![](media/image1.wmf)

**UNITED STATES ENVIRONMENTAL PROTECTION AGENCY**

WASHINGTON D.C., 20460

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

Number range CHAPTER**PC Codes:** 012501, 012502, 013802, 013803, 013806

**DP Barcode:** D309097

**Date**: March 29, 2006

**DRINKING WATER ASSESSMENT**

**SUBJECT**: Response to Registrant Phase I Error Only Comments:

*Drinking Water Assessment for Organic Arsenical Herbicides for the
Reregistration Eligibility Decision (RED)*

**TO:** Diana Locke, Risk Assessor

Number range CHAPTERReregistration Branch II

Health Effects Division (7509C)

Lance Wormell, Chemical Review Manager

Reregistration Branch II

Special Review and Reregistration Division (7508C)

**FROM**: Keara Moore, Chemist

Number range CHAPTEREnvironmental Risk Branch III

Environmental Fate and Effects Division (7507C)

Number range CHAPTER**THROUGH:** Mark Corbin, Senior Environmental
Scientist

Environmental Risk Branch III

Environmental Fate and Effects Division (7505C)

**APPROVED** Daniel Rieder, Branch Chief

**BY:** Environmental Risk Branch III

> Environmental Fate and Effects Division (7507C)

Attached, please find the revised Drinking Water Assessment for organic
arsenical herbicides. Revisions have been made to the previous Drinking
Water Assessment (DP Barcode 309098; February 3, 2006) to correct any
mathematical/ typographical errors and provide clarification in areas
identified by the registrants in their Phase 1 response. Additional
comments were received regarding EPA's methodology and environmental
fate results; these comments will be addressed after the 60-day Phase 3
public comment period scheduled to begin in April 2006.

The revisions made in this document do not alter any EFED conclusions
from the previous assessment. Where appropriate, references to
"degradation" have been replaced with the more suitable term
"metabolism." Language has been added to clarify the discussion of the
potential for transformation of organic arsenicals to inorganic arsenic
and for transformation of dimethylated arsenical species to
monomethylated species. Clarification has also been added in discussion
of the application rates and half lives used in modeling and in
discussion of the sorption properties of arsenicals. Uncertainty in
estimates of surface water exposure resulting from use on turf has been
emphasized by adding further discussion of the issue in the executive
summary of the document.

**EXECUTIVE SUMMARY**

This memorandum presents the results of the Environmental Fate and
Effects Division's (EFED) drinking water assessment, conducted to
support the human health aggregate risk assessment for the
reregistration of organic arsenicals. Number range CHAPTERFive
individual herbicides are included in this assessment: cacodylic acid
(DMA; dimethylarsinic acid), sodium cacodylate (DMA-Na), monosodium
methanearsonate (MSMA), disodium methanearsonate (DSMA), and calcium
acid methanearsonate (CAMA). Past assessments have handled cacodylic
acid and sodium cacodylate separately from the methylarsonate salts
(MSMA, DSMA, CAMA). The current assessment considers all of these
pesticides together as the "organic arsenicals." These pesticides are
all alike in that they contain arsenic in a methylated form. They have
similar chemical structures and environmental fate properties. All have
the potential to metabolize to the more toxic inorganic arsenic. Because
arsenic is elemental and does not degrade, application of any organic
arsenical pesticide may contribute to total arsenic loading, whether as
parent compound or inorganic arsenic, in surface water, groundwater,
soil, or plants, depending on environmental conditions. In light of
these considerations, the environmental fates of these pesticides are
discussed as a group. In addition to estimating concentrations resulting
from application of individual compounds, situations where multiple
organic arsenicals may be applied to the same field are considered, and
the uncertainty resulting from the possibility of multiple uses in a
single watershed is discussed.

The estimated drinking water concentrations (EDWC) are based on
application rates from the set of master labels provided by the
Methanearsonic Acid Research Task Force (MAATF), dated November 14,
2005. These encompass all uses except for application of DMA to turf and
non-crop areas, which will be addressed in a future label. It is the
assumption that any labels for formulated products which exceed these
maximum application rates will be revised to comply with the master
labels. Nearly 3.5 million pounds of these pesticides are applied
annually, with approximately 70% of the total use as an herbicide or a
desiccant on cotton and another 27% as an herbicide on turf. These use
data do not include residential uses, which are expected to be a small
percentage of the total use. Because of the predominance of the cotton
and turf uses, EDWCs are based on those uses.

EFED estimated drinking water concentrations for exposure to surface
water are presented in Table 1. These values were modeled using the
Pesticide Root Zone Model (PRZM 3.12) and the Exposure Analysis Modeling
System, (EXAMS 2.98.04) with the pe4v01 graphical interface and
represent the two most vulnerable available scenarios. The species of
concern in this assessment -- the methylarsonate salts, DMA, and
inorganic arsenic -- all have distinct toxicities; exposure to each
needs to be considered individually. Individual EDWCs are therefore
provided for each, including DMA and inorganic arsenic as potential
metabolites as well as the parent compounds. The total arsenic value
incorporates all arsenical species that may be present as a result of
pesticide application, including inorganic arsenic. The total arsenic
EDWC can be compared to regulatory levels, all of which are defined by
total arsenic. For drinking water, the

**Table 1. EDWCs (ppb) from maximum labeled rates for major uses of
arsenicals.**

  -------------- ------------- -------------- -------------- --------------
                               **Acute**      **Chronic**    **Cancer**

  **TURF**       **MMA^1^**    250.5          127.5          74.6

                 **DMA**       102.3          46.5           28.1

                 **Total       135.2          68.8           40.3
                 As^2^**                                     

  **COTTON**     **MMA^1^**    37.4           11.0           5.3

                 **DMA**       23.6           7.4            4.3

                 **Total       20.9           7.2            3.9
                 As^2^**                                     
  -------------- ------------- -------------- -------------- --------------

> ^1^ Monomethyl arsonic acid (MMA) is the acid equivalent form of the
> methylarsonate salts.
>
> ^2^ Total arsenic is the sum of arsenic (as ppb As) that may be
> present from all applied and metabolite species. It also represents
> the maximum EDWC of inorganic arsenic.

Maximum Contaminant Level (MCL) for total arsenic is 10 ppb and is based
on concerns for long-term exposure. As a conservative assumption, the
entire estimated total arsenic EDWC may be present as inorganic arsenic.
No EDWCs are provided for exposure to groundwater. Based on the
environmental fate properties of organic arsenicals, leaching to
groundwater is not expected to contribute significantly to the already
existing burden of arsenic in groundwater except in highly vulnerable
situations.

Organic arsenicals are stable to hydrolysis and photolysis but in many
conditions, they can be subject to microbial metabolism in soil under
aerobic and anaerobic conditions. The occurrence, rate, and products of
this metabolism are variable, dependent on environmental conditions.
Persistence of applied *parent compounds* can range from days to years,
depending on environmental conditions. Although it may convert to
different forms, however, the arsenic in these pesticides does not
disappear; arsenic from pesticides is not lost but redistributed and
transformed throughout the environment. Organic arsenicals and their
metabolites are strongly sorbing and are expected to be relatively
immobile in soil in most conditions.

Arsenic occurs in the environment naturally in variable concentrations.
A USGS statistical analysis of 50,000 groundwater samples from 30,000
locations found that nearly half of the groundwater samples had *total*
arsenic concentrations \<1 ppb while about 10% exceeded 10 ppb. Areas of
high arsenic groundwater are scattered throughout the country but are
more likely to be found in the Intermountain West and Pacific Coast
regions. A less thorough consideration of a USGS dataset including
40,000 samples from 4500 lake and stream locations found that in surface
water also, half of the samples had total arsenic concentrations ≤1.1
ppb and 10% of the samples exceeded 10 ppb. The limited data available
for speciated arsenic suggest that in both surface and groundwater,
natural arsenic is present primarily in the inorganic form.

Potential exposure to arsenic in drinking water from pesticide
application, separate from natural background levels, was assessed
through evaluation of targeting monitoring data from surface and
groundwater in pesticide use areas as well as through the surface water
modeling discussed above. A summary of groundwater monitoring in areas
in North Dakota, South Dakota, Wisconsin, and Minnesota where high
arsenic concentrations regionally coincided with agricultural use found
that in these areas, the groundwater concentrations were largely
unaffected by use of arsenical pesticides. In Florida golf courses,
however, groundwater detections of total arsenic as high as 123 ppb,
significantly higher than local background, have been attributed to use
of MSMA. Targeted surface water monitoring has been conducted in cotton
use areas as well as in golf course ponds in Florida. In cotton growing
regions of Mississippi, surface water concentrations up to 5.5 ppb total
arsenic were measured. This appears to be higher than natural background
arsenic levels, but the results are inconclusive. In limited sampling of
Florida golf course ponds, the highest total arsenic level found was 24
ppb. For all arsenic monitoring data, there is some uncertainty in
determining the source of elevated levels.

Uncertainties, limitations, and assumptions in the drinking water
assessment include the following:

-   Environmental fate data for DSMA and CAMA are primarily based on
    studies for MSMA because all of these methylarsonate salts
    dissociate to monomethyl arsonic acid (MMA) in aqueous solution.
    Environmental fate studies for both MMA and DMA are included in a
    single discussion based on the assumption that general fate
    processes are similar, even if specific rates and sorption
    coefficients are not identical.

-   For fate discussions and modeling, environmental fate data for all
    organic arsenicals are based on open literature studies as well as
    registrant submitted data. The majority of metabolism data are from
    non-GLP studies that were conducted for less than one year.
    Transformation of applied organic arsenicals to volatile
    alkylarsines is assumed to be a minor dissipation route.

-   Modeling to estimate drinking water concentrations is based on
    application of pesticide to an entire watershed. The results are
    then modified using a percent cropped area factor (PCA). Because of
    the variety of sites where use on turf is possible, no PCA has been
    developed and the estimated concentration is based on the
    unmodified, entire watershed result. This is likely an
    overestimation of exposure but the extent of overestimation is
    undefined. Comparing the modeled result to the very limited
    monitoring data which are available, the highest concentration
    observed is approximately one half of the chronic concentration
    estimated by modeling. For the cotton use, the cotton PCA was used
    in estimating exposure despite the fact that arsenicals may be
    applied to other crops in the same watershed. The cotton exposure
    estimate may therefore be an underestimate, but limited monitoring
    data suggest that the results are reasonable.

-   Several additional assumptions are made in modeling exposure to
    arsenic species other than the parent compound. The estimate of
    metabolism to DMA is based on the assumption that 35% is the maximum
    amount of MMA that may be present as DMA at any one time. Because
    significant transformation from DMA to MMA has not been confirmed in
    field or laboratory studies, in modeling it is assumed that no
    transformation occurs. .Maximum potential concentrations of
    inorganic arsenic are represented by the total arsenic EDWCs,
    calculated as a molar conversion of the EDWCs of parent compounds.
    This is a general estimate of the amount of inorganic arsenic that
    may reach surface water rather than a direct calculation based on
    specific physical processes.

-   Because of the multiple potential sources of arsenic, both natural
    and anthropogenic, it can be difficult to determine the source of
    arsenic found in monitoring studies. Sampling in studies of
    background arsenic is typically not uniformly distributed and not
    designed to limit consideration to only uncontaminated regions. In
    targeted studies, detailed land use histories and pesticide
    application information are not always available and conclusions are
    based primarily on general trends.

**TABLE OF CONTENTS**

[**PESTICIDE USE AND APPLICATION** 9](#__RefHeading___Toc126565947)

[*MSMA and DSMA* 9](#__RefHeading___Toc126565948)

[*CAMA* 11](#__RefHeading___Toc126565949)

[*Cacodylic Acid* 11](#__RefHeading___Toc126565950)

[*Co-occurrence* 11](#__RefHeading___Toc126565951)

[**ENVIRONMENTAL FATE AND TRANSPORT CHARACTERIZATION**
12](#__RefHeading___Toc126565952)

[**GROUNDWATER EXPOSURE** 15](#__RefHeading___Toc126565953)

[**Groundwater Monitoring** 15](#__RefHeading___Toc126565954)

[*Background Arsenic (Non-targeted Monitoring)*
15](#__RefHeading___Toc126565955)

[*Pesticide Impacts (Targeted Monitoring)*
18](#__RefHeading___Toc126565956)

[**SURFACE WATER EXPOSURE** 21](#__RefHeading___Toc126565957)

[**Surface Water Monitoring** 21](#__RefHeading___Toc126565958)

[*Background Arsenic (Non-targeted Monitoring)*
21](#__RefHeading___Toc126565959)

[*Pesticide Impacts (Targeted Monitoring)*
23](#__RefHeading___Toc126565960)

[**Surface Water Modeling** 24](#surface-water-modeling)

[*Input Parameters: Metabolism Rates* 26](#__RefHeading___Toc126565962)

[*Input Parameters: Soil Mobility* 29](#__RefHeading___Toc126565963)

[*Calculation of Metabolites* 30](#__RefHeading___Toc126565964)

[*Percent Cropped Area* 31](#__RefHeading___Toc126565965)

[*Characterization* 31](#__RefHeading___Toc126565966)

[**SOIL ACCUMULATION** 35](#__RefHeading___Toc126565967)

[**UNCERTAINTY** 36](#__RefHeading___Toc126565968)

[**Monitoring** 36](#__RefHeading___Toc126565969)

[**Surface Water Modeling** 36](#__RefHeading___Toc126565970)

[**REFERENCES** 39](#__RefHeading___Toc126565971)

[**Appendix A: PRZM/EXAMS Input Files**
42](#__RefHeading___Toc126565972)

[**Appendix B: PRZM/EXAMS Output Files**
62](#__RefHeading___Toc126565973)

**PESTICIDE USE AND APPLICATION**[]{#__RefHeading___Toc126565947
.anchor}

Organic arsenicals are nonselective contact herbicides used to control
grasses and broadleaf weeds in a variety of agricultural and
non-agricultural applications. This assessment is based on master labels
provided by the registrants on 11/14/05 which have not yet been
finalized but which are assumed to invalidate all previous labels.
Variance from these rates could change the conclusions of this
assessment. Table 2 provides a summary of maximum application rates
allowed by these master labels.

*MSMA and DSMA*[]{#__RefHeading___Toc126565948 .anchor}

Monosodium methanearsonate (MSMA) and disodium methanearsonate (DSMA)
are used in a wide variety of applications. Although applied as
different parent compounds, MSMA and DSMA end up as the same chemical in
the environment, monomethyl arsonic acid (MMA). For this reason, labels
for all uses specify that the maximum number of applications applies to
"either DSMA or MSMA or their combination per crop, per year." Rates for
both are reported here in acid equivalents (ae) to represent the amount
applied as MMA. The main agricultural application for both is as a
pre/post-emergent herbicide on cotton applied prior to the first bloom.
The major use area for both MSMA and DSMA is in the southeastern US,
including Georgia, Arkansas, Mississippi, Alabama, Louisiana, and North
and South Carolina. USGS pesticide maps, based on data from 1995-1998,
show use of MSMA, but not DSMA, in Texas, New Mexico, Arizona, and
California as well (USGS, 2003).

The only other agricultural uses of MSMA and DSMA supported by master
labels are in non-bearing orchards, citrus, and vineyards.
Non-agricultural uses of MSMA and DSMA include use on turf and non-crop
uses. The turf use is both residential and commercial, including
residential lawns, sod farms, golf courses, parks, and other areas. The
non-crop use includes drainage ditch banks, rights-of-way, storage yards
and similar areas. The maximum application rates for all of these uses
are included in Table 2.

BEAD estimates that 100% of agricultural use of DSMA is on cotton at
approximately 200,000 lbs/yr, based on use data from 1998 to 2003 (BEAD,
2005b). Limited information on non-agricultural uses of DSMA is
available but it is expected to be a small percentage of total use. Use
of MSMA is much higher, for both agricultural and non-agriculture uses,
and so more data are available to quantify non-agricultural use. On
cotton, use of MSMA is estimated at 2 million lb/yr, two-thirds of the
total MSMA usage of 3 million lbs/yr. The remaining one-third of use is
primarily on turf, estimated at 930,000 lb/yr and including sod farms,
golf courses, lawn care operators, and other turf uses. This estimate
does not include individual residential use. Golf courses account for
approximately half of the MSMA applied on turf. Interestingly, lawn care
operators treated almost as many acres as golf courses but used around a
quarter of the pounds. Estimates of non-agricultural use of MSMA are
based on proprietary data from 2000. Other uses found for MSMA, in order
of decreasing percentage, include pasture, citrus, pistachios, walnuts,
watermelon, apples, and pecans. Combined, these uses contributed less
than 3% of total annual use (BEAD, 2005a & b).

