Lead is one of the most studied and most dangerous contaminants in drinking water — and one of the most misunderstood. Unlike most contaminants, lead rarely comes from the water source itself. It comes from your own plumbing. That means a water system can meet all federal standards at the treatment plant while still delivering lead-contaminated water to your tap.
Understanding how lead enters water, who’s most at risk, and what you can do about it is essential for protecting your household — especially if you have young children.
Why Lead Is Uniquely Dangerous
The scientific consensus on lead is unambiguous: there is no safe level of lead exposure. The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) both state this explicitly. Unlike many toxins where harm occurs only above a threshold, lead causes measurable neurological damage even at extremely low blood concentrations.
For children, lead is particularly devastating because it interferes with the developing brain and nervous system during critical windows of growth. Even low-level exposure — blood lead levels below the CDC’s reference value of 3.5 micrograms per deciliter — is associated with:
- Reduced IQ (estimated 1–5 IQ points lost per 10 µg/dL increase in blood lead)
- Learning difficulties and attention disorders
- Behavioral problems, including increased aggression
- Delayed language development
- Hearing problems
These effects are largely irreversible. Lead displaces calcium in developing neural tissue and disrupts the formation of synaptic connections. The damage done during early childhood cannot be fully undone.
For adults, lead accumulates in bone tissue over a lifetime and can be remobilized during pregnancy, illness, or aging. Adult exposure is associated with hypertension, cardiovascular disease, kidney damage, and cognitive decline. Pregnant women face additional risk: lead stored in their bones can be released into the bloodstream and cross the placenta, exposing the fetus.
How Lead Gets Into Drinking Water
The most important thing to understand about lead in drinking water is that the water leaving the treatment plant is typically lead-free. The problem is what happens between the treatment plant and your tap.
Lead Service Lines
The greatest source of lead in drinking water is lead service lines (LSLs) — the pipes that connect the water main in the street to the building. These were standard installation practice through the early 20th century and were used in many cities through the 1980s.
The EPA estimates that approximately 9 million lead service lines remain in use across the US. When water sits in or flows through these pipes, it can dissolve lead, particularly if the water is corrosive (acidic or low in mineral content).
Lead Solder
Until Congress banned its use in 1986, lead solder was routinely used to join copper pipes in household plumbing. Homes built before 1986 may have lead solder throughout their internal plumbing. Even after the ban, “lead-free” solder could legally contain up to 8% lead until 2014, when the Safe Drinking Water Act was amended to tighten the definition to 0.25%.
Brass Fixtures and Faucets
Older brass faucets, valves, and fittings can contain significant amounts of lead, which leaches into water — especially when water sits in contact with the fixtures. This is why the “first draw” of water from a tap that’s been sitting overnight is typically highest in lead.
Water Chemistry and Corrosion
Lead doesn’t simply fall off pipes into water. It dissolves when water chemistry promotes corrosion. Soft water (low mineral content), acidic water (low pH), and water with low alkalinity or dissolved oxygen all accelerate lead leaching. Water utilities add corrosion inhibitors — typically orthophosphates — to create a protective mineral coating on the inside of pipes. When this treatment fails or is disrupted, lead levels can spike dramatically.
The Lead and Copper Rule
The federal regulatory framework governing lead in drinking water is the Lead and Copper Rule (LCR), first established in 1991 and significantly revised in 2021 as the Lead and Copper Rule Revisions (LCRR).
The Action Level and Its Limitations
The EPA’s action level for lead is 15 ppb (parts per billion, or micrograms per liter). This is measured using 90th percentile first-draw tap samples — meaning that if more than 10% of sampled sites exceed 15 ppb, the utility must take corrective action.
It’s critical to understand what the action level is and is not. It is a regulatory trigger — a threshold that requires utilities to respond. It is not a declaration that water below 15 ppb is safe. The EPA itself acknowledges this: the agency has proposed reducing the action level to 10 ppb and has set a separate aspirational goal of zero, reflecting the scientific consensus that no level of lead is without risk.
The 2021 LCRR: Lead Service Line Replacement
The most significant change in the 2021 Lead and Copper Rule Revisions is the requirement for utilities to replace all lead service lines within 10 years — a major undertaking given that millions of LSLs remain in service. The LCRR also:
- Requires utilities to inventory all service line materials within five years
- Lowers the trigger for replacing lead service lines to the utility portion from 15 ppb to 10 ppb
- Strengthens testing requirements, including sampling at schools and childcare facilities
- Improves public notification requirements
Progress on LSL replacement varies widely by city. Some municipalities have accelerated programs; others are still completing inventories.
Lessons from Flint, Michigan
The Flint water crisis, which came to public attention in 2014–2015, became the most prominent recent example of how catastrophically lead contamination can occur — and how regulatory failures compound the harm.
In April 2014, Flint switched its water source from Detroit’s Lake Huron supply to the Flint River as a cost-saving measure. The Flint River water was more corrosive than the previous supply. Critically, city and state officials failed to add corrosion inhibitors during the switch — a violation of the Lead and Copper Rule.
