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Why test for Lead and other heavy metals in soils?
Lead in Soil:
- Lead in residential soil comes from several different sources including: lead-based exterior paint, and auto tailpipe emissions from vehicles burning lead gasoline;
- Industrial emissions area also a source of residential soil contamination in certain areas;
- One estimate is that more than 3 million tons of lead-based paint remain in the 57 million homes built before 1980.
- Does not biodegrade or decay;
- Is not rapidly absorbed by plants;
- Remains in soil at elevated levels;
- Lead is estimated to have a half-time in soil of 1,000 years;
- In soils with pH greater than or equal to 5.0 and with at least 5 percent organic matter, lead is retained in the upper 2 to 5 centimeters of undisturbed soil;
- Urban soils or other soils that have been turned under or disturbed may be contaminated to much greater depths from the surface.
- The EPA estimates that 23 percent, or 18 million, of privately owned homes in the USA built before 1980 have soil-lead levels above 400 parts per million (ppm);
- 3 percent, or 2.5 million homes, have levels exceeding 2,000 ppm;
- and 3 percent, or 2.5 million homes, have levels exceeding 5,000 ppm.
How Lead is Deposited in Soil:
- Lead-based paint contaminates soil as the paint weathers and reaches the soil in the form of dust and chips;
- Renovating, remodeling, and performing regular maintenance will also release lead if proper precautions are not observed;
- As the paint deteriorates, lead paint dust and chips concentrate in the soil;
- Dry scraping, sanding, or blasting of this lead-based paint can increase lead concentrations in a short period of time;
- Concentration of lead in soil is typically highest in the drip zone around the building (approximately 3 feet from the perimeter of the building);
- Any lead dust that becomes airborne would migrate until hitting a barrier such as the side of a building, and then adhere to it;
- Rains can then wash this lead dust into the surrounding soil;
- Lead levels within 25 meters of roadways are typically 30 to 2,000 ppm higher than natural or background levels;
- In certain situations, the level can reach as high as 10,000 ppm;
- Some estimate that 4 to 5 million metric tons of lead emitted from autos prior to 1986 remains in the environment in the form of dust and in the soil;
- Researchers have found that soil-lead concentrations typically are highest in older, inner-city neighborhoods, especially those near high traffic routes;
- Soil-lead concentrations decreased with distance from the city center.
How Lead in Soil Enters the Body:
- Outdoor activities where individuals come in contact with lead contaminated soil is a significant pathway;
- When children play outdoors, lead-contaminated soil and dust can get on hands, clothes, toys, and food;
- Putting these items in the mouth can lead to ingest of lead;
- Children can also breathe lead dust or lead contaminated soil stirred up by the wind or by play activities;
- During dry periods, dust from bare patches of contaminated soil can readily become airborne increasing the likelihood of inhalation;
- Airborne dust and lead contaminated soil can settle on clothes and shoes and then be tracked into the home;
- Pets can also track lead contaminated soil into the home in the coats and paws.
Total Soil Lead Concentration (ppm)
Interpretation 100 or less:
Soil lead is at background levels for urban areas. To minimize exposure, follow good hygiene practices during and after handling this soil.
Soil lead is elevated relative to background levels for urban areas, but still less than the federal limit of 400 ppm. To minimize exposure, follow good hygiene practices during and after handling this soil.
Soil shows significant contamination with lead. Although less than the federal limit of 400 ppm, further testing and evaluation are recommended. To minimize exposure, follow good hygiene practices during and after handling this soil. Children should not play in bare soil.
Soil test is above the federal limit of 400 ppm total lead in soil. Further testing and/or evaluation are strongly recommended. This soil should not be used for vegetable gardening. To minimize exposure, follow good hygiene practices during and after handling this soil. Surface 6-8 inches may require treatment or replacement. Children should not play in bare soil. Children exposed to this soil may require a blood lead test. Contact your pediatrician or the Delaware Division of Public Health for further guidance.
- Inorganic arsenic compounds were often used in agricultural pesticides until the 1940s;
- Arsenic in soil results from pesticide use, mining operations, coal burning power plants, and waste disposal;
- Sites of former tanneries generally have large amounts of arsenic in the soil;
- Arsenic was used a wood preservative (copper chromated arsenic [CCA]) and the treated wood referred to as “pressure-treated”;
- In 2003 CCA was phased-out, but wood treated prior to this date could still be used.
- High does of arsenic can be deadly, especially in a short period of time;
- Long term exposure to low levels of arsenic will not cause immediate effects, but those exposed can suffer cancer of the skin, bladder, liver, lungs, and kidneys;
- Children are at more risk of exposure because they put objects in their mouths, eat soil, and spend more time outdoors.
For information on Cadmium and soil contaminated with Cadmium, click on this link.
For information on Chromium and soil contaminated with Chromium, click on this link.
For information on Nickel and soil contaminated with Nickel, click on this link.
UD Soil Testing Program – Lead Test (And other heavy metals):
Upon request, soil samples can be tested for heavy metals (in addition to the Soil Lead Screening test listed above): Arsenic (As), Cadmium (Cd), Chromium (Cr), and Nickel (Ni). Call 302-831-1392 or email Soiltest@udel.edu for specific questions concerning the costs involved and collection of samples.
Also upon request, soil samples can be tested for Sodium (Na). Contact the program at 302-831-1392 or email: Soiltest@udel.edu for additional information on requests for testing for the presence of heavy metals or sodium.
Soil samples for lead and other heavy metal testing are accepted from any state. (Instructions / Information Form).
More Information on Lead and Arsenic in Soil: