Persistence of the DDT pesticide in the Yakima River basin, Washington

By

Joseph F. Rinella, Pixie A. Hamilton, and Stua rt W . McKenzie Graphic design and layout by Joan M . Rubin

Free on application to the Books and Open-File Reports Section

Federal Center, Box 25425 Denver, CO 80225 and quality of the Nation's water resources and to provide information to assist resource managers and policymakers at Federal, State, Tribal, and local levels in making sound management decisions. To a significant extent, these responsibilities are being carried out in the National Water-Quality Assessment (NAWQA) Program, whose goals include providing a sound understanding of the natural and human factors that affect water quality. The NAWQA Program will include investigations in 60 study areas throughout the Nation that represent a variety of geologic, hydrologic, climatic, and cultural conditions. These studies are building blocks for understanding regional differences in physical, chemical, and biological characteristics of the Nation' s ground water and surface water. An important goal of the program is to ensure that key findings are available to the public so that they can be aware of the quality of the Nation' s water resources. This report is part of a series of nontechnical publications based on results from the NAWQA Program. The purpose of these publications is to describe key findings from the individual investigations and to relate those findings to water-quality issues of regional and national concern. By disseminating this information, the U.S. Geological Survey seeks to increase awareness of water-quality concerns when considering the Nation's environmental issues. Established in 1879, the U.S. Geological Survey (USGS) has provided scientific information on the Nation' s water, energy, and mineral resources for the benefit of Americans. A major part of the mission of the U.S. Geological Survey is to assess the quantity

Director

A sa former governor of an arid state, I have a special appreciation for the value of water resources. Unless we have sufficient supplies of good quality water when and where we need it-and understand how natural and human conditions affect water quality-we cannot wisely manage this vital resource. As part of the National Water-Quality Assessment, the U.S. Geological Survey will continue to work with state and local agencies to assess and protect our Nation's water resources. 1: improve the quality of our water, we need to turn greater attention to the polluting effect of water running off our agricultural fields, city streets, and suburban developments. We need a strong Clean Water Act with standards for non-point-source pollution and incentives that will unleash the creative and technological potential of our firms, farmers, and families to reduce and prevent polluted run-off at the source.

NATIONAL WATER-QUALITY ASSESSMENT STUDY AREAS

A major national concern is the degradation of water quality that results from nonpoint sources of pollution, such as agricultural runoff that contains fertilizers and pesticides. Although crop yields are improved greatly by applications of fertilizers and pesticides, the increased production often comes with a price that is measured in terms of effects on human health, streams, fish , and other wildlife. One of the first studies in the National Water-Quality Assessment Program was done to characterize these effects on streams and fish in the Yakima River Basin.' Soil, water, sediment, and fish were sampled for a variety of chemicals that have been and (or) continue to be used in the basin.

This report focuses on the occurrence of one of these chemicals in the Yakima River Basin-the insecticide DDT. Even though two decades have passed since its production and distribution was banned (1972), DDT and its breakdown products DDE and DDD are still widely dispersed in the environment. Concentrations of DDT, DDE, and DDD remain elevated in agricultural soils,

Where do DDT and its breakdown products DDE and DDD [Total DDT (T-DDI) = DDT + DDE + DDD] occur? In agricultural soils? In stream water? In stream sediment? In fish? In birds and mammals? What are the sources ofT-DDT in the basin? How does T-DDT enter streams? Have concentrations of T-DDT decreased in stream water and fish since the ban on the production and distribution of DDT in 1972? How do concentrations ofT-DDT in fish in the Yakima River Basin compare with concentrations elsewhere in the Nation? Are T-DDT concentrations of concern relative to human health and fish predators in the Yakima River Basin?

stream water, suspended and streambed sediment, and fish in the Yakima River Basin. Elevated concentrations of these compounds are a continued concern of residents, resource managers, and policymakers in the basin. Why? Because its broad toxicity can affect many organisms other than insects for which it was designed, such as fish and birds. Its persistence in the environment can lead to dangerous accumulations and adversely affect the reproductive capabilities of birds and other wildlife. And , its cancer-causing potential can possibly affect human health.

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Survey began the National Water-Quality Assessment (NAWQA) study of the Yakima River Basin in 1986. From 1986 to 1991, hydrologists collected samples of soil, water, sediment, and fish for analyses of pesticides and other water-quality constituents at about 400 sites. Analyses were done for more than 90 different pesticides in water and sediment samples, and about 65 pesticides were detected. Many of these pesticides were detected in the lower Yakima River, which is downstream from intense agricultural activities. This report focuses on the occurrence of one of these pesticides-the insecticide known as DDT.

Samples were collected from the headwaters to near the mouth of the river at Kiona and along the major tributaries and agricultural-return flows. The sampling strategy was designed to reflect different soils, seasonal variations associated with weather (snowmelt and rainfall runoff), variations in agricultural activities and irrigation practices, and locations of municipal and industrial discharges . The diversity of samples permits an analysis of the areal distribution of DDT and its breakdown products [Total DDT (T-DDT) = DDT + DDE + DDD] in soil, water, sediment, and fish; seasonal and longer term changes in T-DDT concentrations; and relations between T-DDT concentrations and land- and water-use patterns. The sampling design provides the foundation for understanding where T-DDT occurs, what the sources of T-DDT are in the basin, and whether concentrations of T-DDT have decreased since the ban on the production and distribution of DDT in 1972.

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t ~ DDT was prevalent ror about three decades after its introduction in the early 1940's. As in most agricultural areas of the world, crop yields in the Yakima River Basin were improved by widespread applications. However, after its adverse effects on birds and other wildlife and its cancer-causing potential became well known, the production and distribution of DDT was banned nationwide by the U.S. Environmental Protection Agency in 1972.

Only days after DDT was banned, another chemical, known as dicofol (trade names such as Kelthane, Acarin, Hilfol, Mitigan, and Cekudifol), was registered with the U.S. Environmental Protection Agency as an agent that would kill mites, particularly on citrus and cotton crops. Dicofol originally contained as much as 15 percent DDT. Since about the mid-1980's, U.S. manufacturers of

TRAITS 0 F

dicofol have pledged to reduce

DDT concentrations to 0.1 percent. Although application of dicofol was approved for hops (new plantings only), mint, and apples in the basin, little of the compound has been used because target pests have become resistant.

Does the banning of DDT 20 years ago and the minimal use of dicofol mean that DDT is no longer a threat in the Yakima River Basin? Probably not because some of the characteristics that made DDT desirable as an insecticide make it a potential hazard in the environment for many decades. The persistence of DDT and its breakdown products assure a longlasting presence in soil, streams, fish, birds, and other animals.

How much is too much for human consumption?

How much is too much for aquatic life and fish predators?

DDT is a general-purpose insecticide.

DDT breaks down to other compounds DDE (in the presence of oxygen) and DDD (in the absence of oxygen).

DDT compounds are chlorinated hydrocarbons (also known as an organochlorines) that consist of carbon, chlorine, and hydrogen .

D D T- DichloroDiphenylTrichloroethane D D E- DichloroDipheny ldichloroEthy lene D D D-DichloroDipheny!Dichloroethane DDT and its breakdown products [Total DDT (T-DDT = DDT + DDE + DDD] can affect the human nervous system, liver, kidneys, and skin. The compounds have been classified as probable human carcinogens (compounds that cause cancer) by the U.S. Environmental Protection Agency.

The U.S. Environmental Protection Agency has not set a standard for the protection of human health against which T-DDT concentrations in water or fish can be compared. This report presents preliminary and theoretical degrees of risk that reflect the lifetime (considered to be 70 years) chance of contracting cancer from consumption ofT-DDT in water or fish . Risk calculations are based on the current (1993) understanding of the cancer-causing potency ofT-DDT (extrapolated from studies by the U.S. Environmental Protection Agency of the effects on laboratory animals) . The calculations include some uncertainty because of limited information on human fish-consumption rates and the toxicity ofT-DDT (see p. 17 through 20 for further explanation of human risk) .

Consumption of water-Daily consumption of 2 quarts of drinking water with aT-DDT concentration of 0.1 microgram per liter' by a 150-pound person over a 70-year lifetime corresponds to an incremental increase in cancer risk of 1 per 1 million people.

