A study by Drexel University in Philadelphia, United States (U.S.) and published in Environmental Health Perspectives, has found that cloudy drinking water, even if considered within the limits allowed by some metropolises, is linked to an increased number of cases involving gastrointestinal illness.
When Anneclaire De Roos, PhD, associate professor of Dornsife School of Public Health, reviewed and examined past studies spanning across North America and Europe, she found several connections between water turbidity – a term denoting cloudiness or opacity in water – and acute gastrointestinal illness (AGI).
“More than ten studies found a link between water turbidity and AGI inceidence,” 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 is seen multiple times.”
AGI may be caused by waterborne pathogens such as Cryptosporidium, Giardia, or norovirus, and carry symptoms much like diarrhoea and vomiting, and in the U.S. alone, there are an estimated 12 to 16.4 million cases linked to water systems.
As cloudiness in water is generally caused by material floating in it, research scientists think that the undissolved particles offer harmful pathogens a degree of protection against disinfectants. Additionally, it might also be evidence of runoff into water sources, which may contain not only just sediment, but also harmful pathogens.
But to gain a better understanding of whether water turbidity may be a suitable indicator of issues with pathogens in sources of drinking water, De Roos and collaborating researchers examined a collection of studies looking at the risks posed by contaminated water sources before the resource even entered the distribution systems of the metropolises, looking for links between turbidity levels and the number of people reporting cases of AGI on a daily basis.
What De Roos found was that the turbidity of the drinking water was indeed linked to increased cases of AGI in multiple studies, and not necessarily where there was increased cloudiness in the water.
“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 explained. “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.”
However, there were some differences between the cases in the levels of turbidity connected with AGI, with De Roos noting that it was “important to understand the reasons for those differences.”
“For example, given a similar range of turbidity, is the associated with AGI restricted to a certain season or certain climatic conditions, such as periods of heavy rainfall?” De Roos posed. “Furthermore, does the association disappear if a different treatment method is used – like UV disinfection versus chlorination alone?”
But if links are discovered under certain conditions, water utilities could then better monitor their data to pinpoint periods of vulnerability for contamination.
Dee Roos stated, “While these types of epidemiologic studies can’t give definite answers, they offer a relatively inexpensive tool for screening water supplies in order to prioritise management strategies and further research.”
Source: Drexel University
