“Clean vs. dirty” is a concept that seems easy enough to understand. You know your jeans are dirty when they get grass stains on them, because you can easily see the stains. Seeing bacteria on your food is a different story. All foodborne bacteria are microscopic and can’t be seen with the naked eye, making it difficult to know if your foods have been cross-contaminated. Bacteria may come into with our foods from contaminated cooking equipment, utensils and even our hands. According to the (PDF, 530 KB) Americans are doing well to prevent cross contamination from some common sources, but not all.