosion scale during replacement may release high

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levels of lead for an extended period post-replacement. The lead-copper

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junction is a specific concern due to the potential for galvanic corrosion.3,17

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Elevated lead release owing to a galvanic lead-copper couple has been

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demonstrated in laboratory and pilot studies and is a likely factor in

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persistent high lead levels following partial LSLR.18-21 Mineralogical

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evidence of galvanic corrosion in lead-copper and lead-brass joints

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excavated from several distribution systems has also been reported.22

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Limited residential data suggest that partial LSLR may be associated—at

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best—with insignificant decreases in lead exposure risk. Partial LSLR did

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not reduce the risk of elevated blood lead among children in Washington,


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DC and children living in homes with partial LSLs were more than three

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times as likely to have elevated blood lead (≥ 10 µg dL-1) compared to those

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in homes constructed without LSLs.23 Other residential studies—on 5 or

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fewer sites—have reported lead spikes following partial LSLR and modest

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or minimal subsequent reductions in lead release.3,24,25 Camara et al.26

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reported greater lead release following partial LSLR relative to full LSLR

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but did not provide detailed pre- and post-replacement comparisons.

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In 2011, an advisory board to the U.S. EPA concluded that existing data

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were inadequate to fully assess the effect of partial LSLR on drinking water

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lead levels.27 The board found that the few studies available had

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limitations—including small sample sizes and limited follow-up sampling—

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but did conclude that partial LSLR could not be relied upon to reduce lead

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levels in the short term.27

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The objective of this work was to estimate changes in lead exposure due to

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full and partial LSLR via a standardized profile sampling protocol. This

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protocol was implemented within a water system where Pb(II) compounds—

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in contrast to highly insoluble Pb(IV) oxides28—were presumed to dominate



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based on distributed water quality and consistent observation of peak lead

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levels in samples representative of LSLs. Water distribution infrastructure

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was considered typical of older North American municipalities. Water

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system characteristics featured several risk factors for elevated lead release,

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including 1) a significant number of unlined cast iron distribution mains,26 2)

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distributed water with low alkalinity (20 mg L-1 as CaCO3) and pH (7.3),29 3)

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a low orthophosphate residual (0.5 mg L-1 as PO43-)29 and 4) a chloride-to-

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sulfate mass ratio above the critical threshold (0.5 – 0.77) identified in

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previous work as a driver of galvanic corrosion.30,31 This study contributes to

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literature by helping to address limitations identified in the EPA advisory

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board report—small sample sizes and limited follow-up sampling.27 This

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paper also expands on previous work26 with analysis of a much greater

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volume of data: 74 and 61 full and partial LSL replacements—including

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paired before-and-after comparisons of 18 partial replacements—and 13

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additional sites with LSLs.

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MATERIALS AND METHODS

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Study area. The study area comprised single-unit residences in Halifax, NS

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(CAN) that underwent LSLR between 2011 and 2015. In the event of partial


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LSLR, electrical continuity between lead and copper was expected but not

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verified—following open-trench replacement, lead and copper were

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typically joined via a brass union as described in Clark et al.32 Participating

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residences were predominantly older homes—in areas of widespread pre-

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1950 construction, thousands of LSLs are still in use.26

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Sample sites received distributed water from a treatment facility employing

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free chlorine disinfection—this facility is described in detail elsewhere.33

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Table 1 lists 2013 – 14 typical values for key treated water quality

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parameters—no relevant changes in treatment were made over the study

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period.34 Beginning in 2002, a blended zinc ortho/polyphosphate corrosion

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inhibitor (75% orthophosphate, 25% polyphosphate) was added at a treated

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water residual of 0.5 mg L-1 (as PO43-).

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Sample collection. Residents, with direction from utility staff, collected

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profiles of four sequential 1L standing samples from kitchen cold-water taps,

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beginning with the first draw following a minimum 6-hour standing period.

