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Celery

When researchers at the EWG analyzed 89,000 produce-pesticide tests to determine the most contaminated fruits and vegetables, celery topped the chart. "In terms of the sheer number of chemicals, it was the worst," says Sonya Lunder, senior analyst at the EWG. Celery stalks are very porous, so they retain the pesticides they’re sprayed with—up to 13 of them, according to the EWG analysis. Lunder also advises buying organic bell peppers, spinach and potatoes because they scored high for pesticides, as well.

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