This is the VOA Special English Agriculture Report.
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 grass. Different countries have different levels that they consider acceptable.
Carl Rosen of the University of Minnesota Extension notes that concerns about lead have increased now that more people are planting gardens. But Professor Rosen says plants generally do not absorb much lead. He says there is likely more risk from lead dust on plants or from playing in the soil than from the plant itself.
Still, some plants do absorb more than others. Experts say good choices for the garden include tomatoes, peppers, beans and okra. Among the plants that can absorb more contaminants, they say, are root crops, leafy vegetables and herbs. If you grow carrots, for example, you might want to peel them. Dirt may be harder to remove from some crops than from others. But all produce should be washed.
Gardens should be planted away from roads and structures, especially old buildings. Home gardeners should plant away from the foundation of their house. And lead amounts can be especially high near industrial areas and waste dumps.
Soil should also be tested for its pH level, a measure of the acid and alkaline balance. Experts say the ability to take up lead is reduced when the pH level is above six and a half. Adding organic material such as compost to soil can also make lead less available to plants.
Some people attempt a process called phytoremediation. They try to remove lead from soil by growing certain plants that collect it. But Professor Rosen says the process is complex and may not work.
And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. For more gardening information, go to voaspecialenglish.com. I'm Steve Ember.