By Brooke K. Mayer, PhD, PE
There are many things in nature you may not necessarily want to tangle with (fear-inducing images of quicksand, venomous snakes, or tornadoes may be flashing through your mind’s eye). Lead ought to be one of them. Lead is a potent, bioaccumulating neurotoxin with particularly damaging effects when ingested by children.[1] Sources of lead in the environment can include paint, dust and soil, consumer products, food, cosmetics, medicines, and drinking water.[2] In drinking water, lead is rarely found in significant quantities in natural sources but is instead primarily introduced through the corrosion of lead-containing plumbing materials, as illustrated in Figure 1.
Accordingly, lead pipe awareness is critical for public health protection.
To address the dangers posed by lead in drinking water, the U.S. Environmental Protection Agency (EPA) established the Lead and Copper Rule (LCR) in 1991. The LCR has since undergone multiple revisions and can be succinctly summarized in terms of four basic requirements:[4]
- Require water suppliers to optimize their treatment systems to control corrosion in customers’ plumbing.
- Determine tap water levels of lead and copper for customers who have lead service lines or lead-based solder in their plumbing systems.
- Rule out the source water as a source of significant lead levels.
- If lead action levels are exceeded, require the suppliers to educate their customers about lead and, through public notices and public education programs, suggest actions customers can take to reduce their exposure to lead.
The LCR replaced the previous standard of 50 parts per billion at public water-treatment facilities with a lead action level of 15 parts per million (in more than 10 percent of customer taps sampled); instituted a maximum contaminant level goal of zero; and established a treatment technique to reduce corrosion of lead and copper in the distribution system.[5,6] In 2000 and 2004, the EPA published minor revisions to the LCR aimed at streamlining monitoring and reporting.
Around the same time, Washington, D.C., experienced a crisis of lead in drinking water, triggered by a switch from free chlorine to chloramines, which altered the water chemistry and caused lead to leach into the water.[7] This event helped to spur the 2007 “Short-Term Revisions to the Lead and Copper Rule,” which sought to enhance LCR implementation in monitoring, treatment, customer awareness, and lead service line replacement.[5] The 2014 water crisis in Flint, Michigan, again catapulted lead into the public domain after a switch in source waters increased water corrosivity and lead leached into the system. Subsequently, the EPA adopted the long-term revisions to the LCR in 2021.[5]
The long-term revisions included additional requirements for tap water sampling and testing, corrosion control, public outreach, and continued replacement of lead service lines when the action level is exceeded. The revisions maintained the 15 parts per billion (ppb) action level, with responses to exceedances varying by size of the system and corrosion-control practices. For example, if a large system exceeds the action level, it is required to maintain optimized corrosion control, and if corrosion control is already in place, the system must do the following:
- Notify and educate the public.
- Monitor source water and water quality parameters.
- Begin replacing lead service lines.
The 2021 LCR revisions also established a lead trigger level of 10 ppb, the lowest level that can be reliably measured. Note that neither the action level nor the trigger level constitutes a health-based maximum contaminant level. Instead, the trigger level aims to “help water systems prioritize actions to control lead prior to an action level-exceedance (and reduce the likelihood of an exceedance)”.[8] Figure 2 illustrates this approach.
As part of the LCR revisions, water systems are required to prepare and maintain an inventory of service line materials by October 2024.10 In 1986, Congress prohibited the use of lead pipes, pipe fittings, and fixtures. However, widespread use prior to the ban means that an estimated 6.3 million to 9.3 million homes, in addition to other buildings with lead-containing solder or faucets, may still be served by lead service lines.[8] Estimates of the number of lead service pipes in the United States are shown in Figure 3.
Lead is released from plumbing materials through corrosion, or the electrochemical interactions between metal surfaces and water, causing the release of oxidized metal. Scale naturally builds up on metal surfaces and can include an array of lead-based compounds, such as lead carbonates and lead oxides. Water-quality parameters (e.g., pH, alkalinity, oxidation-reduction
potential, dissolved inorganic carbon, and corrosion inhibitors) influence lead corrosion, the formation and character of scale, and, ultimately, the release of lead into the water.[11] To reduce the risk of lead dissolution, corrosion control is commonly implemented in water systems.
