Fifth Unregulated Contaminant Monitoring Rule Data Finder
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Background
This tool allows people to easily search for, summarize, and download the available analytical results from the fifth Unregulated Contaminant Monitoring Rule (UCMR 5). The EPA uses the Unregulated Contaminant Monitoring Rule (UCMR) to gather information 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. These data can support future regulatory determinations (i.e., the process that addresses potential regulatory actions for unregulated contaminants) and other actions to protect public health.
UCMR 5 requires monitoring by certain public water systems (PWSs) for 29 per- and polyfluoroalkyl substances (PFAS) and lithium in drinking water between 2023 and 2025. All community water systems (CWSs) and non-transient non-community water systems (NTNCWSs) serving more than 10,000 people, all those serving between 3,300 and 10,000 people, and a representative sample of those serving fewer than 3,300 are required to monitor during a single 12-month timeframe in the three years of monitoring.
UCMR 5 data released to date include results received as of October 10, 2024, and represent approximately 55% of the total results that EPA expects to receive until completion of data reporting in 2026. Data are added and possibly removed or updated over the course of this reporting cycle following further review by analytical laboratories, PWSs, states, and the EPA.
Prior to using the UCMR 5 Data Finder:
- Watch the UCMR 5 Data Finder Walkthrough (video),
- Review the Instructions for Accessing UCMR Results and
- Read the UCMR 5 Data Summary.
Data Considerations
On April 10, 2024, the EPA announced the final National Primary Drinking Water Regulation (NPDWR) for six PFAS that are among the 29 PFAS being monitored in UCMR 5. PWSs, specifically community and non-transient non-community water systems, will be required to comply with the PFAS NPDWR Maximum Contaminant Levels (MCLs) starting in April 2029; therefore, UCMR 5 results for the regulated PFAS do not indicate compliance or noncompliance with the MCLs. Information provided on this page for UCMR 5 results is for technical assistance only and does not supersede the PFAS NPDWR requirements in 40 CFR 141 and 40 CFR 142.
The UCMR 5 Data Finder includes two sections:
The top section includes three tabs: All Contaminant Information, Unregulated Contaminant Summary, and All Contaminant Results. Data in the top section can be filtered by PWS ID or name, PWS size, state, EPA Region, contaminant, source water type, results at or above UCMR minimum reporting levels (MRLs), and results above health-based reference concentrations.
The bottom section includes one tab, Regulated Contaminant Summary, which presents the UCMR 5 results to date using sampling location averages and the MCLs from the PFAS NPDWR. Data in the bottom section can be filtered by PWS size, state, EPA Region, contaminant, or source water type. To view individual UCMR 5 results for the regulated PFAS, go to the All Contaminant Results tab in the top section of the UCMR 5 Data Finder.
- Starting in 2029, compliance with the PFAS NPDWR MCLs will be determined by calculating the running annual average of quarterly results for each sample point, based on compliance monitoring data reported to the primacy agency. Recognizing that the UCMR 5 results have no direct implications for PWS MCL compliance, but that many are interested in comparing UCMR 5 data to the MCLs, the EPA calculated annual averages for the UCMR 5 results where such a calculation was possible. The agency then compared those averages to the NPDWR MCLs. For UCMR 5 monitoring, PWSs may have multiple sampling locations, for which there are either two or four sample events over a period of 12 months (for locations with ground water or surface water sources, respectively). Sampling locations were only considered in the comparison to each MCL if they had a corresponding full set of UCMR 5 results (i.e., two or four results). Please note: the UCMR 5 averages for locations with ground water sources are based on two results, not four quarterly results.
- If a particular PWS had averages greater than multiple MCLs, that PWS will be counted in the Regulated Contaminant Summary tab multiple times (i.e., once in each row for the respective PFAS with an average greater than the MCL). To prevent “double counting” by those assessing the data, the summary numbers at the top of the section provide the unique number of PWSs in the selected results, based on the filters applied.
Filters applied in each section and the blue summary numbers at the top of each section apply only to the tab(s) in the respective section. Selected results in each tab can be downloaded as a Microsoft Excel file (.xlsx) (downloads are limited to one million records).
Definitions
- UCMR 5 Minimum Reporting Levels (MRLs) are the lowest concentrations that laboratories may report to the EPA for UCMR 5 monitoring and are determined using data from multiple laboratories that participate in EPA’s UCMR MRL-setting studies. The UCMR 5 MRLs are based on laboratory capability and are not associated with contaminant health effects information. The EPA establishes MRLs to ensure consistency in the quality of the information reported to the agency.
