Think Rosario Dawson's reusable shopping bag safe? Photo: Michael Caulfield, WireImage.com

You're so eco-friendly that your friends are practically green with envy: You bike to work. You only use low-energy light bulbs. And you always, always carry your own shopping bags. No plastic for you, babe.

But, yikes! Scientists are now saying reusable shopping bags could be havens for deadly bacteria.

According to London's Daily Mail, testing on bags from 84 shoppers showed that half had traces of E. coli and many were contaminated with salmonella.

The testing, performed at the University of Arizona -- and funded by the American Chemistry Council, a group that's fighting bans on single-use bags -- found bacteria levels were high enough to "cause a wide range of serious health problems and even death," the Daily Mail reports.

"Our findings suggest a serious threat to public health, especially from bacteria such as E. coli," Professor Charles Gerba, who led the study, tells the newspaper. "Consumers are alarmingly unaware of these risks and the critical need to sanitize their bags weekly."

The Daily Mail reports that although there are no recorded cases of people getting sick from their reusable shopping bags, tossing them in the washing machine and using hot water should kill bugs that can result from your raw-meat packaging. (Anyone else feel like going vegan today?)

We say keep your shopping bags separated and clean -- you don't dare want any germs touching your new Jimmy Choos now, do you?

Oh, and if you think bugs on your bags is bad, just imagine what lurks beneath your flip-flops. Shudder.