**Table 2. Application Rates for Organic Arsenicals, based on 11/14
Master Labels**

+--------------+-----------+-------------+-----------+---+--------------+
| **Number     | **Maximum | **Max.**    | **Appl    | * |              |
| range        | App.      |             | ication** | * |              |
| CHAPTER**    | Rate**    | **No.**     |           | A |              |
|              |           |             | **I       | p |              |
| **Use**      | **(lb     | **Apps.**   | nterval** | p |              |
|              | ai/A)**   |             |           | l |              |
|              |           |             |           | i |              |
|              |           |             |           | c |              |
|              |           |             |           | a |              |
|              |           |             |           | t |              |
|              |           |             |           | i |              |
|              |           |             |           | o |              |
|              |           |             |           | n |              |
|              |           |             |           | * |              |
|              |           |             |           | * |              |
|              |           |             |           |   |              |
|              |           |             |           | * |              |
|              |           |             |           | * |              |
|              |           |             |           | M |              |
|              |           |             |           | e |              |
|              |           |             |           | t |              |
|              |           |             |           | h |              |
|              |           |             |           | o |              |
|              |           |             |           | d |              |
|              |           |             |           | * |              |
|              |           |             |           | * |              |
+==============+===========+=============+===========+===+==============+
| **DSMA**^1^  |           |             |           |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Cotton       | 1.7       | 1           | n/a       |   | ground or    |
|              |           |             |           |   | aerial       |
+--------------+-----------+-------------+-----------+---+--------------+
|              | 1.7       | 2           | 1 -- 3    |   | ground       |
|              |           |             | weeks     |   | (directed)   |
+--------------+-----------+-------------+-----------+---+--------------+
| Turf ^2^     | 2.5       | 4           | 14 days   |   | ground spray |
+--------------+-----------+-------------+-----------+---+--------------+
| Orchards,    | 3.7       | 3           | not       |   | ground       |
| Citrus,      |           |             | specified |   | (directed)   |
| Vineyards    |           |             |           |   |              |
| ^3^          |           |             |           |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Non-crop ^4^ | 3.9       | 4           | 10 -- 14  |   | ground spray |
|              |           |             | days      |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Grass for    | 3.3       | 1           | n/a       |   | not          |
| seed ^5^     |           |             |           |   | specified    |
+--------------+-----------+-------------+-----------+---+--------------+
| **MSMA**^1^  |           |             |           |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Cotton       | 1.7       | 1           | n/a       |   | ground or    |
|              |           |             |           |   | aerial       |
+--------------+-----------+-------------+-----------+---+--------------+
|              | 1.7       | 2           | not       |   | ground       |
|              |           |             | specified |   | (directed)   |
+--------------+-----------+-------------+-----------+---+--------------+
| Turf         | 3.4       | 4           | 10 -- 14  |   | ground spray |
|              |           |             | days      |   |              |
| \- Sod       | 2.2       |             |           |   |              |
| Farms^6^     |           |             |           |   |              |
|              |           |             |           |   |              |
| \- Golf      |           |             |           |   |              |
| Course^6^    |           |             |           |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Orchards,    | 3.7       | 3           | 10 -- 14  |   | ground spray |
| Citrus,      |           |             | days      |   |              |
| Vineyards    |           |             |           |   |              |
| ^3^          |           |             |           |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Non-crop ^4^ | 3.4       | 4           | 10 -- 14  |   | ground spray |
|              |           |             | days      |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Grass for    | 5.3       | 1           | n/a       |   | not          |
| seed ^5^     |           |             |           |   | specified    |
+--------------+-----------+-------------+-----------+---+--------------+
| **CAMA**^1^  |           |             |           |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Turf         | 3.6       | 4           | not       |   | ground spray |
|              |           |             | specified |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
|              | 2.2 --    | 2           | not       |   | ground spray |
|              | 4.4       |             | specified |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| **Cacodylic  |           |             |           |   |              |
| Acid /       |           |             |           |   |              |
| Sodium       |           |             |           |   |              |
| Cacodylate** |           |             |           |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Cotton       | 1.2       | 1           | n/a       |   | ground or    |
|              |           |             |           |   | aerial       |
+--------------+-----------+-------------+-----------+---+--------------+
| Citrus ^3^   | 5.0       | 3           | not       |   | ground spray |
|              |           |             | specified |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Non-crop ^4^ | 8.1       | 3           | not       |   | ground spray |
|              |           |             | specified |   |              |
+--------------+-----------+-------------+-----------+---+--------------+
| Turf         | 5         | not         | not       |   | ground spray |
|              | lb/100gal | specified   | specified |   |              |
| \- general   |           |             |           |   | ground spray |
|              | 8.4 - 21  | not         | 5 days    |   |              |
| \- lawn      |           | specified   |           |   |              |
| renovation   |           |             |           |   |              |
+--------------+-----------+-------------+-----------+---+--------------+

^1^ Reported as lbs acid equivalent/A.

^2^ Prohibited on golf course greens.

^3^ Non-bearing only - not to be used within one year of harvest.
Restricted to spot treatments in Florida.

^4^ Non-crop = "drainage ditchbanks, rights-of-way, storage yards and
similar areas".

^5^ Pacific Northwest only.

^6^ Sod farm rate allowed on sod farms and established Bermuda and
Zoysiagrass. Golf course rate allowed on athletic fields, golf courses,
and parks.

^5^ Pacific Northwest only.

*CAMA*[]{#__RefHeading___Toc126565949 .anchor}

Calcium acid methanearsonate (CAMA) is a minor use contact herbicide
applied to control crabgrass in residential areas. It is only sold at
the retail level and not to commercial or industrial applicators. As
with DSMA and MSMA, in aqueous solution

CAMA dissociates to MMA and so rates are reported as acid equivalents.
The maximum labeled application rate for CAMA is 4 applications at 3.6
lb ae/A. Limited usage data are available for residential uses, but the
total usage of CAMA is estimated to account for less than 1% of total
national usage of the methanearsonate salts.

*Cacodylic Acid*[]{#__RefHeading___Toc126565950 .anchor}

Cacodylic acid (DMA), sometimes formulated with its sodium salt, sodium
cacodylate (DMA-Na), is used primarily as a defoliant on cotton. Number
range CHAPTERCurrent labels for irrigated and dryland cotton allow
application of up to 1.2 lb ai/A annually by either aerial or ground
spray. Treatment on cotton is made when 50% or more of the bolls have
opened (7 to 10 days prior to the anticipated picking date). The most
recent USGS pesticide use maps, based on data from 1995-1998, indicate
that use of DMA on cotton is limited to California and Arizona (USGS,
2003). Based on use data from 1998-2003, BEAD estimates average annual
use of DMA on cotton of 80,000 lbs/yr and for DMA-Na, use is estimated
at 100,000 lbs/yr. The total use of cacodylate on cotton, then, is
180,000 lb/yr. The current BEAD analysis also estimates that 20,000
lb/yr of DMA is used on corn. EFED is not aware of any labeled uses on
corn; it is not a use supported under the proposed master label (BEAD,
2005b).

A small proportion of DMA/DMA-Na use is on non-crop sites, including
utilities, residential outdoor, and weed treatment around the bases of
citrus trees. Application rates for DMA/DMA-Na to non-crop sites are
mostly higher than for cotton; for many products, however, directions
simply specify mixing a certain amount of product in a specified number
of gallons of water and applying the spray solution to the point of
runoff. The labels imply, however, that in these uses DMA is expected to
be applied to a very small area, with most labeled rates described in
terms of how much product to apply to areas from 40 to 1000 square feet.
Application for non-crop sites is by ground only. Because DMA/DMA-Na
produces a top-kill only, repeat applications are needed for season long
weed control. Some labels limit the number of applications to three per
year but many simply state that repeat applications can be made as
needed. The registrants are preparing a master label for these uses
also; that label was not complete at the time of the current assessment
and so has not been considered here. No national use data are available
for non-crop applications. BEAD's agricultural usage analysis found no
use on citrus (BEAD, 2005b).

*Co-occurrence*[]{#__RefHeading___Toc126565951 .anchor}

On cotton, it is possible that DSMA or MSMA, as early-season herbicides,
and DMA, as a late-season desiccant, could be applied to the same field.
BEAD estimates that this co-occurrence is likely to affect less than 1%
of the cotton crop. It is also possible that DMA, MSMA, DSMA, and CAMA
could be applied to multiple crops within the same watershed.

**ENVIRONMENTAL FATE AND TRANSPORT
CHARACTERIZATION**[]{#__RefHeading___Toc126565952 .anchor}

*Note: What follows is a summary of the environmental fate and transport
characteristics of organic arsenicals. A detailed discussion of these
complex processes is included as an appendix in the Ecological Risk
Assessment document (DP Barcode D309100). That discussion includes
references to all registrant conducted and open literature reports
considered.*

MSMA, DSMA, and CAMA are salts of the dibasic weak acid MMA. In aqueous
solution, they dissociate to MMA and the associated companion cations.
DMA is a weak acid with two methyl groups attached to the central
arsenic atom, rather than one as in MMA. These pesticides are all
non-volatile solids that are highly soluble in water. Physicochemical
properties of these compounds are listed in Tables 3a and 3b.

**Table 3a. Physicochemical Properties for MSMA and DSMA.**

+-----------------------+-----------------------+---------------------+
|                       | **DSMA**              | **MSMA**            |
+-----------------------+-----------------------+---------------------+
| Molecular Structure   | ![](medi              | ![](media/im        |
|                       | a/image2.wmf){width=" | age3.wmf){width="0. |
|                       | 1.2236111111111112in" | 9965277777777778in" |
|                       | height="0.76875in"}   | height="0.76875in"} |
+-----------------------+-----------------------+---------------------+
| Empirical Formula     | CH~3~AsNa~2~O~3~      | CH~4~AsNaO~3~       |
+-----------------------+-----------------------+---------------------+
| Molecular Weight      | > 183.92              | > 161.94            |
+-----------------------+-----------------------+---------------------+
| CAS No.               | > 144-21-8            | > 2163-80-6         |
+-----------------------+-----------------------+---------------------+
| PC Code               | > 013802              | > 013803            |
+-----------------------+-----------------------+---------------------+
| Melting Point (*ºC*)  | > \>300               | > 116-121           |
+-----------------------+-----------------------+---------------------+
| Density (*g/mL*)      | > 1.04                | > 1.65              |
+-----------------------+-----------------------+---------------------+
| Vapor Pressure (*mm   | > 1 x 10^-7^          | > 7.5 x 10^-7^      |
| Hg*)                  |                       |                     |
+-----------------------+-----------------------+---------------------+
| log K~ow~             | > \< 1                | > \< 1              |
+-----------------------+-----------------------+---------------------+
| Solubility: Water     | > 3.4 x 10^5^         | > 104               |
| (*mg/L*)              |                       |                     |
+-----------------------+-----------------------+---------------------+
| Methanol              | > 2.6 x 10^5^         | > 16                |
+-----------------------+-----------------------+---------------------+
| Hexanol               | > 25                  | > 0.005             |
+-----------------------+-----------------------+---------------------+
| pK~a1,2~ (approx.)    | > 4.0, 9.0            | > 4.0, 9.0          |
+-----------------------+-----------------------+---------------------+

**Table 3b. Physicochemical Properties for Cacodylic Acid and Sodium
Cacodylate.**

+-----------------------+-----------------------+---------------------+
|                       | **Cacodylic Acid**    | **Sodium            |
|                       |                       | Cacodylate**        |
|                       | (DMA)                 | (DMA-Na)            |
+-----------------------+-----------------------+---------------------+
| Molecular Structure   | Number range CHAPTER  | O                   |
|                       | O                     |                     |
|                       |                       | \|\|                |
|                       | \|\|                  |                     |
|                       |                       | CH~3~--As--O^-^     |
|                       | CH~3~--As--OH         | Na^+^               |
|                       |                       |                     |
|                       | \|                    | \|                  |
|                       |                       |                     |
|                       | CH~3~                 | CH~3~Number range   |
|                       |                       | CHAPTER             |
+-----------------------+-----------------------+---------------------+
| Empirical Formula     | Number range          | C~2~H~6~AsNaO~2~    |
|                       | CHAPTERC~2~H~7~AsO~2~ |                     |
+-----------------------+-----------------------+---------------------+
| Molecular Weight      | > 138.0               | > 160.0             |
+-----------------------+-----------------------+---------------------+
| CAS No.               | > Number range        | > 124-65-2          |
|                       | > CHAPTER75-60-5      |                     |
+-----------------------+-----------------------+---------------------+
| PC Code               | > 012501              | > 012502            |
+-----------------------+-----------------------+---------------------+
| Melting Point (*ºC*)  | > Number range        | > 77 -- 79.5        |
|                       | > CHAPTER192-194      |                     |
+-----------------------+-----------------------+---------------------+
| Density (*g/mL*)      | > 1.10                | > 1.10              |
+-----------------------+-----------------------+---------------------+
| Vapor Pressure (*mm   | > Non-volatile        | > No data           |
| Hg*)                  |                       |                     |
+-----------------------+-----------------------+---------------------+
| K~ow~                 | > \<0.028             | > No data           |
+-----------------------+-----------------------+---------------------+
| Solubility: Water     | > Number range        | > No data           |
| (*mg/L*)              | > CHAPTER\~1 to 3 x   |                     |
|                       | > 10^6^               |                     |
+-----------------------+-----------------------+---------------------+
| Methanol              | > Number range        | > No data           |
|                       | > CHAPTER3.63 x 10^5^ |                     |
+-----------------------+-----------------------+---------------------+
| Hexanol               | > Number range        | > No data           |
|                       | > CHAPTER1.02 x       |                     |
|                       | > 10^-1^              |                     |
+-----------------------+-----------------------+---------------------+
| pK~a~                 | > 6.2                 | > 6.2               |
+-----------------------+-----------------------+---------------------+

Environmental fate laboratory studies show that organic arsenicals are
stable under all tested abiotic conditions; they do not degrade by
hydrolysis or by aquatic or soil photolysis. Arsenicals can be subject
to microbial metabolism in soil under aerobic and anaerobic conditions.
The occurrence, rate, and products of this metabolism are variable,
dependent on environmental conditions. Persistence of applied parent
compounds can range from days to years, depending on soil properties and
ambient conditions such as soil moisture, temperature, chemical
concentration, bacterial population, and amount of organic matter.
Regardless of the form it takes, however, the total amount of arsenic
present does not change; these arsenicals and their transformation
products, in combination with arsenic from the natural background and
from other anthropogenic sources, maintain the total, immutable arsenic
load. Arsenic from pesticides is not lost but redistributed and
transformed throughout the environment (plants, animals, air, soil,
sediment, water) into other arsenic containing substances.

Metabolism rates do not appear to depend linearly on arsenical
concentration; the kinetics are therefore not necessarily first-order
and so "half-life" may not be an appropriate constant for all
concentrations. Despite the uncertainty, first-order half-lives have
been calculated for modeling purposes and as a convenient measure to
compare laboratory results. The estimated half-lives, used in EFED's
current models, may underestimate the faster initial rate of metabolism
but adequately portray the overall transformation and so are assumed to
be protective for chronic exposure, a major concern for arsenicals. The
modeled aerobic soil half-life for MMA, based on two studies with
similar results, is 240 days. No anaerobic soil half-life was determined
for MMA. For DMA, the Agency derived aerobic soil half-life is 173 ± 115
days with a standard upper 90% confidence limit on the mean of 240 days.
The anaerobic soil half-life for DMA was calculated to be 128 ± 38 days
with a standard upper 90% confidence limit on the mean of 168 days.

The effects of environmental factors on the rate of arsenical metabolism
are complex and poorly defined, with different studies leading to
conflicting results. An increase in temperature leads to increased
transformation. The observed influences of soil organic matter or
applied arsenical concentrations are contradictory. The effect of
aerobic versus anaerobic conditions on metabolism rates is also
ambiguous.

Potential metabolites of applied arsenicals include volatile
alkylarsines and inorganic arsenic (as arsenate or arsenite) along with
carbon dioxide. Additionally, DMA may be present as a metabolite of MMA
as well as applied directly. As with the rate, the metabolism pathway is
sensitive to environmental conditions in indeterminate ways with the
major metabolites occurring in widely variable proportions.
Transformation to volatile alkylarsines, the only metabolism route that
would directly reduce soil arsenic loading, has been shown to be
possible in certain circumstances but is generally not expected to be a
major route of dissipation. A maximum of 35% of applied MMA is expected
to be present as DMA at any one time. Theoretically, there is some
possibility for MMA to metabolize to DMA, but significant transformation
has not been observed in current acceptable field or laboratory studies.
Observed metabolism of MMA and DMA to inorganic arsenic has ranged from
undetected after several years to more than 80% transformation in
several months. Generally, arsenate \[As(V)\] is expected to be the
dominant species of inorganic arsenic, but in reducing conditions,
arsenite \[As(III)\] may be more stable.

Some of the variability in metabolism processes is associated with
variability in sorption, because microbial degradation is only likely to
occur while compounds remain dissolved in pore water. Mobility of
arsenicals is typically very low to intermediate and appears to be
independent of organic matter content. Instead, sorption is higher in
soils with higher percentage of clay or with more iron or aluminum
content. Laboratory studies have shown that in some situations,
significant sorption of arsenic compounds may occur within hours of
application, while in others, a large portion of applied arsenic remains
in water-soluble forms for days or months after application.
Remobilization of sorbed arsenic with changing environmental conditions
is also possible. One study found by direct comparison that all
arsenicals were more strongly sorbed than phosphate in the increasing
order: phosphate \< DMA \< arsenate \~ MMA. The lowest non-sand K~d~ for
MMA is 11.4 mL/g. For 20 tested soils, the range of K~d~s spans two
orders of magnitude (0.5 to 95 mL/g, mean 37 mL/g). For DMA, the lowest
non-sand K~d~ from 16 soils is 8.2 mL/g (range 8.2 to 33 mL/g, mean 18
mL/g).