Consumption of fish-Weekly consumption of one 5-ounce serving of fish filets with a T-DDT concentration of 0.01 microgram per gram• of fish by a 150-pound person over a 70-year lifetime corresponds to an incremental increase in cancer risk of 1 per 1 million people.

The Food and Drug Administration established an action level of 5 micrograms ofT-DDT per gram of whole fish (wet weight). Action levels are established to regulate levels of contaminants in human food and animal feed sold to the public. Action levels do not apply to consumers of noncommercial, locally caught fish, such as sport fishermen and their families .

The most conspicuous effect ofT-DDT has been on the reproductive capabilities of fish-eating birds, such as the great blue heron and the bald eagle. Studies have shown that elevated concentrations result in thin egg shells that break easily in the nest.

The chronic-toxicity criterion for T-DDT in water for the protection of freshwater aquatic life, established by the U.S. Environmental Protection Agency and adopted by the Washington State Department of Ecology, is 0.001 microgram per liter.

The guideline for the protection of fish predators, established by the National Academy of Sciences, is 1 microgram ofT-DDT per gram of a whole fish (wet weight) . GOOD FOR FRUITS-Bigger apples, juicier fruits that are free of unsightly worms . . . all benefits resulting from

FOR THE HOME- Helps to make healthier, more comfortable homes . . . protects your family from dangerous insect pests. Use powders and sprays as directed . . . then watch the bugs " bite the dust" ! The great expectations held for DDT have been realized . During 1946, exhaustive scientific tests have shown that, when properly used, DDT kills a host of destructive insect pests, and is a benefactor of all humanity .

GOOD FOR ROW CROPS-25

. . . actual DDT tests have shown crop increases like this!

dusts and sprays help truck farmers pass these gains along to you . GOOD FOR STEERS-Beef grows meatier nowadays . . . for it's a scientific fact that-compared to untreated cattle-beef-steers gain up to 50 pounds extra when protected from horn flies and many other pests with DDT insecticides.

FROM "DDT was a miracle: Highly toxic to insects, virtually insoluble in water ... it seemed to be the universal solution to insect problems."

DDT was the first of a family of synthetic chemicals that revolutionized man's war against insects. It was first produced in 1874 by a German chemist, Othmar Zeidler. Its importance as an insecticide was not • recognized until the work of a Swiss chemist, Paul Muller, in 1939. In 1941, the

used DDT successfully to control the Colorado potato beetle on farms. In 1948, Muller received the Nobel Prize for his work.

DDT seemed to be a miracle insecticide. It was used all over the world to improve crop yields by controlling many pests. From 1940 to 1970, more than 4 billion pounds were used, with 80 percent used in agriculture. Production reached its maximum in the United States in 1961 when 160 million pounds were manufactured; this accounted for nearly one-fourth of the Nation's insecticide use. DDT also was an effective control for insects that carried diseases, such as malaria and yellow fever. It was used during World War II by Allied Forces to control mosquitoes and as a personal insecticide in clothes to control lice. In the 1950's and 1960's, municipal foggers traveled the roads and sprayed DDT into the air to eliminate mosquitoes; gasoline-powered lawn mowers were adapted to drip DDT into the hot exhaust system to assure temporary relief from mosquitoes in the homeowner's yard .

The DDT miracle, however, was short lived. Its broad toxicity affected many organisms other than insects for which it was designed, such as fish and birds. Its persistence led to dangerous accumula-1960's, the "food-chain ' DDT and its breakdown from low to high in the tract public attention. The were on the reproductive peregrine falcon, for inextensive parts of its These environmental health risks associated in Silent Spring by the Rachel Carson. The book citizens all over the counwork for the decision by Protection Agency to ban bution of DDT a decade

MIRACLE TO MENACE

, tions in animals. By the effect" (accumulation of products in organisms food chain) began to atmost conspicuous effects capabilities of birds. The stance, disappeared from North American range. problems and potential with DDT were described distinguished biologist sparked interest among try and laid the groundthe U.S. Environmental the production and distrilater (1972) .

