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COLORADO SPRINGS, COLO. -- It's a trend that's sweeping the nation: using reusable grocery bags instead of plastic ones. But researchers say while the move is environmentally friendly, it could make consumers sick if they’re not aware of the risks of reusable bags.

Two separate studies were done to test how sanitary reusable bags were.

Researchers at the Canadian Plastics Industry Association tested 23 reusable bags.

They found 64 percent of the used bags showed some level of bacteria and close to 30 percent had levels of bacteria higher than what's considered safe in drinking water.

"I don't worry about it. I mean if I were to spill something, yeah I’d wash it out,” said Jessica Murphy, who uses reusable bags.  

In a second study done by the University of Arizona researchers tested 84 used reusable bags.

This time bacteria were detected in 51 percent of the bags, and seven of the bags tested positive for E.Coli.

And while the bags may appear clean to the naked eye, researchers say they can also be breeding grounds for yeast and mold.

So does this mean shoppers should ditch reusable bags and go back to plastic? Not necessarily.

"We really don't have any information that contaminated bags have actually caused illness," said Dr. Bernadette Albanese, Medical Director for the El Paso County Health Department.

Dr. Albanese says it's more important what consumers do with their food once it’s in their kitchen, then how they get it there.

"People underestimate how much contamination they do themselves by handling these other foods, not washing their hands, and then touching each other, or touching ready to eat food and then putting food in their mouths,” said Dr. Albanese.

In the University of Arizona study researchers also found washing reusable bags reduced more than 99 percent of bacteria.

"I haven't [washed them] but now I'm gonna do it," said Melissa Mitchell, who also uses reusable bags.

Researchers also said storing bags in the trunk of a car is the worst possible place to keep them.

"I have like three or four in the car. Then I have some at home," said Mitchell.

Researchers say the warm dark area of a trunk is the perfect spot for bacterial growth.

Still Dr. Albanese says the best protection is properly preparing your foods.

"I think reusable bags are good for the environment. I think if they're washable that makes sense. There's really no harm in taking that extra precaution. But no matter what happens, before that food gets to your plate, before that food gets to your mouth that's when the most important steps can be taken to protect yourself. So wash your fruits and vegetables, keep raw meats and poultry away from other ready to eat foods and very importantly, wash your hands," said Dr. Albanese.