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Basic Information
We are conducting a national freshwater fish contamination survey to estimate the national distribution of selected persistent, bioaccumulative and toxic chemical residues in fish tissue from lakes and reservoirs in the lower 48 states. This four-year study will provide the first national estimates of mean concentrations for 268 chemicals in lake fish, define a national fish contamination baseline to track progress of pollution control activities, and identify areas where contaminant levels are high enough to warrant further investigation.
Print version of this fact sheet (PDF) (2 pp., 53K, About PDF) (October 2005)
- Background
- Why is this study important?
- What are the basic elements of the study design?
- What chemicals did we select for the study?
- Who is participating in the study?
- What are the key study accomplishments and milestones?
- What results are currently available?
- Who do I contact for more information?
Background
Monitoring fish for chemical contamination in lakes and reservoirs is a critical activity for protecting human health because these areas are important for sport fishing and other recreational activities. The 2004 update to our National Listing of Fish Advisories reports that 35% of the nation's lake acres are under fish consumption advisories.
Lakes and reservoirs occur in a variety of landscapes and can receive contaminants from several sources, including direct discharges into the water, air deposition, and agricultural or urban runoff. Lakes are the focus of this study because they are environments where contamination accumulates and is more readily detectable.
We initiated the National Study of Chemical Residues in Lake Fish Tissue (or National Lake Fish Tissue Study) in 1998 as a priority activity under the Agency's Persistent, Bioaccumulative and Toxic (PBT) Chemical Program. It supports the PBT Program by providing data for a large set of chemicals in fish that could affect the health of people and wildlife that eat fish from these environments.
Why is this study important?
The National Lake Fish Tissue Study is important because it:
- Allows us for the first time to develop national estimates of the mean levels of persistent, bioaccumulative and toxic chemicals in lake fish.
- Provides a national baseline for tracking reductions of persistent, bioaccumulative and toxic chemicals in freshwater fish as a result of pollution control activities.
What are the basic elements of the study design?
We worked with partner agencies over a four-year period (2000-2003) to collect fish from 500 lakes and reservoirs selected randomly from the estimated 147,000 target lakes and reservoirs in the lower 48 states. The lakes are divided into six size categories, ranging from 2.5 to over 900,000 surface acres, with a similar number of lakes in each category. Before sampling, field teams verified that each lake is a permanent body of water with a depth of at least one meter.
Sampling teams applied consistent methods nationwide to collect composites of one predator species and one bottom-dwelling species at each lake. Composites consist of 5 adult fish of similar size that are large enough to provide 560 grams (20 ounces) of tissue for analysis of fillets for predators and whole bodies for bottom dwellers. We analyzed each composite for 268 chemicals (including PCB congeners) and added polybrominated diphenyl ether (PBDE) analysis for fourth year fish samples only.
Distribution of Sampling Locations | Print version of map (PDF) (1 page, 18K, About PDF)
What chemicals did we select for the study?
We are analyzing the fish tissue for:
- Two metals (mercury and five forms of arsenic)
- 17 dioxins and furans
- 159 PCB congener measurements
- 46 pesticides
- 40 other semivolatile organics (e.g., phenols)
- 46 PBDE congener measurements (fourth year samples only)
Who is participating in the study?
We formed a national network of study partners to pursue a broad range of activities, from development of the study design to collection of fish for the study. Important contributors include:
- Our Office of Water (Agency lead for the study)
- Our Office of Research and Development
- Our Office of Prevention, Pesticides, and Toxic Substances
- Our regional offices
- State and Tribal Agencies
- National Park Service and Tennessee Valley Authority
What are the key study accomplishments and milestones?
The study consists of four phases:
Planning (1998-1999)
- study design development
- random lake selection
- target chemical selection
Mobilization (1999-2000)
- orientation workshops
- development of partnerships
- production of quality assurance
field sampling plans - lake reconnaissance
Sampling and Tissue Analysis (2000-2005)
- sampling of 500 lakes through 2003
- chemical analysis of 1,003 fish samples through 2005
- chemical analysis of 352 fish samples for PBDES in 2005
- database development
Data Analysis and Reporting (2005-2006)
- statistical analysis of fish tissue data
- production of final report
- data upload into our new STORET database
What results are currently available?
Quality-assured results from all 500 lakes sampled during 2000 through 2003 are now available.