Explain why bleach should not be used to wash produce at home.
The U.S. Food and Drug Administration recommends washing fresh produce thoroughly with tap water before eating. When appropriate, produce should be scrubbed with a brush to remove microorganisms that might be present. The surfaces of firm fruits and vegetables, such as apples, melons, and cucumbers, can withstand scrubbing with a brush. However, fragile produce, such as berries and lettuce, cannot be scrubbed and so should be rinsed thoroughly with clean tap water before eating.
It is important to remember that the Food and Drug Administration does not recommend using anything other than clean tap water to wash fresh produce. However, one sometimes sees recommendations that are contrary to this.
Bleach -- One set of instructions that has circulated includes the use of bleach. One is to mix 1 teaspoon of bleach (must contain sodium hypochlorite and no phosphorous) in 1 gallon of water. This mixture is similar to the sanitizing solution that one uses to sanitize food-contact surfaces after washing. The fresh produce is to be soaked in this solution for 10 minutes and then rinsed thoroughly in another bowl with running water for 5 minutes.
Washing fresh produce using this procedure is safe and relatively effective in killing harmful microroganisms if the directions are followed exactly. It is very important that fresh (less than six months old), unscented bleach is used and the quantity of bleach used should never exceed 1 tablespoon of bleach per gallon of water. Chlorine bleach at the dilution of 1 teaspoon to 1 tablespoon of bleach per gallon of water is safe to use on fresh produce before eating. In fact, these concentrations of chlorine bleach are often used to wash food industry produce. The problem with this recommendation is the concern that consumers might use a higher concentration of bleach. A more highly concentrated solution could be dangerous.
Dish detergent -- It was recommended in an article that appeared in the Nutrition Action newsletter that detergent be used to wash produce before eating. The FDA does not recommend this either because many ingredients in commercial detergents have not been adequately tested for safety for such uses. Detergents can penetrate into fresh produce and might leave chemical residues that could potentially be more harmful than any microorganisms that might have been washed off the produce.
Cooking fresh produce is sufficient to kill any harmful microorganisms. Obviously not all fresh produce will be cooked before eating.