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1988 through December 1989 Concentrations of T-DDT in the Yakima River have decreased since the ban on DDT in 1972. Concentrations in the main stem at Kiona decreased from about 0.06 microgram per liter in 1969 to generally less than 0.01 microgram per liter in 1990 (see graph). However, the 1990 level is still as much as 10 times higher than the chronic-toxicity criterion for the protection of freshwater aquatic life established by the U.S. Environmental Protection Agency. The long-term decrease in concentrations of T-DDT in stream water results, in part, from decreased concentrations of T-DDT in agricultural soils. In addition, the decrease in concentrations ofT-DDT in stream water probably is a consequence of reduced soil erosion from agricultural fields and less suspended sediment. Over the past 20-30 years, erosion of soils in the Yakima River Basin has been reduced because (1) irrigation practices have changed (from less use of ridge and furrow irrigation to more use of sprinkler and drip irrigation), (2) cropping patterns have changed (fewer acres are used to grow row crops, such as sugar beets,

potatoes, com, and beans, and more acres are used to grow permanent crops, such as apples, pears, and grapes), and (3) cover crops of grasses and grains have been planted in orchards and vineyards. Data forT-DDT in soils or suspended sediment in the early 1970's are not available to confirm the relations. Long-term trends in T-DDT concentrations at other sites in the Yakima River and in agricultural-return flows are unknown because historical data are lacking.

Fish acquire some DDT and its breakdown products [Total DDT (T-DDT) = DDT + DDE + DDD] through uptake in food, by feeding on, for example, stream invertebrates or smaller fish that have fed on contaminated plants. Fish also accumulate T-DDT directly from water passing over their gills.

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T-DDT is stored in the fatty tissue of the fish and is not readily metabolized (broken down). The accumulation of T-DDT depends, in part, on fat content-fish with a low fat content do not accumulate as much T-DDT as fish with a high fat content-and, in part, on age, sex, species, and availability of food.

68i)i

River Basin have among the highest concentrations of T-DDf in the Nation, as suggested by a comparison of this study with a national study of fish collected by the U.S. Fish and )Vtldlife Service at 112 statiollS in major rivers in 1984- 85. The median concentration of T-DDT in largescaJ.e suckers· collecied in

agricultural return-flows of the Yakima River Basin (about 1.3 micrograms of T-DDf P._(:r gram of whole Nationwide" concentrations of than at any ti~ since monitoring' of organochlorine pesticides lWlS initiated in the 196o's, in keeping with the removal ofiDDT from the marketplace. U. S. Geological Survey findings for the Nqtional Hbter-Quality 'Assessment of the Yakima Riw;r, which suggest relatively stable, high conc/;ntrations~ atzer. the past decade, {mply that t1U1 soils ;and sediments of the Yakima watershed h)lrbor, a sizeable mass' of resiaual,DDT.

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stations in major rivers across the nation by the U.S. Fish and Wildlife Se~ice in 1976 and 1984-85 indicate that concentrations ofT-DDI' ' in fish showed no significant changes at 91 stations, decreased at 20, and increased at 1. The concentrations in largescale suckers collected in the lowerYa<ima River by the U.S. Geological Survey in 1989-90 were similar ta s tatio~s (more than 90 rcent). Concentrations of -D Df in largescale suckers m the·main stem and agricultural return-flows in the basin are iiliout four times higher than concentrations,ofT-DIJf in largescale suckers in 13 other western streams sampled from 1970• to 1986 by the U.S. Fish and Wtldlife Service (see bar chart). The highest average concentra-

in freshwater fish are lower now

Data collected ·at 112 those collected near Granger in the lower Yakima River by the , U.S. Fish and Wildlife Service from 1970 through 1976 (see bar chart) . This similarity suggests that even though total concentrations of T-DDf in stream water have declined, the amount of T-DDI' in the basin (including in the water, sediment, and invertebrates) remains high enough t6 maintain elevated concentrations in fish.