**GROUNDWATER EXPOSURE**[]{#__RefHeading___Toc126565953 .anchor}

Arsenic compounds sorb strongly to soil and are relatively immobile in
most environments, as discussed in the Environmental Fate Summary.
Significant leaching of organic arsenicals applied according to the
labels is therefore unlikely in most conditions. This conclusion is
supported by several field studies which have not detected arsenic from
pesticide application below the top layers of soil. Natural background
levels of arsenic in groundwater are extremely variable and can reach
levels greater than 100 ppb. National monitoring has found no
relationship between agricultural use of arsenicals and *widespread*
high arsenic concentrations, but recent investigations in Florida have
detected elevated arsenic levels in groundwater below golf courses. In
most situations, Number range CHAPTERorganic arsenical pesticides should
not contribute significantly to the already existing burden of arsenic
in groundwater from all sources, natural and anthropogenic. In certain
vulnerable circumstances in areas with low background arsenic,
application of organic arsenicals may lead to an increase in groundwater
total arsenic.

Modeling of estimated groundwater concentrations was not conducted.
SCI-GROW, the Agency's current screening level groundwater model, is
based on data from groundwater studies for a number of organic
pesticides. The environmental behavior of arsenicals is quite different
from that of typical organic pesticides. A primary difference is that
arsenical sorption tends to correlate with soil mineral properties
rather than the amount of organic matter. For this reason, SCI-GROW is
not an appropriate tool for estimating the groundwater concentrations
that may result from application of organic arsenical pesticides.

**Groundwater Monitoring**[]{#__RefHeading___Toc126565954 .anchor}

*Background Arsenic (Non-targeted
Monitoring)*[]{#__RefHeading___Toc126565955 .anchor}

Data on arsenic in groundwater are abundant, but the majority of
sampling is not targeted specifically to determine the impacts of
organic arsenicals applied as herbicides. Additionally, most monitoring
is conducted for total arsenic, consistent with the regulatory limits,
rather than for speciated forms of arsenic. These non-targeted,
unspeciated results are most useful as a measure of background
concentrations.

The most extensive consideration of groundwater arsenic has been done by
the USGS. A USGS map of total arsenic distribution in ground waters of
the U.S. is shown below in Figure 1 (Ryker, 2001). In one study, USGS
authors retrieved water-quality data from the National Water Information
System (which includes National Water Quality Assessment \[NAWQA\] data)
and other sources totaling about 50,000 samples from about 30,000
locations (Welch, 2000). A subset of about 20,000 analyses from the
years 1973-1997 which met certain criteria were selected for statistical
testing. Only a single analysis for a particular well or spring was used
to avoid bias towards frequently sampled

![](media/image4.wmf){width="5.9944444444444445in"
height="4.069444444444445in"}

**Figure 1. Arsenic in Groundwater in the United States.** Equal-area
map representing arsenic concentrations found in at least 25% of
ground-water samples within a moving 50km radius, based on USGS NAWQA
data. (Ryker, 2001).

sources. Sample sites were not uniformly distributed across the country
and were not specifically targeted for areas where arsenical pesticides
were applied.

Based on this statistical analysis, nearly half of the groundwater
samples were found to have *total* arsenic concentrations \< 1 ppb while
about 10% exceeded 10 ppb (Welch, 2000). The authors conclude that
natural arsenic concentrations exceeding 10 ppb are more widespread than
previously recognized, although they still find that "ground water in
the U.S. typically contains low to very low arsenic concentrations,
particularly in \[the East\]." Some areas of high arsenic concentrations
were associated with point source pollution but most appeared to be
natural. High arsenic concentrations were found throughout the study,
but in general, the Appalachian Highlands and the Atlantic Plain had
very low levels with somewhat greater concentrations in the Rocky
Mountain System and Interior Plains and the highest concentrations found
most frequently in the Intermontane Plateaus and the Pacific Mountain
System. The survey authors report that even in areas that tend to have
naturally high arsenic concentrations there exists some ground water
with low to very low arsenic concentrations. Steep lateral and vertical
concentration gradients exist, showing inherent local spatial
variability. This article provides a thorough review of the
environmental geochemistry of arsenic and arsenic occurrence in relation
to natural sources.

Speciated monitoring data are limited. The Welch report cites
groundwater sampling in northwestern Nevada in an area where organic
arsenical herbicides are not applied (2000). In 30 samples tested for
MMA and DMA, all results were \<0.3 ppb. An additional USGS study
analyzed 6 groundwater samples from Idaho, 10 from Illinois, and 8 from
Nevada (total of 24 sites) for arsenite \[As(III)\], arsenate \[As(V)\],
MMA and DMA (Garbarino and Burkhardt, 1998). Again, none of the sites
were associated with the application of arsenical pesticides. With a
detection limit of approximately 0.2 ppb, there were no measurable
concentrations of the methylated compounds in ground water. In contrast,
arsenite or arsenate concentrations in these groundwater samples ranged
from less than the method detection limit to a concentration as high as
approximately 900 ppb. Their data show that either arsenite or arsenate
or both were detected in all samples, typically at 10-50 ppb.

The USGS water resources database was found to include 798 groundwater
samples with speciated measurement of organic arsenicals, collected
between 2002 and 2004. (The NWISWeb database is available online at
<http://waterdata.usgs.gov/nwis>. Information about data quality
procedures and about the studies represented in the database can be
found at this site.) More than half of the samples were from Kansas
(56%) with nearly a third from Idaho (27%). The remaining samples were
from Maryland, Nevada, New Jersey, Oklahoma, and West Virginia. No
information is available about the land uses in the areas sampled; the
sites are not evenly distributed and are not targeted to pesticide use.
For both DMA and MMA, the median result was less than the detection
limit, which were generally between 0.1 and 1.2 ppb. All values are
reported as arsenic. The averages were 0.23 and 0.15 ppb and the 90^th^
percentile values were 0.5 and 0.3 ppb for DMA and MMA, respectively.
The maximum concentrations for DMA and MMA, 14.9 and 34.8 ppb,
respectively, were both from the same site in Idaho. On the same date,
total arsenic at this site was measured at 858 ppb. Generally, no data
were available about total arsenic at these sites.

*Pesticide Impacts (Targeted Monitoring)*[]{#__RefHeading___Toc126565956
.anchor}

The USGS report on background arsenic in groundwater includes a
discussion of monitoring done in study areas where "high arsenic
concentrations regionally coincide with agricultural use" (Welch, 2000).
Based on studies of agricultural use of *inorganic* arsenical pesticides
in North Dakota, South Dakota, Wisconsin, and Minnesota, the authors
find that "although some contribution of arsenic from historic uses is
possible, \[these studies\] all conclude that ground water is largely
unaffected by use of arsenical pesticides." In the several sites where
groundwater was determined to be affected by anthropogenic arsenic
sources, the detections were associated with disposal or other types of
point source pollution.

The EPA Pesticides in Groundwater Database includes monitoring data for
two sites, both of which show high concentrations of *total arsenic* in
a high percentage of water wells (USEPA, 1992). In localized areas of
Texas, concentrations of 10-680 ppb were found in 91 of 247 wells with
limits of detection (LODs) of 10-25 ppb. The Agency independently
concluded that these detections were associated with use of cacodylic
acid, but not from non-point source, labeled pesticidal application
(Aurelius, 1988). Rather, the high concentrations were most likely
caused by cacodylic acid-treated cotton gin waste which was spread in
the vicinity of poorly cased wells, and by somewhat higher natural
concentrations of arsenic. In the State of Washington, where total
arsenic was found at 1.6-13.3 ppb in 15 of 20 wells (LOD 0.2 ppb), no
connection was found with organic arsenical pesticides (Erickson, 1990).
In this area, natural conditions including historical volcanic activity;
strongly alkaline, sandy soils; hydrology favorable to the migration of
soluble constituents; and thermal waters may have contributed to the
elevated concentrations, as well as possible inputs from former heavy
use of calcium or lead arsenates in orchards (sometimes hundreds of
lbs/A annually) or wastes from mining operations.

All of the targeted monitoring studies reviewed below were conducted in
Florida, an area of concern because of its very sandy soils and shallow
water tables. Although arsenicals are strongly sorbing, lab studies have
shown that leaching in typical Florida soils may be important. Golf
courses, major users of MMA, may be particularly susceptible to leaching
because they typically have well-drained soils and are heavily
irrigated.

Given the variability of natural arsenic, it is useful to have
information about regional background levels to compare with targeted
results. The USGS water resources database included 322 arsenic
groundwater samples from Florida collected at 235 sites between 1990 and
2004. This sampling found an average arsenic concentration of 1.1 ppb
with a 90^th^ percentile value of 2.5 ppb. (All arsenic concentrations
in this discussion of monitoring data are unspeciated, reported as
*total* arsenic, unless otherwise specified.) This sampling is not
uniformly distributed and not directed to specifically capture only
control, non-use areas. When available, background data specific to
targeted monitoring locations are included in this discussion.

One Florida monitoring study, while not targeted to specific uses, found
higher arsenic in groundwater in an urban area than a control region in
the same aquifer (German, 1996). In the control area there were no
detections of arsenic in 10 samples while around the Orlando urban area,
arsenic was detected in 6 of 23 samples with a maximum of 13 ppb. This
demonstrates that anthropogenic inputs of arsenic may reach groundwater
but provides no information about the specific source. In urban areas,
possible inputs include but are not limited to application of organic
arsenicals to golf courses and residential lawns.

Several other Florida monitoring studies focus on groundwater that may
be impacted by golf course uses. The 2 studies reviewed here look at
groundwater at 14 golf courses. The first study, conducted by the USGS
in conjunction with the Florida Department of Environmental Protection
(FDEP), was designed to determine if pesticides used in turf-grass
management were migrating to shallow groundwater (Swancar, 1996). Most
of the 9 golf courses tested were in central Florida with one to the
south in Broward County and one in the panhandle, in Pensacola. Samples
were taken quarterly for a year at 39 wells, most at tees and greens
with 3 wells in pesticide mixing and loading areas. Arsenic was detected
in 6 wells on 4 golf courses. On greens, 4 wells at 3 golf courses had
detections, with concentrations ranging from 11 -- 120 ppb. The average
arsenic concentrations from the 4 samples taken at each well were 21,
28, 30, and 64 ppb. Arsenic was detected in wells from 1 tee site and 1
mixing/loading area, with average concentrations of 3 and 32 ppb,
respectively (Swancar, 1996).

This is not a controlled study and detailed pesticide application
histories are not available. The study shows that in general, pesticides
applied to Florida golf courses may reach groundwater, finding that of
the more than 40 pesticides and metabolites tested for, 13 were detected
in golf course groundwater. Specific to arsenic, recent pesticide
application data coupled to concentration trends, along with known
historical uses, point to MSMA application as a likely source of
groundwater arsenic at these golf courses. At Ventura Golf Course, where
arsenic was detected at 1 green well at an average of 28 ppb, MSMA had
been applied 10 days prior to the 2^nd^ sampling event, when arsenic
concentrations were found to have increased from 11 ppb to 48 ppb.
Concentrations steadily decreased at the following 2 sampling events,
reaching 22 ppb by the last sample, taken approximately 6 months later.
This concentration trend provides evidence that MSMA application
resulted in elevated groundwater arsenic levels. Historically, at least
12 years prior to monitoring, part of this site was a dairy farm. MSMA
was applied monthly at the Highland Golf Course, where arsenic was
detected at 1 green well at levels as high as 120 ppb with a mean of 64
ppb. Prior to development as a golf course, this was open land or
pasture with citrus groves nearby. Bonaventura Golf Course, in south
Florida, had the most arsenic detections, in 2 green wells and 1
mixing/loading area. The first application of MSMA during the sampling
period was between the 2^nd^ and 3^rd^ sampling events in areas not
specific to the greens. There is no particular trend in arsenic levels
at these wells. Before the golf course was established, this land was
part of Everglades National Park (Swancar, 1996).

The results of this study, along with documented violations of soil
cleanup target levels for arsenic, led the Miami-Dade County Department
of Environmental Resources Management (DERM) to conduct monitoring at 5
county golf courses (2002). At each golf course, three well clusters
were installed including one shallow (10-15 ft) and one deep (21-28 ft)
well. All golf courses had one well cluster in a pesticide mixing and
loading area with the other wells evenly divided between tees, greens,
and fairways, and wells were sampled quarterly for one year. In shallow
wells, 76% of all samples exceeded 10 ppb as arsenic with 32% exceeding
50 ppb as arsenic. Groundwater arsenic concentrations at greens were not
found to be significantly higher than those at tees and fairways,
although there were higher concentrations at mixing and loading areas.
In greens, the median concentration was 13.6 ppb with a maximum of 55
ppb. On fairways, the median was 17.8 ppb and the maximum was 56 ppb. In
tee areas, the median was 81.8 ppb and a maximum of 123 ppb. In
mixing/loading areas, concentrations reached as high as 815 ppb with a
median of 31.8 ppb (DERM, 2002). Concentrations were much lower in
deeper wells, with a maximum of 44 ppb. Arsenic was only detected in
deeper groundwater at 3 of the 5 golf courses, with 18% of the samples
having concentrations greater than 10 ppb. The highest concentrations
were found in mixing/loading areas. Only tees, with a maximum of 11 ppb
and a median of 3 ppb, exceeded the detection limit in more than 50% of
the samples (DERM, 2002).

To establish background levels, three pre-existing shallow monitoring
wells in nearby residential areas were monitored concurrently. Based on
10 total samples, the maximum concentration was 5 ppb and the median was
less than the detection limit. Additionally, historical data was
gathered from wells at similar depths in the Ambient Water Quality
Monitoring network. Based on 22 total samples, the maximum was 13.9 ppb
and the median was 2.0 ppb (DERM, 2002). These data indicate that the
golf course arsenic levels are higher than background levels.

Other potential arsenic sources in these areas are discussed, including
historical land uses and arsenic from fertilizers. All golf courses in
the study were established prior to 1975 with some more than 50 years
old. One course was built on undeveloped land, one on farmland, and a
portion of one was used as a municipal dump 25 years prior to sampling.
No historical land use information is provided for the other two
courses. The highest shallow groundwater concentrations in
mixing/loading areas and fairways are from the previously undeveloped
site while the landfill site had more detections of arsenic in deep
groundwater than most other golf courses. These past uses are potential
arsenic sources, but at those courses, the available data are not
sufficient to rule out modern or historical contributions to arsenic
contamination. Fertilizer samples were collected from the participating
golf courses and analyzed for arsenic. Arsenic concentrations in
fertilizer ranged from below detection limit to 15 mg/kg, with a mean of
3.27 mg/kg (DERM, 2002).

A third report, by the Florida Department of Environmental Protection,
describes investigations done at golf course sites where levels of
arsenic have been found to exceed local regulatory limits (FDEP, 2002).
In some cases, FDEP was able to rule out pesticide applications as a
primary source of arsenic contamination, but in at least 3 sites,
pesticide application was linked to contamination. This report focuses
on soil arsenic levels, but groundwater arsenic is measured as well. At
two golf courses, although groundwater levels reach 472 ppb at one and
1300 ppb at the other, concentrations are only reported for maintenance
areas, so it cannot be determined whether there are impacts from
non-point sources. At the Palm Beach Lakes Golf Course, two sets of
shallow groundwater sampling were conducted. The first, focusing on
former green areas, found arsenic levels exceeding 10 ppb in all 20
samples. The second set, in a different parcel of the course, consisted
only of playing areas and found exceedances of the 10 ppb MCL in 22 of
27 samples.

These are not controlled studies. Nevertheless, considered as a group,
they show a trend of groundwater arsenic at Florida golf courses well
above local background levels and in many cases exceeding the federal
MCL. Although evidence of the source of arsenic is generally not
conclusive, pesticide application is a probable contributor to these
levels, and in some cases, appears to be the likely source. The
registrants and the State of Florida are currently negotiating a plan
for a prospective groundwater study designed to investigate potential
leaching of organic arsenicals in this vulnerable setting. This study is
expected to lead to more conclusive evidence of whether or not applied
arsenicals may reach groundwater.

**SURFACE WATER EXPOSURE**[]{#__RefHeading___Toc126565957 .anchor}

Arsenical pesticides and their metabolites may be transported to surface
waters and sediments through runoff water, eroding soils, or drift
during application. Both monitoring data and modeling results, discussed
below, suggest that these routes of exposure are likely to lead to local
elevations above background arsenic levels in surface water bodies. This
is true for both the turf and the cotton uses, although the higher
application rates for turf and potentially more widespread application
lead to higher estimated concentrations.

