Contamination from trace metals, such as arsenic (As) and lead (Pb) in soils, can lead to potential health risks from inhalation and ingestion of the soil or vegetables grown in the soil. While it is well known that different molecular forms of As and Pb have different toxicological effects, the correlation between elemental species in the soil and the bioaccessibility of the metals from that soil has not been well established. For instance, tetraethyllead was historically added to gasoline, while lead chromate, lead oxide, and lead carbonate were common pigments added to paint. All of these compounds could be present in contaminated soil and each has a different degree of bioaccessibility.

Typical risk assessment models assume that 60 to 100% of contaminant metals in a soil sample are bioaccessible; however, these assumptions can result in incorrect health risk assessments and unnecessarily high remediation costs because it has been demonstrated that actual bioaccessibility can range from 0 to 100%. In vivo animal studies are often used to determine bioaccessibility, which are expensive and time consuming. The demand for reliable and affordable methods to improve the accuracy of risk assessments and assist regulators in making responsible remedial decisions, while still protecting human health, has been growing in recent years. This demand is being met with methods such as EPA Method 1340 “In Vitro Bioaccessibility Assay for Lead in Soil”. This method was validated for Pb-contaminated soil under field conditions and released in February 2017.

The California Department of Toxic Substances Control (DTSC) worked with The Ohio State University to develop an in vitro method for As bioaccessibility. The California Arsenic Bioaccessibility (CAB) Method was validated against the swine method, which is historically the most commonly used animal model for evaluating site-specific arsenic toxicity. The CAB Method has been approved for use in evaluating site-specific relative bioavailability of As in contaminated soils in the State of California as outlined by DTSC’s Human Health Risk Assessment Note 6.

Understanding the details of these methods and the appropriate applicability for each is part of the expert customer service you can expect from Brooks Applied Labs. Please feel free to contact us to discuss how your project might benefit from analyses for bioaccessible metals.