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The 4 × 1L sample profile (L1-4) was followed by a 5-minute flush of the

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outlet and subsequent collection of a fifth 1L sample (L5). Profile sampling



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was carried out before and at four follow-up rounds (3 days, 1 month, 3

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months, and 6 months) after LSLR. Residents were instructed to record

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exact stagnation times (median 7 hrs. 40 min., min. 6 hrs., max. 23 hrs.), and

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to sample at a constant flow rate, but were not instructed to remove faucet

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aerators prior to sample collection. Sampling instructions given to residents

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are provided as Supplementary Information—data were excluded from

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analysis when these instructions were not followed.

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A complete series of pre- and post-replacement sample profiles was not

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available for every residential site, owing to incomplete resident

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participation. For this reason, sample sizes for before-and-after comparisons

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differ by follow-up round. However, lead levels at a given follow-up round

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were not significantly different (two-tailed rank-sum tests, α = 0.05) at sites

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where residents participated at the next round compared to sites where they

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did not—reporting lead levels to residents did not appear to influence

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subsequent participation.

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In order to assess the effect of water temperature on lead release, 13 × 1L

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sample profiles were collected from kitchen cold-water taps at two other


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sites with LSLs (denoted sites A and B), following a 5-minute flush of the

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outlet and subsequent 30-minute stagnation. The final litre of the 13 × 1L

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profile was a free-flowing sample collected after a second 5-minute flush of

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the outlet. Sample collection by the authors at these 2 sites, as opposed to

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residents, necessitated use of an alternate sampling protocol, however

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differences in collection methods limit the comparisons that can be made

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between these two sites and the rest of the data. Samples were collected

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weekly over a period of 7 or 8 weeks (sites A and B, respectively). Water

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temperature was measured, using a glass thermometer, in the first and last

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litre of each profile from the second week on.

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Analytical methods. Total lead, copper, iron, and aluminum were measured

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by ICP-MS (Thermofisher X Series II) according to Standard Methods 3125

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and 3030.35 Reporting limits for Pb, Cu, Fe, and Al were 0.4, 0.7, 6.0, and

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4.0 µg L-1, respectively. Lead was also quantified in 0.45 µm filtrate for a

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subset of 386 sample profiles. Filtration via cellulose nitrate membrane

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filters was generally performed within 2 days of sample collection (but prior

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to acid-preservation), so results should be interpreted with care—changes in

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speciation between collection and filtration cannot be ruled out. Loss of lead



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to sample bottles was estimated at 1.2% (std. dev. 17.3%) by comparing

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total lead in 10 mL aliquots drawn from well-mixed 1L samples before and

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24 hours after acid preservation of the entire sample (N = 82 5 × 1L sample

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profiles).36 Losses due to filtration were estimated at 21.1% (std. dev. 0.4%)

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by comparing lead in 10 mL aliquots filtered once with lead in 10 mL

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aliquots filtered twice, using a new filter each time.36 Polyethylene (HDPE)

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bottles and caps were immersed in ~ 2M reagent grade HNO3 for a

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minimum of 24 hours and rinsed three times with ultrapure water prior to

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use, and method blanks were prepared by holding ultrapure water preserved

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with trace metal grade HNO3 in acid-washed bottles for 24 hours at 4˚C.

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Data analysis. Lead levels at each of the four follow-up rounds after LSLR

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were compared with pre-replacement lead levels. Sample profiles collected

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after full LSLR (Table 2) were compared, using two-tailed rank-sum tests,37

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with an independent set of 45 profiles collected at sites with full LSLs.

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Differences between groups were multiplicative (i.e., best described as

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ratios) but a natural log transformation yielded additive differences (i.e., best

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described as constants). Changes in lead level were quantified using a

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Hodges-Lehmann estimator, c, where c = median (yi / xj) for all i=1,...,n and


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j=1,...,m. Variables x and y denote lead levels observed at m and n sites with

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full and fully replaced LSLs, respectively. The quantity c estimates the ratio

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of lead levels between the two groups, where y = cx.38

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Sample profiles collected before and after partial LSLR were paired by

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address and compared using two-tailed signed rank tests by profile litre and

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follow-up round.37 Natural log transformations were applied to the paired

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data to achieve symmetry in the distribution of differences. Multiplicative

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differences in before-and-after replacement lead levels were also quantified

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using a Hodges-Lehmann estimator—details, though similar to those

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provided above, may be found elsewhere.38 No control of the family-wise

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error rate for multiple comparisons was employed.

