Minimum Reporting Limit. Where available, MRLs reflect the Method Detection Limits (MDLs) set by the U.S. Environmental Protection Agency or the Detection Limits for Purposes of Reporting (DLRs).These values are set by the agencies to reflect the lowest concentration of each substance that can be accurately quantified by applicable testing methods, and are also the minimum reporting thresholds applicable to the Consumer Confidence Reports produced by tap water suppliers.