Test results from the Environmental Protection Agency (EPA) show that in 2012, 12 percent of commercial airplanes in the United States — that’s about one in every 10 planes — tested positive for coliform bacteria, which is usually an indicator of other sickness-inducing bacteria like E. coli.

Or, in other words: “There’s poop in the water if there’s E. coli in the water, and that’s not a good thing," Brenda Wiles, a lab manager certified to test drinking water aboard aircraft, told NBC 5.

The results were made public after Dallas’ NBC 5 requested reports from the EPA through a Freedom of Information Act Request. Coliform, though not necessarily harmful on its own, normally indicates the presence of E. coli, which can cause abdominal cramps, vomiting, and diarrhea if ingested. The EPA put a major initiative in place to reduce the amount of bacteria in plane water after 15 percent of planes tested positive for coliform in 2004. But nine years later, it seems the problem persists.

“I would say that’s still a high percentage,” said Bill Honker, deputy director of the Water Quality Protection Division, EPA Region 6, in Dallas. “I think there is more that needs to be done. So we’re expecting to see further improvement by all the airlines in the country.”

A representative from the airline advocacy group, Airlines for America (AFA), told the Huffington Post that the results are not as bad as they seem because airlines are aware of the problem and making every effort to ensure that the drinking water is safe on planes.

"In very rare cases a water sample test will suggest that the water does not meet drinking water guidelines," the representative said. "In those instances, the airlines follow up by implementing a rigorous disinfection process and resample the aircraft’s water to ensure that water quality criteria are being met."

While passengers may decide to opt for a bottled water instead of drinking tap on their next flight, Honker echoes the AFA’s sentiments, saying the industry knows the problem and is paying close attention to address it.

“I can assure you the industry is getting the message,” said Honker.