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RESULTS AND DISCUSSION

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Pre-replacement lead levels. Lead and copper levels representing 5 × 1L

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sample profiles collected at 45 sites with full LSLs are provided in Figure 1.

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Peak copper levels occurred in L1 (90th percentile: 151 µg L-1) and peak lead

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levels in L4 (90th percentile: 44 µg L-1). For single-unit residences, peak



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lead levels are often observed by L4 of the sample profile.39 The higher

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median (11 µg L-1) and increased variability in L3 lead levels (90th

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percentile: 29 µg L-1) suggest that L3 stagnated at least partially within the

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LSL at some of the 45 sites. This is consistent with previous work—Cartier

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et al.40 estimated median (mean) premise plumbing volumes in 88 pre-1970

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homes at 2.0 L (2.3 L). At sites with full LSLs, L1 significantly

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underestimated peak lead levels—in systems where lead (II) compounds

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form preferentially, lead in water that contacted the LSL during stagnation

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may be considerably higher than lead in the first-draw sample.26,28,41

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Longer sample profiles (13 × 1L) collected at two residential sites with LSLs

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(sites A and B, Figure 2) provide insight into the ability of the 5 × 1L profile

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to estimate lead exposure. Plumbing configuration can be inferred by

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comparing lead and copper levels over each profile, although mixing among

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profile litres and the 5-minute flush prior to stagnation (sites A and B only)

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may have influenced apparent plumbing volumes. Site A is a typical

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example of the single-unit residences that underwent LSLR (the large

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apparent premise plumbing volume of 8-9 L at site B is explained by sample

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collection from a second-level kitchen). The apparent premise plumbing


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volume at site A was 2-3 L—copper declined sharply after the first 2 L and

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quickly approached the level of the flushed sample (L13, 10 µg L-1). Peak

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lead levels were observed by L4, although L3-9, or parts thereof, appear to

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have stagnated within the LSL. In light of LSL lead release observed at sites

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A and B following 30 minutes of stagnation (max. 28 and 14 µg L-1,

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respectively), apparent LSL lead release at the 45 sites represented in Figure

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1 was lower than expected (min. 6-hour stagnation, 90th percentile of 44 µg

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L-1 in L4). This suggests that L4 may sometimes have fallen short of the

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LSL. Furthermore, while L4 does appear to have reached the LSL in at least

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some cases, it may not have reached the lead-copper junction at sites with

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partial LSLs, as sample profiles reported in previous work have shown.42

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Thus, 4 × 1L standing sample profiles may only provide an indirect

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assessment of the effect of galvanic corrosion following partial LSLR.

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Influence of water temperature. Pre-replacement profiles were collected in

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summer—collection dates at the initial round had a July median. This

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introduces water temperature as a potential confounding variable. One-

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month follow-up collection dates had a September median, and on this

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interval the variation in water temperature is likely to have been low—



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typical 5-minute flushed sample temperature was 17.9 ˚C in July (this study)

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and 17.8 ˚C in October.43 Comparisons between full and partial LSLR at the

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same follow-up round are also unlikely to have been strongly influenced by

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temperature. However, partial LSL profile collection dates at the 3 and 6-

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month follow-up rounds had December and April medians, respectively.

