Local Health Officials Use DNA Testing to Pinpoint Sources of Water Pollution


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Falling short of determining the source of fecal bacteria in local waters, health officials in Darien, Westport and Branford are hoping to expand on a recent study that uses DNA to pinpoint sources of water pollution.

The three local health departments used DNA source tracking, a new method to identify human and nonhuman sources of contamination. But while the study, completed in 2019, found no significant evidence of human or pet bacteria, officials have yet to determine the exact source of contamination.

According to Microbial Insights, an environmental biotechnology testing lab, microbial contaminants in recreational waters were responsible for about 90 million illnesses each year. 

Reached by email, health directors David Knauf of Darien, Mark Cooper of Westport and Michael Pascucilla of Branford emphasized the importance of continuing the work. 

“If contamination sources are identified, efforts to mitigate that contamination could be undertaken and the potential risk to public health better understood,” they told CT Examiner in a joint statement. “Water-based recreational areas, beaches and shellfishing resources could be managed more effectively.”

In an interview with Darien TV-79, Knauf said he was pleased to announce that the report was published in the December 2022 edition of Journal of Environmental Health, bringing the group one step closer to expanding their study.

“What we’re hoping is that with the publication of this article, we’re actually lobbying for additional funds to take this a little further because we really think that the current method of doing water testing – getting the results back a day later – is a little archaic, and really is not protective of public health,” Knauff told TV79.

Project leaders told CT Examiner that they felt their findings should be shared with not just their Connecticut peers, but also with their national and international colleagues. They said they wanted to expand the study to include more watersheds, possibly moving into New York as they also identified local impaired waterbodies.

The original analysis – in collaboration with Yale University and funded by a $50,000 grant from the Connecticut Department of Energy and Environmental Protection – collected freshwater samples once a month in 2016 from Goodwives River in Darien, Sasco Brook in Westport and Lower Farm River in Branford as all three had a history of elevated bacteria counts.

The group used DNA markers to assess levels of human, poultry, canine, cattle, bird, sheep and deer fecal bacteria, but was not able to test for seagulls, geese or rodents.

Even though bacteria and viruses that are reliably detectable at low concentrations can offer a surrogate means of evaluating water pollution, the health directors said that, with sufficient funding and additional study areas, DNA source tracking could provide a tool to better evaluate, understand and eliminate sources that endanger public health.

“Public Health Officials need to go beyond the reoccurring cycle of closing and opening bathing areas, beaches, shellfish beds and other recreational activities, especially when the time between sampling and results is so significant,” urged the health officials.