While the problem is pervasive in urban areas, suburban homes that were built near apple orchards are also at risk, because lead arsenate was once used regularly as a pesticide.
Soil around homes can contain everything from arsenic to motor oil, but lead is one of the most common contaminants, and to children, one of the most dangerous. Even tiny amounts of lead in the blood can cause learning disabilities and behavioral problems. In adults, lead can contribute to high blood pressure, reproductive problems, and memory loss.
Backyard vegetable gardens are making a comeback as gas and food prices soar, and as more people are becoming aware of the health benefits of eating organic. Few things can compare to the pleasure of picking guaranteed fresh, in season ingredients for your dinner right out of your backyard.
Lead contamination, however, is no trivial matter.
Chronic high levels of lead in your blood is associated with decreased intelligence and neurological impairment in children -- including the potential of permanent brain damage if they’re exposed to high levels at an early age -- and hypertension, reproductive problems and memory loss in adults.
Making Sure Your Garden Vegetables are Safe to Eat
If you live in an urban area, it’s probably best to assume that your soil is contaminated with lead to some extent or another. According to the article above, about 10 percent of soil samples test positive for unsafe levels of lead.
The U.S. Environmental Protection Agency (EPA) considers garden soil contaminated if it contains more than 400 parts per million (ppm) of lead. Some urban areas test as high as 1,000 ppm on average.
Unfortunately, lead can persist in soil for hundreds of years, so waiting for it to clear up won’t do you much good. Instead, if you’re planting a garden, it’s most wise to take precautions to prevent your vegetables from absorbing the heavy metal. Plant foods do tend to contain some level of lead naturally, as plants absorb soil lead very efficiently, and also retain the lead they have absorbed.
Approximately 7 percent of the lead in the soil will be taken up by the plants growing in it. Excessive lead levels will kill the plant entirely.
Additional lead fallout from the air tends to remain in the top inch of the soil, making shallow-rooted plants such as root vegetables, potatoes, and leafy vegetables particularly vulnerable to higher contamination levels.
Good varieties to grow due to their reduced lead uptake include:
Your best bet is to build or buy a raised garden container, and fill it with organic topsoil. That way you know what your vegetables are growing in. Adding mulch on top of other areas of your yard, such as your flowerbeds, will keep any contamination there from spreading to your vegetable garden.
This HGTV.com article shows you how to build a stylish and functional raised garden from scratch.
How to Test Your Soil for Lead
There are a couple of options available to test your soil for lead contamination, if you do decide you don't want a raised garden. You can pick up home test kits at reasonable prices, however, as with most home tests, the various solutions and swabs leave a lot of room for non-professional human error.
The soil should be sampled by taking 6 to 12 subsamples from the area in question. For garden soils, take your samples 3 to 4 inches from the surface. Mix the subsamples thoroughly in a plastic pail, then remove about one cup for testing. Make sure you use a clean container.
If you suspect high levels of lead in your soil, it may be more desirable to send your soil sample out to a professional lab.
IATL offers several different types of testing, worldwide, including lead tests. Several laboratories in Minnesota also have the facilities to analyze soils for lead content, including the University of Minnesota Soil Testing Laboratory.
The Ecology Center website offers a directory of various California labs that provide lead testing, or you can look in the phone directory under “Laboratories” to obtain information about testing laboratories in your local area.
What You Need to Know About Lead Poisoning
There are many sources of lead around your house, in your water supply, and in consumer products such as toys, which is why I recommend getting your, and especially your child’s blood lead levels tested regularly.
According to the 2005 updated guidelines from the CDC, children’s blood levels should be no higher than 6 µg/dl to avoid subtle neurological symptoms. Symptoms usually become evident above 10 µg/dl. Blood lead levels of 380 ug/dL can cause convulsions, coma, and even death.
Unfortunately, studies have shown that fluoridated water supplies can increase children's absorption of lead, and, when lead is introduced into your body in sufficient quantities it displaces zinc, which also disrupts brain cell growth. Therefore, installing a high quality water filter in your home is always a prudent idea, especially if you have children.
Adults should not have levels over 25 µg/dl to avoid hypertensive symptoms.
Pregnant women, however, must be especially cautious, as both spontaneous abortion and potential damage to your fetus can occur if your blood level is just 10 µg/dl or more.
A chelating process called DMSA can help extract not only lead, but also mercury, cadmium, arsenic, antimony, and many other heavy metals from your body. Heavy metals suppress the effect of a number of enzymes, some of which can be easily tested to see if you may be suffering from an excess of these heavy metals.
For more in-depth information about this process, I recommend reading my Mercury Detox Autism Protocol.
Please keep in mind that the “maximum levels” mentioned above are no guarantee of safety – no one definitive threshold has been established, and NO particular cutoff level can be defended based on existing data as being “totally safe.”
For more information about the warning signs of lead poisoning, and your most common sources of lead, please see my previous article, How Do You Know if You Have Lead Poisoning?