Lead service lines raise infant blood lead 1.6 times. Most infants are never tested in the window when this matters.

2025 JAMA Network Open study analyzed 1,210 Milwaukee infants 12 months or younger. Living in a residence with a lead service line raised the odds of an elevated blood lead level (3.5 µg/dL or higher) by 1.6 times after adjustment, and 2.26 times at the higher 5 µg/dL cutoff.

1.60x
adjusted odds of BLL above 3.5 µg/dL with LSL (95% CI 1.04-2.46)
2.26x
adjusted odds at higher BLL cutoff of 5 µg/dL (95% CI 1.23-4.16)
9.2M
estimated US homes with lead service lines (EPA 2023)

The dose-response is sharper at higher cutoffs.

Balza et al. 2025 ran logistic regressions at three different elevated-blood-lead cutoffs. The relative risk of LSL exposure increases as the cutoff increases, suggesting that LSL water is contributing meaningfully to the upper tail of childhood blood lead distribution, not just nudging a low-level baseline.

Adjusted odds of elevated infant BLL with LSL at primary residence
Balza et al. 2025, JAMA Network Open 8(12):e2550444. Adjusted for age, sex, race/ethnicity, Medicaid status, zip-code poverty, season of testing, age of residence.

Why infants are the worst case.

Infants 0-6 months reconstitute formula with tap water. They consume an average of 800 mL of formula per day, scaled to a 5-7 kg body weight. Per kilogram of body weight, that is roughly 6-8x the daily water consumption of an adult. If the source water has 5 ppb lead from corrosion of an LSL, the infant's effective dose is multiplied accordingly.

Lead absorption in young children is also higher than in adults: 40-50% of ingested lead is absorbed in children 0-6, vs 10-15% in adults. Combine the higher per-kg consumption with the higher absorption rate and the developing brain, and the infant exposure window is the worst case in the entire human life cycle. CDC's recommendation to begin screening at age 1 misses this window entirely.

What you can verify yourself in 10 minutes.

Find out if your home has an LSL: most US water utilities now publish an interactive map of service line materials by address. Search "[your city] lead service line lookup." If your municipality does not have one, your house was probably built before 1986 and your service connection should be assumed lead until verified.

The screening starts at age one. The damage from reconstituted formula starts at day one. That gap is not a rounding error. It is the entire exposure window for the most vulnerable period in human neurological development.

If you have an LSL, the corrective interventions are concrete: run cold-water taps for 30-60 seconds before drawing water after any period of standing (overnight, after work). Use NSF/ANSI 53-certified filters for cooking and drinking. Never use hot tap water for formula or cooking — hot water dissolves more lead than cold. Replace the line on your side of the curb stop when financially feasible. Many municipalities now offer subsidized replacement programs.

If you have an infant being formula-fed, the highest-leverage intervention is simple: do not reconstitute formula with hot tap water, run the cold tap before drawing, and use bottled or filtered water for the first year. These are evidence-based and they cost less than a single can of formula.

Try it yourself.

Tap water guide
Is your tap water safe from lead?
Why this matters
824 million IQ points lost
Infant kit
Baby-proof your home

Test the source closest to the formula bottle: your kitchen tap.

Fluoro-Spec is for painted dishware, the second-biggest direct exposure source after water. For water lead, use an NSF/ANSI 53 filter. For dishware, use Fluoro-Spec. Both are necessary.

Get the Double Kit — $88 → Just one kit — $50

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The filter you bought may not cover lead.

NSF 42 doesn't. NSF 53 does. The pipe from the main to the meter may still be lead. This is not a historical problem.

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Citations

  1. Balza JS, Dawson AZ, Nelson D, Kaeppler C, Cusatis R, Flynn KE. Lead service lines and infant blood lead levels. JAMA Network Open. 2025;8(12):e2550444.
  2. Hanna-Attisha M, LaChance J, Sadler RC, Champney Schnepp A. Elevated blood lead levels in children associated with the Flint drinking water crisis. Am J Public Health. 2016;106(2):283-290.
  3. EPA Lead Service Line Inventory and Lead and Copper Rule Revisions. 2023.