U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011–3011

February 2011 Printed on recycled paper

Prepared in cooperation with Wyoming Department of Agriculture

Pesticides in Wyoming’s Rivers, 2006–10

By Cheryl A. Eddy-Miller

90

25

25

80

20

26

26

16

85

80

80

16

85

287

14

191

189

14

30

89

89

90

287

287

Cody

Kane

Basin

Casper

Lander

Lovell

Laramie

Rawlins

Worland

Buffalo

CHEYENNE

Evanston

Riverton

Gillette

Sheridan

Wheatland

Newcastle

Torrington

Thermopolis

Rock

Springs

Jackson

Douglas

Saratoga Green

River

Moorcroft

Wind

River

River

River

Boysen

Reservoir River

YELLOWSTONE

 LAKE

JACKSON

 LAKE

Green

River Fontenelle

Reservoir

Flaming

Gorge

Reservoir

River

Belle Fourche

River

Powder

Shoshone

Greybull Bighorn

River

Cheyenne

River

Platte

North

River

Pathfinder

Reservoir

Seminoe

 Reservoir River

Laramie

Snake River

Sweetwater

Grayrocks

Reservoir

0

0

50

50

100 MILES

100 KILOMETERS

Base modified from U.S. Geological Survey Digital Chart of the World 

digital data, 2002

Albers Equal-Area Conic projection, Standard parallels 29°30′ and 45°30′, 

central meridian -107°30′

06664000

06285100

06274300

06279500

44° 

45° 

111° 110° 109° 108° 107° 106° 105° 

43° 

42° 

41° 

09127000 09217000

06426500

06645000

06674500

Bear

Big Horn

Cheyenne

Great Divide-Upper Green

Great Salt Lake

Missouri Headwaters

Missouri-Little Missouri

Niobrara

North Platte

Powder-Tongue

South Platte

Upper Snake

Upper Yellowstone

White-Yampa

Sampling site and number—Site sampled 2009−10

EXPLANATION

09217000

Sampling site and number—Site sampled 2006 and 2009−10 06674500

Sampling site and number—Site sampled 2006

River basins

06664000

North Platte River below Casper, Wyoming sampling site.

Introduction

In 2006, the U.S. Geological Survey 

(USGS) completed a study in cooperation 

with the Wyoming Department of Agriculture (WDA) to determine the occurrence of 

pesticides in four major rivers within the 

Bighorn and North Platte River Basins in 

Wyoming (Eddy-Miller and others, 2007). 

Surface-water samples were collected at 

five sites (fig. 1) during three different times 

of the year and detectable concentrations 

of pesticides were measured in samples 

collected during all three sampling events 

(table 1). In 2009–10, the USGS, in cooperation with the WDA, resampled three of the 

sites from the 2006 study and three additional sites (fig. 1) located in areas of interest 

to the State of Wyoming to further describe 

the occurrence of pesticides in Wyoming’s 

rivers. The change was made in order to 

include sites located near cities and towns. 

Results from the 2009–10 sampling along 

with comparisons to data collected in 2006 

are presented in this fact sheet.

Sample Collection and Analyses

For the 2009–10 sampling, two samples 

were collected from each of the six sites, one 

in late summer (August or September) 2009 

and one in mid-spring (April or May) 2010. 

The late summer sampling corresponded 

with the late growing season and the midspring sampling corresponded with postapplication of pesticides. The samples were 

collected using standard methods described 

in the National Field Manual for the Collection of Water-Quality Data (U.S. Geological Survey, variously dated) and sent to the 

Figure 1. Sites sampled in 2009–10 were located in the Bighorn, North Platte, 

Green, and Belle Fourche River Basins.
Table 1. Pesticides and degradates analyzed in 2006 (Eddy-Miller and others, 2007) and 2009–10 sampling.

