Urban gardens have become a popular pastime for city dwellers looking to add a touch of beauty and homegrown vegetables into their lives. However, the chances of toxins lurking below your homegrown tomatoes and carrots are dangerously high. Unhealthy concentrations of heavy metals in urban gardening soil are becoming an increasing concern in metropolitan areas throughout the United States. Read on to learn more about where these toxins came from and what you can do about them.
What are heavy metals?
Heavy metals are a group of metals that are toxic to humans and animals if ingested in high quantities. Lead, mercury, copper, zinc, cadmium, nickel and iron are some of the more common heavy metals that present a danger to the food chain. These toxic metals can cause serious disorders in the human nervous system, as well as being detrimental to the blood system.
Most heavy metals occur naturally in trace amounts in all earth. Lead, for example, can be found at an average rate of 10 parts per million (ppm) in all surface agricultural soil. It can range from as little as 7 ppm to as much as 20 ppm naturally. Lead levels above this amount are usually a result of industrial contamination from lead-based paint and auto emissions.
Sources of lead exposure
Lead contamination in soil is highest around building foundations and near highly trafficked streets. “It comes mostly from past historical use. A lot of it is industrial and anything that has to do with heavy auto equipment,” says expert Allison Turner, who published a paper last year on Urban Agriculture and Soil Contamination through the Center for Environmental Policy and Management at the University of Louisville.