Sethoxydim Risk Assessment

COMMON UNIT CONVERSIONS AND ABBREVIATIONS  
To convert ... 
Into ... 
Multiply by ...  
acres 
hectares (ha) 
0.4047 
acres 
square meters (m
2
) 
4,047 
atmospheres 
millimeters of mercury 
760 
centigrade 
Fahrenheit 
1.8C°+32 
centimeters 
inches 
0.3937 
cubic meters (m
3
) 
liters (L) 
1,000 
Fahrenheit 
centigrade 
0.556F°-17.8 
feet per second (ft/sec) 
miles/hour (mi/hr) 
0.6818 
gallons (gal) 
liters (L) 
3.785 
gallons per acre (gal/acre) 
liters per hectare (L/ha) 
9.34 
grams (g) 
ounces,  (oz) 
0.03527 
grams (g) 
pounds,  (oz) 
0.002205 
hectares (ha) 
acres 
2.471 
hectares (ha) 
square meters 
10,000 
inches (in) 
centimeters (cm) 
2.540 
kilograms (kg) 
ounces,  (oz) 
35.274 
kilograms (kg) 
pounds,  (lb) 
2.2046 
kilograms per hectare (hg/ha) 
pounds per acre (lb/acre) 
0.892 
kilometers (km) 
miles (mi) 
0.6214 
liters (L) 
cubic centimeters (cm
3
) 
1,000 
liters (L) 
gallons (gal) 
0.2642 
liters (L) 
ounces, fluid (oz) 
33.814 
miles (mi) 
kilometers (km) 
1.609 
miles per hour (mi/hr) 
cm/sec 
44.70 
milligrams (mg) 
ounces (oz) 
0.000035 
meters (m) 
feet 
3.281 
ounces (oz) 
grams (g) 
28.3495 
ounces per acre (oz/acre) 
grams per hectare (g/ha) 
70.1 
ounces per acre (oz/acre) 
kilograms per hectare (kg/ha) 
0.0701 
ounces fluid 
cubic centimeters (cm
3
) 
29.5735 
pounds  (lb) 
grams (g) 
453.6 
pounds  (lb) 
kilograms (kg) 
0.4536 
pounds per acre (lb/acre) 
kilograms per hectare (kg/ha) 
1.121 
pounds per acre (lb/acre) 
mg/square meter (mg/m
2
) 
112.1 
pounds per acre (lb/acre) 
:
g/square centimeter (
:
g/cm
2
) 
11.21 
pounds per gallon (lb/gal) 
grams per liter (g/L) 
119.8 
square centimeters (cm
2
) 
square inches (in
2
) 
0.155 
square centimeters (cm
2
) 
square meters (m
2
) 
0.0001 
square meters (m
2
) 
square centimeters (cm
2
) 
10,000 
yards 
meters 
0.9144 
Note: All references to pounds and ounces refer to avoirdupois weights unless otherwise specified. 
viii 

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CONVERSION OF SCIENTIFIC NOTATION 
Scientific 
Decimal 
Verbal 
Notation 
Equivalent 
Expression 
1 
@
 10
-10 
0.0000000001 
One in ten billion 
1 
@
 10
-9 
0.000000001 
One in one billion 
1 
@
 10
-8 
0.00000001 
One in one hundred million 
1 
@
 10
-7 
0.0000001 
One in ten million 
1 
@
 10
-6 
0.000001 
One in one million 
1 
@
 10
-5 
0.00001 
One in one hundred thousand 
1 
@
 10
-4 
0.0001 
One in ten thousand 
1 
@
 10
-3 
0.001 
One in one thousand 
1 
@
 10
-2 
0.01 
One in one hundred 
1 
@
 10
-1 
0.1 
One in ten 
1 
@
 10
0 
1 
One 
1 
@
 10
1 
10 
Ten 
1 
@
 10
2 
100 
One hundred 
1 
@
 10
3 
1,000 
One thousand 
1 
@
 10
4 
10,000 
Ten thousand 
1 
@
 10
5 
100,000 
One hundred thousand 
1 
@
 10
6 
1,000,000 
One million 
1 
@
 10
7 
10,000,000 
Ten million 
1 
@
 10
8 
100,000,000 
One hundred million 
1 
@
 10
9 
1,000,000,000 
One billion 
1 
@
 10
10 
10,000,000,000 
Ten billion 
ix 

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EXECUTIVE SUMMARY  
INTRODUCTION 
This document provides risk assessments for human health effects and ecological effects to 
support an assessment of the environmental consequences of using sethoxydim in Forest Service 
programs.  The USDA Forest Service uses the herbicide, sethoxydim, in its vegetation 
management programs.  The USDA Forest Service plans on using only one commercial 
formulation, Poast. 
This document has four chapters: the introduction, program description, risk assessment for 
human health effects, and risk assessment for ecological effects or effects on wildlife species. 
Each of the two risk assessment chapters has four major sections, including an identification of 
the hazards associated with sethoxydim, an assessment of potential exposure to this compound, an 
assessment of the dose-response relationships, and a characterization of the risks associated with 
plausible levels of exposure. 
Almost no risk estimate presented in this document is given as a single number.  Instead, risk is 
expressed as a central estimate and a range, which is sometimes very large.  Because of the need 
to encompass many different types of exposure as well as the need to express the uncertainties in 
the assessment, this risk assessment involves numerous calculations.  Most of the calculations are 
relatively simple, and the very simple calculations are included in the body of the document. 
Some of the calculations, however, are  cumbersome.  For those calculations, a set of worksheets 
is included as an attachment to the risk assessment.  The worksheets provide the detail for the 
estimates cited in the body of the document.  two versions of the worksheets are available: one in 
a word processing format and one in a spreadsheet format.  The worksheets that are in the 
spreadsheet format are used only as a check of the worksheets that are in the word processing 
format.  Both sets of worksheets are provided with the hard-text copy of this risk assessment as 
well as with the electronic version of the risk assessment.  Documentation for the use of these 
worksheets is provided in a separate document that also accompanies this risk assessment. 
PROGRAM DESCRIPTION 
Poast is a commercial formulation of sethoxydim, available from BASF, that is used by the USDA 
Forest Service.  Sethoxydim is recommended as selective postemergence herbicides for the 
control of annual or perennial grass weeds.  Poast is labeled for application to a number of 
different crops.  Poast Plus is labeled for application to alfalfa, citrus, clover, corn, cotton, 
peanuts, and soybeans  as well as for deciduous trees, non-food crop areas, and fallow lands.  The 
Forest Service will used Poast only in non-crop areas and the only use contemplated by the Forest 
Service and considered in this risk assessment involves the control of unwanted vegetation in 
nurseries. 
The most common method of application for sethoxydim in Forest Service programs will involve 
broadcast foliar applications.  Although Poast is registered for aerial applications, this application 
method will not be used in Forest Service programs.  The labeled application rates for Poast range 
x 

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