Water Research 157 (2019) 40e54 Contents lists available at ScienceDirect Water Research journal homepage: www.elsevier.com/locate/watres Sequential drinking water sampling as a tool for evaluating lead in flint, Michigan * Darren A. Lytle a, , Michael R. Schock a, Kory Wait a, Kelly Cahalan a, Valerie Bosscher b, Andrea Porter b, Miguel Del Toral b a U.S. Environmental Protection Agency, ORD, NRMRL, WSWRD, TTEB, 26 W. Martin Luther King Drive, Cincinnati, OH 45268, USA b U.S. Environmental Protection Agency, Region 5, Ground Water & Drinking Water Branch, 77 Jackson Blvd, Chicago, IL 60604, USA article info abstract Article history: Eliminating the sources of human lead exposure is an ongoing public health goal. Identifying the make- Received 11 October 2018 up of household plumbing and service line material type is important for many reasons including un- Received in revised form derstanding lead release sources and mechanisms, targeting locations for lead service line (LSL) removal, 15 March 2019 and assessing the effectiveness of lead remediation strategies. As part of the response to Flint, Michigan's Accepted 21 March 2019 drinking water lead public health crisis, a return to their original drinking water source (Lake Huron) and Available online 24 March 2019 an increase in orthophosphate dose was implemented in late 2015. In 2016, EPA performed multiple rounds of sequential or “profiling” water sampling to evaluate corrosion control effectiveness and Keywords: Lead identify lead sources in homes and service lines, as well as to evaluate the effectiveness of corrosion Drinking water control treatment with time on the different plumbing components. The results showed that lead levels, sequential samples including high lead levels likely associated with particles, decreased with time in homes sampled during Orthophosphate the 11-month evaluation period. Although sequential sampling indicated that brass fittings, brass fix- tures, and galvanized pipes were lead sources, LSLs were the greatest source of lead when present. Following the removal of LSLs, the total mass of lead contributed to the drinking water decreased by 86% on average. Published by Elsevier Ltd. 1. Introduction to be used for the screening of children (CDC, 2012; CDC, 2016). Recent research has indicated intellectual, behavioral, and atten- Eliminating the sources of lead exposure from the environment tion deficits linked to children's BLLs below 5 mg/dL (NTP, 2012; EPA, is an ongoing public health goal. Lead is a neurotoxicant that can 2013). In order to mitigate health effects, efforts to eliminate lead cause permanent cognitive and behavioral impairments in chil- sources continue. dren, and cardiovascular and kidney problems in adults (Fowler Although lead levels in water have decreased since the 1970s and Duval, 1991; ATSDR, 2007; Lanphear et al. 2018). Major regu- (Karalekas et al. 1975), drinking water can still be the dominant latory and primary prevention strides have reduced lead concen- source of total daily lead exposure (Triantafyllidou et al. 2007). Lead trations in water, paint, dust, gasoline and soil, with corresponding in drinking water originates from the corrosion or dissolution of reductions in observed blood lead levels (BLL) (Pirkle et al. 1994; lead-containing plumbing materials. Lead service lines (LSLs), Jain, 2016; Tsoi et al. 2016). These changes, however, have not which connect the water main to the premise (i.e., indoor or occurred fast enough to keep up with the continually decreasing household) plumbing, are considered the largest contributor to threshold for the level of lead exposure known to be harmful. In total lead in drinking water, responsible for up to 75% of the lead 2012, after concluding that no BLL could be considered “safe,” the measured in drinking water (Sandvig et al. 2008). The use of LSLs Centers for Disease Control and Prevention (CDC) reduced its was banned in the United States in 1986 (U.S. EPA, 1986). Estimates former BLL of concern from 10 mg/dL to a reference value of 5 mg/dL vary widely for the number of full or partial LSLs remaining, ranging from approximately 6.1 million (Cornwell et al. 2016) to 10.2 million (EPA, 1991a; 1991b, 1991c, 1992). Other important plumbing sources of lead include brass fixtures and fittings, lead * Corresponding author. solder (Subramanian et al. 1995), flux, water meters, lead E-mail address: [email protected] (D.A. Lytle). https://doi.org/10.1016/j.watres.2019.03.042 0043-1354/Published by Elsevier Ltd. D.A. Lytle et al. / Water Research 157 (2019) 40e54 41 goosenecks, and galvanized steel pipes (HDR Engineering, Inc., concentration profile of the plumbing from the faucet all the way to 2009). the water main. Matching the water sample volumes to the Identifying the make-up and material type of drinking water plumbing volume can identify which part of the plumbing is the service lines and premise plumbing is important for many reasons, biggest source of lead (van den Hoven and Slaats, 2005; Sandvig including understanding lead release sources and release mecha- et al. 