PFAS Risk Assessment: The Key Components, Challenges, and Use Cases
by: Robert LeeAddressing PFAS contamination is a complex, rapidly evolving challenge in environmental due diligence, investigation and remediation. Due to their persistence and mobility, PFAS can migrate through multiple environmental pathways, affect media and receptors, and prompt a wide range of regulatory responses.
As federal and state agencies continue to update screening levels, toxicity values, and cleanup standards, organizations need a reliable method for assessing site-specific PFAS risk. A structured risk assessment links environmental data to regulatory benchmarks, helping teams evaluate protectiveness and make informed decisions about remediation, site use and long-term management.
To safeguard human health and the environment, PFAS risk assessments provide the necessary foundation for confident, defensible action.
Key takeaways
- A PFAS risk assessment requires a known contaminant of concern, a complete exposure pathway, and a human or ecological receptor to evaluate risk and make informed decisions.
- The process links site conditions to federal and state criteria to support compliance planning.
- Regular updates help projects stay aligned with changing guidance and avoid disruption.
Core components of a PFAS risk assessment
PFAS risk assessments help teams build more accurate site conceptual models, evaluate complete exposure pathways and potential receptors, and anticipate regulatory expectations. These components work together to characterize contamination, evaluate exposure, and quantify risk in a defensible way.
Identifying PFAS sources and release pathways
A clear understanding of where PFAS originate and how they move through the environment is foundational to an effective site risk assessment. This early step informs sampling design, exposure modeling, and long-term remediation planning.
Common contributors include:
- Industrial manufacturing and processing
- Historical waste disposal practices
- Use of aqueous film-forming foam (AFFF)
- Handling and storage of PFAS-containing products
- Discharges from wastewater treatment plants or industrial outfalls
Key PFAS release pathways:
- Leaching through unsaturated soil into groundwater
- Surface runoff to adjacent water bodies
- Airborne deposition from incineration or manufacturing
- Infiltration via stormwater or spills
- Migration through utility corridors or preferential pathways
By identifying sources and pathways early, project teams can better predict PFAS distribution, assess exposure potential, and align investigations with regulatory and stakeholder expectations.
Sampling strategies and data quality considerations
Effective PFAS sampling considers both source areas and environmental transport mechanisms. The goal is to collect representative data that accurately reflects real-world site conditions and inform reliable risk evaluations.
Key factors in PFAS sampling design include:
- Groundwater flow direction and velocity
- Soil type, permeability, and geochemistry
- Historical site operations and waste management practices
- Surrounding land use and potential offsite contributors
Data quality is equally critical. Well-defined data quality objectives (DQOs) guide decisions around:
- Sample containers and field equipment to prevent cross-contamination
- Use of field blanks and trip blanks to verify sample integrity
- Laboratory selection based on PFAS-specific capabilities
- Detection and reporting limits that meet regulatory or project thresholds
For example, selecting a lab with sufficiently low detection limits is essential to avoid underreporting PFAS concentrations that may drive risk or trigger remediation requirements.
Evaluating exposure pathways and receptors
Exposure pathways describe how PFAS move from a source to a receptor, such as a person, animal, or ecological system. Each complete pathway involves a source, a transport medium, a point of exposure, and a receptor.
Common PFAS exposure pathways include:
- Ingestion of contaminated drinking water (such as private or public wells)
- Incidental ingestion of contaminated soil or dust during outdoor activities or site work
- Dermal contact with impacted soil or water
- Inhalation of airborne particulates or volatilized PFAS
- Direct contact with contaminated surface water during recreation or site work
Identifying which pathways are complete or potentially complete helps risk assessors quantify human health and ecological risks. Evaluating the frequency and duration of exposure supports more accurate risk estimates and informs appropriate mitigation strategies.
Understanding toxicity values and risk benchmarks
Toxicity values indicate the potential effects of PFAS compounds on human health and ecological receptors at various exposure levels. These values are foundational to calculating risk and determining whether site conditions exceed acceptable thresholds.
