Cloudy drinking water, even if it's within the limits allowed by some cities, was linked to increased cases of gastrointestinal illness, according to new Drexel University analysis.
In reviewing past studies from cities across North America and Europe, Anneclaire De Roos, PhD, associate professor in the Dornsife School of Public Health, found associations between acute gastrointestinal illness (AGI) and water turbidity, a term meaning cloudiness or opacity.
"More than 10 studies found a link between water turbidity and AGI incidence," De Roos said. "These results suggest that exposures through drinking water caused a low but detectable number of AGI cases in the regions and time periods studied. There is no clear, alternative explanation for the patterns of associations -- particularly when a similar pattern was seen multiple times."
Acute gastrointestinal illness could be caused by waterborne pathogens like norovirus, Giardia, or Cryptosporidium and carry symptoms like diarrhea and vomiting. Cases linked to water systems have been estimated at between 12 and 16.4 million annually in the United States alone.
Since cloudiness in water is caused by material floating in it, the thought is that undissolved particles may actually provide some protection for harmful pathogens against disinfectants. Additionally, cloudiness could be evidence of runoff into water sources, which could contain not just sediment but also harmful pathogens.
To get a better idea of whether turbidity could be a good indicator of issues with pathogens in drinking water supplies, De Roos and her collaborators looked into a collection of studies that had been done on the topic. These studies were designed to evaluate risks from contamination of source waters (usually rivers in the cities studied), before the water entered cities' distribution systems. The basic strategy of the studies was to correlate turbidity levels with the number of people coming down with AGI, on a day-by-day basis.
De Roos found that turbidity of drinking water was linked to increased AGI in multiple studies, and not just when there was increased cloudiness.
"As expected, the association between turbidity and AGI was found in cities with relatively high turbidity levels, often in unfiltered drinking water supplies," De Roos said. "The findings that go against the conventional wisdom are the associations between turbidity and AGI that were seen at very low levels of turbidity -- levels lower than the regulatory limits."
For example, one city that was studied was Philadelphia, where an association between drinking water turbidity and AGI in children and the elderly had been reported. Turbidity in these studies in the 1990s was actually fairly low, by standards both then and now.
Since there were some differences between the studies in the levels of turbidity that were linked with AGI, De Roos said it is "important to understand the reasons for those differences." That means future research should focus on the specific conditions under which turbidity leads to AGI.
"For example, given a similar range of turbidity, is the association with AGI restricted to a certain season or certain climatic conditions, such as periods of heavy rainfall?" De Roos said. "Furthermore, does the association disappear if a different treatment method is used -- like UV disinfection versus chlorination alone?"
If links are found under specific conditions, then water utilities could better monitor their data to identify periods of vulnerability for contamination.
"While these types of epidemiologic studies can't give definitive answers, they offer a relatively inexpensive tool for screening water supplies in order to prioritize management strategies and further research," De Roos said.
Source: Drexel University
Stay prepared and protected with Infection Control Today's newsletter, delivering essential updates, best practices, and expert insights for infection preventionists.
Reducing Hidden Risks: Why Sharps Injuries Still Go Unreported
July 18th 2025Despite being a well-known occupational hazard, sharps injuries continue to occur in health care facilities and are often underreported, underestimated, and inadequately addressed. A recent interview with sharps safety advocate Amanda Heitman, BSN, RN, CNOR, a perioperative educational consultant, reveals why change is overdue and what new tools and guidance can help.
New Study Explores Oral Vancomycin to Prevent C difficile Recurrence, But Questions Remain
July 17th 2025A new clinical trial explores the use of low-dose oral vancomycin to prevent Clostridioides difficile recurrence in high-risk patients taking antibiotics. While the data suggest a possible benefit, the findings stop short of statistical significance and raise red flags about vancomycin-resistant Enterococcus (VRE), underscoring the delicate balance between prevention and antimicrobial stewardship.
What Lies Beneath: Why Borescopes Are Essential for Verifying Surgical Instrument Cleanliness
July 16th 2025Despite their smooth, polished exteriors, surgical instruments often harbor dangerous contaminants deep inside their lumens. At the HSPA25 and APIC25 conferences, Cori L. Ofstead, MSPH, and her colleagues revealed why borescopes are an indispensable tool for sterile processing teams, offering the only reliable way to verify internal cleanliness and improve sterile processing effectiveness to prevent patient harm.
The Next Frontier in Infection Control: AI-Driven Operating Rooms
Published: July 15th 2025 | Updated: July 15th 2025Discover how AI-powered sensors, smart surveillance, and advanced analytics are revolutionizing infection prevention in the OR. Herman DeBoard, PhD, discusses how these technologies safeguard sterile fields, reduce SSIs, and help hospitals balance operational efficiency with patient safety.
Targeting Uncertainty: Why Pregnancy May Be the Best Time to Build Vaccine Confidence
July 15th 2025New national survey data reveal high uncertainty among pregnant individuals—especially first-time parents—about vaccinating their future children, underscoring the value of proactive engagement to strengthen infection prevention.