Certain chemical elements occur naturally in soil but may be toxic in high concentrations. Soil testing determines the level of toxic contaminants in soil. “There is no single standard that defines acceptable levels of contaminants in soil,” according to the Cornell University Waste Management Institute, but “soil screening guidance provided by the U.S. Environmental Protection Agency may be a helpful place to start.”
The EPA has established a framework for risk-based soil testing levels for the protection of human health. It is a tool to standardize and accelerate the evaluation and cleanup of sites of future residential development. “The SSG (Soil Screening Guidance) focuses on a simple methodology for developing site-specific screening levels,” according to the EPA’s paper on soil screening guidance.
Soil Screening Levels
Soil screening levels (SSL) are not national standards for cleaning up soil contamination. The EPA testing identifies and defines soils that do not require further federal testing or cleanup response. Soil that is contaminated above acceptable levels is marked for further study or investigation, but not necessarily cleanup.
Pathways of Exposure
EPA soil testing screens also address the issue of pathways of exposure in residential settings. Exposure to toxic chemicals can include inhalation, ingestion through food crops, drinking contaminated ground water, skin absorption and migration into basements. Additional pathways of toxic chemical exposure are eating fish from polluted waters, heavy truck traffic on paved roads and raising livestock.
Soil can be tested for toxic levels of arsenic, cadmium, chromium, copper, lead, nickel and zinc. Low-level lead contamination is common in urban settings because of the widespread use of lead-based paint and industrial waste processes. Wind carries contaminants that then settle into residential soil. High blood levels of lead are often found in children who live in homes built before the 1940s, according to a report on lead contamination by the Agroecology and Sustainable Agriculture Program.
Risk Sites and Solutions
Soil testing for contaminants is indicated for areas of high traffic, industrial or commercial businesses, exposure to treated wood, petroleum spills, car or machine repair shops, furniture refinishing, fires, landfills or garbage dumps. Composted soil is able to transmute many toxic contaminants such as wood preservatives and pesticides, according to the EPA report on the environmental benefits of composting.