Updated Arsenic Toxicity Values Have Implications for Soil Cleanup in Florida
In 2024, SCS Engineers published an article about the ongoing update to the U.S. EPA’s Integrated Risk Information System (IRIS) Program toxicological review of inorganic arsenic. The update included proposed changes to the oral cancer slope factor (CSFo) and the oral reference dose (RfDo). In January 2025, the final IRIS Toxicological Review of Inorganic Arsenic was released.
The final review proposes a combined oral cancer slope factor (CSFo) of 32 (mg/kg·day)⁻¹, which accounts for both lung and bladder cancer risks. This replaces the previous CSFo of 1.5 (mg/kg·day)⁻¹, a significant increase in assumed potency compared to earlier assessments.
The updated, more conservative CSFo for arsenic will substantially lower allowable soil concentrations. Specifically, the residential soil cleanup target level (SCTL) decreases from 2.1 mg/kg to 0.1 mg/kg, and the commercial/industrial SCTL decreases from 12 mg/kg to 0.6 mg/kg, assuming all other input parameters remain the same. Note that there will be no direct change to the arsenic groundwater cleanup target level (GCTL), as Florida uses the drinking water standard under Rule 62-550 FAC as the GCTL.
Most residential sites already require background studies because it is often infeasible to meet the current residential SCTL of 2.1 mg/kg. Moving forward, background studies will also be important for commercial/industrial sites, which could affect project planning and site management.
Even though the updated CSFO has not yet been incorporated into the current Florida soil standards, staying aware of state and county regulatory changes is critical for anyone involved in property transactions. For buyers, this means that potential environmental liabilities could increase if cleanup standards change. For sellers, understanding potential changes in SCTLs can help them proactively address environmental issues and avoid delays in property sales or redevelopment. Completing remediation under the current rules can reassure buyers and streamline the transaction.
Changes in SCTLs don’t just affect compliance; they also influence risk assessments, remediation strategies, and resource allocation. For clients with pending transactions or redevelopment plans, this knowledge helps you make decisions proactively, saving time, money, and effort and reducing regulatory uncertainty. By keeping track of regulatory updates and understanding how SCTLs might change, we as consultants can guide our clients, both buyers and sellers, to protect themselves, plan, and ensure smoother property transactions.
The following links will direct you to the proposed toxicological review and additional resources:
Anabel Rodriguez-Garcia is an environmental scientist with a decade of experience in the sustainable management of soil, including heavy metal contamination, and in organic fertilizers, as well as in the physical, chemical, and biological characterization of soils, including sample collection and documentation. She serves SCS clients as a senior project professional and is particularly valuable for environmental site assessments. She has worked on projects for government agencies, including the Florida Department of Transportation and Miami-Dade County Regulatory and Economic Resources; public utilities; and private-sector clients.
Lisa L. Smith has three decades of experience across a variety of roles in environmental science. Lisa serves SCS clients as a senior technical advisor and expert in risk-based corrective action (RBCA). She has worked as an environmental regulator at the Miami-Dade County Department of Environmental Resources Management (DERM), a risk assessor at a national environmental consulting firm, and a research chemist at the University of Florida.
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