**Surface Water Monitoring**[]{#__RefHeading___Toc126565958 .anchor}

*Background Arsenic (Non-targeted
Monitoring)*[]{#__RefHeading___Toc126565959 .anchor}

As with groundwater, unspeciated surface water arsenic data not targeted
to pesticide use areas are abundant. Unlike groundwater, no major
statistical effort has been undertaken to interpret these surface water
data. A less complete consideration of these data can still provide
useful information about typical arsenic concentrations. Unless
otherwise specified, all USGS data discussed in this section is from the
publicly available NWISWeb database. The database, as well as
information about data quality procedures and about the studies
represented, can be accessed at <http://waterdata.usgs.gov/nwis>. The
USGS dataset includes nearly 40,000 lake and stream samples collected
nationally between 1990 and 2004 at around 4500 locations. Sample sites
were not uniformly distributed across the country and these data have
not been corrected for bias resulting from frequently sampled sources.
The data also include sampling from point sources such as mine waste but
specific land use information has not been considered. Half of the
samples had total arsenic concentrations ≤1.1 ppb and 10% of the samples
exceeded the MCL of 10 ppb. With the exception of a mine in
Pennsylvania, the very high arsenic concentrations, greater than 100
ppb, are all in the western U.S. with New Mexico and North Dakota as the
furthest east samples. For concentrations between 50 and 100 ppb, there
are only 2 sites in the eastern region not obviously associated with a
point source. Perhaps coincidentally, both are in heavy cotton producing
areas, one in Texas and one in Mississippi. The USGS groundwater report
included a brief consideration of surface water arsenic, finding that
the most common natural cause of elevated arsenic in surface water is
discharge of geothermal water (Welch, 2002).

The BASINS and STORET databases maintained by the US EPA also provide a
large body of data (many tens of thousands of entries) on *total*
arsenic concentrations in surface waters of the U.S. As with the USGS
surface water data, the wide ranging concentrations in space and time
and the multiplicity of possible major sources of arsenic make any
attempt to associate these with pesticide use impractical. Nevertheless,
even casual inspection of the data from the databases shows that it is
not unusual for total arsenic concentrations in raw surface water in
many different sites to be several parts per billion. Spatial
variability is the rule. The data for Georgia and Texas are discussed
here as illustrative of this variability and are not meant to imply a
special situation. In Georgia, as presented in BASINS, upper 85^th^
percentile concentrations of total arsenic at different sites ranged
from less than 1 ppb to 338 ppb. More typical high values fall in the
range of 10 to 50 ppb. The most probable concentration appears to fall
in the range of \<1 to 2 or 3 ppb. The STORET database for Georgia and
Texas show similar results, with Texas seeming to average several parts
per billion more. Some of the highest values reported in STORET for
Georgia and Texas (79,000 entries) approach 1000 ppb and can often be
associated with anthropogenic point source pollution. As previously
mentioned, natural sources (especially in places in the western U.S.)
also produce such high concentrations.

Speciated data on arsenic in surface waters are sparse. A search of the
USGS database found only 26 samples, not enough to overcome the
limitations of the dataset with regard to site distribution and unknown
land uses. One open literature study tested 10 natural waters in the
vicinity of Tampa, Florida (Braman and Foreback, 1973). There were six
surface fresh water bodies (two rivers, two ponds, two lakes) and three
saline waters (two bays, one tidal flat) included in the study. One
groundwater site was also included, a well in a remote camping area.
Analysis was for the four arsenic species: DMA, MMA, arsenite, and
arsenate. All concentrations reported below are as arsenic equivalents.
Concentrations of DMA in the natural waters ranged up to 1.0 ppb. At one
site, the Hillsborough River, concentrations were below a remarkably low
detection limit of 0.02 ppb, while the median value for DMA at the other
nine sites was approximately 0.3 ppb As. Concentrations of arsenate,
detected at all ten sites, were similar to cacodylic acid. Arsenite was
detected at only six of the ten sites, but had the highest concentration
(2.7 ppb) of all species. MMA, detected in eight of the ten sites, was
generally present at lower concentrations, the highest being 0.22 ppb
As. However, in a broader sense, considering the few samples, surface
water concentrations of all four were similar. Total arsenic
concentrations ranged from approximately 0.3 to 3.6 ppb. The extent to
which these concentrations represent the natural background in the Tampa
area or are influenced by introduction of artificial sources is unknown.
However, the study authors considered the sampled sites as "natural"
waters.

A California study measured speciated arsenic in 14 water bodies
(10 lakes, estuaries, or reservoirs, and 4 rivers or creeks) in order to
compare concentrations of methylated arsenical forms to inorganic forms
(Anderson, 1991). The authors indicate that the sampling represents
drainage basins both affected and unaffected by agricultural runoff but
do not distinguish between the two. All sites had measurable arsenic,
although in 8 of the 14 sites, total arsenic was less than 2 ppb and in
1 site, Mono Lake, inorganic arsenic was extremely high (17 *ppm*),
likely due to its unique hydrogeology. At Mono Lake, analysis for
organic arsenic was impossible and so this site will not be considered
further in this discussion. The highest measured concentrations of MMA
and DMA were equivalent to 0.6 ppb and 2.5 ppb as arsenic, respectively.
These were found in the Salton Sea, where the total arsenic
concentration was 12.8 ppb. The Salton Sea receives a substantial amount
of agricultural runoff, including from cotton-growing areas, but also
has geothermal activity, a possible source of natural arsenic. The
stream sites had total arsenic concentrations ranging from 0.7 to 7.4
ppb but had no detectable concentrations (\<0.1 nM) of MMA or DMA. Of
the 9 other sites, 7 had measurable concentrations of MMA and all 9 had
measurable concentrations of DMA. In these sites, the average
concentration of MMA, as arsenic, was 0.15 ppb with a standard deviation
of 0.2 ppb. The average concentration of DMA was higher, at 0.62 ppb
with a standard deviation of 0.8 ppb. Except for one site, which had 57%
of total arsenic present in methylated form, inorganic arsenic was found
in much higher concentrations than organic, which ranged from 1% to 39%
of total arsenic.

*Pesticide Impacts (Targeted Monitoring)*[]{#__RefHeading___Toc126565960
.anchor}

There are several monitoring studies available targeted to measure the
impact of organic arsenical herbicides on surface water. One study
collected surface water samples at one or two week intervals from early
March through the middle of September of 1997 from two drainage basins
in high cotton producing areas of Mississippi (Bednar, 2002). Sampling
dates and times varied between sites and were not correlated. A total of
24 samples were analyzed from each the Yazoo and the Bogue Philia
drainages. Analyses were for MMA, DMA, arsenite, and arsenate. Maximum
concentrations, as arsenic, of MMA at Yazoo and Bogue Philia were
approximately 2 ppb and 5 ppb, respectively, and were relatively
short-lived. The highest concentrations were seen in June and July, at
the end of the period when MSMA is most likely to be applied.
Concentrations of DMA were at or below the detection limit of 0.2 ug/L,
except for one sample which registered approximately 0.6 ug/L. Arsenate
and arsenite reached maximum concentrations similar to those from MMA;
both approximately 2 ppb at Yazoo and approximately 3.5 ppb (arsenite)
and 5.5 ppb (arsenate) at Bogue Philia. The higher concentrations of
inorganic arsenic were measured more frequently than those for MMA. In
all samples, one species tended to dominate; the comparable
concentrations of arsenite and arsenate is also noteworthy. At the Bogue
Philia site, inorganic arsenic concentrations increased after the MMA
maximum was measured, possibly indicating transformation of the organic
arsenical or a secondary source of arsenic (Bednar, 2002; in previous
REDs, the same data were cited from Garbarino, 1998).

Detailed histories of MSMA application in this area are not available
and the location of water bodies relative to application sites was not
published. Without baseline data for arsenic concentrations in areas
without arsenical application, which are not provided in this study, it
cannot be concluded whether the fluctuations seen here are part of the
natural arsenic cycle or influenced by pesticide application. For
comparison, the Agency retrieved surface water arsenic concentrations
from the USGS database, which included 65 samples in Mississippi. The
samples are not uniformly distributed and information about land use
patterns is not available. The average total arsenic concentration found
was 3.4 ppb with a 90^th^ percentile value of 4 ppb. All samples with
arsenic concentrations higher than 4 ppb were from a single water body
where levels reached as high as 72 ppb. Presumably this water body is
impacted by a pollution source and therefore not representative of
background levels. If these data are not included, the average of the 60
remaining samples is 1.1 ppb with a 90^th^ percentile of 2 ppb. While
still not conclusive, this suggests that at least the higher arsenic
concentrations found in the Bednar report, above 5 ppb, are higher than
would be expected from background arsenic alone.

Limited monitoring has been done in surface water bodies on golf courses
as well. Golf course ponds are relatively small water bodies and are
typically completely surrounded by potential application areas, and
therefore runoff sources. Consequently, these ponds are likely to
represent the upper end of possible surface water concentrations.
Limited monitoring, however, cannot be expected to capture peak
concentrations. One USGS study, also discussed in the groundwater
monitoring section, sampled ponds at 6 golf courses, all in central
Florida, for multiple pesticide residues (Swancar, 1996). Ponds were
sampled 4 or 5 times over the course of one year. Arsenic was below the
detection limit (1 ppb) at 2 of the golf courses and at a third, was
detected in only 1 out of 5 samples, measured at the MCL of 10 ppb. At
the other 3 golf course ponds, concentrations ranged from 5 to 24 ppb.
Of the 13 samples from these 3 ponds, the mean total arsenic
concentration was 11.6 ppb. It is interesting to note that detectable
levels of arsenic were not found in any of the groundwater samples
collected at these 3 locations.

## Surface Water Modeling

Modeling of the application of arsenical pesticides was performed to
predict acute and chronic concentrations that may reach drinking water.
Although there are extensive monitoring data available for arsenic, some
of it even targeted to heavy use areas, modeling remains a valuable tool
to supplement the limitations of monitoring. Most monitoring measures
total arsenic and does not provide information on speciation. Monitoring
data do not generally allow for determination of the source of
contamination. This is particularly important for arsenic, which has
multiple potential sources, both from natural background and from
various anthropogenic activities. Even for those monitoring studies
targeted to heavy use areas, specific information about application
rates and land use history are not always available. Additionally, even
targeted studies cannot be expected to capture short-lived peak
concentrations. In light of these factors, and considering the
variability of arsenic's environmental behavior with variable
environmental conditions, modeling is useful for providing high-end
estimates of speciated arsenic concentrations resulting from pesticide
applications under the most vulnerable conditions.

Number range CHAPTERTo determine estimated drinking water concentrations
(EDWCs) in surface water, the Pesticide Root Zone Model (PRZM 3.12;
5/7/98), which simulates transport off the agricultural field, is run in
tandem with the Exposure Analysis Modeling System, (EXAMS 2.98.04;
6/13/97), which simulates the fate of chemicals in the water body. These
are operated using the pe4v01 shell program (8/13/03). Additional
information about these models can be found at the EPA's water modeling
website,
[[http://www.epa.gov/oppefed1/models/water/]{.underline}](http://www.epa.gov/oppefed1/models/water/).
The simulated watershed is based on an Index Reservoir (IR) scenario,
and a percent cropped area (PCA) adjustment factor is used to adjust for
the area within the watershed that is planted to the modeled crop (OPP,
2000). Models are run for 30 years and the reported EDWCs represent the
values that are expected once every ten years, based on the 30 years of
daily values generated during the simulation.

The crop scenarios used in PRZM/EXAMS represent sites that are highly
vulnerable to runoff. In this assessment, the Mississippi cotton and
Florida turf scenarios are modeled to represent the major uses of
arsenicals. Other cotton and turf scenarios were run to confirm that
these are the most vulnerable of available scenarios. The Mississippi
cotton scenario is located in Yazoo County*,* the number one county in a
state that ranks fourth in cotton production (EFED, 2003). The Florida
turf scenario is located in Osceola County. Golf courses and other areas
of turf cultivation in Florida use a significant amount of arsenical
pesticides each year (Swancar, 1995; Ma, 2002). Minor crop scenarios,
including those for orchards and citrus, were also modeled to provide
characterization.

All species of concern in this assessment (MMA, DMA, and iAs) have
distinct toxicities; exposure to each needs to be considered
individually. Estimated concentrations of each of these compounds are
therefore provided for each use. Compounds resulting from metabolism are
considered as well as directly applied pesticides. Applied MMA may
metabolize to DMA. On cotton, MMA and DMA can be applied to the same
field. Reported cotton MMA EDWCs, therefore, result from direct
application while cotton DMA EDWCs result both from direct application
and from transformation of MMA. On turf, all EDWCs are the result of MMA
application. Both MMA and DMA may also metabolize to inorganic arsenic.
It is impossible to determine the exact concentration of each species
that will be present at any one time and each species will reach its
highest level at different times; the reported EDWCs for parent and
metabolite compounds represent maximum potential concentrations for each
species and are not additive to a total possible concentration. When the
concentration of one species is at its highest, the other species'
concentration will be lower. An EDWC for "total arsenic" has been
reported to indicate the maximum amount of arsenic that may be in
surface water as a **sum** of **all** species present. It is this EDWC
that would be compared to regulatory levels, which are set as total
arsenic. Since it is possible that all arsenic would be present in the
form of inorganic arsenic, this EDWC also represents the maximum
potential concentration of inorganic arsenic. EDWCs resulting from the
maximum labeled application rates for cotton and turf are presented in
Table 4. The input parameters used

**Table 4. EDWCs (ppb) from maximum labeled rates for major uses of
arsenicals.**

  --------------- ------------- -------------- -------------- --------------
                                **Acute**      **Chronic**    **Cancer**

  **TURF**^1^     **MMA**       250.5          127.5          74.6

                  **DMA**       102.3          46.5           28.1

                  **Total       135.2          68.8           40.3
                  As^3^**                                     

  **COTTON**^2^   **MMA**       37.4           11.0           5.3

                  **DMA**       23.6           7.4            4.3

                  **Total       20.9           7.2            3.9
                  As^3^**                                     
  --------------- ------------- -------------- -------------- --------------

> ^1^ MSMA applied 4 times at 3.35 lbs ae/A.
>
> ^2^ DSMA applied 2 times at 1.74 lbs ae/A & DMA applied 1 time at 1.2
> lb/A.
>
> ^3^ Total arsenic is the sum, reported as ppb As, of arsenic that may
> be present from all applied and metabolite species. It also represents
> the maximum EDWC of inorganic arsenic.

are presented in Tables 5 and 6 and more detailed discussion of
parameter selection, methods of determining metabolites, and uncertainty
is included below. The PRZM/EXAMS input files are provided in Appendix A
and the output files in Appendix B.

*Input Parameters: Metabolism Rates*[]{#__RefHeading___Toc126565962
.anchor}

The input parameters used in PRZM/EXAMS modeling in this assessment
(Tables 5 and 6) are based primarily on the values determined for the
most recent REDs (DP Barcodes D210451, D212449, D255226 and DP Barcode
D277223). The validity of each parameter has been considered
individually and, while most have been confirmed, several have been
adjusted to take into account new data or different interpretations of
older data. In part, this process has been a response to concerns
expressed by the registrant regarding the parameterization of the
original modeling. In particular, the registrant argues that thesoil
metabolism half-life inputs used do not account for the biphasic nature
of arsenical metabolism (MAATF, 2005). It is true that arsenical
metabolism appears to be biphasic, occurring more rapidly prior to
sorption. Current EFED modeling requires first order linear rate
constants. Even if biphasic rates could be incorporated, because of the
variability of sorption processes there are insufficient data to allow
for determination of two separate rates. Because chronic exposure is a
major concern for arsenicals, it is assumed to be protective to use a
long term half-life that is less accurate in representing the faster
initial rate of metabolism but that better portrays the overall
transformation.