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Pre- and post-replacement comparisons on these intervals are subject to

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decreases in water temperature of approximately 10 ˚C—typical 5-minute

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flushed sample temperature in February was 7.2 ˚C.43

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The effect of water temperature on lead release is complex—the positive

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effect of temperature on the rate of electrochemical reactions may be

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counterbalanced by the reduced solubility of lead minerals at higher

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temperatures, depending on the composition of corrosion scale.44

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Temperature effects also depend on whether the source of lead is premise

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plumbing—where seasonal variation is expected to be minimal—or LSLs—

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where variation is greater.17 Previous work has shown that lead release can

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be temperature-dependent,40,45 and data from 13 × 1L profiles collected at

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sites A and B show that lead release was moderately-to-highly correlated

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with water temperature (R2 = 0.46 – 0.98, average of 0.79). Between 13 and


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19 ˚C, a 1 ˚C increase in 5-min. flushed sample temperature accompanied an

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average 1.1 µg L-1 increase in lead release from LSLs (Figure S1), although

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other seasonally varying water quality parameters, such as free chlorine

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residual, could have influenced observed lead levels.

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Water temperature was correlated with lead release from premise plumbing

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at sites A and B as well—likely a consequence of the short (30-min.)

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stagnation time. More generally, lead release from premise plumbing does

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not often exhibit strong temperature dependence, provided that stagnation

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time is sufficient for standing water to reach building temperatures (e.g., 6

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hours).17 In a survey of 365 U.S. drinking water utilities, 90th percentile first-

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draw lead levels—collected following a minimum 6-hour stagnation—were

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not a function of season.46 Within the present study area, first-draw lead

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levels (min. 6-hr. stagnation, 34 residential sites) were no higher in October

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than in February.43

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Owing to the effect of water temperature on lead release from LSLs, long-

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term (3 and 6 month) pre- and post-replacement comparisons were only

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interpreted for the portion of the sample profile least likely to have been



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influenced by temperature—L1 and L2. It is possible that, for sites with very

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small premise plumbing volumes, L2 lead levels were affected by

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temperature variation, but no significant drop in L2 lead levels from summer

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to winter was observed following partial LSLR (Table 2). For L3 and L4,

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however, decreasing water temperature likely contributed to— and may have

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been entirely responsible for—observed reductions in lead release.

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Effect of full LSL replacement. For each profile litre and follow-up round,

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the fraction of pre-replacement lead remaining after LSLR was estimated

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(Table 2)—full LSLR reduced lead levels in every litre of the sample profile

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within 1 month. Before-and-after differences were multiplicative (not

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additive), meaning that sites with high lead levels pre-replacement tended to

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see greater reductions in lead post-replacement. For a given profile litre, a

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ratio less than one signifies a reduction in lead over pre-replacement levels

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and a ratio greater than one signifies an increase.

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At sites that underwent full LSLR, public and private LSL sections were not

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often replaced on the same day, and a delay of several months was not

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uncommon. In many cases, the pre-replacement profile represented the


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partial LSL configuration. In order to properly evaluate the effect of full

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LSLR, lead levels after full replacement were compared, without pairing,

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against 45 sites with full LSLs—41 of these 45 underwent partial LSLR

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only. Unpaired comparisons have the advantage of larger sample sizes, but

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they are expected to be less accurate when other sources of lead are present

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(e.g., in L1 and L2). A key benefit of pairwise comparisons is that they tend

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to account for variation due to uncontrolled factors (e.g., other sources of

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lead, variations in flow rate).47

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Reductions in lead following full LSLR were immediate—lead levels in L3-

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5 were less than half of their pre-replacement counterparts at the 3-day

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follow-up (Table 2). One month after full replacement, lead release from

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premise plumbing (L1-2) had dropped significantly as well. Distribution

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quantiles, representing before-and-after full LSLR comparisons at the 1-

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month follow-up, are provided in Figure 3. Quantiles adhered well to the

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ratio estimates listed in Table 2, except in the upper extremes, where outliers

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occasionally deviated. One month-post replacement, 90th percentile lead

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levels ranged from 2 to 12 µg L-1 (L5 and L1, respectively), while pre-

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replacement 90th percentiles ranged from 10 to 44 µg L-1 (L5 and L4,



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respectively). Reductions in lead release from premise plumbing (L1-2) may

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be attributed to gradual flushing of lead that had accumulated pre-

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replacement, as previous work has suggested.3 Since premise plumbing

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upgrades were not performed in conjunction with LSLR, leaded solder and