Even though two decades have passed since its production and distribution was banned, DDT and its breakdown products [Total DDT (T-DDT) = DDT + DDE + DDD] are still widely dispersed in the environment. Concentrations of T-DDT remain elevated in agricultural soil, stream water, suspended and streambed sediment, and fish in the Yakima River Basin. Concentrations in water commonly exceed the chronic-toxicity criterion for the protection of freshwater aquatic life, which was established by the U.S. Environmental Protection Agency and adopted as the water-quality standard by the Washington State Department of Ecology. Concentrations of T-DDT in fish in the basin are among the highest in the Nation and commonly exceed the guideline for the protection of fish predators established by the National Academy of Sciences. Highest concentrations in water and fish occur in agricultural-return flows in the lower 110 river miles in the basin.

Are concentrations of T-DDT of concern relative to human health in the Yakima River Basin? Currently (1993) , no standards for the protection of human health exist against which T-DDT concentrations in water or fish tissue can be compared. Preliminary and theoretical degrees of risk reflect the lifetime chance of contracting cancer from consumption of T-DDT in water or fish tissue. A " lifetime" generally is considered to be 70 years. Calculated risks are only theoretical estimates that provide guidance to agencies that regulate water quality or protect human health and information for identifying potential health concerns to researchers and the public. The risks are calculated on the basis of current understanding of the cancer-causing potency of T-DDT (extrapolated from U .S. Environmental Protection Agency studies of laboratory animals, primarily rats and mice). These calculations include some uncertainty and assumptions, including possible differences in toxicological response of humans and laboratory animals toT-DDT and are based on limited information on relevant factors, such as fi shconsumption rates. A human-health impact analysis is being conducted by the Washington State Department of Health to assess ifT-DDT concentrations reported in this study pose a health threat to people who consume fish from the Yakima River Basin.

In June 1989, treated Naches River water from the city of Yakima Treatment Plant was sampled; no data were available for treated river water at Cle Elum. The in concentration of the drinking-water supply was 0.00036 microgram ofT-DDT per liter. Daily consumption of 2 quarts of city of Yakima drinking water by a 150- pound over a 70-year lifetime incremental increase in cancer risk of about 4 per 1 billion people (see inset on human risks). concentrations are low in the drinking-water supply because the intake is located upstream from intense agriculture and because the treatment process used by the facility removes most of the sediment and, thus, most of the T-DDT associated with Samples of resident fish collected in 1989-90 in the Yakima River Basin show that is detectable in fish throughout most of the basin. Concentrations of T-DDT in all fish collected in 1989-90 are below an action level of 5 micrograms of T-DDT per gram of food that has been established by the Food and Drug Administration to regulate concentrations in human food and animal feed sold to the public. The action level represents the limit at which the Food and Drug Administration can remove products from the market. Action levels do not apply to consumers of noncommercial, locally caught fish, such as sport fishermen and their families.

WHAT DO THESE FINDINGS MEAN TO PEOPLE WHO DRINK THE WATER? incremental increase in In June 1989, treated Naches River water from the billion people (see inset on city of Yakima Treatment human risks). T-DDT con- Plant was sampled; no data centrations are low in the were available for treated drinking-water supply be- concentration of T-DDT in stream from intense agri- the drinking-water supply was

EAT THE FISH? FINDINGS MEAN TO PEOPLE WHO WHAT DO THESE fish from the headwaters of estimated concentration of incremental increase in Samples of resident about 0.008 microgram of 1 fish collected in 1989-90 in T-DDT per gram of fish centration of T-DDT in 1 million people. the Yakima River Basin show filet') in species that reside Human-health risks that T-DDT is detectable in Yakima fish occurred in Sulphur Creek Wasteway (4.8 associated with ingestion of in the near-pristine forested fish throughout most of the micrograms of T-DDT per headwaters, such as rainbow basin. Concentrations of trout from the Teanaway River are higher than those estimated 2 .6 micrograms of associated with ingestion of River. Consumption of one 1989-90 are below an action 5-ounce serving of rainbow T-DDT per gram of filet). treated Naches River water level of 5 micrograms of The incremental increase in from the city of Yakima has been established by the cancer risk associated with lifetime corresponds to an ' Treatment Plant. The con- Food and Drug Administra- incremental increase in centration of T-DDT in this concentration is 250 per 1 million people. Concentra- tion to regulate concentrations mountain whitefish from the mouth of the Naches River tions ofT-DDT in mountain in human food and animal whitefish and large-scale human risks) . was 0 .75 microgram of Concentrations of T-DDT per gram of whole action level represents the T-DDT are highest in species Yakima River at Kiona ranged fish, or an estimated concen- Drug Administration can that reside in agricultural- tration of about 0.60 micro- remove products from the T-DDT per gram of whole gram ofT-DDT per gram of market. Action levels do not fish filet . Consumption of apply to consumers of non- such as largescale suckers and concentration of 1.4 micro- one 5-ounce serving of mountain whitefish. Human- commercial, locally caught grams ofT-DDT per gram of mountain whitefish from the health risks associated with Naches River per week over fish filet. Consumption of one fish, such as sport fishermen ingestion ofT-DDT in fish in 5-ounce serving of mountain and their families. a 70-year lifetime corre- whitefish or largescale sucker Concentrations of sponds to an incremental T-DDT are lowest (about 0.01 Yakima River are, therefore, increase in cancer risk of from the lower Yakima River microgram of T-DDT per higher than those associated with ingestion ofT-DDT in time corresponds to an

