Recently, numerous requests with varying motivations have been received from homeowners to test for lead in garden and landscape soils. Most of these requests have been received from Jasper, Jefferson, Camden, Iron, Reynolds, Madison and East St. Louis Counties where lead smelting has occurred, and also from community gardens concerned about contamination in city lots. We have also received requests to test for lead in soil from concerned parents worried about their children playing in the yard or vegetable garden. However, of these samples, none have been at contaminated levels, so I thought it would be useful and informative to write an article on soil testing for lead to bring awareness and education to homeowners and gardeners.
Lead is a heavy metal that is hazardous if found in high levels in soils. The natural level of lead in soils ranges 10–50 parts per million (ppm). There are several sources of lead in soils. In urban areas, contamination can be caused by industry, and in older homes (built before 1978) it can be the result of chipping and peeling paint or due to extensive home renovations or lead in gasoline. Even though lead in paints and gasoline have been removed and are no longer in use, contamination that occurred during years of use can still remain. Lead can also be a problem in areas near existing smelters, tailings from metal and ore mines, fossil fuel-fired electrical plants, or cement factories. Historic records show Missouri was the largest lead producer in the country. Lead mining, smelting and milling has contributed to lead contamination in soils in various locations in the state. Since lead moves very little and is not easily dispersed or broken down, it can persist in the soil for a long time. As a result, lead contamination of soils from these sources continues to be a concern. Therefore, the federal and state programs have responded by cleaning up of residential soils to eliminate the problem.
|Soil test lead in ppm||Recommendations|
|Less than 50 ppm||Little or no lead contamination in soil.|
|50 to 400 ppm||Some lead present from human activities. Grow any vegetable crops. Choose gardening practices that limit dust or soil consumption by children.|
|400 to 1200 ppm||Do not grow leafy vegetables or root crops. (These crops carry the highest risk of lead contamination.) Choose gardening practices that limit dust or soil consumption by children.|
|Greater than 1,200 ppm||Not recommended for vegetable gardening. Mulch and plant perennial shrubs, ground cover, or grass. Use clean soil in raised beds or containers for vegetable gardening.|
|Source: Angima, S.D. and D.M. Sullivan. 2008. Evaluating and Reducing Lead Hazard in Gardens and Landscapes. Extension Guide EC-1616-E. March 2008. Oregon State University Extension Service.|
Higher levels of lead in soil and environment in contaminated areas can result in important health problems. Children can come into contact with soil that is contaminated with lead by playing in the soil and by putting soiled hands and toys into their mouths. Lead from soil can also be carried into homes on shoes or clothing or by pets digging in the contaminated soils, attaching particles and dust to their paws and fur. Lead is also found in airborne dust. If you are living in a home built before 1978, you can incur lead contamination from chipped and peeling lead-based paints. The older the home, the higher the likelihood of lead contamination due to more coats of paint applied over time. Properties adjacent to heavily travelled streets and roadways also bring a higher susceptibility and occurrence of lead contamination.
If you suspect the possibility of lead contamination in your garden or landscape soil and you have young children who might be exposed to contaminated soil, it is wise to test your soil for lead. According to the U.S. Environmental Protection Agency, a tested soil level of 400 ppm in garden soil is considered contaminated (EPA URL: http://www.epa.gov/lead/ ). The soil should be sampled by taking 6 to 12 random subsamples from the surface 3 to 4 inches. ince lead doesn’t move significantly in soil, it stays in the surface unless the soil has been tilled or mixed in land preparation. Mix the subsamples well and send 1 ½ cupfuls to the lab for lead analysis. Provided is a table adopted from the Oregon State University Extension Guide on Evaluating and Reducing Lead Hazard in Gardens and Landscapes, authored by S. D. Angima and D. M. Sullivan for interpretation of lead soil tests for gardens.
The MU Soil and Plant Testing lab located at 23 Mumford Hall, University of Missouri, Columbia, MO 65211, offers lead and heavy metals testing. If you would like your garden or landscape soil tested please contact the lab by calling (573) 883-0623 or by visiting the lab’s website at http:// soilplantlab.missouri.edu/soil/
REVISED: September 30, 2015