At first blush, the idea of washing a lemon before it's used might seem redundant. After all, they're usually squeezed to release their juice, and the juice in turn is protected by the fruit's tough rind. In truth, as with other fruit, lemons are exposed to a wide range of agricultural pesticides, bacteria and plain old dirt as they progress from the tree to your supermarket. Washing them carefully removes most of these contaminants, as well as the waxy coating that's applied to extend their shelf life.
Wash your hands scrupulously before you start or don a fresh pair of disposable kitchen gloves. Otherwise, your own hands can introduce new bacteria to the lemons.
Run your cold water tap briefly to purge any water that's been sitting in the lines. Hold your first lemon under the running water, rubbing away any visible soil with your thumb or fingers.
Brush the textured surface of the fruit's skin with a short, stiff brush, such as a toothbrush, nail brush or vegetable brush that's reserved solely for cleaning produce. Be diligent in cleaning the lemon's entire surface.
Shake off any excess moisture, then rest the clean lemon on several layers of fresh paper towel to drain. Repeat for any additional lemons.
Dry the lemons completely with fresh paper towels, then use them immediately or place them in a food-grade bag or container for storage.