Source Molecular Holds MST Workshop in California

Source Molecular Corporation co-hosted a microbial source tracking or MST workshop with the California Water Board Region 5 on January 23 at the EPA headquarters in Sacramento. It was attended by regulators, environmental consultants and watershed managers throughout California as well as other interested parties across North America.

Source Molecular’s CEO Mauricio Larenas presented on Leveraging Fecal DNA to Enhance Water Quality while Dr. Yiping Cao, VP of Technology, discussed “Human Fecal Score™: A standardized method for MST data interpretation“.

Mr. Larenas explained how MST has evolved and matured making it a more superior tool for water quality monitoring than fecal indicator bacteria (FIB) and other legacy technologies. Current tools for water quality monitoring are ineffective in identifying fecal sources.

“There’s tremendous amount of precedent in the utilization of this technology at this point,” Mr. Larenas said, citing successful case studies around the nation where MST was used to effectively investigate bacterial impairment.

Source Molecular aided Martin County in Florida in prioritizing and ranking sites that would have the most effect in lowering human fecal pollution. This could only be achieved with MST and not legacy technologies. Mr. Larenas also shared Source Molecular’s involvement in the award-winning project led by Geosyntec for the Boston Water and Sewer Commission. It was the first ever effectiveness assessment of MS4 IDDE program using DNA markers. In California, MST technology helped Santa Barbara not only to identify pollution sources at their beaches but also to measure the impact of their best management practices (BMP).

MST Workshop Tackles Data Interpretation

Dr. Cao discussed how to make sense of data from MST analysis. Data interpretation and site assessment are crucial to make management decisions. However, the current practice of relying on best professional judgment has been shown to be highly variable.

Dr. Cao and fellow researchers from the Southern California Coastal Water Research Project, the U.S. EPA, and Stanford University saw the need for a standardized mathematically defined objective approach to data interpretation and site prioritization. They came up with a Human Fecal Score™ (HFS).

HFS is essentially a site average concentration of the human fecal marker HF183.  It uses all data — the quantifiable, the detected but not quantifiable, and the non-detect. Dr. Cao noted that some people simply ignore non-detect data.  However, “Absence of detection is not detection of absence,” she stressed. Others may arbitrarily assign a number to non-detect and the detected but not quantifiable, adding arbitrary information into the data. On the contrary, HFS uses everything, adds nothing, and uses a statistically based framework and Bayesian modeling to integrate all data and uncertainty to provide objective site assessment. Dr. Cao noted that the HFS can be applied to to BMP effectiveness, site ranking, CSO consent decree compliance and QMRA site eligibility.

To request a copy of the published journal article on HFS, email Source Molecular at

For questions and comments on the presentations, just select a convenient time to speak with Source Molecular’s representatives.