Recent research reveals that companies aren't just rinsing the leaves in water, they're using chemicals like bleach, which contains chlorine. Why is the rinsing agent for leaves so harsh? It turns out the Food and Drug Administration (FDA) actually encourages using bleach because it kills off E.coli and salmonella in greens. Unfortunately, traces of the strong cleaners will linger on your lettuce and make it into your mouth if you're not careful. Since bleach, even diluted in water, is toxic in high quantities, it's best to re-wash your salad components yourself before you dig in. (Here's our guide to easily cleaning up produce.)

The real kicker here? It seems that chemically washing the lettuce isn't all that effective. The University of California - Riverside performed a study that showed that only 10 percent of bacteria is removed with this bleach solution, which means that most of what the bleach is trying to remove from your spinach still makes it all the way to your kitchen. (The study only reported on baby spinach, but it makes us wary of any pre-washed salad greens.) The troubling fact is, pre-washed or unwashed, grocery store produce has bacteria and traces of pesticides and chemicals used to grow and ship foods. The pre-washed stuff isn't worse than the unwashed stuff, but it's no better, so don't get all comfortable about it.

The best solution? Wash all your grocery produce yourself. We like to use a mixture of water and vinegar in a first wash, and then rinse with plain cold water. (Then make sure fresh items last as long as possible by storing them in the right part of your fridge.) Feeling inspired to clean more than just the lettuce?