For [MSMA and DSMA]{.underline}, the modeled half-lives are unchanged
from those used in the 2001 RED (DP Barcode D277223). The *aerobic soil
and aquatic metabolism half-lives* are based on one registrant study
(MRID 44767601; Acceptable) and on a non-GLP open literature study
reviewed in the previous RED (Gao and Burau, 1997). The registrant
submitted a review of additional literature which includes several
studies that quantify shorter half-lives than those used in the initial
RED (MAATF, 2005). Even if those values are included in the calculation,
the 90% confidence half-life only changes from 240 days to 220 days,
which has a minimal effect on the outcome and does not justify the

**Table 5. PRZM/EXAMS Input Parameters for DSMA/MSMA on Cotton and
Turf**

+---------------+---------------+---+---------------+------------------+
| **Model       | **Value**     | * |               | **Source**       |
| Parameter**   |               | * |               |                  |
|               |               | C |               |                  |
|               |               | o |               |                  |
|               |               | m |               |                  |
|               |               | m |               |                  |
|               |               | e |               |                  |
|               |               | n |               |                  |
|               |               | t |               |                  |
|               |               | s |               |                  |
|               |               | * |               |                  |
|               |               | * |               |                  |
+---------------+---------------+---+---------------+------------------+
| Single        | *Cotton*:     |   |               | Master Label     |
| Application   | Number range  |   |               |                  |
| Rate (# of    | CHAPTER1.95   |   |               |                  |
| applications) | kg ae/ha      |   |               |                  |
|               |               |   |               |                  |
|               | (2 apps)      |   |               |                  |
|               |               |   |               |                  |
|               | *Turf*: 3.75  |   |               |                  |
|               | kg ae/ha      |   |               |                  |
|               |               |   |               |                  |
|               | (4 apps)      |   |               |                  |
+---------------+---------------+---+---------------+------------------+
| Application   | *Cotton*:     |   |               | *Cotton:*        |
| Date          | Number range  |   |               |                  |
|               | CHAPTER5/7 (7 |   |               | USDA-NASS        |
| (Intervals)   | days)         |   |               | Planting &       |
|               |               |   |               |                  |
|               | *Turf*: 3/14  |   |               | Harvest Dates    |
|               | (10 days)     |   |               | (12/97)*^1^*     |
|               |               |   |               |                  |
|               |               |   |               | *Turf ^2^*       |
+---------------+---------------+---+---------------+------------------+
| Application   | *Cotton &     | N |               |                  |
| Method        | Turf:*        | u |               |                  |
|               |               | m |               |                  |
|               | Foliar;       | b |               |                  |
|               | ground        | e |               |                  |
|               | applied*^3^*  | r |               |                  |
|               |               | r |               |                  |
|               |               | a |               |                  |
|               |               | n |               |                  |
|               |               | g |               |                  |
|               |               | e |               |                  |
|               |               | C |               |                  |
|               |               | H |               |                  |
|               |               | A |               |                  |
|               |               | P |               |                  |
|               |               | T |               |                  |
|               |               | E |               |                  |
|               |               | R |               |                  |
|               |               | L |               |                  |
|               |               | e |               |                  |
|               |               | a |               |                  |
|               |               | d |               |                  |
|               |               | s |               |                  |
|               |               | t |               |                  |
|               |               | o |               |                  |
|               |               | d |               |                  |
|               |               | e |               |                  |
|               |               | f |               |                  |
|               |               | a |               |                  |
|               |               | u |               |                  |
|               |               | l |               |                  |
|               |               | t |               |                  |
|               |               | v |               |                  |
|               |               | a |               |                  |
|               |               | l |               |                  |
|               |               | u |               |                  |
|               |               | e |               |                  |
|               |               | s |               |                  |
|               |               | o |               |                  |
|               |               | f |               |                  |
|               |               |   |               |                  |
|               |               | 6 |               |                  |
|               |               | . |               |                  |
|               |               | 4 |               |                  |
|               |               | % |               |                  |
|               |               | S |               |                  |
|               |               | p |               |                  |
|               |               | r |               |                  |
|               |               | a |               |                  |
|               |               | y |               |                  |
|               |               | d |               |                  |
|               |               | r |               |                  |
|               |               | i |               |                  |
|               |               | f |               |                  |
|               |               | t |               |                  |
|               |               |   |               |                  |
|               |               | 9 |               |                  |
|               |               | 9 |               |                  |
|               |               | % |               |                  |
|               |               | A |               |                  |
|               |               | p |               |                  |
|               |               | p |               |                  |
|               |               | . |               |                  |
|               |               | e |               |                  |
|               |               | f |               |                  |
|               |               | f |               |                  |
|               |               | i |               |                  |
|               |               | c |               |                  |
|               |               | i |               |                  |
|               |               | e |               |                  |
|               |               | n |               |                  |
|               |               | c |               |                  |
|               |               | y |               |                  |
+---------------+---------------+---+---------------+------------------+
| Incorporation | *Cotton       |   |               |                  |
| Depth         | &Turf:* 0 cm  |   |               |                  |
+---------------+---------------+---+---------------+------------------+
| Aerobic Soil  | 240 days      | 9 |               | Gao & Burau,     |
|               |               | 0 |               | 1997             |
| Metabolism    |               | % |               |                  |
| Half-Life     |               | u |               | MRID 44767601    |
|               |               | p |               |                  |
|               |               | p |               |                  |
|               |               | e |               |                  |
|               |               | r |               |                  |
|               |               | c |               |                  |
|               |               | o |               |                  |
|               |               | n |               |                  |
|               |               | f |               |                  |
|               |               | i |               |                  |
|               |               | d |               |                  |
|               |               | e |               |                  |
|               |               | n |               |                  |
|               |               | c |               |                  |
|               |               | e |               |                  |
|               |               | b |               |                  |
|               |               | o |               |                  |
|               |               | u |               |                  |
|               |               | n |               |                  |
|               |               | d |               |                  |
|               |               | , |               |                  |
|               |               | b |               |                  |
|               |               | a |               |                  |
|               |               | s |               |                  |
|               |               | e |               |                  |
|               |               | d |               |                  |
|               |               | o |               |                  |
|               |               | n |               |                  |
|               |               | 2 |               |                  |
|               |               | v |               |                  |
|               |               | a |               |                  |
|               |               | l |               |                  |
|               |               | u |               |                  |
|               |               | e |               |                  |
|               |               | s |               |                  |
|               |               | . |               |                  |
+---------------+---------------+---+---------------+------------------+
| Anaerobic     | \-\--         | N |               |                  |
| Soil          |               | o |               |                  |
| Metabolism    |               | r |               |                  |
| Half-Life     |               | e |               |                  |
|               |               | p |               |                  |
|               |               | o |               |                  |
|               |               | r |               |                  |
|               |               | t |               |                  |
|               |               | e |               |                  |
|               |               | d |               |                  |
|               |               | d |               |                  |
|               |               | a |               |                  |
|               |               | t |               |                  |
|               |               | a |               |                  |
|               |               | , |               |                  |
|               |               | n |               |                  |
|               |               | o |               |                  |
|               |               | t |               |                  |
|               |               | u |               |                  |
|               |               | s |               |                  |
|               |               | e |               |                  |
|               |               | d |               |                  |
|               |               | a |               |                  |
|               |               | s |               |                  |
|               |               | i |               |                  |
|               |               | n |               |                  |
|               |               | p |               |                  |
|               |               | u |               |                  |
|               |               | t |               |                  |
|               |               | p |               |                  |
|               |               | a |               |                  |
|               |               | r |               |                  |
|               |               | a |               |                  |
|               |               | m |               |                  |
|               |               | e |               |                  |
|               |               | t |               |                  |
|               |               | e |               |                  |
|               |               | r |               |                  |
+---------------+---------------+---+---------------+------------------+
| Aerobic       | 480 days      | N |               | Input Parameter  |
| Aquatic       |               | o |               | Guidance*^4^*    |
| Metabolism    |               | r |               |                  |
| Half-life     |               | e |               |                  |
|               |               | p |               |                  |
|               |               | o |               |                  |
|               |               | r |               |                  |
|               |               | t |               |                  |
|               |               | e |               |                  |
|               |               | d |               |                  |
|               |               | d |               |                  |
|               |               | a |               |                  |
|               |               | t |               |                  |
|               |               | a |               |                  |
|               |               | , |               |                  |
|               |               | u |               |                  |
|               |               | s |               |                  |
|               |               | e |               |                  |
|               |               | ½ |               |                  |
|               |               | o |               |                  |
|               |               | f |               |                  |
|               |               | a |               |                  |
|               |               | e |               |                  |
|               |               | r |               |                  |
|               |               | o |               |                  |
|               |               | b |               |                  |
|               |               | i |               |                  |
|               |               | c |               |                  |
|               |               | s |               |                  |
|               |               | o |               |                  |
|               |               | i |               |                  |
|               |               | l |               |                  |
|               |               | r |               |                  |
|               |               | a |               |                  |
|               |               | t |               |                  |
|               |               | e |               |                  |
+---------------+---------------+---+---------------+------------------+
| Anaerobic     | 2300 days     | 3 |               | MRID 44767602    |
| Aquatic       |               | t |               |                  |
| Metabolism    |               | i |               |                  |
| Half-life     |               | m |               |                  |
|               |               | e |               |                  |
|               |               | s |               |                  |
|               |               | s |               |                  |
|               |               | i |               |                  |
|               |               | n |               |                  |
|               |               | g |               |                  |
|               |               | l |               |                  |
|               |               | e |               |                  |
|               |               | r |               |                  |
|               |               | e |               |                  |
|               |               | p |               |                  |
|               |               | o |               |                  |
|               |               | r |               |                  |
|               |               | t |               |                  |
|               |               | e |               |                  |
|               |               | d |               |                  |
|               |               | v |               |                  |
|               |               | a |               |                  |
|               |               | l |               |                  |
|               |               | u |               |                  |
|               |               | e |               |                  |
+---------------+---------------+---+---------------+------------------+
| Aqueous       | Stable        |   |               | MRID 41903902    |
| Photolysis    |               |   |               |                  |
|               |               |   |               |                  |
| Half-life     |               |   |               |                  |
+---------------+---------------+---+---------------+------------------+
| Hydrolysis    | Stable        | S |               | MRID 42363001    |
| Half-life     |               | t |               |                  |
|               |               | a |               |                  |
|               |               | b |               |                  |
|               |               | l |               |                  |
|               |               | e |               |                  |
|               |               | a |               |                  |
|               |               | t |               |                  |
|               |               | a |               |                  |
|               |               | l |               |                  |
|               |               | l |               |                  |
|               |               | p |               |                  |
|               |               | H |               |                  |
+---------------+---------------+---+---------------+------------------+
| K~d~          | 11.4 ml/g     | L |               | Wauchope, 1975   |
|               | *^5^*         | o |               |                  |
|               |               | w |               | MRID 41651906    |
|               |               | e |               |                  |
|               |               | s |               |                  |
|               |               | t |               |                  |
|               |               | n |               |                  |
|               |               | o |               |                  |
|               |               | n |               |                  |
|               |               | - |               |                  |
|               |               | s |               |                  |
|               |               | a |               |                  |
|               |               | n |               |                  |
|               |               | d |               |                  |
|               |               | K |               |                  |
|               |               | ~ |               |                  |
|               |               | d |               |                  |
|               |               | ~ |               |                  |
|               |               | f |               |                  |
|               |               | r |               |                  |
|               |               | o |               |                  |
|               |               | m |               |                  |
|               |               | 1 |               |                  |
|               |               | 9 |               |                  |
|               |               | s |               |                  |
|               |               | o |               |                  |
|               |               | i |               |                  |
|               |               | l |               |                  |
|               |               | s |               |                  |
|               |               | . |               |                  |
+---------------+---------------+---+---------------+------------------+
| Molecular     | 139 g/mol     | a |               |                  |
| Weight        | *^5^*         | s |               |                  |
|               |               | M |               |                  |
|               |               | M |               |                  |
|               |               | A |               |                  |
+---------------+---------------+---+---------------+------------------+
| Water         | 1 x 10^6^     |   |               | 2001 RED         |
| Solubility    | mg/L          |   |               | (D277223)        |
+---------------+---------------+---+---------------+------------------+
| Vapor         | 1 x 10^-7^    |   |               | 2001 RED         |
| Pressure      | torr          |   |               | (D277223)        |
+---------------+---------------+---+---------------+------------------+
| Percent       | *Cotton*: 20% |   |               | Drinking Water   |
| Cropped Area  |               |   |               | Screening Level  |
| (PCA)         | *Turf*: 100%  |   |               | Assessment       |
|               |               |   |               | Guidance, Part B |
|               |               |   |               | *^6^*            |
+---------------+---------------+---+---------------+------------------+

^1^
<http://usda.mannlib.cornell.edu/reports/nassr/field/planting/uph97.html>

^2^ A spring application date was chosen to represent the period when
crabgrass and goosegrass are most prevalent. MSMA can be applied at any
time of year.

^3^ Cotton is labeled for aerial application but ground application
leads to more conservative EDWCs.

^4^ <http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm>

^5^ Different from input for 2001 RED (DP Barcode D277223).

^6^ <http://www.epa.gov/oppfead1/trac/science/reservoir.pdf>

**Table 6. PRZM/EXAMS Input Parameters for Cacodylic Acid on Cotton**

+---------------+---------------+-----------------+------------------+
| **Model       | **Value**     | **Comments**    | **Source**       |
| Parameter**   |               |                 |                  |
+---------------+---------------+-----------------+------------------+
| Single        | Number range  |                 | Master Label     |
| Application   | CHAPTER1.34   |                 |                  |
| Rate (# of    | kg/ha         |                 |                  |
| applications) |               |                 |                  |
|               | (1            |                 |                  |
|               | application)  |                 |                  |
+---------------+---------------+-----------------+------------------+
| Application   | 10/10         |                 | USDA-NASS        |
| Date          |               |                 | Planting and     |
|               |               |                 | Harvest Dates    |
|               |               |                 | (12/97)*^1^*     |
+---------------+---------------+-----------------+------------------+
| Application   | Foliar;       | Number range    |                  |
| Method        | aerial        | CHAPTERLeads to |                  |
|               | applied       | default values  |                  |
|               |               | of              |                  |
|               |               |                 |                  |
|               |               | 16% Spray drift |                  |
|               |               |                 |                  |
|               |               | 95% App.        |                  |
|               |               | efficiency      |                  |
+---------------+---------------+-----------------+------------------+
| Incorporation | 0 cm          |                 |                  |
| Depth         |               |                 |                  |
+---------------+---------------+-----------------+------------------+
| Aerobic Soil  | 240 days*^2^* | 90% upper       | Woolson &        |
|               |               | confidence      | Kearney, 1973    |
| Metabolism    |               | bound, based on |                  |
| Half-Life     |               | 6 values.       | Woolson, 1982    |
|               |               |                 |                  |
|               |               |                 | Gao & Burau,     |
|               |               |                 | 1997             |
|               |               |                 |                  |
|               |               |                 | MRID 44767601    |
+---------------+---------------+-----------------+------------------+
| Anaerobic     | 168 days      | 90% upper       | Woolson &        |
| Soil          |               | confidence      | Kearney, 1973    |
| Metabolism    |               | bound, based on |                  |
| Half-Life     |               | 3 values.       |                  |
+---------------+---------------+-----------------+------------------+
| Aerobic       | 480 days*^2^* | No reported     | Input Parameter  |
| Aquatic       |               | data, use ½ of  | Guidance*^3^*    |
| Metabolism    |               | aerobic soil    |                  |
| Half-life     |               | rate            |                  |
+---------------+---------------+-----------------+------------------+
| Anaerobic     | 336 days      | No reported     | Input Parameter  |
| Aquatic       |               | data, use ½ of  | Guidance*^3^*    |
| Metabolism    |               | anaerobic soil  |                  |
| Half-life     |               | rate            |                  |
+---------------+---------------+-----------------+------------------+
| Aqueous       | Stable        |                 | MRID 41662601    |
| Photolysis    |               |                 |                  |
|               |               |                 |                  |
| Half-life     |               |                 |                  |
+---------------+---------------+-----------------+------------------+
| Hydrolysis    | Stable        | Stable at all   | MRID 42059201    |
| Half-life     |               | pH              |                  |
+---------------+---------------+-----------------+------------------+
| K~d~          | 8.2 ml/g      | Lowest non-sand | Wauchope, 1975   |
|               |               | K~d~ from 16    |                  |
|               |               | soils. Reviewer |                  |
|               |               | calculated.     |                  |
+---------------+---------------+-----------------+------------------+
| Molecular     | 138 g/mol     |                 |                  |
| Weight        |               |                 |                  |
+---------------+---------------+-----------------+------------------+
| Water         | 1 x 10^6^     |                 | 2000 RED         |
| Solubility    | mg/L          |                 | (D210451,        |
|               |               |                 | D212449, 255226) |
+---------------+---------------+-----------------+------------------+
| Vapor         | 0             |                 | 2000 RED         |
| Pressure      |               |                 | (D210451,        |
|               |               |                 | D212449, 255226) |
+---------------+---------------+-----------------+------------------+
| Percent       | 20%           |                 | Drinking Water   |
| Cropped Area  |               |                 | Screening Level  |
| (PCA)         |               |                 | Assessment       |
|               |               |                 | Guidance, Part B |
|               |               |                 | *^4^*            |
+---------------+---------------+-----------------+------------------+

^1^
<http://usda.mannlib.cornell.edu/reports/nassr/field/planting/uph97.html>

^2^ Different from input for 2000 RED (DP Barcodes D210451, D212449,
255226).

^3^ <http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm>

^4^ <http://www.epa.gov/oppfead1/trac/science/reservoir.pdf>

inclusion of unreviewed non-GLP studies from an incomplete literature
review. The *anaerobic aquatic metabolism half-life* is based on the
value from one registrant study (MRID 44767602; Acceptable) which is
multiplied by three to account for the uncertainty when only a single
value is available, as directed by the input guidance (EFED, 2002). This
leads to a half-life that is significantly longer than the aerobic
values. Although this is not entirely supported by the literature, which
indicates that anaerobic metabolism may be faster than aerobic
metabolism (Akkari, 1986; Gao and Burau, 1997), adjusting this value
makes no difference in the results and so no change was made.