The UCMR 5 MRLs can be found in the All Contaminant Information and Unregulated Contaminant Summary tabs of the UCMR 5 Data Finder.
- Health-Based Reference Concentrations (abbreviated as Health-Based Ref Conc) are provided for unregulated UCMR 5 contaminants where there is publicly available health and toxicological information and are taken from available health assessments published by the EPA (e.g., health reference level [HRL] for lithium) or other governmental agencies (e.g., USGS health-based screening levels [HBSLs] for PFBA and PFHxA). They are not legally enforceable federal standards and are subject to change as new health assessments are completed. Since the agency is still gathering information about the unregulated contaminants, health effects information may be limited. Therefore, health-based reference concentrations may not be available.
The health-based reference concentrations and other toxicological information, if available, can be found in the following tabs of the UCMR 5 Data Finder: All Contaminant Information, Unregulated Contaminant Summary, and All Contaminant Results. - Maximum Contaminant Levels (MCLs) are provided for regulated UCMR 5 contaminants. An MCL is the highest level of a contaminant that is allowed in drinking water. MCLs are legally enforceable standards. The All Contaminant Information tab of the UCMR 5 Data Finder provides the MCLs for five individual PFAS in the Regulatory Level column. The Regulated Contaminant Summary tab also provides the MCLs for five individual PFAS and the PFAS Hazard Index (HI) MCL.
- Hazard Index (HI) MCL is a legally enforceable drinking water standard for mixtures containing two or more of PFNA, PFHxS, HFPO-DA, and PFBS. For more information, refer to the “Understanding the Final PFAS NPDWR HI MCL” Fact Sheet on the EPA’s PFAS NPDWR website.
A full set of definitions for the UCMR 5 Data Finder are provided in the UCMR 5 Data Summary.
Understanding the Results
If you cannot find results for a specific PWS, the PWS may not be required to monitor for UCMR 5, or the results have not been reported yet. For more information, visit the UCMR 5 website.
Results are provided in micrograms/liter (µg/L, or parts per billion). To convert results in µg/L to nanograms/liter (ng/L, or parts per trillion), multiply the value by 1,000.
Results below the UCMR 5 minimum reporting level (MRL) are shown as “< MRL” because the UCMR 5 MRL is the lowest concentration that can be reported for UCMR 5. The UCMR 5 MRLs are based on laboratory capability and are not associated with contaminant health effects information.
Each result represents a single contaminant in drinking water for one sampling point and sampling event from a PWS.
In the UCMR 5 Data Finder, when comparing results for unregulated contaminants to the available health-based reference concentrations, or when comparing sampling location averages for regulated PFAS to the NPDWR MCLs, the following rounding considerations apply:
- The health-based reference concentrations are expressed with one significant digit; comparison of UCMR 5 results to the health-based reference concentrations is therefore based on one significant digit. Results ≥15 µg/L for lithium round to 20 µg/L; results ≥6.5 µg/L for PFBA round to 7 µg/L; and results ≥3.5 µg/L for PFHxA round to 4 µg/L and are identified as above the health-based reference concentrations.
- The MCLs for PFOA and PFOS are expressed with two significant digits; the MCLs for HFPO-DA, PFHxS, PFNA, and the HI are expressed with one significant digit. Comparison of UCMR 5 averages to the MCLs is based on the corresponding number of significant digits. An average is counted as greater than the MCL for PFOS or PFOA if it is ≥0.00405 µg/L. An average is counted as greater than the MCL for HFPO-DA, PFHxS, or PFNA if it is ≥0.015 µg/L. An average is counted as greater than the HI MCL if it is ≥1.5 and at least two PFAS included in the average are measured at or above the UCMR MRL.
Additional Resources
Refer to the UCMR 5 Data Summary and the PFAS NPDWR website for more information. For answers to common questions regarding accessing and understanding the UCMR 5 data and PFAS and lithium in drinking water, visit the UCMR 5 website.
For those interested in large-scale data processing using statistical or data analysis software, use the UCMR 5 occurrence data text files which contain the UCMR 5 analytical results to date as well as additional data element and ZIP Code information.
Data Refresh Interval
Data last refreshed on October 10, 2024. UCMR 5 results will be updated in the UCMR 5 Data Finder, Data Summary, and occurrence data text files on a quarterly basis until completion of data reporting in 2026.