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Is bottled water left in your hot car safe to drink?

HOUSTON – How often do you leave a plastic water bottle in your car and take a couple of days to finish it? A drink here, a swig there. Meanwhile, the summer sun is heating up your car and that plastic bottle. 

You've heard the warnings about toxins that can leach from the bottle into the water and ultimately make you sick.  Consumer expert Amy Davis wanted to test those claims. 

You probably planned to drink that whole bottle of water that you carried into your car in one sitting; but then you put it in the cup holder. Davis took one of those unfinished water bottles to Envirodyne Laboratories to find out what was in the water.

She also took a new unopened bottle that had been sitting in her hot car for the same period of time.

They didn't test for the potentially cancer-causing toxins, but other researchers have before. 

A University of Florida study measured the level of BPA that leached into water from 16 plastic bottles heated to 158 degrees over 4 weeks. Only one exceeded the federal standard for BPA. Researchers concluded "storage at warm temperatures would seem to not be a big problem" when it comes to cancer concerns. 

What testers found in Davis' water bottle was troubling. 

"We had total coliform counts greater than 2420," explained Laura Bojonia of Envirodyne. "We had heterotrophic plate counts greater than 73,000." 

There were unsafe levels of bacteria. While total coliform can be found in the dirt and dust in the air, its presence indicates that conditions are perfect for its friends, like E-coli, to move in. 

"And with the warm conditions of a car in the summertime, it's a breeding ground for the bacteria," Bonjonia said.  

The unopened bottle had no coliform, E-coli or other bacteria. The bottle shared between Davis and her children had levels that would make a public water system issue health warnings. 

"Then that's when they even have to go into the boil water notices and public notices and that sort of thing," Bonjonia explained.  

Bacteria like E-coli can cause gastrointestinal issues like vomiting and diarrhea. If you're a parent, you would just assume your kid picked up a bug from school or day care when it could be that hot bottle of water in your car. Bonjonia said of you don't finish a bottle of water before you get out of your car, you should take it with you. Refrigeration helps slow the growth of bacteria.