- Author: Betsy Buxton
Several weeks ago at the Vallejo Farmers' Market, a couple had an interesting question: “Where or who tests soil for lead?”. Never having had a question like that, the three of us looked at each other and started giving out the usual suggestions. Those suggestions included the Agricultural Commissioner's Office, the Vallejo Public Health Department, and of course, the Internet. When the folks left, we chuckled to each other as who would do or need to test soil for lead. As it turns out, probably a lot of us.
At home, I started out to research possible answers to the question; what I found has truly given me a quite an education into a subject I never gave a thought about! But I do now!
There was information on the subject of lead in the home soil on the UNITED STATES ENVIRONMENTAL PROTECTION AGENCY website with pages and pages of test laboratories across the United States, including 16 in California alone. Not just any labs are recognized as testing labs. The NLLAP (The National Lead Laboratory Accreditation Program) is an EPA program which defines the minimum requirements and abilities that a laboratory must meet to attain EPA recognition as an accredited lead testing laboratory and have therefore demonstrated the ability to accurately analyze paint chips, dust, or soil samples for lead.
If you own a home that was built before 1978 and/or live on a heavily-trafficked street, chances are very good that you have lead in your soil due to prior house painting or the then use of leaded gasoline. Good news is that lead does not travel easily through soil and is probably confined to the top 2 inches of soil; the bad news is that children play in the soil and some soil can go into their mouths. Testing for lead should be done if: 1. your house has chipped or peeling paint; 2. your house has bare soil in the yard where children play; 3. you plan to repaint, remodel or renovate the house; 4. a child living in the house has had a blood lead test result indicating lead exposure; 5. or, the was built before 1950 – those homes almost always have some lead-based paint.
The places to test for lead-contaminated soil are around the foundation, where children play, unpaved pathways, under windows or walls with peeling or chipping paint, where PETS play or rest, and areas near traffic zones (automobiles).
The following are the EPA limits for paint (5,000 ppm [parts per million]); for bare soil the limit is 400 ppm in bare soil in areas where children play (1,000 ppm or more in other areas); and 40 micrograms of lead per SQUARE FOOT in dust from interior floors and exterior floors.
Testing for lead is not a recommended do-it-yourself job. Only an accredited laboratory should do the testing. Whichever lab is chosen will give thorough instructions for collecting, containing, and labeling your samples. But remember, the results will be only for samples collected not the entire yard or area.
The most serious source of exposure to soil lead is through direct ingestion or eating of contaminated soil or dust. In general most plants do not take up lead or accumulate lead, however, in areas with lead results, higher concentrations are more likely to be found in leafy vegetables (i.e. lettuces, etc) and on the surface of root crops (i.e. carrots, turnips, beets).
If you find high lead test results, the best growing areas will be raised beds for vegetable gardening and the use of mulch to keep children and pets from bare soil contact.
After reading all of this information, I shudder that I chuckled at the couple's question and the truly inadequate information we gave them that day. I really learned a lot doing this research!
A List of Sources:
United States Environmental Protective Agency
University of Minnesota Extension, Carl J. Rosen
PennState Extension, No author Listed
KQED Public Media, Eliza Barclay
Testing Your Home For Lead In Paint and Soil, Internet article no author cited