Concentrations of are lowest (about 0.01 microgram of per gram of whole fish, or an estimated concentration of about 0.008 microgram of

filet') in species that reside in the near-pristine forested headwaters, such as rainbow trout from the Teanaway River. Consumption of one 5-ounce serving of rainbow trout per week over a 70-year lifetime corresponds to an ' incremental increase in cancer risk of about 1 per 1 million people (see inset, on 1 human risks) .

that reside in agricultural-return flows and in the lower llO miles of the Yakima River, such as largescale suckers and mountain whitefish. Human-health risks associated with ingestion ofT-DDT in fish in the lower llO miles of the Yakima River are, therefore, higher than those associated with ingestion ofT-DDT in per gram of fish

Concentrations of are highest in species

• fish, or an estimated average

fish from the headwaters of the basin . The highest concentration of T-DDT in Yakima fish occurred in Sulphur Creek Wasteway (4.8 micrograms of per gram of whole fish or an estimated 2 .6 micrograms of per gram of filet). The incremental increase in cancer risk associated with this concentration is 250 per 1 million people. Concentrations ofT-DDT in mountain whitefish and large-scale suckers near the mouth of the Yakima River at Kiona ranged from 1.7 to 2.8 micrograms of per gram of whole

concentration of 1.4 micrograms ofT-DDT per gram of fish filet. Consumption of one 5-ounce serving of mountain whitefish or largescale sucker from the lower Yakima River per week over a 70-year lifetime corresponds to an incremental increase in cancer risk of about 130 per 1 million people.

Human-health risks associated with ingestion of T-DDT in fish in the Naches River are higher than those associated with ingestion of treated Naches River water from the city of Yakima Treatment Plant. The concentration of T-DDT in mountain whitefish from the mouth of the Naches River was 0 . 75 microgram of T-DDT per gram of whole fish, or an estimated concentration of about 0.60 microgram ofT-DDT per gram of fish filet . Consumption of one 5-ounce serving of mountain whitefish from the Naches River per week over a 70-year lifetime corresponds to an incremental increase in cancer risk of about 60 per 1 million people (see inset on human risks) .

Concentrations of T-DDf in fish collected from agricultural-return flows and

River, including near ilie mouili at Kiona, exceed guidelines (1 microgram of T-DDf per gram of whole fish) established by ilie National Academy of Sciences for ilie protection of fish predators, such as ilie bald eagle. Information is not available on concentrations of T-DDf in fish predators iliat reside

Lynn A. Brown, State Conservationist, Soil Conservation Service

.j

in ilie Yakima River Basin. Recent studies by ilie U.S. Fish and Wildlife Service, however, show elevated concentrations of DDE in bald eagle eggs from birds iliat nest near ilie mouili of ilie Columbia River. The Yakima River, which is located about 300 miles above ilie mouili of ilie Columbia River, is one of several sources in Washington and Oregon iliat are contributors of T-DDT to ilie Columbia River.

W er-quality improvement is a high priority goal of ilie USDA

Soil Conservation Service. Wiili the technical potential to achieve

"zero " return flows from irrigated agriculture, we can significantly

reduce boili sediment-borne and in-solution contamination of surface

water. This is especially true of DDT

and its breakdown products ,

DDE and DDD.

