The EPA’s Lead and Copper Rule: Why Action Levels Are Not Safety Thresholds

The most common misunderstanding of the Lead and Copper Rule (LCR) is that the action level defines what is safe to drink. It does not. The rule measures system-wide corrosion-control performance, not household safety.

The LCR has a different regulatory framework than most other regulated contaminants because lead contaminates drinking water differently.  Unlike most chemical contaminants that are treated for at the treatment plant, lead enters drinking water when it leaches out of lead-containing pipes, plumbing components, and solder.  This is why the EPA’s framework for lead requires water systems to test and monitor lead levels at faucets and use treatment protocols that prevent corrosion of pipes. 

In 2024, the EPA finalized the Lead and Copper Rule Improvements (LCRI), which lowered the action level, strengthened tap sampling, and required broad lead service line replacement. 

Executive Summary

• The CDC and American Academy of Pediatrics say that there is no safe level of lead in children, and the EPA’s unenforceable health-based target is zero. 
• Action levels are not Maximum Contaminant Levels. Under the Lead and Copper Rule, an action level is a regulatory trigger within a treatment-technique framework. It is not a health-based ceiling for water delivered to every household. 
• Lead is regulated differently from most other contaminants because it contaminates drinking water after it has left the treatment plant. 
• The 90th-percentile methodology is a system-level performance measure, not a household safety determination. By design, individual homes can have elevated lead while the system does not register an action level exceedance. 
• The 2024 Lead and Copper Rule Improvements (LCRI) finalized a 10 ppb lead action level (AL) and a mandatory lead service line replacement framework, but water systems generally do not transition to the revised compliance regime until November 1, 2027. Until then, the EPA states that systems continue to comply with the existing LCR, subject to certain carried-forward requirements. 

Maximum Contaminant Levels vs. Maximum Contaminant Level Goals vs. Action Levels

There are substantive differences between Maximum Contaminant Level Goals (MCLGs), Maximum Contaminant Levels (MCLs), and action levels. Recognizing those differences will make it easier to understand lead regulations as a whole. 

Maximum Contaminant Level Goal (MCLG)

A Maximum Contaminant Level Goal (MCLG) is a non-enforceable, health-based level where the concentration has no known or anticipated adverse effect on human health. For lead, the EPA’s MCLG is zero, which means that there’s no safe level of lead in drinking water. 

Maximum Contaminant Level (MCL)

A Maximum Contaminant Level is the legally enforceable standard for the highest level of a contaminant allowed in water delivered by a public water system. The EPA generally sets MCLs as close as feasible to the MCLG, but MCLs do take cost and technical feasibility into account when they’re being set.  

Because it typically enters drinking water downstream of the treatment plant, lead is regulated differently from most other contaminants. That makes a conventional MCL measured at the plant or entry point a poor fit for the actual exposure problem. In other words, lead has no formal MCL; it has an action level. 

Action Level 

Instead of an MCL, LCR uses an Action Level (AL) as the metric that triggers specified regulatory obligations (e.g., corrosion control, public notification) if the lead level is exceeded at the 90th percentile within the LCR’s sampling protocol. 

It is not a health-based limit, and it’s not representative of what a consumer should expect to be coming out of their faucet.  

Historically, the AL for lead has been 15 ppb, but the LCRI calls for that threshold to be changed to 10 ppb in 2027.   

How Water Systems Test for Lead Under the Lead and Copper Rule 

Because lead contamination is introduced by plumbing and infrastructure, not source water, water systems need to sample at the tap, not at the treatment plant, to characterize risk where lead enters the water.  

Through LCR, water systems are required to build a site sample plan using service line and plumbing-material records to identify which homes are of highest risk for lead contamination, then select from the highest-risk tier available. Tier 1 sites are single-family homes with lead service lines and/or plumbing, while Tier 2 sites are other buildings, including multifamily residences, with the same criteria. 

If a system cannot meet its required sample count from Tier 1 and Tier 2 sites, it will sample sites with lead connectors, galvanized service lines or plumbing ever downstream of lead, older copper plumbing with lead solder, and only then to representative lower-risk sites.  

The testing protocol is built around first-draw sampling, which means that the home’s water must go unused for at least six hours before a sample is collected from the faucet to capture stagnant conditions where lead contamination is most likely to occur.  Under LCRI, homes served by lead service lines require more than a traditional one-liter first-draw sample: the sampler fills five consecutive one-liter bottles without shutting the water off, and the system analyzes both the first-liter and fifth-liter bottles for lead. The first sample is intended to capture lead contributed closer to the tap and interior plumbing, while the fifth liter is intended to collect the water that has been sitting in the service line itself.  

After analysis, the system’s sample results are ranked to determine the 90th-percentile lead value and whether the action level has been exceeded.  For systems with sufficient Tier 1 and Tier 2 sites, the rule uses the higher of the first-liter and fifth-liter lead result from each eligible site, places those results in ascending order, multiplies the total number of samples by 0.9, and identifies the result at that position as the 90th-percentile value. 

If a system does not have enough Tier 1 and Tier 2 sites, it uses the next available tier.  In other words, the 90th percentile value is intentionally weighted toward higher-risk sites.    

What Changed in 2024, and What Has Not Yet Changed in Practice 

The 2024 LCRI changes are meaningful, but as with all water quality regulations, there’s a multi-year timeline before full compliance must be met.  

The final rule lowers the action level to 10 ppb, strengthens tap sampling, and modernizes communication requirements, but does not require full compliance until late 2027.  Until then, systems continue to comply with the existing LCR except for a limited set of carried-forward requirements, including initial service line inventories, service line notifications, and 24-hour Tier 1 public notice of a lead action level exceedance at 15 ppb.

For most systems, lead and galvanized-requiring-replacement service lines under the system’s control must be replaced within 10 years of the November 2027 compliance date.   

Current Legal Challenges to LCRI 

American Water Works Association (AWWA) has challenged LCRI in the DC Circuit court and is arguing that the LCRI is too costly for water systems to comply with. Additionally, they argue that the 2037 timeline for lead service line replacement is not feasible.  

The EPA has indicated that it intends to defend the rule in court. The case remains active, briefing has advanced, and public materials indicate oral argument is likely after briefing, though no argument date appears to be publicly calendared as of March 2026. 

What This Means in Practice

The EPA is moving toward lower action levels and full lead service line replacement. That should reduce exposure across systems, but it does not change the basic point of this article: compliance with the rule is not a household safety guarantee. 

At the individual level, it’s important to remember that the EPA’s health-based MCLG for lead is zero. A water system can be in compliance while individual homes still have high levels of lead at the tap.