Is your tap water ever cloudy? That’s a sign of turbidity. Unfortunately, most of the time it’s not that obvious.
Turbidity happens when particles of clay, silt, decaying plants, parasites, and other matter become suspended in the water. It’s not just a cosmetic or taste problem. Disease-causing microorganisms can cling to the particles and escape destruction by chlorination and other disinfection methods.
Public water utilities are supposed to constantly monitor their water supplies and remove the particles when turbidity becomes excessive.
But that’s not always good enough.
In 1993 in Philadelphia, for example, emergency room visits and hospital admissions for children with gastrointestinal illness increased by about ten percent whenever the turbidity of the city’s public drinking water increased significantly, but remained below the legal limit and wasn’t visible to consumers.
And about ten days after the spikes in turbidity, hospital admissions of the elderly for GI tract illnesses increased by nine percent.
Evidence from around the world
Now, a newly-published review of 14 studies confirms that this impact of turbidity occurs consistently all over the United States and the world. The studies looked at turbidity levels in Milwaukee, Philadelphia, Seattle, Massachusetts, New York City, three cities in Canada, two in France, and one in Russia between the years 1992 and 2007.
The study researchers then checked hospital, emergency room, physician, and prescription drug records.
Turbidity in drinking water “caused a low but detectable number of acute gastrointestinal illness cases in the regions and time periods studied,” says lead researcher Anneclaire De Roos of Drexel University in Philadelphia.
The illnesses usually occurred six to ten days after water got turbid and happened after both low and high levels of turbidity.
“Even in ordinary tap water at levels that pass federal standards, ten percent of gastrointestinal illnesses in children and the elderly may be due to turbidity,” says Joel Schwartz of the Harvard School of Public Health, who led several of the studies in the review.
What can you do?
Check your Consumer Confidence Report, if you get your water from a public utility. It’s obligated to report once a year the amount of turbidity in its drinking water.
To see your report, which water utilities are required to issue every year, go to epa.gov/ccr or call the EPA’s Safe Drinking Water Hotline at 800-426-4791.
Many home water filters, some of them relatively inexpensive, are certified to reduce turbidity. For example, several popular brands of filters that you mount on the faucet, costing $23 to $32, can reduce turbidity in your drinking water.
Check out our article “Do you know what your water filter removes?” to find out how to check the NSF website for which brands and models are certified to do this.
Source: Anneclaire J. De Roos et al. Review of Epidemiological Studies of Drinking-Water Turbidity in Relation to Acute Gastrointestinal Illness. Environmental Health Perspectives 2017 doi.org/10.1289/EHP1090
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