The Environmental Protection Agency (EPA) is authorized by the Safe Drinking Water Act (SDWA) to set, monitor, and enforce national health-based standards for drinking water. Within the SDWA, the EPA is required to issue a list of unregulated contaminants that are to be monitored by public water systems (PWSs). 

This rule, known as the Unregulated Contaminant Monitoring Rule (UCMR), is used by the EPA to collect data from PWSs on contaminants that do not have health-based standards set by the SDWA, and are suspected to be in drinking water.

link to EPA’s UCMR webpage

Why was the UCMR Program developed? 

The 1996 Amendments to the SDWA and the amendments by Section 2021 of America’s Water Infrastructure Act of 2018 facilitate for: 

• A monitoring program for priority unregulated contaminants in drinking water that is revised every five years
• Monitoring of all large PWSs in the United States that serve more than 10,000 people
• Monitoring of all small PWSs that serve between 3,000 and 10,000 people, and a representative sample of PWSs that serve populations under 3,000 people
• Analytical data is stored in the National Contaminant Occurrence Data (NCOD) which can be accessed here 

Data collected through the UCMR program is used to support the Administrator’s determination of whether to regulate particular contaminants in the interest of protecting public health.

The Public Health benefits of UCMR.

Collection of the scientifically valid data provides the EPA and other entities with a means to conduct exposure assessments to the contaminants in drinking water for both national and specific geographical populations. In addition to this, the UCMR data is one of the key data sources used by the EPA to inform future regulatory and other risk management decisions for drinking water contaminants.

Definitions

Minimum Reporting Levels (MRLs) are derived from the capability of the analytical method.  

Maximum Contaminant Levels (MCLs) are the highest levels of a contaminant that is allowed in drinking water. This is a drinking water regulation enforced by EPA.  

Health Advisory Levels are estimated acceptable levels of a contaminant in drinking water based on health effects information. They are not regulations but serve as technical guidance from EPA.  

Reference Concentrations are health-based levels above which adverse health effects have been documented. They are not regulations, and not all contaminants have reference concentrations.  

Detected Compounds (µg/L, or parts per Billion)

1 microgram per Liter (µg/L), or 1 part per billion (ppb) is the equivalent of a few drops of water in an Olympic-sized swimming pool.​

Contaminants monitored and results:

UCMR5 link

UCRM4 link

UCRM3 link  

UCMR5

UCMR5 requires utilities to monitor and submit data for: 

• UCMR5 requires utilities to monitor and submit data for:
  • 29 per- and polyfluoroalkyl substances (PFAS) known as forever chemicals
    • link to DC Water’s PFAS page
  • Lithium, a soft and silvery-white alkali metal that is commonly used in rechargeable batteries
    • Read about Lithium in Drinking Water Here

Table 1. Contaminants Detected in 2024 UCMR5 Samples