For [DMA]{.underline}, the soil and aquatic metabolism half-lives are
all based on non-GLP data. Although these values have uncertainty, there
are no acceptable GLP studies of DMA available. The *aerobic soil
metabolism half-life* is based on the same 3 literature studies

considered in the 2000 RED (DP Barcodes D210451, D212449, D255226) as
well as data on DMA as a metabolite from a GLP study of MSMA (MRID
44767601). For one study, the half-lives used were recalculated based on
data from the complete 32 week study rather than data from the first 24
weeks, as was originally used (Woolson & Kearney, 1973). Because of
decreasing transformation with time, this leads to a longer half-life. A
half-life for DMA was derived from the MSMA study by performing
non-linear regression on its formation and decline using StatMost
software (StatMost, 1994). The half-life was calculated using the
simplifying assumption that metabolism occurred as two individual first
order processes: MMA transforming to DMA followed by transformation to
inorganic arsenic. Although there is some uncertainty in this approach,
this is the only GLP study with data for DMA metabolism and the only
study available that was carried out for a full year so it still
provides valuable information. The *aerobic aquatic metabolism
half-life* is based on the aerobic soil value, as per EFED guidance
(EFED, 2002) and so increased as well. The *anaerobic aquatic metabolism
half-life* was calculated based on anaerobic soil metabolism data from
one literature study (Woolson & Kearney, 1973). Another study was
discussed in the 2000 RED (Woolson, 1982), but because it was carried
out in atypical conditions it was not included in calculations.

*Input Parameters: Soil Mobility*[]{#__RefHeading___Toc126565963
.anchor}

For MMA, the K~d~ value used in the 2000 RED, 13 mL/g, was not
referenced and so could not be confirmed. Data from a registrant study
(MRID 41651906; Supplemental) were considered along with data reported
by Wauchope (1975) leading to a lowest non-sand K~d~ value of 11.4 mL/g.
For DMA, the original K~d~ value of 8.2 mL/g was not changed. It is the
lowest non-sand value calculated from data reported by Wauchope (1975).

Use of the lowest non-sand K~d~ provides a conservative estimate of
potential runoff in agricultural soils that do not promote sorption. The
effect of variable K~d~ values on modeling results was examined. For
MMA, the median of the 19 K~d~ values considered was 28 and the average
was 37 mL/g (Wauchope, 1975; MRID 41651906). For DMA, 16 values were
considered with a median of 15 and an average of 18 mL/g (Wauchope,
1975). To estimate exposure from typical soils, a K~d~ of 20 was used
for modeling DMA and 30 for MMA. This led to decreased peak EDWCs for
cotton and had less of an impact on chronic values. Little change was
seen in turf peak or chronic EDWCs, while the cancer EDWCs actually
increased slightly. See the characterization discussion for more detail.

*Calculation of Metabolites*[]{#__RefHeading___Toc126565964 .anchor}

MMA metabolism to DMA was simulated by modeling DMA applied at 35% of
the MMA rate with DMA input parameters. For cotton, where DMA and MMA
can both be applied to the same field at different times in the same
season, the time series of concentrations resulting from DMA applied
directly was added to that resulting from DMA as a metabolite of MMA.
The upper 90% confidence limit was determined for peak and average
annual values from this 30 year time series.

This simulation is based on the assumption that a maximum of 35% of
applied MMA may be present as DMA at any one time. This is based on one
registrant aerobic soil study submitted in 2001 (MRID 44767601;
Acceptable). After 1 year, 32% of the applied MSMA was present as DMA.
At the end of this study, the amount of DMA present was still rising, so
it is possible that after 1 year, a greater percentage of the applied
amount is present as DMA. The 35% estimate is supported by calculations
of the formation and decline of DMA using the same half-lives as
included in the PRZM/EXAMS modeling.

There is uncertainty associated with this assumption, which is based on
the results of a lab study on the metabolism of MMA and on calculations
using the modeled half-lives of MMA and DMA. In both of these
approaches, the DMA present is being metabolized as it is formed and so,
without metabolism, would be present in higher amounts. The estimate of
35%, therefore, already takes into account some amount of
transformation. The model then simulates metabolism as well, possibly
leading to an underestimation of the maximum amount of DMA present at
any time. Despite this uncertainty, 35% is considered sufficiently
conservative because even incorporating some transformation, it is still
significantly higher than the amount of DMA seen in any other field or
lab study reviewed, many of which found no DMA at all. Additional
uncertainty results from modeling the DMA metabolite as if it were
applied at the same time as the MMA parent. Metabolism to DMA is not a
rapid transformation and so in fact, when present, the metabolite will
appear at a later date dependent on the environmental conditions.

Total arsenic was estimated as a direct molar conversion of the EDWC
predicted for the applied, parent organic arsenical(s). (The reported
EDWCs for parent and metabolite compounds represent maximum potential
concentrations for each species and are not additive to a total possible
concentration. When the concentration of one species is at its highest,
the other species' concentration will be lower.) The total arsenic value
is also used as the inorganic arsenic EDWC. For maximum inorganic
arsenic, a direct molar conversion of the parent compound's aquatic
concentration does not necessarily represent the actual physical process
-- inorganic arsenic is likely formed through metabolism in the soil,
rather than after reaching surface water. This calculation still
provides a conservative estimate of the amount of inorganic arsenic that
may reach surface water. The estimate is supported by a targeted
monitoring study in cotton growing areas which found that typically, one
arsenic species at a time was dominant. Immediately following the period
of typical application, MMA was the dominant species and several weeks
to months later it the primary form of arsenic was inorganic, present at
approximately the same total arsenic concentration as the earlier MMA
(Bednar, 2002).

*Percent Cropped Area*[]{#__RefHeading___Toc126565965 .anchor}

For cotton, a 20% PCA is applied to the modeling results, according to
division policy which estimates that 20% is the maximum area of any
watershed planted in cotton (OPP, 2000). It is possible that arsenicals
are applied to other crops within the same watershed, which could lead
to higher amounts of pesticide reaching surface water. Use as an
herbicide on turf is the only other application of arsenicals extensive
enough to potentially increase watershed scale concentrations.
Monitoring data suggest, however, that the 20% PCA still leads to
protective estimates of exposure. A study targeted to estimate the
impacts of arsenical use on cotton sampled surface water weekly from May
to September in heavy cotton growing areas in Yazoo County, Mississippi
(site of the Mississippi cotton scenario), and in Arkansas (Bednar,
2002). The highest concentration of total arsenic found in any of those
samples (6 ppb as arsenic = 11 ppb as MMA) is similar to the modeled
chronic EDWC for MMA on cotton as parent compound only and so is less
than the chronic total arsenic concentrations, which would include
metabolites as well. Weekly targeted monitoring of this type can be
expected to capture chronic concentrations but not acute concentrations.
These monitoring values, in the range of modeled chronic concentrations
and less than modeled acute concentrations, suggest that the EDWCs are
reasonable.

No appropriate PCA has been determined for application of pesticides to
turf. In order to be protective, at this time division policy is to not
apply any PCA for turf. The modeled EDWCs for turf are therefore based
on the assumption that the entire modeled watershed has been treated
with pesticide, which may lead to overestimation of potential exposure.
Limited surface water monitoring data targeted to golf course use are
available. Two studies measured arsenic in golf course ponds. In one
study, 6 ponds were sampled with arsenic concentrations ranging from
below detection limits to 24 ppb (as total arsenic; Swancar, 1996). In
the other study, arsenic concentrations at four ponds ranged from below
detection limits to 30 ppb with a median of 19.75 ppb (as total
arsenic). These values were reported to be an order of magnitude higher
than other surface water concentrations in the same area (DERM, 2002).
This monitoring involves relatively small surface water bodies that are
completely surrounded by turf that may be treated with arsenicals, so
they represent high potential exposure relative to the index reservoir.
Nevertheless, they demonstrate that a significant amount of arsenic may
reach surface water from turf applications of arsenicals and that
modeled turf EDWCs are on the same scale as concentrations that have
been measured in monitoring. The chronic turf total arsenic EDWC is 68.8
ppb, approximately twice that found in monitoring. These data are
discussed in more detail in the monitoring section.

*Characterization*[]{#__RefHeading___Toc126565966 .anchor}

The reported EDWCs are based on maximum labeled application rates under
the most vulnerable circumstances. A variety of management practices,
environmental conditions, and application rates are possible and can
lead to different concentrations. This section characterizes how
exposure to arsenicals may be affected by less vulnerable soils, typical
application rates, application to minor crops, or practices such as
irrigation or spot treatment.

Sorption of arsenical pesticides varies with soil characteristics.
Sorption is expected to be higher in soils with a higher percentage of
clay or with more iron or aluminum content (Matera, 2001). Surface water
concentrations were estimated using higher K~d~ values to characterize
possible exposure from application to less vulnerable soils. Considering
the parent compound only, for application of MMA or DMA to cotton, the
typical K~d~ led to peak concentrations approximately 30% less than
those from more vulnerable soils. Kd had less of an effect on chronic
exposure from cotton application with a 15% decrease for MMA and a 3%
decrease for DMA. There was little change for cancer EDWCs. For MMA
applied to turf, a higher K~d~ led to less than a 10% decrease for peak
and chronic exposures and actually led to a slight increase in estimated
cancer concentrations.

EDWCs are modeled using the maximum labeled application rates. For turf,
this maximum rate is allowed for sod farms and other well established
Bermudagrass and Zoysiagrass, but use on golf courses, parks, and
athletic fields is limited by the label to a lower application rate. For
MSMA, the "golf course" rate is 2.6 lb/A, compared to the maximum rate
of 3.9 lb/A. Additionally, the new master label specifies that
arsenicals cannot be applied to golf course greens. While greens
generally make up less than 3% of golf course area (EFED, 2005), they
are typically the areas treated most heavily with pesticides and are
also designed to promote drainage, so limiting application to greens may
lead to lower concentrations. A 2002 report by the Florida Center for
Solid and Hazardous Waste Management at the University of Florida
estimated that typical use of MSMA on golf courses was 3 annual
applications at 3 lbs/A. Based on responses from 15% of Florida golf
courses, the report estimated that 80% of golf courses apply MSMA

**Table 7**. Surface water concentrations (ppb) from applications of
MSMA to turf at less than the maximum labeled rate.

  -------------- ----------- -------------- --------------- -------------
                             **Acute**      **Chronic**     **Cancer**

  **Golf course                                             
  rate^1^**                                                 

                 **MMA**     166.7          85.2            49.7

                 **DMA**     68.0           33.7            18.9

                 **Total     89.9           46.0            26.8
                 As**                                       

  **"Typical"                                               
  use rate^2^**                                             

                 **MMA**     180.6          80.5            45.2

                 **DMA**     64.6           27.6            14.8

                 **Total     97.4           43.4            24.4
                 As**                                       

  **Single app.;                                            
  max rate^3^**                                             

                 **MMA**     77.7           34.8            18.5

                 **DMA**     33.2           13.4            7.0

                 **Total     41.9           18.9            10.0
                 As**                                       
  -------------- ----------- -------------- --------------- -------------

^1^ On golf courses, parks, and athletic fields, maximum rate is 4
applications at 2.49 lbs ae/A .

^2^ "Typical use" on golf courses = 3 applications MSMA at 2.57lbs ae/A.
(Ma, 2002)

^3^ One application of MSMA at 3.35 lbs ae/A.

at this rate or lower (Ma, 2002). These application rates were modeled
with PRZM/EXAMS and the estimated concentrations are presented in Table
7. It should be emphasized that modeling at the maximum labeled rate is
the most protective and these concentrations are provided for
characterization only.

The most conservative estimate of use of arsenicals on cotton assumes
that DSMA or MSMA is applied as an early season herbicide followed by
DMA as a late season defoliant on the same field. This combined use is
allowed by the labels and is known to be used in some areas. It is more
common that either one or the other product is used individually (BEAD,
2005a) and so these uses were modeled as well for characterization.
Table 8 includes estimated concentrations for maximum labeled
applications to cotton of only one type of arsenical, either MMA as an
herbicide or DMA as a defoliant. These values are based on the same
input parameters described in Table 5 and Table 6 including the 20% PCA
adjustment.

**Table 8. Surface water concentrations (ppb) from applications of
individual arsenicals to cotton.**

  -------------- ----------- -------------- --------------- -------------
                             **Acute**      **Chronic**     **Cancer**

  **Max rate,                                               
  DMA only^1^**                                             

                 **MMA**     \-\--          \-\--           \-\--

                 **DMA**     18.3           2.9             2.0

                 **Total     9.9            1.6             1.1
                 As**                                       

  **Max rate,                                               
  MMA only^2^**                                             

                 **MMA**     37.4           11.0            5.3

                 **DMA**     17.8           5.1             2.3

                 **Total     20.2           5.9             2.9
                 As**                                       

  **Single app.,                                            
  MMA only^3^**                                             

                 **MMA**     18.4           5.4             2.6

                 **DMA**     8.7            2.5             1.2

                 **Total     9.9            2.9             1.4
                 As**                                       
  -------------- ----------- -------------- --------------- -------------

^1^ Based on 1 application of DMA as a defoliant at 1.2 lb/A.

^2^ Based on 2 applications of DSMA as an herbicide at 1.74 lbs ae/A.

^3^ Based on 1 application of DSMA as an herbicide at 1.74 lbs ae/A.

Labels for DSMA and MSMA also allow application to orchards, citrus, and
vineyards and the DMA label includes a use on citrus, although this is
prohibited in Florida. All available scenarios were modeled to
characterize concentrations resulting from

application to these minor crops. The Oregon grass seed scenario was
modeled as well to account for the labeled application of DSMA and MSMA
to grass seed in the Pacific Northwest. Concentrations resulting from
application of arsenicals to the most vulnerable of these scenarios are
presented in Table 9. Although application rates for some of these crops
are higher than for use on turf or cotton, turf and cotton represent at
least 97% of the total national use of arsenicals and so those uses are
expected to have the greatest impact (BEAD, 2005a & b).

The values in Table 9 are screening estimates that do not account for
the labeled restriction that arsenicals can only be applied to
non-bearing fields of orchards, citrus, and vineyards and cannot be
applied within one year of harvest. As a worst-case scenario, then,
arsenicals would only be applied to these crops every second or third
year so a refined estimate would limit the years of application, leading
to much lower estimated concentrations. Additionally, these estimated
concentrations use the default PCA adjustment of 87%. Given the low
estimated usage of arsenicals on these crops, the actual usage area
within a watershed is likely notably lower than that. These modeled
values therefore overestimate the likely concentrations of arsenicals on
orchards, citrus, and vineyards. The EDWCs from application to turf are
considered protective relative to these uses.

**Table 9**. Screening estimate of surface water concentrations (ppb) of
parent compound from application of MMA or DMA to minor crops.

  ------------ ------------------ -------------- --------------- -------------
                                  **Acute**      **Chronic**     **Cancer**

  **MMA^1^**                                                     

               **CA almond**      193.0          128.2           80.0

               **GA pecan**       330.6          81.4            44.5

               **MI cherry**      191.4          143.2           102.2

               **OR grass seed**  145.9          102.5           76.4

  **DMA^2^**                                                     

               **CA citrus**      116.3          93.7            76.8
  ------------ ------------------ -------------- --------------- -------------

^1^ Orchard, citrus, and vineyard based on 3 applications of DSMA at 3.7
lb ae/A. Grass seed based on 1 application of MSMA at 5.3 lb ae/A.

^2^ Based on 2 applications of DMA at 4.96 lbs/A.

The reported EDWCs do not account for the potential impact of irrigation
because it is not calculated effectively by the model versions currently
available. Irrigation tends to be very important in turf cultivation;
golf courses often irrigate at rates of over 100,000 gallons per day
(Swancar, 1996) with some estimates of average irrigation as high as
350,000 gpd (Ma, 2002). A provisional version of PRZM has been designed
to account for the effects of irrigation, although this irrigated model
is currently approved only to provide characterization of modeling
results and not to quantify EDWCs. This model, run using a version of
the Florida turf scenario edited to include irrigation, estimated that
surface water concentrations of MMA from irrigated turf can be expected
to be 8 to 33% lower than those from non-irrigated fields. Using the
inputs listed in Table 5, the irrigated model estimates MMA surface
water concentrations of 230 ppb (acute), 102 ppb (chronic), and 50 ppb
(cancer). Especially on well drained soils like those in Florida golf
courses, irrigation can decrease runoff by increasing the potential for
leaching to groundwater.

Turf EDWCs are also expected to be lower if arsenicals are applied as
spot treatments rather than as broadcast sprays, which appears to be a
common practice. There is a possibility that this will be included as a
restriction on the labels for DSMA and MSMA. Spot treatments are applied
to less area than broadcast sprays and so lead to lower exposure. If
application rate or area is limited on the label by a quantifiable
amount, the estimated concentrations will be reduced by a proportional
amount. For example, if treatment of arsenicals on all turf uses is
limited to 50% of a field, the EDWCs will go down to one half of the
original value.

