Oct. 9, 2023 – A small study in California revealed that 4 in 10 samples taken from soda fountains contained potentially dangerous contaminants. The study also raised concerns about the safety of water that is sold at stores by refilling large take-home jugs.
The research from microbiologists at Loma Linda University was published recently in the journal Water Supply.
For the study, researchers took 72 samples from three types of water sources: soda fountains, water vending machines, and tap water faucets at the stores where the water vending machines were. Water vending machines are those that fill large jugs, typically at grocery stores, which consumers then take home.
All of the samples for the study were taken from the desert region of Southern California called the Eastern Coachella Valley.
The fast-food restaurants where the samples were collected were not aware of the study, and the researchers purchased a meal and drink at the places where the samples were collected.
They found bacteria called total coliforms in:
- 41% of soda fountain samples
- 20% of the water vending machine samples
- 50% of faucet samples from the stores where the water vending machines were
- 88% of swab samples from inside spigots taken from the water vending machines and tap water faucets
According to the U.S. Environmental Protection Agency, “the presence of coliform bacteria in tap water suggests that there could be a problem with existing equipment or treatment systems, contamination of the source water or a breach in the distribution system that could introduce E. coli contamination.”
E. coli contamination of water typically involves the presence of fecal matter, according to the EPA. But samples that are positive for total coliforms do not necessarily mean the water is contaminated with E. coli, and the EPA recommends further testing of water that is positive for total coliforms.
The Loma Linda researchers also tested water directly from the local water authority and found the samples were all within safety limits. They concluded the sources of contamination of their other tests were lines and equipment.
“Although the Coachella Water District provided clean water, according to results published on their website and the analysis of the water tank we analyzed, we can infer that the [tap water] spigots, fixtures, or other premise plumbing are likely to be contaminated with biofilms,” the authors wrote.
Biofilms are a slime layer of microorganisms that form on surfaces in contact with water.
A water research expert from Michigan State University, who was not involved in the study, said the findings show that more surveillance is needed.
“It’s a concern that they found these pathogens,” Michigan State microbiologist Joan Rose, PhD, told USA Today. “It’s clearly an indicator that we need to do more investigations like this. We just don’t know how big the threat is.”
A representative of the National Restaurant Association told the news outlet that soda fountains are required by federal guidelines to be cleaned regularly and noted that there are known tap water quality issues in the community where the study was done.
“We encourage restaurant operators to work with their suppliers to know and understand the best ways to clean and sanitize all food contact surfaces in accordance with the food code and prevailing local statutes, regulations, and policies,” said Patrick Guzzle, MA, vice president of food science at the National Restaurant Association.
The authors stressed that their findings warrant concern.
“The presence of pathogenic microorganisms in drinking water is a serious public health concern and cannot be overemphasized,” they wrote.