[Pesticide trade names1 and degradate names in parentheses if different from pesticide name (Meister, 2002); pesticide abbreviations are given in braces; pesticides in 

color were detected in the corresponding year(s): yellow, 2006; pink, 2006 and 2009–10; purple, 2009–10]

Pesticide name Pesticide name Pesticide name Pesticide name

Acetochlor (Guardian, Harness, Relay) 2,4-D (Dacamine, Weed-B-Gon) Fipronil sulfone (fipronil degradate) Oxamyl (Vydate)

Acifluorfen (Blazer, Tackle 2S, Astic) 2,4-D methyl ester Flumetsulam (Broadstrike) Oxyfluorfen (Offside, Goal)

Alachlor (Alanex, Lasso, Shroud) 2,4-DB (Butoxone, Butyrac) Fluometuron (Cotoran) Paraoxon-methyl (parathion-methyl 

degradate)

Aldicarb (Temik) Dacthal Fonofos (Dyfonate) Parathion-methyl (Alkron, Bladan, 

Fighter)

Aldicarb sulfone (Standak, aldicarb 

degradate)

Dacthal monoacid (Dacthal degradate) Glufosinate2 Pendimethalin (Prowl, Stomp)

Aldicarb sulfoxide (aldicarb degradate) Desulfinylfipronil (Fipronil degradate) Glyphosate2 cis-Permethrin (Ambush, Pounce)

Aminomethylphosphonic acid 

(glyphosate degradate)2

Desulfinylfipronil amide (Fipronil 

degradate)

Hexazinone (Velpar) Phorate (Thimet, Rampart)

Atrazine (Aatrex, Atranex) Diazinon (Basudin, Spectracide, 

Knoxout)

3-Hydroxycarbofuran (carbofuran 

degradate)

Phosmet (Imidan)

Azinphos-methyl (Guthion, Crysthyon) Dicamba (Banvel, Banex) 2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine {OIET} (atrazine 

degradate)

Picloram (Tordon)

Azinphos-methyl-oxon (azinphos-methyl 

degradate)

3,4-Dichloroaniline (Chloramben 

degradate)

Imazaquin (Scepter) Prometon (Pramitol, Gesafram)

Barban 3,5-Dichloroaniline (Diuron degradate) Imazethapyr (New Path, Pursuit) Prometryn (Cotton-pro)

Bendiocarb (Ficam, Garrox, Turcam) Dichlorprop (Weedone, Polymone) Imidacloprid (Admire, Provado) Propanil (Stamp)

Benfluralin (Balan, Benefin) Dichlorvos (DDVP) Iprodione (Kidan) Propargite (Comite, Omite)

Benomyl (Benlate, Benex) Dicrotophos (Bidrin) Isofenphos (Oftanol, Lighter) Propham (Chem Hoe)

Bensulfuron-methyl (Escuri, Londax) Dieldrin (Panoram D-31, Octalox) lambda-Cyhalothrin (Charge, Karate) Propiconazole (Banner)

Bentazon (Basagram, Bentzone) 2,6-Diethylaniline (alachlor degradate) Linuron (Linurex, Lorox) cis-Propiconazole (Banner)

Bromacil (Hyvar X) Dimethoate (Trounce) Malaoxon (malathion degradate) trans-Propiconazole (Banner)

Bromoxynil (Buctril, Brominal, Agristar) Dinoseb (Premerge) Malathion (Cythion, Malaspray) Propoxur (Baygone, Suncide)

Carbaryl (Carbatox, Sevin) Diphenamid (Dymid, Enide) MCPA (Solve, MCP) Propyzamide (Kerb)

Carbofuran (Furadan, Futura) Disulfoton (Di-Syston) MCPB (Butoxone M40, Thistrol) Siduron (Tupersan)

Chloramben, methyl ester (Chloramben) Disulfoton sulfone (disulfoton degradate) Metalaxyl (Apron, Ridamil, Subdue) Simazine (Aquazine, Princep)