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brass were not expected to have contributed to changes in lead release post-

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replacement. Accumulation of lead in premise plumbing may have been

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driven in part by adsorption to iron deposits or surfaces—as described

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elsewhere, colloidal lead (< 0.45 µm) was strongly associated with colloidal

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iron at residential sites within the same water system.36 Previous work has

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accounted for a correlation between iron and lead at the point of use with

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reference to the strong tendency for lead to adsorb to iron oxide deposits or

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galvanized iron plumbing.42,48,49 Manganese deposits in premise plumbing

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have also been implicated as a sink for—and subsequent source of—lead in

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drinking water.50

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Effect of partial LSL replacement. Partial LSLR more than doubled

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premise plumbing (L1-2) lead levels at the 3-day follow-up (Table 2). One

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month post-replacement, L1 was still elevated by more than 60%, while

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subsequent standing sample lead levels (L2-4) had not changed significantly


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relative to their pre-replacement counterparts. Even 6 months after partial

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LSLR, no significant reductions in L1-2 lead levels were observed.

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Reductions in L3-4 lead release at the 3 and 6-month follow-up rounds were

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expected to have been enhanced by—and could have been entirely due to—

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decreasing water temperature. (Increases, relative to pre- replacement, in

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LSL lead release at 3 and 6 months were sometimes observed despite

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temperature differences—see Figure S2.) Applying a 1.1 µg L-1 ˚C-1

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correction (described in the Supplementary Information), based on expected

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water temperature differences, eliminated statistically significant reductions

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in L3-4 lead release that would otherwise have been attributed to partial

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LSLR.

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In contrast to standing samples, L5 lead levels were not significantly

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different from their pre-replacement counterparts at the 3-day follow-up

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(90th percentile of 14 µg L-1) and were significantly lower at the 1-month

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follow-up (90th percentile of 6 µg L-1). However, data from this study do not

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support 5 minutes of flushing as a strategy for protecting against the short-

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term effects of partial LSLR— 9% of L5 samples were greater than 15 µg L-

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1

at the 3-day follow-up compared with just 4% pre-replacement. Moreover,



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an L5 sample collected 3 days post-replacement measured 230 µg L-1.

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Changes in lead release due to partial LSLR are illustrated in Figure 4

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(bottom), which displays the distribution of pairwise differences in lead

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release (after – before), grouped by profile litre for the first two follow-up

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rounds (3 days and 1 month). Positive differences correspond to an increase

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in lead release post-replacement, and negative differences correspond to a

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decrease (sample sizes are provided in Table 2). Increased lead release

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following partial LSLR is evident, especially at the 3-day follow-up—on this

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interval, more than a quarter of sites saw increases of 20 µg L-1 in at least

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one standing sample (L1-4). On the 1-month interval, L3 and/or L4 lead

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increased by 10 µg L-1 at more than a quarter of sites.

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Increased lead release to L1 and L2 can likely be attributed to accumulation

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of particulate lead in premise plumbing following replacement-induced

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destabilization of LSL corrosion scale.3 Galvanic corrosion at the lead-

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copper junction has been linked with elevated particulate lead release as

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well.18-21 Occurrence of particulate lead (> 0.45 µm) was more frequent

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following partial (relative to full) LSLR (Figure 5). At the 3-day follow-up,


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11 and 26% of samples collected following full and partial LSLR,

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respectively, had more than 10 µg L-1 of particulate lead (compared to 3%

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pre-replacement). Elevated lead release in general was dominated by

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particles—at higher total lead levels the particulate fraction was larger,

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approaching unity at lead levels higher than approximately 100 µg L-1

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(Figure 5). Available data suggest that lead in 0.45 µm filtrate was

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dominated by colloidal particles (0.05 – 0.45 µm).36

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Post-replacement lead exposure. Serious spikes in lead sometimes

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followed LSLR and were much more frequent following partial LSLR—

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elevated lead levels after partial replacement have been reported in previous

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work as well.3,24,25,51 Trends in post-replacement lead release diverged

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immediately according to replacement type. At sites with full LSLs (pre-