Key types of PFAS toxicity criteria include:
- Toxicological Reference Values (TRVs): A category of toxicity benchmarks used in risk assessment, including reference doses and cancer slope factors.
- Reference doses (RfDs): EPA-derived estimates of daily oral exposure unlikely to cause adverse effects over a lifetime.
- Health advisories (HAs): Non-regulatory drinking water concentrations where adverse effects are not expected.
- Maximum contaminant levels (MCLs): Enforceable drinking water standards set by federal or state authorities.
- Screening levels and cleanup criteria: Thresholds used to assess soil, groundwater, or sediment and inform site decisions.
Federal and state agencies regularly update these benchmarks in response to evolving toxicological research. Risk assessments must reflect the most current and relevant values to remain scientifically defensible and compliant with regulatory expectations.
Using risk assessment to inform remediation and site decisions
Risk assessments guide strategic decision-making by identifying where action is necessary and calibrating the intensity of that response. Rather than relying on conservative assumptions that can drive up costs or delay progress, teams can use risk-based findings to align remedies with actual exposure potential.
Risk findings help project teams determine whether remediation, containment, engineering controls, or long-term monitoring is the most appropriate approach for a given site. When uncertainty persists, additional modeling or targeted sampling can clarify exposure scenarios and support more informed remediation decisions. This approach supports more predictable budgets, schedules, and permitting outcomes by allowing project teams to anticipate impacts early in the process.
PFAS risk assessment in redevelopment and due diligence
PFAS assessments are critical to property transactions and redevelopment planning. Buyers, sellers, and lenders need to understand whether PFAS introduce environmental liability, affect site value, or impact redevelopment feasibility.
During due diligence, risk assessments quantify how PFAS may influence design, permitting, and construction. For example, PFAS in soil or groundwater may require special handling during soil export or treatment during dewatering activities. Identifying these issues early supports informed negotiations, clear responsibility allocation, and smoother project execution after closing.
Regulatory considerations for PFAS risk assessment
PFAS regulatory standards continue to evolve, with both federal and state agencies updating toxicity values, screening levels, and cleanup criteria based on emerging science.
These updates can lead to variation in acceptable PFAS concentrations depending on location and timing. As guidance shifts, concentrations previously deemed acceptable may require re-evaluation. Risk assessments that fail to reflect evolving regulations may lead to permitting delays or project complications.
Maintaining awareness of current and anticipated regulatory updates helps teams align with compliance expectations and reduce the likelihood of costly redesigns or additional fieldwork.
How Langan supports PFAS risk assessment and management
Langan brings together technical investigation and advanced site analysis to help organizations understand how PFAS behave at their properties. The team develops a site-specific conceptual model that reflects real environmental conditions and current regulatory expectations. This provides a grounded basis for evaluating potential migration, exposure, and compliance needs.
The firm’s experience spans redevelopment projects, utility corridors, industrial facilities, and large corporate campuses. Langan collaborates with clients to align risk management with project objectives so design, permitting, and remediation planning proceed with accuracy and predictable outcomes.
Contact Langan to explore PFAS risk assessment solutions that advance project goals and regulatory readiness.
PFAS risk assessment FAQs
What is a PFAS risk assessment?
A PFAS risk assessment identifies the presence of PFAS, evaluates how people or ecological receptors may be exposed, and determines whether those exposures exceed federal or state risk thresholds.
How do you assess PFAS risk at a contaminated site?
The process includes identifying potential sources, designing a sampling strategy, evaluating exposure pathways, applying appropriate toxicity values, and calculating risk estimates. When uncertainty exists, additional testing or modeling may be used to refine results.
Which exposure pathways are evaluated in a PFAS risk assessment?
Common pathways include ingestion of contaminated drinking water, incidental soil ingestion, inhalation of airborne particulates, and ecological contact with impacted surface water or sediment. The relevance of each pathway depends on site-specific conditions.
How does PFAS risk assessment affect redevelopment or due diligence decisions?
Risk assessments help quantify potential liability, inform buyer-seller negotiations, and clarify what mitigation or engineering controls may be necessary. This supports realistic project planning and ensures environmental responsibilities are understood early in the process.