With rising concerns about pesticides in food, terms like ‘Clean 15’ and ‘Dirty Dozen’ have become buzzwords for health-conscious shoppers. But what do these lists actually mean?

“Citrus is a classic, nontoxic way to clean your home that really works,” says Shira Gill, a professional organizer in San Francisco and the author of “LifeStyled: Your Guide to a More Organ ...