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replacement), 29% of standing sample (L1-4) lead levels were greater than

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15 µg L-1 (45 sites). Three days after partial LSLR, 45% of L1-4 lead levels

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were greater than 15 µg L-1 (34 sites), while 3 days after full LSLR, just 14%

422

were greater (48 sites). Lead levels exceeding 15 µg L-1, by follow-up round

423

and LSL configuration, are displayed in Figure 4 (top). This threshold

424

represents a concentration above which the Centers for Disease Control and



425

Prevention considers drinking water unsuitable for consumption by children

426

and pregnant women.52 At the 3-day follow-up, 3 observations also exceeded

427

the U.S. Consumer Product Safety Commission’s acute exposure level for

428

children (700 µg L-1, based on a 250 mL intake)53—all at sites with partial

429

LSLs. These extreme lead levels, including a sample with 10,340 µg L-1,

430

were associated with premise plumbing (L1 or L2). High-velocity, multiple

431

outlet flushing post-replacement is a possible strategy for protecting against

432

these short-term spikes in lead.51

433 434

Unusually high lead levels were also observed at several sites following full

435

LSLR (Figure 4, top). The highest observations at 1 and 6 months were both

436

first-draw samples, and the highest four observations at 3-months represent

437

standing samples (L1-4) collected at a single site. Lead in these 4 samples

438

was more than 90% particulate (> 0.45 µm). These samples were also

439

unusually rich in particulate iron, copper, and aluminum, suggesting that the

440

source was corrosion scale within premise plumbing that had accumulated

441

multiple contaminants over time. In the case of full LSLR, public and

442

private LSL replacements were not often performed simultaneously, and

443

disturbances associated with two replacements—as well as possible galvanic

444

corrosion in the interim—may have contributed to elevated lead release and


Page 22 of 44

Page 23 of 44


445

accumulation of particulate lead within premise plumbing. While full LSLR

446

was associated with substantial reductions in lead levels, staggered

447

replacements may have caused the true benefit of full replacement to be

448

underestimated.

449 450

In the long term, elevated lead was observed more often at sites with partial

451

LSLs than at sites with either full LSLs or with full copper service lines

452

(post-LSLR). At the 6-month follow-up after partial LSLR, 22% of premise

453

plumbing (L1-2) lead levels—and 30% of service line lead levels (L3 and

454

L4)—were greater than 15 µg L-1 (30 sites). At sites with copper service

455

lines, 7% of L1-2 samples—and none of the L3 or L4 samples—were

456

greater than 15 µg L-1 (45 sites). The frequency of high (> 15 µg L-1) L1-2

457

lead levels was substantially greater— even 6 months post-replacement—at

458

sites with partial LSLs relative to sites with full LSLs (22 vs. 16%

459

respectively). Moreover, the fraction of first-draw samples greater than 15

460

µg L-1 at 6 months was double the pre- replacement fraction (27% vs. 13%).

461

Despite the possibility that the sample profile did not reach the lead-copper

462

junction—and that the flow regime did not represent a worst-case scenario—

463

these data captured the greater tendency, identified in previous work,19,20 for

464

elevated lead at sites with partial LSLs compared to sites with full LSLs.



465

466

Implications for controlling drinking water lead. This study used a

467

standardized profile sampling protocol to assess the effect of full and partial

468

LSLR on lead release to drinking water. The strength of this work was the

469

comparatively large volume of data collected pre- and post-replacement, and

470

the principal limitations were the inevitable uncertainties associated with

471

sample collection by residents and the lack of information on plumbing

472

volumes and configurations that limits a mechanistic understanding of the

473

results.

474

475

Full LSLR reduced service line (L3-4) and 5-minute flushed sample (L5)

476

lead levels within 3 days. At 1 month, full replacement had caused lead level

477

reductions in every litre of the sample profile. Partial LSLR, on the other

478

hand, caused substantial short-term increases in premise plumbing (L1-2)

479

lead levels and did not significantly reduce L1-2 lead levels within 6 months.