Chlordiamino-s-triazine {CAAT} (Atrazine degradate)3Diuron (Durashield, Karmex) Methidathion (Supra) Sulfometuron-methyl (Oust)

Chlorimuron-ethyl (Classic, Darban, 

Lory)

alpha-Endosulfan (Thiodan, Tiovel) Methiocarb (Mesurol) 2,4,5-T

2-Chloro-2,6-diethylacetanilide (alachlor 

degradate)

Endosulfan sulfate (alpha-endosulfan 

degradate)

Methomyl (Lannate, Nudrin) Tebuconazole (Elite)

2-Chloro-4-isopropylamino-6-amino-striazine {CIAT} (atrazine degradate)EPTC (Eptam, Eradicane) Metolachlor (Bicep, Dual) Tebuthiuron (Graslan, Spike)

2-Chloro-6-ethylamino-4-amino-s-triazine {CEAT} (atrazine degradate)Ethion (Ethanox, Rhodocide) Metribuzin (Lexone, Sencor) Tefluthrin (Force)

4-Chloro-2-methylphenol (MCPA 

degradate)

Ethoprophos (Mocap, Prophos) Metsulfuron methyl (Ally, Escort) Terbacil (Sinbar, Herbicide 732)

3(4-Chlorophenyl)-1-methyl urea (diuron 

degradate)

2-Ethyl-6-methylaniline (metalachlor 

degradate)

Molinate (Hydram, Ordram) Terbufos (Counter, Contraven)

Chlorpyrifos (Dursban, Lorsban) Fenamiphos Myclobutanil (Eagle, Nova) Terbuthylazine (Gardoprim)

Clopyralid (Stinger, Lontrel) Fenamiphos sulfone (fenamiphos degradate)1-Naphthol (carbaryl degradate) Thiobencarb (Bolero, Saturn)

Cyanazine (Bladex) Fenamiphos sulfoxide (fenamiphos 

degradate)

Neburon (Granurex, Propuron) Tribufos (DEF 6)

Cycloate (Ro-Neet) Fenuron Nicosulfuron (Accent, OneHope) Triclopyr (Garlon)

Cyfluthrin (Decathlon) Fipronil (Regent) Norflurazon (Zorial, Solicam) Trifluralin (Treflan, Trim)

Cypermethrin Fipronil sulfide (fipronil degradate) Oryzalin (Surflan)

1

The use of trade, product, industry, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government or the Wyoming State Government.

2

Pesticide or degradate not analyzed for in 2006.

3

Pesticide or degradate not analyzed for in 2009–10.
USGS National Water Quality Laboratory in Lakewood, Colorado, 

and to the USGS Organic Geochemistry Research Laboratory in 

Lawrence, Kansas. The two laboratories analyzed for 134 different 

pesticides and degradates (compounds that result from pesticides 

breaking down) in the samples collected during 2009–10 (table 1; 

Furlong and others, 2001; Sandstrom and others, 2001; Zimmerman

and others, 2001).

Pesticide Occurrence

Complete analytical results from all samples collected can be 

found at http://nwis.waterdata.usgs.gov/wy/nwis/qwdata using the 

site numbers shown on figure 1. Twenty-eight different pesticides or 

degradates were detected in 2009–10 (table 1); however, all concentrations were much less than associated drinking-water standards 

(table 2). In comparison to pesticide results from samples collected 

in 2006, 12 compounds were detected in samples collected in 2009–

10 that were not detected in 2006, whereas 4 compounds detected in 

2006 were not detected in samples collected in 2009–10 (table 1). 

An additional two compounds that were not analyzed for in the 2006 

samples were detected in the 2009–10 samples, and one compound 

detected in 2006 samples was not analyzed for in 2009–10 samples 

because of changes in the analytical schedules by the laboratory.

At least one pesticide or degradate was detected in samples 

collected from five of the sites in 2009 and from all six sites in 

2010 (fig. 2). All sites had a larger number of pesticides detected in 

the mid-spring samples (2010) compared the late summer samples 

(2009). 

