Central Columbia Plateau - Yakima River Basin NAWQA Study -- Publications
USGS Fact Sheet FS-170-96
by S.J. Gruber and M.D. Munn
Organochlorine Pesticides and PCBs in Aquatic Ecosystems of the Central Columbia Plateau
Organochlorine pesticides and PCBs were detected in streambed sediment and
fish from streams in the Central Columbia Plateau of central Washington
and northern Idaho, one of 60 study units in the U.S. Geological Survey's
National Water Quality Assessment (NAWQA) Program. Concentrations of
some compounds were at levels that may pose a threat to fish and wildlife
of the region.
What Are Organochlorine Pesticides and PCBs?
Organochlorine pesticides are man-made organic chemicals that have been used
to control everything from fungus to grasshoppers. DDT was the first that was
used on a large scale in the U.S.; it was heavily applied in agricultural
regions. Most organochlorine pesticides are no longer sold for use in the U.S.
PCBs are not pesticides but do have many of the same properties. They are
by-products and constituents of a variety of industrial products, such as
Where Do We Find Organochlorines?
Many organochlorine pesticides are extremely persistent in the environment.
Although most are no longer used in the U.S., many are manufactured here for
use elsewhere, especially in developing countries. Although concentrations of
these compounds are usually greatest where they are used the most (such as in
agricultural areas), low levels of some compounds, such as DDT, have been
found all over the world.
How Do Organochlorines Affect Wildlife?
Scientists have known since the early 1970s that DDT causes eggshell thinning
in the bald eagle and other birds. Since that time, many organochlorine
pesticides and PCBs have been linked to hormone disruption and reproductive
problems in aquatic invertebrates, fish, birds, and mammals (see review by
Colborn and others, 1993). These effects combined with a slow rate of breakdown
make many organochlorines a long-term environmental concern.
Organochlorines in the Food Chain
(GIF, 21970 bytes)
- Organochlorine pesticides and PCBs persist in aquatic ecosystems of the study unit, even though most are no longer used.
- p,p'-DDE, a common breakdown product of DDT, was the most frequently
- Land use practices, such as irrigated farming, dryland farming and
urbanization, greatly influence the distribution of organochlorines.
- Erosion transports organochlorines to aquatic ecosystems.
- Wildlife in the area may be at risk because concentrations of several
compounds in both streambed sediment and fish exceeded guidelines for the
protection of wildlife.
The Study Unit
The Central Columbia Plateau Study Unit covers approximately 13,000 mi2 in
east-central Washington and northwestern Idaho. It is bounded by the Palouse
Mountains in the east, the Columbia River to the north and west, and the Snake
River to the south.
Samples of streambed sediment and fish tissue were analyzed for 33
organochlorine pesticides and total PCBs at 23 sites: 16 for sediment and fish
and seven for sediment only. Five to 10 samples of streambed sediment were
collected at each site and composited for analysis. We collected six species
of fish: carp, bridgelip sucker, largescale sucker, rainbow trout, largemouth
bass, and sculpin. Bottom-feeding fish (carp and suckers) were taken at most
sites. Composite samples of four to eight whole fish of the same species were
Land Use in the Quincy-Pasco Basins
The Quincy-Pasco Basins contain one of the most productive agricultural
regions in the country. Irrigated farming is the dominant land use,
made possible by a large system of canals and wasteways.
Several pesticides were detected in both streambed sediment and fish.
The sites with the largest number of pesticides and the highest concentrations were found in the irrigated farming areas.
Land Use in the Palouse River Basin
The major land use in the Palouse River Basin is dryland farming, but
urban areas such as Pullman, Washington, and Moscow, Idaho, impact
surface waters through urban runoff and sewage treatment plant effluent.
About the same number of compounds were detected in the Palouse River Basin as
in the Quincy-Pasco area. However, for some compounds, the effects of
historical land use practices were apparent. For instance, PCBs were
found only in fish and sediment at the urban sites near the towns of Pullman
and Moscow. Hexachlorobenzene, which was used primarily with wheat seed,
was found much more frequently in dryland sites than in irrigated sites.