**SOIL ACCUMULATION**[]{#__RefHeading___Toc126565967 .anchor}

Accumulation of persistent pesticides in soil is not typically addressed
in drinking water assessments. Because of the possible implications for
human health, a summary of the issue is presented here. A more detailed
discussion of potential buildup of arsenic in soil resulting from
pesticide application can be found in the Ecological Risk Assessment (DP
Barcode D309100). The relative immobility of arsenicals along with
arsenic's elemental nature make buildup in soil after repeated
applications an important consideration. Field studies, monitoring of
soil in use areas, and modeling all suggest that it is likely that
applied arsenicals will build up in soil over time. Arsenic accumulation
is likely to be limited to the top layers of soil, with studies
suggesting that it is unlikely to occur at depths greater than 30 cm.

Registrant terrestrial field dissipation studies have measured the
impact of one season of pesticide applications on soil concentrations.
Two studies at rates similar to the maximum labeled cotton and turf
rates found that a single year of application is unlikely to lead to
significantly elevated soil arsenic levels but, since most of the
applied arsenic remained in the top 6 inches of soil, repeated
application may lead to significant accumulation. Higher application
rates, possible in some of the non-crop uses, led to elevated soil
arsenic levels after a single year of application. Few studies have
evaluated the longer term impact of repeated application of organic
arsenicals. Those that have been conducted have conflicting results,
with some reporting no arsenic buildup despite very high application
rates and others finding substantial buildup at rates similar to current
labels, although most reports do not contain adequate explanations to
account for observed loss of arsenic. Monitoring of soil in areas where
arsenicals are known to have been applied, including golf courses and
roadside areas, has found significant increases of arsenic levels
relative to background concentrations. In Miami, an area with low
background arsenic levels, arsenic was the most common contaminant found
in documented soil violations at golf courses.

Soil modeling based on median sorption and maximum application rates
suggest that over the long term, the buildup of total arsenic in the top
10 cm of soil for MMA would level off at chronic concentrations of
approximately 13 ppm and 45 ppm on cotton and turf, respectively. The
higher application rates allowed for DMA in non-crop and some turf uses
would be expected to lead to higher soil concentrations, assuming annual
application at those rates. Routes of dissipation accounted for in the
modeling include runoff, leaching, and soil erosion. The field and
monitoring studies support these modeling results as a reasonable
representation of potential accumulation.

### 

**UNCERTAINTY**[]{#__RefHeading___Toc126565968 .anchor}

**Monitoring**[]{#__RefHeading___Toc126565969 .anchor}

For arsenic, monitoring data serve two separate functions -- to
establish natural background arsenic levels in surface and groundwater
and to provide information about potential impacts from pesticide
applications. The uncertainty associated with the monitoring data is
different for these different roles.

For most of the data used in discussing natural background arsenic
levels, data collection sites are not uniformly distributed and have not
been specifically selected to exclude anthropogenic arsenic sources --
some sites even represent known point sources of arsenic. The percentage
of sites impacted by these sources, however, is quite small relative to
the large national USGS datasets, each with more than 30,000 samples.
For groundwater, the uncertainty was further reduced by using
statistical criteria to limit the data incorporated and therefore
minimizing potential bias. This was not done for the surface water
dataset which therefore may include some bias towards more frequently
sampled sites. The data on individual arsenic species, rather than total
arsenic, are not nationally representative, for surface or groundwater.
There is uncertainty in extrapolating the results from these sites to a
wider assumption regarding background levels.

There is greater uncertainty in the targeted monitoring data. Specific
sources of uncertainty are included in the discussion of each individual
study. In general, even targeted sampling is likely to underestimate
both acute exposures and the frequency of occurrence due to the limited
number of samples and the extended time between sampling events. For
arsenic, additional uncertainty comes from the multiple possible arsenic
sources. In most cases, detailed pesticide application and land use
history information are not available. Natural background arsenic levels
are not well defined in all areas.

**Surface Water Modeling**[]{#__RefHeading___Toc126565970 .anchor}

Modeling relies on estimated fate parameters and assumed agricultural
practices to predict concentrations of pesticides to which humans may be
exposed. There is uncertainty in all fate inputs used in this
assessment. The values used as half-lives include uncertainty both due
to the limited available data and due to the complexity of arsenic's
environmental fate. The majority of data are from non-GLP studies that
were conducted for less than one year, ranging in length from 60 days to
32 weeks. Additionally, in most cases complete time series were not
available, so rates were calculated based on initial and final
concentrations only. One set of values included in calculations was
normalized by the reviewer to standard conditions, based on up to six
replications performed under a variety of conditions (Gao, 1997). All of
these factors could have an impact on the calculated half-lives.
Modeling with infinite half-lives provides an upper boundary of the
extent to which a modification in half-life inputs could change
estimated results. Using infinite half-lives, acute EDWCs are increased
by up to 17% while chronic and cancer EDWCs are increased by
approximately one-third.

As discussed above, there is also uncertainty associated with the method
of estimating concentrations of the major metabolites, DMA and inorganic
arsenic. The estimate of metabolism to DMA is based on the assumption
that 35% is the maximum amount of MAA that may be present as DMA at any
one time. Because this value is based on data that already includes some
transformation, it may lead to some underestimation of DMA
concentrations. The estimation of concentrations of inorganic arsenic is
also uncertain. Maximum potential concentrations of inorganic arsenic
are represented by the total arsenic EDWCs, calculated as a molar
conversion of the EDWCs of parent compounds. This is a general estimate
of the amount of inorganic arsenic that may reach surface water rather
than a direct calculation based on specific physical processes.
Transformation of applied organic arsenicals to inorganic arsenic is a
long term process that occurs primarily through microbial activity in
the soil, not a rapid conversion upon reaching water. Because of the
nature of these transformation processes and because of inorganic
arsenic's tendency to bind more strongly to soil than the organic
arsenicals do, the EDWC of the parent compounds represents a reasonable
upper bound on the EDWCs of inorganic arsenic. This assumption is
supported by empirical evidence from a targeted monitoring study which
found that the maximum concentrations of inorganic arsenic found in
surface water in areas of heavy application was similar to the total
arsenic resulting from parent compounds (Bednar, 2002).

Number range CHAPTERPRZM/EXAMS requires information on agricultural
practices as inputs, such as specific application dates and rates to be
applied. In reality, application dates and rates applied across the
United States and even within a single watershed will vary depending on
geography, pest pressure, climatic factors, and changes in agricultural
cropping patterns. EFED attempts to capture some of this variability by
modeling as many representative scenarios as possible and by using
meteorological data which covers a time span sufficient to capture
climatic variations which are likely to occur. However, the model is
limited in its ability to capture all of the natural variation which
occurs for any pesticide application and this adds uncertainty to the
drinking water assessment. This is of particular importance for the turf
scenario, because the application of pesticides to turf is not limited
to a specific planting season. It can be applied most of the year,
especially in areas like that modeled, where winter dormancy is not
expected. In this case, a spring application date was chosen because the
primary use of arsenicals on turf is to control crabgrass and
goosegrass, pests which emerge in the spring months. Application of
arsenicals to turf at other times of year is possible and could lead to
higher exposure, especially if applied during periods of heavier
rainfall which would increase runoff and leaching. For use on cotton,
the application dates within the typical use season that led to the most
conservative EDWCs were chosen.

The area of a watershed which is treated with a pesticide is another
factor influencing the estimated exposure. As discussed previously, for
cotton, a PCA of 20% was applied. If arsenicals are applied to
additional crops within the same watershed, this may lead to higher
EDWCs than those reported. For turf, no PCA was applied, which likely
leads to some overestimation of the EDWC, although the probable extent
of the overestimation is undefined.

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Number range CHAPTER**Appendix A: PRZM/EXAMS Input
Files**[]{#__RefHeading___Toc126565972 .anchor}

**MMA on Cotton; *Parent Compound***

MS Cotton; 8/13/2001

\"Yazoo County; MLRA 134; Metfile: W03940.dvf (old: Met131.met),\"

\*\*\* Record 3:

0.74 0.15 0 17 1 1

\*\*\* Record 6 \-- ERFLAG

4

\*\*\* Record 7:

0.49 0.4 0.75 172.8 4 6 600

\*\*\* Record 8

3

\*\*\* Record 9

1 0.2 125 98 3 99 93 92 0 120

2 0.2 125 98 3 94 84 83 0 120

3 0.2 125 98 3 99 83 83 0 120

\*\*\* Record 9a-d

1 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

2 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

3 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

\*\*\* Record 10 \-- NCPDS, the number of cropping periods

30

\*\*\* Record 11

010561 070961 220961 1

010562 070962 220962 2

010563 070963 220963 3

010564 070964 220964 1

010565 070965 220965 2

010566 070966 220966 3

010567 070967 220967 1

010568 070968 220968 2

010569 070969 220969 3

010570 070970 220970 1

010571 070971 220971 2

010572 070972 220972 3

010573 070973 220973 1

010574 070974 220974 2

010575 070975 220975 3

010576 070976 220976 1

010577 070977 220977 2

010578 070978 220978 3

010579 070979 220979 1

010580 070980 220980 2

010581 070981 220981 3

010582 070982 220982 1

010583 070983 220983 2

010584 070984 220984 3

010585 070985 220985 1

010586 070986 220986 2

010587 070987 220987 3

010588 070988 220988 1

010589 070989 220989 2

010590 070990 220990 3

\*\*\* Record 12 \-- PTITLE

MAA - 2 applications @ 1.95 kg/ha

\*\*\* Record 13

60 1 0 0

\*\*\* Record 15 \-- PSTNAM

MAA

\*\*\* Record 16

070561 0 2 0.0 1.95 0.990.064

140561 0 2 0.0 1.95 0.990.064

070562 0 2 0.0 1.95 0.990.064

140562 0 2 0.0 1.95 0.990.064

070563 0 2 0.0 1.95 0.990.064

140563 0 2 0.0 1.95 0.990.064

070564 0 2 0.0 1.95 0.990.064

140564 0 2 0.0 1.95 0.990.064

070565 0 2 0.0 1.95 0.990.064

140565 0 2 0.0 1.95 0.990.064

070566 0 2 0.0 1.95 0.990.064

140566 0 2 0.0 1.95 0.990.064

070567 0 2 0.0 1.95 0.990.064

140567 0 2 0.0 1.95 0.990.064

070568 0 2 0.0 1.95 0.990.064

140568 0 2 0.0 1.95 0.990.064

070569 0 2 0.0 1.95 0.990.064

140569 0 2 0.0 1.95 0.990.064

070570 0 2 0.0 1.95 0.990.064

140570 0 2 0.0 1.95 0.990.064

070571 0 2 0.0 1.95 0.990.064

140571 0 2 0.0 1.95 0.990.064

070572 0 2 0.0 1.95 0.990.064

140572 0 2 0.0 1.95 0.990.064

070573 0 2 0.0 1.95 0.990.064

140573 0 2 0.0 1.95 0.990.064

070574 0 2 0.0 1.95 0.990.064

140574 0 2 0.0 1.95 0.990.064

070575 0 2 0.0 1.95 0.990.064

140575 0 2 0.0 1.95 0.990.064

070576 0 2 0.0 1.95 0.990.064

140576 0 2 0.0 1.95 0.990.064

070577 0 2 0.0 1.95 0.990.064

140577 0 2 0.0 1.95 0.990.064

070578 0 2 0.0 1.95 0.990.064

140578 0 2 0.0 1.95 0.990.064

070579 0 2 0.0 1.95 0.990.064

140579 0 2 0.0 1.95 0.990.064

070580 0 2 0.0 1.95 0.990.064

140580 0 2 0.0 1.95 0.990.064

070581 0 2 0.0 1.95 0.990.064

140581 0 2 0.0 1.95 0.990.064

070582 0 2 0.0 1.95 0.990.064

140582 0 2 0.0 1.95 0.990.064

070583 0 2 0.0 1.95 0.990.064

140583 0 2 0.0 1.95 0.990.064

070584 0 2 0.0 1.95 0.990.064

140584 0 2 0.0 1.95 0.990.064

070585 0 2 0.0 1.95 0.990.064

140585 0 2 0.0 1.95 0.990.064

070586 0 2 0.0 1.95 0.990.064

140586 0 2 0.0 1.95 0.990.064

070587 0 2 0.0 1.95 0.990.064

140587 0 2 0.0 1.95 0.990.064

070588 0 2 0.0 1.95 0.990.064

140588 0 2 0.0 1.95 0.990.064

070589 0 2 0.0 1.95 0.990.064

140589 0 2 0.0 1.95 0.990.064

070590 0 2 0.0 1.95 0.990.064

140590 0 2 0.0 1.95 0.990.064

\*\*\* Record 17

0 2 0

\*\*\* Record 18

0 0 0.5

\*\*\* Record 19 \-- STITLE

Loring Silt Loam; HYDG: C

\*\*\* Record 20

155 0 0 0 0 0 0 0 0 0

\*\*\* Record 26

0 0 0

\*\*\* Record 33

6

1 13 1.4 0.385 0 0 0

0.0028880.002888 0

0.1 0.385 0.151 2.18 11.4

2 23 1.4 0.37 0 0 0

0.0028880.002888 0

1 0.37 0.146 0.49 11.4

3 33 1.4 0.37 0 0 0

0.0028880.002888 0

3 0.37 0.146 0.16 11.4

4 30 1.45 0.34 0 0 0

0.0028880.002888 0

5 0.34 0.125 0.124 11.4

5 23 1.49 0.335 0 0 0

0.0028880.002888 0

1 0.335 0.137 0.07 11.4

6 33 1.51 0.343 0 0 0

0.0028880.002888 0

3 0.343 0.147 0.06 11.4

\*\*\*Record 40

0

YEAR 10 YEAR 10 YEAR 10 1

1

1 \-\-\-\--

7 YEAR

PRCP TCUM 0 0

RUNF TCUM 0 0

INFL TCUM 1 1

ESLS TCUM 0 0 1.0E3

RFLX TCUM 0 0 1.0E5

EFLX TCUM 0 0 1.0E5

RZFX TCUM 0 0 1.0E5

**DMA on Cotton; *Parent Compound***

MS Cotton; 8/13/2001

\"Yazoo County; MLRA 134; Metfile: W03940.dvf (old: Met131.met),\"

\*\*\* Record 3:

0.74 0.15 0 17 1 1

\*\*\* Record 6 \-- ERFLAG

4

\*\*\* Record 7:

0.49 0.4 0.75 172.8 4 6 600

\*\*\* Record 8

3

\*\*\* Record 9

1 0.2 125 98 3 99 93 92 0 120

2 0.2 125 98 3 94 84 83 0 120

3 0.2 125 98 3 99 83 83 0 120

\*\*\* Record 9a-d

1 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

2 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

3 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

\*\*\* Record 10 \-- NCPDS, the number of cropping periods

30

\*\*\* Record 11

010561 070961 220961 1

010562 070962 220962 2

010563 070963 220963 3

010564 070964 220964 1

010565 070965 220965 2

010566 070966 220966 3

010567 070967 220967 1

010568 070968 220968 2

010569 070969 220969 3

010570 070970 220970 1

010571 070971 220971 2

010572 070972 220972 3

010573 070973 220973 1

010574 070974 220974 2

010575 070975 220975 3

010576 070976 220976 1

010577 070977 220977 2

010578 070978 220978 3

010579 070979 220979 1

010580 070980 220980 2

010581 070981 220981 3

010582 070982 220982 1

010583 070983 220983 2

010584 070984 220984 3

010585 070985 220985 1

010586 070986 220986 2

010587 070987 220987 3

010588 070988 220988 1

010589 070989 220989 2

010590 070990 220990 3

\*\*\* Record 12 \-- PTITLE

DMA - 1 applications @ 1.34 kg/ha

\*\*\* Record 13

30 1 0 0

\*\*\* Record 15 \-- PSTNAM

DMA

\*\*\* Record 16

101061 0 2 0.0 1.34 0.95 0.16

101062 0 2 0.0 1.34 0.95 0.16

101063 0 2 0.0 1.34 0.95 0.16

101064 0 2 0.0 1.34 0.95 0.16

101065 0 2 0.0 1.34 0.95 0.16

101066 0 2 0.0 1.34 0.95 0.16

101067 0 2 0.0 1.34 0.95 0.16

101068 0 2 0.0 1.34 0.95 0.16

101069 0 2 0.0 1.34 0.95 0.16

101070 0 2 0.0 1.34 0.95 0.16

101071 0 2 0.0 1.34 0.95 0.16

101072 0 2 0.0 1.34 0.95 0.16

101073 0 2 0.0 1.34 0.95 0.16

101074 0 2 0.0 1.34 0.95 0.16

101075 0 2 0.0 1.34 0.95 0.16

101076 0 2 0.0 1.34 0.95 0.16

101077 0 2 0.0 1.34 0.95 0.16

101078 0 2 0.0 1.34 0.95 0.16

101079 0 2 0.0 1.34 0.95 0.16

101080 0 2 0.0 1.34 0.95 0.16

101081 0 2 0.0 1.34 0.95 0.16

101082 0 2 0.0 1.34 0.95 0.16

101083 0 2 0.0 1.34 0.95 0.16

101084 0 2 0.0 1.34 0.95 0.16

101085 0 2 0.0 1.34 0.95 0.16

101086 0 2 0.0 1.34 0.95 0.16

101087 0 2 0.0 1.34 0.95 0.16

101088 0 2 0.0 1.34 0.95 0.16

101089 0 2 0.0 1.34 0.95 0.16

101090 0 2 0.0 1.34 0.95 0.16

\*\*\* Record 17

0 2 0

\*\*\* Record 18

0 0 0.5

\*\*\* Record 19 \-- STITLE

Loring Silt Loam; HYDG: C

\*\*\* Record 20

155 0 0 0 0 0 0 0 0 0

\*\*\* Record 26

0 0 0

\*\*\* Record 33

6

1 13 1.4 0.385 0 0 0

0.0028880.002888 0

0.1 0.385 0.151 2.18 8.2

2 23 1.4 0.37 0 0 0

0.0028880.002888 0

1 0.37 0.146 0.49 8.2

3 33 1.4 0.37 0 0 0

0.0028880.002888 0

3 0.37 0.146 0.16 8.2

4 30 1.45 0.34 0 0 0

0.0028880.002888 0

5 0.34 0.125 0.124 8.2

5 23 1.49 0.335 0 0 0

0.0028880.002888 0

1 0.335 0.137 0.07 8.2

6 33 1.51 0.343 0 0 0

0.0028880.002888 0

3 0.343 0.147 0.06 8.2

\*\*\*Record 40

0

YEAR 10 YEAR 10 YEAR 10 1

1

1 \-\-\-\--

7 YEAR

PRCP TCUM 0 0

RUNF TCUM 0 0

INFL TCUM 1 1

ESLS TCUM 0 0 1.0E3

RFLX TCUM 0 0 1.0E5

EFLX TCUM 0 0 1.0E5

RZFX TCUM 0 0 1.0E5

**DMA on Cotton; *Metabolite of Parent MMA***

MS Cotton; 8/13/2001

\"Yazoo County; MLRA 134; Metfile: W03940.dvf (old: Met131.met),\"