Corrosion-control treatments differ with water system size. Phosphate-based materials (containing orthophosphate, PO43-) are most commonly used for lead-corrosion control, as they bind divalent lead, keeping it in the solid form rather than releasing the dissolved metal into the water. Hence, lead is sequestered in the piping system rather than released into the drinking water, where it poses an acute or chronic health risk. Target orthophosphate residual levels at the tap are often approximately one to three milligrams per liter as PO4, although higher levels may be used in higher lead risk scenarios. The EPA offers guidance to assist in selecting appropriate corrosion-control treatment strategies.[11]
Beyond utility-scale responses in the form of corrosion control and lead service line replacement, point-of-use (POU) treatments are also available for controlling lead levels in drinking water. In selecting a POU option, consumers should look for technologies with accredited third-party certification such as NSF/ANSI 53 for lead removal using POU filters (and NSF/ANSI 42 for particulate removal).12 By implementing an integrated portfolio of lead-mitigation approaches, including at scales ranging from POU to treatment facility to municipal, state, and national mapping and lead-component replacement efforts, we can continue to reduce the dangerous health risks associated with lead ingestion.
References
1 . U.S. Environmental Protection Agency (EPA). “Basic Information About Lead in Drinking Water.” Ground Water and Drinking Water, updated January 27, 2023. https://www.epa.gov/ground-water-and-drinking-water/basic-information-about-lead-drinking-water.
2 . U.S. Centers for Disease Control and Prevention (CDC). “Overview of Childhood Lead Poisoning Prevention.”Childhood Lead Poisoning Prevention, reviewed January 19, 2023. https://www.cdc.gov/nceh/lead/overview.html.
3 . EPA. “Concerned About Lead in Your Drinking Water?” accessed February 11, 2023. https://www.epa.gov/sites/default/files/ 2017-08/documents/epa_lead_in_drinking_water_final_ 8.21.17.pdf.
4. CDC. “What Are U.S. Standards for Lead Levels?” Agency for Toxic Substances and Disease Registry: Environmental Health and Medicine Education, reviewed July 2, 2019. https://www.atsdr.cdc.gov/csem/leadtoxicity/safety_standards.html#:~:text=EPA’s action level for lead,systems is 15 μg%2FL.
5. EPA. “Lead and Copper Rule.” Drinking Water Requirements for States and Public Water Systems, updated November 30, 2022. https://www.epa.gov/dwreginfo/lead-and-copper-rule.
6. Tee L. Guidotti et al. “Elevated Lead in Drinking Water in Washington, D.C., 2003-2004: The Public Health Response,” Environmental Health Perspectives 115, no. 5 (May 2007): 1,618-23. https://doi.org/10.1289/ehp.8722.
7. Marc Edwards et al. “Elevated Blood Lead Levels in Young Children Due to Lead-Contaminated Drinking Water:Washington, D.C., 2001-2004,” Environmental Science
Technology 43, no. 5 (January 2009): 1,618-23. https://doi.org/ 10.1021/es802789w.
8. Elena Humphreys, Addressing Lead in Drinking Water: The Lead and Copper Rule Revisions (LCRR), report updated June 22, 2021. https://sgp.fas.org/crs/misc/R46794.pdf.
9. Roger Arnold et al. “Lead and Copper Rule Revisions,” Hazen and Sawyer: A Hazen Interactive, modified July 1, 2022. https://www.hazenandsawyer.com/articles/lead-and-copper-rule-revisions.
10. EPA. “EPA Issues Guidance to Help Communities Locate Lead Pipes That Can Contaminate Drinking Water,” published August 4, 2022. https://www.epa.gov/newsreleases/epa-issues-guidance-help-communities-locate-lead-pipes-can-contaminate-drinking-water#:~:text=Under the Lead and Copper,materials by October 16%2C 2024.
11. EPA. Optimal Corrosion Control Treatment Evaluation Technical Recommendations for Primacy Agencies and Public Water Systems, report updated March 2016. https:// www.epa.gov/sites/production/files/2016-03/documents/ occtmarch2016.pdf.
12. EPA. “A Consumer Tool for Identifying Point of Use (POU) Drinking Water Filters Certified to Reduce Lead,” updated December 26, 2018. https://www.epa.gov/water-research/consumer-tool-identifying-pou-drinking-water-filters- certified-reduce-lead.
About the Author
Dr. Brooke K. Mayer is an Associate Professor in the Department of Civil, Construction and Environmental Engineering as part of the Opus College of Engineering at Marquette University. She holds Bachelors, Masters and Doctorate degrees in civil engineering with an emphasis in environmental engineering from Arizona State University. She is a registered Professional Engineer in the state of Arizona.