Fifth Unregulated Contaminant Monitoring Rule Data Finder
UPDATE (04/10/2024): PFAS NATIONAL PRIMARY DRINKING WATER REGULATION (NPDWR)
This tool was developed to provide access to UCMR 5 results reported to date; as a preliminary, partial data set, it is not an effective tool for predicting which, or how many, PWSs will need to take action in the future to comply with the agency’s recently announced PFAS NPDWR maximum contaminant levels (MCLs). Additional discussion about the preliminary, partial set of UCMR 5 PFAS results, relative to the NPDWR, is available in Section VI.G (UCMR 5 Partial Dataset Analysis) of the Federal Register Notice for the Final PFAS NPDWR.
The EPA will be updating this tool every quarter through 2026 and will revise future presentations of the UCMR 5 data (including the presentation of results relative to “reference concentrations”) to reflect the fact that the agency now regulates six of the 29 PFAS for which monitoring data are being collected. The EPA anticipates publishing the next data release, addressing results received as of April 2024, by early May 2024. In the meantime, this version of the UCMR 5 Data Finder (i.e., January 2024) continues to present data from the perspective of the NPDWR as a proposed action.
On this page:
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 (subject to availability of appropriations and sufficient laboratory capacity), 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.
Results in the UCMR 5 Data Finder can be filtered using multiple data fields, including PWS, state, contaminant, source water type, results at or above UCMR minimum reporting levels (MRLs), and results above health-based reference concentrations.
Data Considerations
UCMR 5 data released to date include results received as of January 11, 2024, and represent approximately 24% 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, public water systems (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.
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 Summary Pivot Table or the Contaminant Information in the UCMR 5 Data Finder.
- Health-Based Reference Concentrations (abbreviated in the UCMR 5 Data Finder as Health-Based Ref Conc) are provided for 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., lifetime health advisory [HA] levels and health reference levels [HRLs]) or other governmental agencies. They are not legally enforceable federal standards and are subject to change as new health assessments are completed.
Since these are unregulated contaminants and the agency is still gathering information about them, health effects information may be limited. Therefore, health-based reference concentrations may not be available. Health-based reference concentrations are provided for context (especially where the UCMR 5 MRL is much lower than the health-based reference concentration).
The health-based reference concentrations for PFOA and PFOS are below the levels that can be reliably measured by laboratories (i.e., the UCMR 5 MRLs). However, only PFOA and PFOS results that can be reliably measured at or above the UCMR 5 MRL are counted as above the health-based reference concentration. Because of this, the actual number of PWSs with PFOA and/or PFOS results above the health-based reference concentration may be greater than the number of PWSs with results at or above the UCMR 5 MRL as displayed in the Summary Pivot Table in the UCMR 5 Data Finder.
The health-based reference concentrations and other toxicological information, if available, can be found in all three tabs of the UCMR 5 Data Finder: Summary Pivot Table, Review Data Table, and Contaminant Information.
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; UCMR 5 results do not represent locational running annual averages.
When comparing results to health-based reference concentrations in the UCMR 5 Data Finder, the following rounding considerations apply:
- The health-based reference concentrations (i.e., EPA lifetime health advisory [HA] levels and health reference levels [HRLs]) are expressed with one significant digit; comparison of UCMR results to health-based reference concentrations is therefore based on one significant digit.
- Results >0.015 µg/L for HFPO-DA (GenX chemicals) and >2.5 µg/L for PFBS round to >0.02 µg/L and >3 µg/L, respectively, and are identified as above health-based reference concentrations. Results for lithium are likewise identified as above the health-based reference concentration if they are >15 µg/L.
More information about the UCMR 5 results can be found in the UCMR 5 Data Summary.
Additional Resources
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 January 11, 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.
UPDATE (04/10/2024): PFAS NATIONAL PRIMARY DRINKING WATER REGULATION (NPDWR)
In developing the final NPDWR for PFAS in drinking water, the EPA conducted extensive analyses using best available science and is confident in its estimate that between 6-10% of regulated drinking water systems will have to take action to reduce PFAS in their drinking water in accordance with the PFAS NPDWR. Compliance with the PFAS NPDWR will be determined by calculating the locational running annual average (LRAA) which considers the results of all samples from a particular location(s) at a PWS over the previous year. In contrast, the Summary Pivot Table and interactive summary statistics at the top of the UCMR 5 Data Finder (i.e., Total PWSs with Results, Total Results) currently present the UCMR 5 results of single sample events and aggregate results by PWS in comparison to the health-based reference concentration. Therefore, please note the following:
- The Summary Pivot Table and interactive summary statistics logically yield a higher estimate of PWSs above a reference concentration, versus those with LRAA results above one or more of the recently announced maximum contaminant levels (MCLs). For example, if a PWS has a UCMR 5 PFOA result at the 0.004 µg/L (4 ppt) UCMR MRL in one quarter and results below the UCMR MRL in the other three quarters, the Summary Pivot Table and interactive summary statistics counts would include that PWS (as a PWS with one or more PFOA results at or above the UCMR MRL and above the reference concentration). However, if that PWS were calculating its LRAA for compliance purposes (adding 4.0+0+0+0 and dividing by 4, resulting in an LRAA of 1.0 ppt), the PWS would be below the MCL of 4.0 ppt.
- If a particular PWS has one or more results above the reference concentration for multiple PFAS, that PWS will be counted in the Summary Pivot Table multiple times (i.e., once in each row for the respective PFAS with a result above the reference concentration). If this is not considered by those assessing the data, it would result in “double counting.”