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Project: Sediment Contaminant Effects on Humans and Wildlife

Background and Objectives

Researchers at SCCWRP are developing assessment frameworks and tools to investigate sediment contaminant effects in California's coastal estuaries and bays. This work applies to aquatic organisms in direct contact with contaminated sediments, as well as humans and wildlife that consume food containing bioaccumulated contaminants. The State of California will use this information to assess sediment quality in bays and estuaries as part of their Sediment Quality Objectives (SQOs).

Several influential factors add complexity to analyzing sediment contamination effects in humans and wildlife. These factors include: the portion of sediment contaminants biologically available to prey species, food web complexity, receptor organism movements, food consumption rate, and species-specific chemical sensitivities. The State of California requires a framework that incorporates these factors and provides a consistent scientific foundation for sediment quality assessment.

The objectives of this research are: 1) to develop assessment frameworks for evaluating sediment contamination effects on humans and wildlife, and 2) to develop tools for applying the framework to California bays and estuaries.


This study was initiated in 2005 with anticipated completion in 2015.


With input from the project’s Scientific Steering Committee, Advisory Committee, and State Water Board staff, scientists first developed a framework to assess human health impacts caused by sediment contamination. It focuses on PCBs and chlorinated pesticides transferring from sediments into fish and from fish into wildlife and humans through the food chain. Scientists reviewed other local and national programs for evaluating sediment contamination effects on humans and wildlife, ultimately adapting San Francisco Bay bioaccumulation models to develop a suitable assessment framework for all of California's bays and estuaries. Factors considered in the framework's conceptual approach included:

• Assessing human health risk based on tissue and sediment contamination at a site,
• Adding additional contaminants to the currently proposed framework,
• Using existing data or new data obtained at reasonable cost to make assessments,
• Reflecting current scientific knowledge in assessment methods,
• Maintaining transparent data integration and evaluation processes, and
• Conducting comparable assessments across separate water bodies.
To refine and validate the proposed framework, water body and chemistry data are being evaluated for multiple water bodies across California.


The proposed assessment framework uses tiers based on two indicators: consumption risk and linkage to sediment contamination. For the consumption risk, the framework will determine if pollutant concentrations in seafood pose unacceptable health risks to human consumers. For the sediment linkage, the framework will determine if sediment contamination at a site is a significant contributor to seafood contamination.

The assessment framework includes three tiers. Tier I is a rapid screening assessment to determine if sediments at a site pose a potential human health hazard justifying further evaluation. Contaminants that pose a potential hazard based on Tier I will proceed to a Tier II evaluation. Tier II is a complete site assessment that evaluates tissue and sediment data to determine human health risk using available site-specific information. Tier II results in a site categorization that integrates information from consumption risk and sediment linkage. Tier III incorporates additional site specific data or more complex data analyses to determine the contribution of a site's sediment versus other contamination sources. A draft Decision Support Tool (DST) has been developed to facilitate the Tier II data analysis.

Tiered assessment framework

This preliminary framework will be refined with additional Advisory Committee input and information obtained from the California statewide study. Several technical documents are available to provide more information regarding the framework development and to explain the tiered approach. These documents can be found on the framework support documents page.


State Water Resources Control Board
San Francisco Estuary Institute


Assessment of sediment quality impacts on human health - September 2013 presentation to the Advisory Committee


A Tiered Assessment Framework to Evaluate Human Health Risk of Contaminated Sediment
For more information on Sediment Contaminant Effects on Humans and Wildlife, contact Steve Bay at (714) 755-3204.
This page was last updated on: 7/30/2015