Soil naturally contains harmless amounts of lead, along with other metals. Because of pollution, however, the amounts are higher the closer you get to cities and towns. But experts say this should not stop gardeners from growing food if they take safety measures.

David Johnson is a chemistry professor in the State University of New York's College of Environmental Science and Forestry. He explains that lead can enter the ground from leaded paint and leaded fuel and from industry.

And once lead gets into the soil, it stays a long time. It remains an environmental threat especially to children. Lead can harm mental and physical development even in babies before they are born.

If a test finds that soil has too much lead, you might be advised to remove the soil or cover it with sod