The Unregulated Contaminant Monitoring Rule (UCMR)
Why was the UCMR program developed?
The EPA uses the Unregulated Contaminant Monitoring Rule (UCMR) to collect data for contaminants that are suspected to be present in drinking water and do not have health-based standards set under the Safe Drinking Water Act (SDWA).
The SDWA Amendments of 1996 and the amendments by Section 2021 of America’s Water Infrastructure Act of 2018 (AWIA) provide for:
- Establishing a program to monitor for priority unregulated contaminants in drinking water every five years.
- Monitoring all large systems serving greater than 10,000 people.
- Monitoring all small public water systems (PWSs) serving between 3,300 and 10,000 people, and a representative sample of small PWSs serving fewer than 3,300 people; this expanded scope is conditioned on the availability of appropriations and sufficient laboratory capacity.
- Storing analytical results in a National Contaminant Occurrence Database (NCOD).
The UCMR program was developed in coordination with the Contaminant Candidate List (CCL) a list of contaminants that:
- Are not regulated by the National Primary Drinking Water Regulations.
- Are known or anticipated to occur at PWSs.
- May warrant regulation under the SDWA.
Definition of a “Contaminant”
The Safe Drinking Water Act (SDWA) defines a “contaminant” as any physical, chemical, biological or radiological substance or matter in water.
Drinking water may reasonably be expected to contain at least small amounts of some contaminants. Some contaminants may be harmful if consumed at certain levels in drinking water. The presence of contaminants does not necessarily indicate that the water poses a health risk. Therefore, the law defines “contaminant” very broadly as being anything other than water molecules.
The SDWA defines a “contaminant” as being anything other than water molecules.
The following are general categories of drinking water contaminants and examples of each:
- Physical contaminants primarily impact the physical appearance or other physical properties of water. Examples of physical contaminants are sediment or organic material suspended in the water of lakes, rivers and streams from soil erosion.
- Chemical contaminants are elements or compounds. These contaminants may be naturally occurring or man-made. Examples of chemical contaminants include nitrogen, bleach, salts, pesticides, metals, toxins produced by bacteria, and human or animal drugs.
- Biological contaminants are organisms in water. They are also referred to as microbes or microbiological contaminants. Examples of biological or microbial contaminants include bacteria, viruses, protozoa, and parasites.
- Radiological contaminants are chemical elements with an unbalanced number of protons and neutrons resulting in unstable atoms that can emit ionizing radiation. Examples of radiological contaminants include cesium, plutonium and uranium.
Only a small number of the universe of contaminants as defined above are listed on the Contaminant Candidate List (CCL). The CCL serves as the first level of evaluation for unregulated drinking water contaminants that may need further investigation of potential health effects and the levels at which they are found in drinking water.
How does the EPA select the contaminants for the UCMR?
In establishing the list of contaminants for each UCMR cycle, the EPA considers the CCL and other priority contaminants. Further, the EPA considered the opportunity to use multi-contaminant methods to collect occurrence data in an efficient, cost-effective manner.
The EPA evaluates candidate UCMR contaminants using a multi-step prioritization process. The first step includes identifying contaminants that: (1) were not monitored under prior UCMR cycles; (2) may occur in drinking water; and (3) are expected to have a completed, validated drinking water method in time for rule proposal.
The next step is to consider the following: availability of health assessments or other health-effects information (e.g., critical health endpoints suggesting carcinogenicity); public interest (e.g., PFAS); active use (e.g., pesticides that are registered for use); and availability of occurrence data.
During the final step, EPA considers stakeholder input; looks at cost-effectiveness of the potential monitoring approaches; considers implementation factors (e.g., laboratory capacity); and further evaluates health effects, occurrence, and persistence/mobility data to identify the list of proposed UCMR contaminants.
What are the public health benefits of the UCMR?
The UCMR provides the EPA and others with scientifically valid data on the occurrence of these contaminants in drinking water. This permits assessment of the population being exposed and the levels of exposure.
The UCMR data represent one of the primary sources of national occurrence data in drinking water that the EPA uses to inform regulatory and other risk management decisions for drinking water contaminant candidates. This data will ensure science-based decision-making and help prioritize protection of disadvantaged communities.
The EPA has set legal limits on over 90 contaminants in drinking water. The legal limit for a contaminant reflects the level that protects human health and that water systems can achieve using the best available technology. The EPA rules also set water-testing schedules and methods that water systems must follow.
The Safe Drinking Water Act (SDWA) gives individual states the opportunity to set and enforce their own drinking water standards if the standards are at a minimum as stringent as EPA’s national standards.
The Fifth Unregulated Contaminant Monitoring Rule
The Safe Drinking Water Act (SDWA) requires that once every five years the EPA issue a list of unregulated contaminants to be monitored by public water systems (PWSs).
The fifth Unregulated Contaminant Monitoring Rule (UCMR 5) was published on December 27, 2021. UCMR 5 requires sample collection for 30 chemical contaminants between 2023 and 2025 using analytical methods developed by the EPA and consensus organizations. This action provides the EPA and other interested parties with scientifically valid data on the national occurrence of these contaminants in drinking water.
Consistent with the EPA’s PFAS Strategic Roadmap, the UCMR 5 will provide new data that is critically needed to improve the EPA’s understanding of the frequency that 29 PFAS (and lithium) are found in the nation’s drinking water systems and at what levels. This data will ensure science-based decision-making and help prioritize protection of disadvantaged communities.
Monitoring Scope
- All PWSs serving more than 10,000 people (i.e., large systems).
- PWSs serving 3,300 to 10,000 people.
- 800 representative PWSs serving fewer than 3,300 will monitor, subject to availability of appropriations and sufficient laboratory capacity.
PWSs will collect samples for 29 per- and polyfluoroalkyl substances (PFAS) and lithium, during a 12-month period from January 2023 through December 2025.
If EPA does not receive the appropriations needed in a given year, then a reduced number of small systems will perform monitoring.
As the EPA finalizes its sampling design plan for each sample collection year, the Agency will notify the participating small systems. The EPA is undergoing its planning anticipating that necessary appropriations will become available.
The EPA continues to be responsible for all analytical costs associated with monitoring at systems serving 10,000 or fewer.
Important Dates for UCMR 5
- March 2022 – Public webinar on the final Revisions to the Unregulated Contaminant Monitoring Rule for the Fifth Monitoring Cycle (UCMR 5).
- August 1, 2022 – Deadline for laboratories seeking approval to complete and submit the necessary registration form and application materials.
- December 31, 2022 – Deadline for large systems to update sampling location(s) and zip code(s). If applicable, the system may update their monitoring schedule; and small systems to update sampling location(s), shipping address, and zip code(s).