Skip to main content
U.S. flag

An official website of the United States government

Here’s how you know

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

HTTPS

Secure .gov websites use HTTPS
A lock (LockA locked padlock) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

    • Environmental Topics
    • Air
    • Bed Bugs
    • Cancer
    • Chemicals, Toxics, and Pesticide
    • Emergency Response
    • Environmental Information by Location
    • Health
    • Land, Waste, and Cleanup
    • Lead
    • Mold
    • Radon
    • Research
    • Science Topics
    • Water Topics
    • A-Z Topic Index
    • Laws & Regulations
    • By Business Sector
    • By Topic
    • Compliance
    • Enforcement
    • Laws and Executive Orders
    • Regulations
    • Report a Violation
    • Environmental Violations
    • Fraud, Waste or Abuse
    • About EPA
    • Our Mission and What We Do
    • Headquarters Offices
    • Regional Offices
    • Labs and Research Centers
    • Planning, Budget, and Results
    • Organization Chart
    • EPA History

Breadcrumb

  1. Home
  2. Lead

I am looking at a water report for my public water system. Under the contaminant heading for lead and copper there is a column heading titled 90th percentile. What does this column mean?

Answer:

The Consumer Confidence Report must include the 90th percentile concentration of the most recent round(s) of sampling for lead and copper. If the “90th percentile” level is above the action level, this is called an action level exceedance. The action level is the concentration of a contaminant which, if exceeded, triggers treatment actions or other requirements which a water system must follow. The lead action level is exceeded if the concentration of lead in more than 10 percent of tap water samples is greater than 0.015 mg/L (i.e., if the"90th percentile" lead level is greater than 0.015 mg/L). The copper action level is exceeded if the concentration of copper in more than 10 percent of tap water samples is greater than 1.3 mg/L (i.e., if the"90th percentile" copper level is greater than 1.3 mg/L) (40 CFR Section 141.80(c)). 

Question (23002-32408)

Find a printable PDF copy of all frequent questions pertaining to lead.

Other Frequent Questions about Lead

General Information about Lead
Testing for Lead
Renovation, Repair and Painting
Abatement, Risk Assessment and Inspection

Applying for Certification or Accreditation
Lead-Based Paint Program Fees
EPA/HUD Real Estate Notification & Disclosure Rule

Lead in Products
Lead in Drinking Water
Lead at Superfund Sites

Lead

  • Learn About Lead
  • Protect Your Family
  • Renovation, Repair and Painting Program
  • Evaluating & Addressing Lead-Based Paint Hazards
  • Real Estate Disclosure
  • Lead Laws and Regulations
  • En español: Plomo
Contact Us about Lead
Contact Us to ask a question, provide feedback, or report a problem.
Last updated on November 5, 2024
  • Assistance
  • Spanish
  • Arabic
  • Chinese (simplified)
  • Chinese (traditional)
  • French
  • Haitian Creole
  • Korean
  • Portuguese
  • Russian
  • Tagalog
  • Vietnamese
United States Environmental Protection Agency

Discover.

  • Accessibility Statement
  • Budget & Performance
  • Contracting
  • EPA www Web Snapshot
  • Grants
  • No FEAR Act Data
  • Plain Writing
  • Privacy
  • Privacy and Security Notice

Connect.

  • Data
  • Inspector General
  • Jobs
  • Newsroom
  • Regulations.gov
  • Subscribe
  • USA.gov
  • White House

Ask.

  • Contact EPA
  • EPA Disclaimers
  • Hotlines
  • FOIA Requests
  • Frequent Questions
  • Site Feedback

Follow.