Most pesticides or degradates detected during the 2009 and 

2010 sampling were herbicides or their degradates (table 2). Two 

insecticides and one fungicide also were detected. The most commonly detected compound was the glyphosate degradate, aminomethylphosphonic acid, which was found in 75 percent of all 

samples (fig. 3). 

0

5

10

15

Bighorn River

at

Kane,Wyo.

(06279500) 

Shoshone River

near

Lovell,Wyo.

(06285100) 

Belle Fourche

River

below

Moorcroft,

Wyo.

(06426500) 

North Platte

River

below

Casper,

Wyo.

(06645000) 

North Platte

River

at WY-NE

State Line

(06674500) 

Green River

near

Green River,

Wyo.

(09217000) 

Number of Pesticides or Degradates Detected

Site name and number

Late summer 2009

Mid-spring 2010

1,160

982

745

304

3.1

20

1,010

1,160

1,050

230

958

772

230

EXPLANATION

Instantaneous streamflow

in river at time of

sampling (cubic feet per

second) (U.S. Geological

Survey, 2010)

Figure 2. A larger number of pesticides were detected in 

samples collected in the mid-spring than in the late summer 

at all sites.

Table 2. All concentrations of detected pesticides in 

2009–10 were less than any associated drinking-water 

standard. Pesticides and degradates (in italics) are shown 

in color to represent type of pesticide: dark green, herbicide; 

light green, herbicide degradates; blue, fungicide; orange, 

insecticide; light orange, insecticide degradate.

[USEPA, U.S. Environmental Protection Agency; μg/L, micrograms per 

liter; --, not established]

Detected 

pesticide 

or 

degradate

Maximum 

concentration 

detected during 

2009–10 

sampling (μg/L)

USEPA 

standard 

or health 

advisory 

level (μg/L)

Aldicarb 0.01 13 (MCL)

Aldicarb sulfoxide 0.074 1

4 (MCL)

Atrazine 0.028 13 (MCL)

2-Chloro-4-isopropylamino6-amino-s-triazine

0.018 --

2-Hydroxy-4-isopropylamino-6-ethylaminos-triazine

0.006 --

Benfluralin 0.009 --

Benomyl 0.063 --

Bentazon 0.01 2200 (LHA)

Chloramben3 -- 2100 (LHA)

3,4-Dichloroaniline 0.024 --

2,4-D 0.12 170 (MCL)

2,4-DB 0.01 --

Diuron 0.19 4200 (RSD4)

EPTC 0.036 --

Fipronil 0.004 --

Desulfinylfipronil 0.008 --

Glyphosate 0.16 1700 (MCL)

Aminomethylphosphonic acid 0.27 --

Hexazinone 0.027 2400 (LHA)

Malathion 0.015 2100 (LHA)

MCPA 0.04 230 (LHA)

4-Chloro-2-methylphenol 0.006 --

Metalaxyl 0.01 --

Metolachlor 0.011 2700 (LHA)

Metribuzin 0.02 270 (LHA)

Pendimethalin 0.016 --

Prometon 0.07 2100 (LHA)

Sulfometuron-methyl 0.004 --

Trifluralin 0.007 210 (LHA)

1

 MCL, USEPA Maximum Contaminant Level (U.S. Environmental 

Protection Agency, 2006).

2

 LHA, USEPA Lifetime Health Advisory Level (U.S. Environmental 

Protection Agency, 2006).

3

 Chloramben was not detected, however, it is the parent compound 

for 3,4-dichloroaniline, and is included in the table for clarification.

4

 RSD4, USEPA Risk-Specific Dose at 10-4 Cancer Risk (U.S. 

Environmental Protection Agency, 2006).
References Cited

Eddy-Miller, C.A., Boughton, G.K., and Woodruff, R.E., 2007, 

Pesticides in surface water in the Bighorn River and North Platte 

River Basins, Wyoming, 2006: U.S. Geological Survey Fact Sheet 

2007–3017, 4 p.

