High concentrations of contaminants are usually due to gasoline auto emissions and lead-based paints from walls and windows that may have chipped over time and mixed with the surrounding soil. “Lead is a chemical element, so it can’t break down any further than it already is,” explains Extension Associate Hannah Shayler of the Cornell Waste Management Institute. Lead dust can also float through the air and land on people, plants, animals and water sources and is dangerous if inhaled or ingested.
Another source of contamination comes from the remnants of old pesticides that were made with lead arsenate. “Syracuse, for example, used to be apple orchards and up until the 1940′s or so, they used to spray those orchards with lead arsenate pesticides. Therefore there’s high levels of lead in many areas of Syracuse,” says Venera Jouraeva, a visiting Assistant Professor at the State University of New York Oswego.
Lead in Garden Plants
Luckily, most vegetable and fruit crops don’t absorb high levels of lead into themselves even if planted in areas with lead contamination. “Each plant has various degrees of absorbance,” says Jouraeva. “But lead is usually not transmitted through shoots.” The most danger with regard to lead poisoning comes instead through direct ingestion of contaminated soil. This usually happens when children play in toxic soil and get it into their mouths or when people eat contaminated soil found on the exterior of unwashed produce.
If children aren’t a concern and you are vigilant about washing home grown produce, it is generally considered safe to do your gardening in soils that have a total lead level of less than 300 ppm, according to the U.S. Environmental Protection Agency. If, however, you have children playing in or near your garden, then the possibility of hand to mouth activity heightens the chances of lead ingestion. Children are also more vulnerable to lead poisoning because their nervous systems are not yet fully developed and their bodies offer higher absorption from the gastrointestinal tract than in adults. Therefore, if children play on or near your property, it’s safest if you only do your gardening in land that tests out at lead levels of less than 100 ppm.
As long as your soil’s lead level meets the requirements as explained above, then all you have to do is simply wash away the unsafe dirt on the outside of crops like corn, beans, squash, tomatoes, strawberries and apples. You have to be a bit more careful with leafy vegetables and root crops that have the potential to absorb more toxins from contaminated soil. In these cases, you will need to remove the outer leaves of plants like lettuce or peel off the outer layer of vegetables like potatoes and carrots. In all cases, you should carefully wash any produce that may have been exposed to lead with water and vinegar or soap.