DDE - The Most Common Compound Detected
of land use and p,p'-DDE concentrations (GIF, 54488 bytes)
p,p'-DDE, the most persistent breakdown product of DDT, was
found throughout the study unit except for the forested site and comprised an
average of 80 percent of the total DDT in sediment and 91 percent in fish.
In streambed sediment, p,p'-DDE concentrations at 22 percent of
the sites exceeded guidelines established for the protection of aquatic life.
At these concentrations, adverse effects on aquatic life are expected to occur
frequently. The concentration was highest at Lind Coulee, which may act
as a source of DDE to Potholes Reservoir.
In fish, p,p'-DDE concentrations exceeded guidelines for the
protection of fish-eating wildlife at two sites: Lind Coulee and Royal Lake,
which is in the Columbia National Wildlife Refuge. In fish, p,p'-DDE
concentrations exceeded guidelines for the protection of fish-eating wildlife
at two sites: Lind Coulee and Royal Lake, which is in the
Columbia National Wildlife Refuge.
Other Organochlorines Detected (GIF,
Guidelines for Organochlorines (GIF, 10118 bytes)
Effects of Gravity Irrigation on Erosion
(GIF, 11594 bytes)
Effects of Organochlorines
Concentrations of several organochlorines exceeded guidelines for the
protection of wildlife. Wildlife in two areas may be particularly vulnerable:
Royal Lake in the Columbia National Wildlife Refuge, home to thousands of
migratory and resident birds; and Lind Coulee, which drains into Potholes
Reservoir, a major recreational fishing area. p,p'-DDE concentrations
in fish at these sites are among the highest in the country (Schmitt and
others, 1990). Assessing the impacts of organochlorines on fish and wildlife
is becoming increasingly important because of recent evidence suggesting that
some organochlorines, even at low concentrations, disrupt the endocrine system,
which is responsible for proper hormone balance. Further studies are needed to
assess the impacts of organochlorines on animals, especially in agricultural
areas where these compounds are most prevalent.
Keeping Organochlorines out of Streams
With the exception of a few compounds still in use, such as DCPA (Dacthal) and
Lindane, most organochlorines found in the study area were applied to
agricultural fields in the past. Agricultural soils thus act as reservoirs of
these contaminants. The strong correlations between the percentage of irrigated
land with gravity irrigation, the amount of sediment in streams, and the
concentration of DDT in streambed sediment and fish suggest that the most
effective way to prevent the entry of organochlorine pesticides into streams
is to control erosion of agricultural soils.
USGS Fact Sheet 170-96
By S.J. Gruber and M.D. Munn
Colborn, T., VomSaal, F.S., and Soto, A.M., 1993, Developmental effects of
endocrine-disrupting chemicals in wildlife and humans: Environmental Health
Perspectives, v. 101; p. 378-384.
Environment Canada, 1995, Interim Sediment Quality Guidelines: Ecosystem
Conservation Directorate Evaluation and Interpretation Branch Ottawa, Ontario,
National Academy of Sciences and National Academy of Engineering (NAS/NAE),
1973 , Water quality criteria, 1972: U.S. Environmental Protection
Agency, EPA R3-73-033, 594 p.
Schmitt, C.J., Zajicek, J.L., and Peterman, P.H., 1990, National Contaminant
Biomonitoring Program -residues of organochlorine chemicals in U.S. freshwater
fish, 1976-1984: Archives of Environmental Contamination and Toxicology,
v. 19, p. 748-781.
For further information, contact:
1201 Pacific Ave., Suite 600
Tacoma, WA 98402
Phone:(253) 593-6530 ext 2687; -6514 fax
Gruber, S.J., and Munn, M.D., 1996, Organochlorine pesticides and PCBs in aquatic ecosystems of the Central Columbia Plateau: U.S. Geological Survey Fact Sheet FS-170-96, on line at <URL: http://wa.water.usgs.gov/ccyk/fs-170-96.html>, accessed October 17, 1997.
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