Fourth Unregulated Contaminant Monitoring Rule (UCMR 4) - EH: Minnesota Department of Health

Fourth Unregulated Contaminant Monitoring Rule (UCMR 4)

UCMR 4 Overview

Every five years, the U.S. Environmental Protection Agency (EPA) implements the Unregulated Contaminant Monitoring Rule (UCMR). The purpose of UCMR is to collect data from across the country on contaminants that may be present in drinking water. EPA uses this data to decide if the contaminants occur at frequencies and concentrations high enough to be regulated in the future.

The fourth round of UCMR, UCMR 4, requires monitoring for 30 contaminants between 2018 and 2020. The contaminants include 2 metals, 9 pesticides, 3 alcohols, 3 semi-volatiles, 3 brominated haloacetic-acid groups, 2 disinfection by-product indicators, and, for surface water systems, 10 cyanotoxins. These contaminants are not regulated under the Safe Drinking Water Act.

More information is available at EPA’s Fourth Unregulated Contaminant Monitoring Rule.

Human Health-Based Comparison Values for the UCMR 4 Contaminants

The UCMR 4 contaminants are being studied at very low levels. The levels are based on how low we can detect them in a lab. They are not based on a level established as “significant” or “harmful.”  The levels at which we can detect the UCMR 4 contaminants are often below current human health-based guidance values, such as EPA health advisories (HAs) and MDH Health Based Values (HBVs) - to the extent these values have been established.

The detection of a UCMR 4 contaminant does not represent cause for concern, in and of itself. The meaning of a detection should be determined considering current health effects information. This information is often still under development or being refined for unregulated contaminants.

The intent of the following table is to identify human health-based UCMR comparison values, where possible. These comparison values provide context around the detection of a particular UCMR contaminant. A person drinking water with a contaminant at or below the comparison value would be at little or no risk for harmful health effects. The comparison value does not represent an “action level.” Because these contaminants are unregulated, EPA and MDH require no particular action based on detection of a UCMR 4 contaminant.

Table of Comparison Values

Contaminant Comparison Value (μg/L) Value Type
1-Butanol 700 MDH HRL
2-Methoxyethanol Not available Not available
2-Propen-1-ol 35 EPA CCL4 HRL
Alpha-Hexachlorocyclohexane 0.02 MDH Rapid Assessment


Toxicological Summary for Anatoxin-a (PDF)

Information Sheet: Anatoxin-a in Drinking Water (PDF)

Butylated hydroxyl anisole Not available Not available


Toxicological Summary for Chlorpyrifos (PDF)

Information Sheet: Chlorpyrifos and Drinking Water (PDF)

Cylindrospermopsin 0.7 EPA HA
Dimethipin 140 EPA HHBP
Ethoprop 1.14 EPA HHBP
Germanium Not available Not available
HAA6BR Not available Not available
HAA9 Not available Not available


Toxicological Summary for Manganese (PDF)

Manganese in Drinking Water





Microcystin LR

Toxicological Summary for Microcystin-LR (PDF)

Information Sheet: Microcystin-LR in Drinking Water (PDF)

Microsystin - Total 0.3 EPA HA
Nodularin-R Not available Not available
o-Toluidine Not available Not available
Oxyfluorfen 0.437 EPA HHBP
Profenofos 0.3 EPA HHBP


Toxicological Summary for Quinoline (PDF)

Information Sheet: Quinoline and Groundwater (PDF)

0.04 MDH HBV
Tebuconazole 30 MDH Rapid Assessment
Permethrins - Total 10 MDH Rapid Assessment
Tribufos 0.6 EPA HHBP

*Note: HAA5 is regulated under EPA's Disinfectants and Disinfection Byproducts Rule. Under this rule, HAA5 has a maximum contaminant level (MCL) of 60 μg/L.


  • EPA: U.S. Environmental Protection Agency
  • EPA CCL4 HRL: U.S. Environmental Protection Agency Contaminant Candidate List 4 Health Reference Level
  • EPA HA: U.S. Environmental Protection Agency Health Advisory
  • EPA HHBP: U.S. Environmental Protection Agency Human Health Benchmarks for Pesticides (PDF)
  • HAA: Haloacetic acids
  • μg/L (micrograms per liter): One μg/L is the same as one part per billion (ppb), which is like one drop in one billion drops of water.
  • MDH HBV: Minnesota Department of Health Health-Based Value
  • MDH HRL: Minnesota Department of Health Health Risk Limit
  • MDH RAA: Minnesota Department of Health Risk Assessment Advice
  • MDH Rapid Assessment
  • Not available: No MDH or EPA comparison value available
Updated Friday, 22-Oct-2021 14:17:06 CDT