Colorado public health lab completes next step in data review; review found no evidence of risk to the public’s health

DENVER (June 13, 2025) –  The Colorado Department of Public Health and Environment has completed another portion of the review of data produced by its chemistry laboratory from 2018 to 2024 for certain contaminants of concern. This follows the discovery of quality control irregularities last year, and a subsequent thorough review of historical data out of an abundance of caution. The review found no evidence of risk to the public’s health. The analysis covered 32,951 test results from 2018 to 2024, including compliance samples, environmental monitoring samples, and private customer tests.

“This was a thorough and meticulous review, and I’m pleased to share that we found no evidence of a public health risk,” said Dr. Ned Calonge, Chief Medical Officer, CDPHE. “This is an important step in fully understanding what occurred, strengthening our quality assurance processes, and rebuilding public trust in our laboratory systems.”

The review focused on results from EPA Method 200.8, which is used to detect metals such as lead, mercury, arsenic, and uranium in drinking water and environmental samples. Of nearly 33,000 additional samples reviewed, 1.3% (526 results from 425 samples) were flagged for recall out of an abundance of caution.

Fifteen samples related to drinking water compliance were affected, and all tested contaminant levels were well below health-based action limits, which is used to determine health risk to the public.

In total:

• 49 samples (0.15%) were affected by data irregularities.
• The other recalled samples were due to quality control errors—and often showed only minor bias, such as slightly high or low values still far below concern thresholds.
• Affected customers include water utilities, private wells, and programs that monitor rivers, streams, and environmental health outcomes.

We are now:

• Processing recalls to notify affected customers and partners. 
• The Water Quality Control Division will review the recalled samples to decide if repeat testing is needed. Newer test results may already exist, for example.
• Offering free repeat testing at an external lab when needed.
• Continuing to share updates with the U.S. Environmental Protection Agency and determining what additional reviews may be needed.

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