Furlong, E.T., Anderson, B.D., Werner, S.L., Soliven, P.P., Coffey, 

L.J., and Burkhardt, M.R., 2001, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory—

Determination of pesticides in water by graphitized carbon-based 

solid-phase extraction and high-performance liquid chromatography/

mass spectrometry: U.S. Geological Survey 

Water-Resources Investigations Report 01–4134, 73 p.

Meister, R.T., 2002, Farm chemicals handbook: Willoughby, Ohio, 

Meister Publishing Co., variable pagination.

Sandstrom, M.W., Stroppel, M.E., Foreman, W.T., and Schroeder, M.P., 

2001, Methods of analysis by the U.S. Geological Survey National 

Water Quality Laboratory—Determination of moderate-use pesticides and selected degradates in water by C-18 solid-phase extraction and gas chromatography/mass spectrometry: U.S. Geological 

Survey Water-Resources Investigations Report 01–4098, 70 p.

U.S. Environmental Protection Agency, 2006, 2006 Edition of the 

drinking-water standards and health advisories: Washington, D.C., 

U.S. Environmental Protection Agency, Office of Water, EPA 822– 

R–06–013, summer 2006, 11 p., accessed January 22, 2008, at 

http://www.epa.gov/waterscience/criteria/drinking/dwstandards.pdf.

U.S. Geological Survey, variously dated, National field manual for the 

collection of water-quality data: U.S. Geological Survey Techniques 

of Water-Resources Investigations, book 9, chaps. A1–A9, accessed 

November 29, 2010, at http://pubs.water.usgs.gov/twri9A.

U.S. Geological Survey, 2010, National Water Information System, 

accessed November 18, 2010 at: http://nwis.waterdata.usgs.gov/wy/

nwis/.

Zimmerman, L.R., Strahan, A.P., and Thurman, E. M., 2001, Methods 

of analysis and quality-assurance practices by the U.S. Geological 

Survey Organic Geochemistry Research Group—Determination of 

four selected mosquito insecticides and a synergist in water using 

liquid-liquid extraction and gas chromatography/mass spectrometry: 

U.S. Geological Survey Open-File Report 01–273, 11 p.

Figure 3. Seventy-five percent of the 12 samples collected in 2009–10 had a detection of a glyphosate degradate. 

Chloramben was not detected, however, it is the parent compound for 3,4-dichloroaniline, and is included in the 

figure for clarification.

0 10 20 30 40 50 60 70 80 90 100

Aldicarb

Aldicarb sulfoxide

Atrazine

2-Chloro-4-isopropylamino-6-amino-s-triazine

2-Hydroxy-4-isopropylamino-6-ethylamino-s-triazine

Benfluralin

Benomyl

Bentazon

Chloramben

2,4-D

2,4-DB

Diuron

EPTC

Fipronil

Desulfinylfipronil

Glyphosate

Aminomethylphosphonic acid

Hexazinone

Malathion

MCPA

Metalaxyl

Metolachlor

Metribuzin

Pendimethalin

Prometon

Sulfometuron-methyl

Trifluralin

Percentage of detections

Herbicide

Herbicide degradate

Fungicide

Insecticide

Insecticide degradate

Pesticide or degradate

EXPLANATION

3,4-Dichloroaniline

4-Chloro-2-methylphenol

For More Information:

Visit the USGS Wyoming Water Science Center Web site at 

http://wy.water.usgs.gov/projects/pesticide/index.htm, or contact:

Cheryl A. Eddy-Miller, U.S. Geological Survey, 2617 E. 

Lincolnway, Suite B, Cheyenne, WY 82001, 307-775-9167, 

cemiller@usgs.gov or

Hank Uhden, Wyoming Department of Agriculture, 2219 Carey 

Avenue, Cheyenne, WY 82002, 307-777-6574, 

huhden@state.wy.us.