For half a century, meat producers have fed antibiotics to farm animals to increase their growth and stave off infections. Now scientists have discovered that those drugs are sprouting up in unexpected places.

Vegetables such as corn, potatoes and lettuce absorb antibiotics when grown in soil fertilized with livestock manure, according to tests conducted at the University of Minnesota.

Today, close to 70 percent of the total antibiotics and related drugs produced in the United States are fed to cattle, pigs and poultry, according to the Union of Concerned Scientists. Although this practice sustains a growing demand for meat, it also generates public health fears associated with the expanding presence of antibiotics in the food chain.