Polycyclic Aromatic Hydrocarbon (PAH) Contamination in Urban Soils: Testing and Management Melissa Chilinski, Paul Grossl, and Melanie Stock Polycyclic aromatic hydrocarbons (PAHs) are a large class of chemicals and common environmental pollutants. Understanding which PAHs and soil test levels may impact human health is an important aspect of gardening and micro-farming, particularly in urban environments that are at increased risk of soil contamination. Land use histories, such as sites associated with vehicle and industrial emissions, burning, and dumping, can elevate concentrations of PAHs in soils. This fact sheet provides instructions on assessing your site for PAHs that may present health risks to humans, testing the soil, and first steps for interpretation and management.
Common Contamination Sources
refuse from previous dumping, i.e., spent coal and oil, chunks of asphalt, charred wood, or other refuse left in the soil, and particles in fumes emitted during repaving, especially when using coal tar-based pavement sealers (U.S. Geological Survey [USGS], 2019). Land-use histories from previous owners are often unknown. The United States Environmental Protection Agency’s (US EPA) Superfund: National Priorities List (NPL) map is a helpful resource for determining areas with greater risk of contamination. Testing for PAHs (Figure 1) is highly recommended if any potential risk factors from Table 1 are identified on the property, the history is unknown, and/or food crops will be grown.
Polycyclic aromatic hydrocarbons (PAHs) can occur naturally from volcanic eruptions and wildfires, but in urban or industrial areas, soil contamination is most often caused by human activity. Wind can deposit PAHs onto the soil where PAHs can persist on the surface for 1 to 2 years until they degrade fully (Gan et al., 2009; CRC CARE, 2017). The most common and widespread, continuous (i.e., repeated) sources of PAHs are industrial and vehicle emissions (Table 1). Particles in exhaust and fumes created during engine combustion can enter the air and can be deposited onto the soil. Areas within 500 feet of a busy road, highway, train track, or industry (e.g., incinerators, refineries, power plants) can be at increased risk for elevated contamination levels. Other, smaller-scale continuous sources include grilling and burning wood or garbage. One-time events or noncontinuous point sources can also cause soil contamination (Table 1). Examples include
Figure 1. Soil sample collected in a laboratory-supplied vial for polycyclic aromatic hydrocarbon (PAH) testing that will be stored in a cooler for delivery to the laboratory.
Utah State University Extension | April 2023 | Peer-Reviewed Fact Sheet | Soil/01
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