T-DDf contamination of streams and fish is an ongoing process, in part, because contaminated soils are eroded during ilie irrigation season and periods of heavy rainfall in agricultural areas. The presence of T-DDf in agricultural soils is attributed to historic applications and to ilie persistent chemical makeup of ilie compounds. Information to assess the environmental persistence and fate of DDf and its breakdown products in ilie agricultural soils in ilie Yakima River Basin is insufficient; ilie amount of time it takes for DDf compounds to break down in ilie soils depends on environmental conditions, soil type, and many complex chemical processes. It is, ilierefore, difficult to quantify when T-DDf contamination in ilie streams and fish in ilie Yakima River Basin will subside or end. Results of this study indicare, however, iliat chemical breakdown of T-DDf is slow because, despire ilie ban on ilie production and distribution of DDf in 1972, concentrations of T-DDf in ilie Yakima River near Kiona commonly exceeded ilie chronic-toxicity crirerion for ilie protection of freshwater aquatic life between 1972 and 1990. The contaminated agricultural soils could, ilierefore, provide a large and long-rerm reservoir ofT-DDf to streams and fish in ilie Yakima River Basin for decades to come.

Federal, Stare, Tribal, and local programs have been implemented in ilie basin to reduce erosion of contaminated soils, iliereby reducing ilie amount of T-DDf iliat enrers streams. Over ilie past 20--30 years, erosion has been reduced because irrigation practices and cropping patrerns have changed and cover crops of grasses and grains have been planted in orchards and vineyards . Erosioncontrol programs implemented in ilie basin wiiliin ilie last 10 years include mulching furrows with straw and irrigating wiili underground drip units. These newest methods help maintain adequare soil moisture and help promore less tillage and surface runoff. The erosioncontrol programs, which have been provided wiili technical and cost assistance from local Conservation Districts, ilie Agricultural Stabilization and Conservation Service, and ilie Soil Conservation Service, have been implemented by farmers. Such programs will help reduce ilie amounts of suspended sediment and T-DDf iliat enrer streams.

IMPLICATIONS OF FINDINGS ON SAMPLING AND RESEARCH STRATEGIES

in agricultural soils, stream water, suspended and streambed sediment, and fish. For example, concentrations T-DDT in stream water are directly related to concentrations of suspended sediment in the water, and those in fish are correlated with concentrations in stream water and sediment. These relations imply that knowledge of concentrations ofT-DDT in one medium provides an estimate of concentrations in other media. For example, analyses of streambed sediment might be used to estimate relative accumulation in fish. Such relations can be useful for optimizing resources required for monitoring T-DDT in the Yakima and other river basins. The contmuous replenishment and widespread dispersal of T-DDT among different media in the Yakima River Basin has raised concern by researchers of many disciplines (fish biologists, health scientists, soil scientists, waterresource managers, and hydrologists). Coordination and cooperation among agencies and organizations at all levels are essential to implement and maintain an effective program to assess where T-DDT occurs and to determine the sources in the Yakima River Basin.

Coordination among agencies aiui organizations at all levels is essential to understanding the distribution and variability ofT-DDT in the Yakimo River Basin. This publication was coordinated with the following Federal, State, Tribal, and local agencies and nonprofit organizations. These organizations also provide reports on mony aspects of the Yakimo River Basin, including the distribution of surface water, chemical quality of the water, biological studies, and general water resources. General informotion on water resources can be obtained by writing to:

Much appreciation is extended to US. Geological Survey employees for their expertise in the production of illustrations by Leslie J. Robinson and James 0 Whitmer; type composition by Shirlie A. McManus; and photography by David F. Usher.

Appreciation is also extended to those individuals and agencies that contributed photographs:

Charlie Collins, U.S. Geological Survey Lynn Hatcher, Yakima Indian Nation, Fisheries Program Gregory K. Scott, Nature Photos, Gilman, Wisconsin Bureau of Reclamation Central Washington Agricultural Museum Columbia River Inter-Tribal Fish Commission U.S. Fish and Wildlife Service Yakima Valley Museum and Historical Society

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