2008; Clark et al. 2014). Taking the appropriate number of nisms, targeting locations for LSL removal, and assessing the samples at the appropriate sample volume, combined with the effectiveness of lead corrosion control strategies. However, service accurate mapping of these volumes, has been shown to achieve lines and other plumbing materials are often buried beneath soil or acceptable resolution of the different plumbing parts (Schock and inside finished walls, preventing direct observation. Uncertain and Lemieux, 2010). Samples as small as 50 mL can successfully detail unique configurations of mixed premise plumbing materials, as materials down to the contribution of lead-tin solder (Hoekstra well as nonexistent or unreliable utility LSL records (Karalekas et al. et al. 2004; Triantafyllidou et al. 2015). Lytle et al. (1996) applied 1975), also make identifying plumbing materials a challenge. sequential sampling to identify lead sources in a new building with Furthermore, unpredictable and inconsistent drinking water lead elevated lead levels and evaluate the success of corrosion control levels across the distribution system of a community (Del Toral strategies (orthophosphate and silicate addition) to reduce lead et al. 2013; Wang et al. 2014), in addition to other water quality corrosion. A series of 30-mL and 60-mL samples were used to fluctuations, are often observed. There is a critical need to establish distinguish between brass and leaded solder lead sources and a drinking water sampling protocol that can inform and address demonstrate the relative effectiveness of the corrosion inhibitors to these challenges. reduce lead (Lytle et al. 1996). Many reasons to perform lead drinking water sampling exist, Sequential sampling is particularly informative when combined including lead exposure assessment, corrosion control efficacy with the identification of other metals within the sample. For benchmarking, lead source determination, LSL identification, and example, the presence of lead along with an appreciable concen- regulatory compliance assessment. Also, many factors can affect tration of tin suggests the lead source is lead-tin solder, while the lead sample concentration and potential variability in lead con- co-occurrence of zinc and lead may indicate that a brass fixture is centrations. Therefore, the sampling protocol must be carefully the lead contributor. Diffusion effects will skew the metal contri- selected and implemented to allow meaningful results and butions to a degree (Hayes et al. 2013; Leer et al. 2002), and this interpretation. effect is seen as a gentle curve (approximately bell shaped) with the “Sequential” sampling or “profiling” can be a valuable approach middle of the LSL at the peak, instead of sharp increases (Giani et al. to identify lead sources in plumbing and service lines, as well as to 2004). However, not all peaks necessarily correspond to the LSL. For evaluate corrosion control effectiveness over time. Plumbing example, lead stagnation profile peaks after 6 h of stagnation in one lengths and inside diameter (ID), and visible material are surveyed report varied from 9.1 mg/L to 96.5 mg/L at LSL sites, and lead peaks for interior premise plumbing and service lines, using the did not always correspond to the LSL volume-estimated location approximate route to the water main. After stagnation, a series of (Hayes et al. 2016). Because discrete lead contributions can be successive drinking water samples are collected. Sample volumes diluted by larger sample volumes (Cartier et al. 2011), accurately can vary depending on the precision needed to differentiate com- isolating smaller fixtures requires appropriately small samples ponents such as bubblers, faucets, valves, tubing, and inside-wall (Schock, 1990) and an accurate plumbing inspection (Hoekstra et al. plumbing. Sample results for metals including lead (Pb), zinc 2009). At the lowest end of the sample size spectrum, the large (Zn), copper (Cu), tin (Sn), and iron (Fe) can then be related to number of samples to represent the plumbing volume would in- plumbing volumes and distance from a sampling faucet to identify crease the analytical costs. the location of leaded materials, including a partial LSL. “Spikes” occasionally occur in the profiling samples, represent- Although there are multiple potential assessment benefits of ing the presence of colloidal or particulate lead-containing mate- sequential sampling, very little work has demonstrated the prac- rials suspended in the water. The exact source of the particles tical value of sequential sampling particularly in a full-scale field cannot be precisely determined, because it is physically unlikely setting. An extensive sequential sampling effort was initiated and that they were carried along with the background “parcel” of water documented by EPA in Flint, Michigan. The objective of this work is with the dissolved lead. However, it can be inferred that the par- to summarize the findings of the sequential sampling program in ticulates originated somewhere between the tap where the sample Flint.