Now that warm weather is here, you are no doubt starting your garden again. One thing you may not have considered is the amount of lead in the soil in your garden. Lead poisoning can cause children to be overly active, inattentive, and even a small amount in a child can lower intelligence and slow nervous system development. A recent expose entitled “Ghost Factories: Poison in the Ground” was published in USA TODAY on April 20, 2012 and it pointed out the seriousness of lead contamination in geographic areas on or near old lead smelters. Lead levels in the soil samples collected by USA TODAY were generally highest in locations like Chicago, Cleveland and Philadelphia, usually in the areas where industrial sites are or were located. With the increasing popularity of growing fruits, vegetables and herbs, often in urban gardens, more people (especially children) are at risk for increased lead exposure. Testing your soil for contaminants is a great way to get the information needed to protect yourself.
How can you test your soil?
Testing for lead in soil is easy.
- Collect: Collect a sample of soil at least six inches below the surface, which will be in the root level of most plants. Lead generally stays concentrated near the surface. Any common gardening tool can be used to perform this process.
- Contain: A half-quart size zip lock bag of soil is enough for the analysis. A representative sample of the garden is recommended. If the garden soil is evenly tilled, then you can just take one sample. However, if the soil is unevenly distributed or extends close to a building or road, it may be a good idea to collect about 6 to 10 samples from different areas of the garden.
- Test: The samples can then be sent to a laboratory recognized by the National Lead Laboratory Accreditation Program (NLLAP) that is proficient in soil analysis. You can locate a nearby laboratory by calling 800-424-LEAD or refer to the list of three Environmental Protection Agency (EPA) approved laboratories in Illinois (listed at the end of this article) that will accept soil samples from the general public.
So what do you do when soil lead levels are high?
Fortunately, the presence of lead in your soil doesn’t mean that gardening is out of the question. It may however require that you change your plot design and/or choice of crops. If lead levels are high, the best course of action is removing the soil and replacing it with fresh/non contaminated soil in a raised bed.
Some states have stricter standards, but the U.S. EPA recommends lead levels less than 400 ppm for gardening soil. However, according to Gabriel Filippelli, a professor and director of Earth Sciences at Purdue University, test results less than 200 ppm is preferred and may benefit from high phosphate fertilizer to immobilize lead.
It isn’t recommended to grow edibles in the ground with high lead concentration. Instead, lay heavy-duty fabric over the ground, construct raised beds at least 18 inches tall, and add fresh, uncontaminated soil. If you are NOT growing edibles, raised beds aren’t necessary. However, to protect playing kids, always lay landscape fabric and top it with mulch and have children wash their hands immediately after playing around the area.
Recommendations for Urban Gardeners:
- Have your soil tested for lead!
- Plant your garden away from where lead dust may accumulate (i.e. roads, industrial buildings)
- Test new top soil before using it and annually retest the garden soil to monitor for re-contamination
- Herbs, leafy greens and root crops collect more lead in the edible parts than fruiting crops do, so avoid growing these type of plants in contaminated soil
- Cover bare areas of soil with mulch or grass to prevent contaminated lead dust from moving
For more information about testing lead levels and gardening in urban areas, the EPA website contains a wealth of information for regulations and course of action regarding lead.
Approved laboratories in Illinois
- Stat Analysis Corporation
2242 West Harrison Street
Chicago, IL 60612
- EMSL Analytical, Inc
2225 West Hubbard St
Chicago, IL 60612
(800)220-3675 x 2
- RCM Laboratories
5400 East Avenue
Countryside, IL 60525