from http://www.nrtco.net/~lead/soil.htm

Lead in Soil

(From: Lead’s Urban Legacy)
 

Howard Mielke is a geoscientist who believes that soil can be one of the greatest sources of exposure for children. In his article "Lead in the Inner Cities" (1) he illustrates his argument with a number of interesting isopleths, atype of two point graph which shows an almost hand in hand relationship between soil lead levels and blood lead levels in children. In areas where graphed soil lead levels swoop upwards, so do blood lead levels. Soil lead levels increased during the 1970’s and 80’s when emissions from cars using leaded gasoline reached their peak.  Lead particles were released in automobile exhaust.  These particles traveled through air until  they were interrupted  by hitting a barrier, usually the side of a house or apartment building. And these particles have remained on buildings until rain has washed them down into soil – where they remain to this day.
Lead doesn’t break down in soil; it remains for long periods, clinging to clays and organic matter. Soil-lead concentrations in large cities are 10 to 100 times greater than samples taken from smaller cities. Soil lead concentrations diminish the greater the distance from a city center (where traffic was lighter). Lead levels in inner cities can be astonishingly high. Tests done by Mielke found that the quantity of lead in a New Orleans inner city soils contained about the same amount as that found in a lead-smelter community such as Trail, British Columbia.
Studies done in the mid 1970’s in Canada found background lead  concentrations in Toronto downtown areas as high as 482 micrograms per gram of soil. More recent surveys show that urban soils now on average, contain 122 parts per million (ppm) of lead.
How to Protect Yourself
Protect your children by washing their hands before meals, and at regular intervals, especially after playing outside.
Remove outside shoes when entering a house.
Plant shrubs and plants near "drip lines," the area where water runs off roofs onto soil and near areas where old chipped and flaking paint may have fallen into soil.
Old apple orchards can contain soil contaminated by the use of lead arsenate that was used as an insecticide. This practice which is now prohibited left soils in many former agricultural areas with high heavy-metal levels.
If your home has been built over what was once a commercial orchard,
there may be potential for heavy metals on site.
Build containers or raised beds filled with "new" soil where you
intend to grow food crops. If the soil below has been tested and
found contaminated.  Don't put in permanent edible crops that might
grow roots down into the contaminated soil. A barrier such as a
plastic layer can prevent root growth, but it's necessary to provide
for bed drainage if you use any impermeable barrier.
Add organic soil amendments.
Wash soil particles off all food thoroughly before eating. Root crops and tuberous crops such as potatoes may have the highest lead or arsenic concentrations. Wash and peel all crops before cooking.
Grow ornamentals instead of food in areas that might carry heavy metals, such as the landscape beds around my 1904 home.
Keep children from playing on bare soil. Plant turf grass or ground covers. Fence off seriously contaminated areas.
When working in the garden, don't eat, drink or smoke.
Wear a dust mask if the area is extremely dusty. Keep soil moist to avoid inhaling dust.
Wash off tools and store them outside.
Remove shoes before entering the house.
Store garden clothing outside, and wash it separately from other
household laundry.
For more information, read "Gardening on Lead and Arsenic
Contaminated Soils," by Frank Peryea, EB 1884, Washington State
University, 1999. It's available online from
cru.cahe.wsu.edu/CEPublications/eb1884/eb1884.pdf.
(Gardening tips adapted from: The Practical Gardener / Mary Robson Sunday, April 28, 2002 – The Seattle Times).

Have your soil tested for lead. A list of accredited laboratories can be obtained from:
Standards Council of Canada
45 O'Connor Street, Suite 1200
Ottawa, ON K1P 6N7
Tel: (613) 238-3222

Canadian Association for Environmental Analytical Laboratories
265 Carling Avenue, Suite 300
Ottawa, ON K1S 2E1
Tel: (613) 233-5300
Either your provincial Department or Ministry of Agriculture or the Ministry of the Environment may provide soil testing for a small fee. You can contact us: Lead Environmental Awareness and Detection lead@nrtco.net. We can help you.
Endnotes
(1)Mielke HW. Lead in the Inner Cities. American Scientist, 87; Jan-Feb 1999; p. 62-73.
(2)Fleming S and Ursitti F. Scientific Criteria Document for Multimedia Environmental Standards Development – Lead. Standards Development Branch, ( MOEE) Ontario Ministry of the Environment and Energy. Toronto: Queen’s Printer for Ontario, 1994; p.90.

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