480

Furthermore, first-draw lead levels were greater than 15 µg L-1 at a

481

considerably higher frequency than at sites with full LSLs, even 6 months

482

post-replacement. This finding could have important implications in

483

jurisdictions where drinking water lead is regulated based on the first-draw


Page 24 of 44

Page 25 of 44

484


sample.

485

486

This study generated a considerable volume of data corroborating previous

487

work that showed 1) full LSLR—in addition to removing the primary source

488

of lead—is effective for reducing lead release from premise plumbing, 2)

489

partial LSLR dramatically increases lead at the point of use in the short term,

490

3) partial LSLR may be worse than leaving the LSL intact due to the

491

potential for elevated lead release in the long term, 4) in Pb(II)-dominated

492

water systems, first-draw lead levels are likely to underestimate lead

493

exposure at residences with LSLs, and 5) lead release from LSLs is

494

sometimes strongly influenced by water temperature.

495

496

The short-term elevated lead levels that sometimes followed partial LSLR

497

are a serious concern—some were high enough to pose acute health risks.

498

High-velocity flushing of outlets,51 use of pipe cutting methods that

499

minimize disturbances to LSLs,3 and point-of-use lead removal54 are

500

potential strategies that could be implemented to reduce health risks

501

associated with this mode of exposure. In assessing the effects of full and

502

partial LSLR, the potential for dramatically elevated lead levels post-



503

replacement is an important consideration. While the rapid reductions in lead

504

that typically follow full LSLR outweigh the risk of short-term disturbance-

505

induced spikes, the modest long-term benefits from partial LSLR described

506

in some previous work24,25 may be overshadowed by the greater risk of

507

elevated lead in both the short and long term.

508

509

SUPPORTING INFORMATION

510

Supplementary figures, a description of temperature correction methods, a

511

transcription of the sampling instructions given to residents. This material is

512

available free of charge via the Internet at http://pubs.acs.org.

513

514

ACKNOWLEDGEMENTS

515

This work was funded by the Natural Sciences and Engineering Research

516

Council (NSERC)/Halifax Water Industrial Research Chair in Water Quality

517

and Treatment (Grant No. IRCPJ 349838-11). The authors also acknowledge

518

the technical support of Heather Daurie, Elliott Wright, Krysta Montreuil,

519

Alisha Knowles, Everett Sneider, and Halifax Water staff.

520


Page 26 of 44

Page 27 of 44


521 522

TABLES

523 524

Table 1. Typical values for treated water quality parameters, pre-distribution. Parameter Zinc ortho/polyphosphate (as PO43-) Alkalinity (as CaCO3) Free chlorine Hardness (as CaCO3) Total organic carbon pH Chloride Sulfate Turbidity Iron Lead

525 526 527 528 529

Table 2. Estimated fraction of pre-replacement lead levels remaining after full and partial LSLR.

Partial LSLR (paired) Full LSLR (unpaired)c 530 531 532 533

Typical value 0.5 mg L-1 20.0 mg L-1 1.2 mg L-1 12.0 mg L-1 1.5 mg L-1 7.3 9 mg L-1 8.5 mg L-1 0.06 NTU 0.45 µm (µg L−1 )

(10340,10288) (902,876) (749,723) (475,464) (441,426) (324,283) (217,211) (147,140) (143,74) (473,459) ● (340,328) (162,150)

● Pre−replacement ● Partial LSLR

100

Full LSLR

●

75 ● ●

y=x

50 ●

25

0

Page 38 of 44

●●

● ● ●● ● ● ● ●● ●● ● ● ● ●● ● ● ● ● ●●●● ● ● ● ● ● ● ●● ● ● ● ● ● ●● ● ● ●●● ●● ● ● ● ● ●● ● ● ● ● ● ● ● ●● ● ● ● ● ● ●● ● ● ●●● ●● ● ● ● ● ● ●● ● ●● ● ●● ● ● ●● ● ● ● ● ● ● ● ● ● ● ●● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●● ● ●● ● ● ● ● ● ● ●● ● ● ●● ● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

0

25

50

●

75

●

● ● ●

100 −1

Total lead (µg L

y = 0.21 x (~100% of Pb < 0.45 µm)

125

150

)

Figure 5. Particulate (> 0.45 µm) lead release as a function of total lead, pre-replacement and at the first two follow-up rounds (72 hrs. and 1 mo. post-replacement). Points beyond the plot limits are represented as (x,y) coordinates and the line y = 0.21 x represents the estimated loss due to 0.45 µm filtration (~100% of lead < 0.45 µm).