The corrosive water dissolved the protective mineral scale inside the city’s lead service lines and internal plumbing, releasing lead into drinking water throughout the city. Blood lead levels in Flint children rose significantly. State officials initially dismissed residents’ concerns and disputed independent testing that showed elevated lead levels.
The Flint crisis illustrated several critical lessons:
- Corrosion control is not optional. Disrupting established water chemistry — even temporarily — can have serious, lasting consequences.
- Regulatory oversight must be independent. Conflicts of interest between utilities and their state regulators contributed to delayed action.
- Environmental justice matters. Flint is a majority-Black city with high poverty rates. Research has documented that environmental hazards, including water contamination, are disproportionately borne by communities of color and low-income communities.
- Lead service lines are infrastructure, not a footnote. The scale of LSL replacement needed nationwide — estimated to cost $45–60 billion — requires federal investment.
Who Is at Highest Risk
Not all homes and neighborhoods face equal lead risk. The following factors increase the likelihood of lead exposure from drinking water:
- Homes built before 1986: Most likely to have lead solder in internal plumbing
- Homes built before 1930: Most likely to have original lead service lines connecting to the street
- Apartment buildings with older plumbing: Lead from shared building plumbing can affect all units
- Areas with corrosive water: Soft water or low-pH water accelerates lead leaching
- Homes near lead service line replacement work: Disturbance of nearby pipes can temporarily increase lead in adjacent homes
- Any home served by a lead service line: Regardless of age
Your water utility is required to maintain a service line inventory. Contact them to ask whether your home is served by a lead service line.
Testing for Lead
Because lead contamination occurs in household plumbing, testing your specific tap water is the only reliable way to know your actual exposure. General utility testing may not capture what’s coming out of your faucet.
First-Draw Sampling
The standard method for capturing worst-case lead levels is a first-draw sample: collect water from the kitchen tap after water has sat stagnant for at least 6 hours (overnight is ideal). Collect the first liter of water that comes out. This sample reflects lead that has dissolved from fixtures and plumbing during the stagnant period.
Do not run the faucet before collecting. Do not collect a flushed sample if you want to measure peak exposure.
Getting Water Tested
- Certified labs: The EPA maintains a list of state-certified drinking water laboratories. Search “EPA certified drinking water lab” plus your state. Typical cost: $20–50 per sample.
- Utility testing programs: Many utilities offer free lead testing kits or testing services, particularly in older neighborhoods or those known to have lead service lines. Contact your utility directly.
- State health department programs: Some states provide free testing, especially for homes with young children or for schools.
Results are reported in micrograms per liter (µg/L) or parts per billion (ppb) — these units are equivalent.
Reducing Lead Exposure
If lead is detected in your water — or if you’re unsure and want to take precautions — the following measures are effective.
Flush Before Use
Running your cold water tap for 30 seconds to 2 minutes before use flushes water that has been in contact with household plumbing. Longer flushing (up to 5 minutes) is recommended if you have a lead service line. While flushing wastes water and doesn’t eliminate lead from service lines, it significantly reduces the concentration at the tap.
Always Use Cold Water
Hot water dissolves lead faster than cold water. Never use hot tap water for drinking, cooking, or — critically — making infant formula. Run the cold tap and heat it separately if needed.
Use Certified Filtration
The most reliable ongoing solution is a water filter certified to remove lead. Look for NSF/ANSI Standard 53 certification (specifically for lead reduction), which confirms independent testing of the filter’s performance.
Effective filter types include:
- Pitcher filters (e.g., some Brita and PUR models with NSF 53 certification): Convenient and low-cost, but require frequent cartridge replacement and only treat small volumes
- Faucet-mount filters: Treat water at the point of use; NSF 53 certified options available
- Under-sink filters: More capacity and less maintenance than pitcher filters
- Reverse osmosis systems: Highly effective (removes 95%+ of lead) but requires installation and produces wastewater
Always verify the specific model’s NSF 53 certification for lead — not all filters in a product line are certified for the same contaminants. Check the NSF International database at nsf.org to confirm.
Replace Lead Service Lines
Flushing and filtering treat the symptom, not the cause. If your home is served by a lead service line, advocating for its replacement is the most important long-term action. Many utilities now have LSL replacement programs, and federal infrastructure funding (the Infrastructure Investment and Jobs Act of 2021 included $15 billion specifically for lead service line replacement) has expanded these efforts.
Note that replacing only the utility’s portion of the service line (up to the property line) may temporarily increase lead in household water due to disturbance of existing scale. If your utility is replacing lines in your neighborhood, follow their guidance on flushing and filtration during and after the work.
A Note on Infant Formula
Infants who are formula-fed face particular risk from lead in tap water because formula reconstituted with lead-contaminated water provides a large proportion of their daily fluid intake. The American Academy of Pediatrics recommends using filtered or bottled water to prepare infant formula if you have any uncertainty about your tap water’s lead content — or until you have tested results showing no lead.
Ready-to-feed formula (which does not require mixing with water) eliminates this risk entirely.