6 mo. post−LSLR (µg L−1 )

● & Technology 200 Environmental Page 39 of 44 Science ●

y=x

150 100 50 0

● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●● ● ACS Paragon ● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0

50

●

Plus 100

Quantiles

● Full LSLR ● Partial LSLR Environment 150

Pre−LSLR (µg L−1 )

200

180

Environmental Science & Technology Page 40 of 44

Total lead (µg L−1 )

40

160

Copper Lead

35

140

30

120

25

100

20

80

15

60

10

40

5

20

ACS Paragon Plus Environment 0

0 L1

L2

L3

Profile litre

L4

L5

Total copper (µg L−1 )

45

25

100

20

80

15

60

10

40

5

20

0

0

Copper Lead

25

100

20

80

15

60

10

40

5

20

0

ACS Paragon Plus Environment 1

2

3

4

5

6

7

8

9

Profile litre

Total copper (µg L−1 )

Total lead (µg L−1 )

PageEnvironmental 41 of 44 Science & Technology

10

11

12

13

0

1 mo. post−replacement (µg L−1 )

80Environmental Profile litre ● ● ●

60

● ●

Science & Technology Page 42 of 44

L1 L2 L3 L4 L5

y=x ●

0.65 ●

40

● ●

0.43 ●

20

(103, 32)

● ●

●

●

● ● ●

0

●● ●● ● ●●● ● ● ●● ●● ●● ● ● ● ● ● ● ● ● ● ● ● ●●● ● ●● ●● ● ● ●● ● ●● ● ●●● ● ● ● ●● ● ● ● ● ● ● ● ●●● ● ● ● ●●● ● ● ● ● ●● ● ● ●●● ●●●● ●● ●●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ●

0.20 0.13 0.13


0

20

40

60

−1

Pre−replacement (µg L

80

)

−1

lead (µg L ) PageEnvironmental 43 of 44 Total Science & Technology 10

100

1000

10000

Before 3 d. 1 mo.

Observations > 15 µg L−1

3 mo.

Before Full LSLR Partial LSLR

6 mo. ● ●

Increase in total lead (µg L−1 )

80

60

85 246 312 10,330

88

676

238

227

●

●

Sample round ●

40

●

3 d. 1 mo.

●

20

●

0 ● ●

−20

●

ACS Paragon Plus Environment L1

L2

L3

L4

Profile litre

L5

Environmental Science & Technology Page (10340,10288) 44(902,876) of 44

● Pre−replacement ● Partial LSLR

Lead > 0.45 µm (µg L−1 )

100

(749,723) (475,464) (441,426) (324,283) (217,211) (147,140) (143,74) (473,459) ● (340,328) (162,150)

Full LSLR

●

75 ● ●

y=x

50 ●

25

0

●

●●

● ● ●● ● ● ● ●● ●● ● ● ● ●● ● ● ● ● ●●●● ● ● ● ● ● ● ●● ● ● ● ● ● ●● ● ● ●●● ●● ● ● ● ● ●● ● ● ● ● ● ● ● ●● ● ● ● ● ● ●● ● ● ●●● ●● ● ● ● ● ● ●● ● ●● ● ●● ● ● ●● ● ● ● ● ● ● ● ● ● ● ●● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●● ● ●● ● ● ● ● ● ● ●● ● ● ●● ● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

●

● ● ●

y = 0.21 x (~100% of Pb < 0.45 µm)


0

25

50

75

100 −1

Total lead (µg L

125

)

150

Evaluating the Effects of Full and Partial Lead Service Line

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