\*\*\* Record 3:

0.74 0.15 0 17 1 1

\*\*\* Record 6 \-- ERFLAG

4

\*\*\* Record 7:

0.49 0.4 0.75 172.8 4 6 600

\*\*\* Record 8

3

\*\*\* Record 9

1 0.2 125 98 3 99 93 92 0 120

2 0.2 125 98 3 94 84 83 0 120

3 0.2 125 98 3 99 83 83 0 120

\*\*\* Record 9a-d

1 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

2 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

3 25

0101 1601 0102 1602 0103 1603 0104 1604 2504 0105 1605 0106 1606 0107
1607 0108

.500 .517 .532 .549 .567 .591 .617 .667 .705 .718 .699 .620 .496 .354
.303 .305

.014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014 .014
.014 .014

1608 0109 1609 0110 1610 0111 1611 0112 1612

.289 .343 .359 .223 .327 .376 .425 .465 .494

.014 .014 .014 .014 .014 .014 .014 .014 .014

\*\*\* Record 10 \-- NCPDS, the number of cropping periods

30

\*\*\* Record 11

010561 070961 220961 1

010562 070962 220962 2

010563 070963 220963 3

010564 070964 220964 1

010565 070965 220965 2

010566 070966 220966 3

010567 070967 220967 1

010568 070968 220968 2

010569 070969 220969 3

010570 070970 220970 1

010571 070971 220971 2

010572 070972 220972 3

010573 070973 220973 1

010574 070974 220974 2

010575 070975 220975 3

010576 070976 220976 1

010577 070977 220977 2

010578 070978 220978 3

010579 070979 220979 1

010580 070980 220980 2

010581 070981 220981 3

010582 070982 220982 1

010583 070983 220983 2

010584 070984 220984 3

010585 070985 220985 1

010586 070986 220986 2

010587 070987 220987 3

010588 070988 220988 1

010589 070989 220989 2

010590 070990 220990 3

\*\*\* Record 12 \-- PTITLE

DMA - 2 applications @ .90 kg/ha

\*\*\* Record 13

60 1 0 0

\*\*\* Record 15 \-- PSTNAM

DMA

\*\*\* Record 16

070561 0 2 0.0 0.9 0.990.064

140561 0 2 0.0 0.9 0.990.064

070562 0 2 0.0 0.9 0.990.064

140562 0 2 0.0 0.9 0.990.064

070563 0 2 0.0 0.9 0.990.064

140563 0 2 0.0 0.9 0.990.064

070564 0 2 0.0 0.9 0.990.064

140564 0 2 0.0 0.9 0.990.064

070565 0 2 0.0 0.9 0.990.064

140565 0 2 0.0 0.9 0.990.064

070566 0 2 0.0 0.9 0.990.064

140566 0 2 0.0 0.9 0.990.064

070567 0 2 0.0 0.9 0.990.064

140567 0 2 0.0 0.9 0.990.064

070568 0 2 0.0 0.9 0.990.064

140568 0 2 0.0 0.9 0.990.064

070569 0 2 0.0 0.9 0.990.064

140569 0 2 0.0 0.9 0.990.064

070570 0 2 0.0 0.9 0.990.064

140570 0 2 0.0 0.9 0.990.064

070571 0 2 0.0 0.9 0.990.064

140571 0 2 0.0 0.9 0.990.064

070572 0 2 0.0 0.9 0.990.064

140572 0 2 0.0 0.9 0.990.064

070573 0 2 0.0 0.9 0.990.064

140573 0 2 0.0 0.9 0.990.064

070574 0 2 0.0 0.9 0.990.064

140574 0 2 0.0 0.9 0.990.064

070575 0 2 0.0 0.9 0.990.064

140575 0 2 0.0 0.9 0.990.064

070576 0 2 0.0 0.9 0.990.064

140576 0 2 0.0 0.9 0.990.064

070577 0 2 0.0 0.9 0.990.064

140577 0 2 0.0 0.9 0.990.064

070578 0 2 0.0 0.9 0.990.064

140578 0 2 0.0 0.9 0.990.064

070579 0 2 0.0 0.9 0.990.064

140579 0 2 0.0 0.9 0.990.064

070580 0 2 0.0 0.9 0.990.064

140580 0 2 0.0 0.9 0.990.064

070581 0 2 0.0 0.9 0.990.064

140581 0 2 0.0 0.9 0.990.064

070582 0 2 0.0 0.9 0.990.064

140582 0 2 0.0 0.9 0.990.064

070583 0 2 0.0 0.9 0.990.064

140583 0 2 0.0 0.9 0.990.064

070584 0 2 0.0 0.9 0.990.064

140584 0 2 0.0 0.9 0.990.064

070585 0 2 0.0 0.9 0.990.064

140585 0 2 0.0 0.9 0.990.064

070586 0 2 0.0 0.9 0.990.064

140586 0 2 0.0 0.9 0.990.064

070587 0 2 0.0 0.9 0.990.064

140587 0 2 0.0 0.9 0.990.064

070588 0 2 0.0 0.9 0.990.064

140588 0 2 0.0 0.9 0.990.064

070589 0 2 0.0 0.9 0.990.064

140589 0 2 0.0 0.9 0.990.064

070590 0 2 0.0 0.9 0.990.064

140590 0 2 0.0 0.9 0.990.064

\*\*\* Record 17

0 2 0

\*\*\* Record 18

0 0 0.5

\*\*\* Record 19 \-- STITLE

Loring Silt Loam; HYDG: C

\*\*\* Record 20

155 0 0 0 0 0 0 0 0 0

\*\*\* Record 26

0 0 0

\*\*\* Record 33

6

1 13 1.4 0.385 0 0 0

0.0028880.002888 0

0.1 0.385 0.151 2.18 8.2

2 23 1.4 0.37 0 0 0

0.0028880.002888 0

1 0.37 0.146 0.49 8.2

3 33 1.4 0.37 0 0 0

0.0028880.002888 0

3 0.37 0.146 0.16 8.2

4 30 1.45 0.34 0 0 0

0.0028880.002888 0

5 0.34 0.125 0.124 8.2

5 23 1.49 0.335 0 0 0

0.0028880.002888 0

1 0.335 0.137 0.07 8.2

6 33 1.51 0.343 0 0 0

0.0028880.002888 0

3 0.343 0.147 0.06 8.2

\*\*\*Record 40

0

YEAR 10 YEAR 10 YEAR 10 1

1

1 \-\-\-\--

7 YEAR

PRCP TCUM 0 0

RUNF TCUM 0 0

INFL TCUM 1 1

ESLS TCUM 0 0 1.0E3

RFLX TCUM 0 0 1.0E5

EFLX TCUM 0 0 1.0E5

RZFX TCUM 0 0 1.0E5

**MMA on Turf; *Parent Compound***

FL Turf 8/09/2001

Osceola County; Representation of the Lake Kissimmee/Indian River
Region; MLRA 156A; Metfile: W12834.dvf \[Daytona Beach\] (old:
Met156A.met)

\*\*\* Record 3:

0.78 0 0 25 1 3

\*\*\* Record 6 \-- ERFLAG

4

\*\*\* Record 7:

0.04 0.303 1 172.8 4 2 600

\*\*\* Record 8

1

\*\*\* Record 9

1 0.1 10 100 3 74 74 74 0 5

\*\*\* Record 9a-d

1 25

0101 1601 0102 1602 0103 1603 0104 1604 0105 1605 0106 1606 0107 1507
1607 0108

.023 .026 .030 .035 .042 .050 .056 .060 .063 .068 .074 .079 .082 .125
.148 .189

.023 .023 .023 .023 .023 .023 .023 .023 .023 .023 .023 .023 .023 .023
.023 .023

1608 0109 1609 0110 1610 0111 1611 0112 1612

.229 .265 .294 .314 .326 .017 .018 .019 .021

.023 .023 .023 .023 .023 .023 .023 .023 .023

\*\*\* Record 10 \-- NCPDS, the number of cropping periods

30

\*\*\* Record 11

010261 150261 151261 1

010262 150262 151262 1

010263 150263 151263 1

010264 150264 151264 1

010265 150265 151265 1

010266 150266 151266 1

010267 150267 151267 1

010268 150268 151268 1

010269 150269 151269 1

010270 150270 151270 1

010271 150271 151271 1

010272 150272 151272 1

010273 150273 151273 1

010274 150274 151274 1

010275 150275 151275 1

010276 150276 151276 1

010277 150277 151277 1

010278 150278 151278 1

010279 150279 151279 1

010280 150280 151280 1

010281 150281 151281 1

010282 150282 151282 1

010283 150283 151283 1

010284 150284 151284 1

010285 150285 151285 1

010286 150286 151286 1

010287 150287 151287 1

010288 150288 151288 1

010289 150289 151289 1

010290 150290 151290 1

\*\*\* Record 12 \-- PTITLE

MAA - 4 applications @ 3.75 kg/ha

\*\*\* Record 13

120 1 0 0

\*\*\* Record 15 \-- PSTNAM

MAA

\*\*\* Record 16

140361 0 2 0.0 3.75 0.990.064

240361 0 2 0.0 3.75 0.990.064

030461 0 2 0.0 3.75 0.990.064

130461 0 2 0.0 3.75 0.990.064

140362 0 2 0.0 3.75 0.990.064

240362 0 2 0.0 3.75 0.990.064

030462 0 2 0.0 3.75 0.990.064

130462 0 2 0.0 3.75 0.990.064

140363 0 2 0.0 3.75 0.990.064

240363 0 2 0.0 3.75 0.990.064

030463 0 2 0.0 3.75 0.990.064

130463 0 2 0.0 3.75 0.990.064

140364 0 2 0.0 3.75 0.990.064

240364 0 2 0.0 3.75 0.990.064

030464 0 2 0.0 3.75 0.990.064

130464 0 2 0.0 3.75 0.990.064

140365 0 2 0.0 3.75 0.990.064

240365 0 2 0.0 3.75 0.990.064

030465 0 2 0.0 3.75 0.990.064

130465 0 2 0.0 3.75 0.990.064

140366 0 2 0.0 3.75 0.990.064

240366 0 2 0.0 3.75 0.990.064

030466 0 2 0.0 3.75 0.990.064

130466 0 2 0.0 3.75 0.990.064

140367 0 2 0.0 3.75 0.990.064

240367 0 2 0.0 3.75 0.990.064

030467 0 2 0.0 3.75 0.990.064

130467 0 2 0.0 3.75 0.990.064

140368 0 2 0.0 3.75 0.990.064

240368 0 2 0.0 3.75 0.990.064

030468 0 2 0.0 3.75 0.990.064

130468 0 2 0.0 3.75 0.990.064

140369 0 2 0.0 3.75 0.990.064

240369 0 2 0.0 3.75 0.990.064

030469 0 2 0.0 3.75 0.990.064

130469 0 2 0.0 3.75 0.990.064

140370 0 2 0.0 3.75 0.990.064

240370 0 2 0.0 3.75 0.990.064

030470 0 2 0.0 3.75 0.990.064

130470 0 2 0.0 3.75 0.990.064

140371 0 2 0.0 3.75 0.990.064

240371 0 2 0.0 3.75 0.990.064

030471 0 2 0.0 3.75 0.990.064

130471 0 2 0.0 3.75 0.990.064

140372 0 2 0.0 3.75 0.990.064

240372 0 2 0.0 3.75 0.990.064

030472 0 2 0.0 3.75 0.990.064

130472 0 2 0.0 3.75 0.990.064

140373 0 2 0.0 3.75 0.990.064

240373 0 2 0.0 3.75 0.990.064

030473 0 2 0.0 3.75 0.990.064

130473 0 2 0.0 3.75 0.990.064

140374 0 2 0.0 3.75 0.990.064

240374 0 2 0.0 3.75 0.990.064

030474 0 2 0.0 3.75 0.990.064

130474 0 2 0.0 3.75 0.990.064

140375 0 2 0.0 3.75 0.990.064

240375 0 2 0.0 3.75 0.990.064

030475 0 2 0.0 3.75 0.990.064

130475 0 2 0.0 3.75 0.990.064

140376 0 2 0.0 3.75 0.990.064

240376 0 2 0.0 3.75 0.990.064

030476 0 2 0.0 3.75 0.990.064

130476 0 2 0.0 3.75 0.990.064

140377 0 2 0.0 3.75 0.990.064

240377 0 2 0.0 3.75 0.990.064

030477 0 2 0.0 3.75 0.990.064

130477 0 2 0.0 3.75 0.990.064

140378 0 2 0.0 3.75 0.990.064

240378 0 2 0.0 3.75 0.990.064

030478 0 2 0.0 3.75 0.990.064

130478 0 2 0.0 3.75 0.990.064

140379 0 2 0.0 3.75 0.990.064

240379 0 2 0.0 3.75 0.990.064

030479 0 2 0.0 3.75 0.990.064

130479 0 2 0.0 3.75 0.990.064

140380 0 2 0.0 3.75 0.990.064

240380 0 2 0.0 3.75 0.990.064

030480 0 2 0.0 3.75 0.990.064

130480 0 2 0.0 3.75 0.990.064

140381 0 2 0.0 3.75 0.990.064

240381 0 2 0.0 3.75 0.990.064

030481 0 2 0.0 3.75 0.990.064

130481 0 2 0.0 3.75 0.990.064

140382 0 2 0.0 3.75 0.990.064

240382 0 2 0.0 3.75 0.990.064

030482 0 2 0.0 3.75 0.990.064

130482 0 2 0.0 3.75 0.990.064

140383 0 2 0.0 3.75 0.990.064

240383 0 2 0.0 3.75 0.990.064

030483 0 2 0.0 3.75 0.990.064

130483 0 2 0.0 3.75 0.990.064

140384 0 2 0.0 3.75 0.990.064

240384 0 2 0.0 3.75 0.990.064

030484 0 2 0.0 3.75 0.990.064

130484 0 2 0.0 3.75 0.990.064

140385 0 2 0.0 3.75 0.990.064

240385 0 2 0.0 3.75 0.990.064

030485 0 2 0.0 3.75 0.990.064

130485 0 2 0.0 3.75 0.990.064

140386 0 2 0.0 3.75 0.990.064

240386 0 2 0.0 3.75 0.990.064

030486 0 2 0.0 3.75 0.990.064

130486 0 2 0.0 3.75 0.990.064

140387 0 2 0.0 3.75 0.990.064

240387 0 2 0.0 3.75 0.990.064

030487 0 2 0.0 3.75 0.990.064

130487 0 2 0.0 3.75 0.990.064

140388 0 2 0.0 3.75 0.990.064

240388 0 2 0.0 3.75 0.990.064

030488 0 2 0.0 3.75 0.990.064

130488 0 2 0.0 3.75 0.990.064

140389 0 2 0.0 3.75 0.990.064

240389 0 2 0.0 3.75 0.990.064

030489 0 2 0.0 3.75 0.990.064

130489 0 2 0.0 3.75 0.990.064

140390 0 2 0.0 3.75 0.990.064

240390 0 2 0.0 3.75 0.990.064

030490 0 2 0.0 3.75 0.990.064

130490 0 2 0.0 3.75 0.990.064

\*\*\* Record 17

0 2 0

\*\*\* Record 18

0 0 0.5

\*\*\* Record 19 \-- STITLE

Adamsville Sand; Hydrologic Group C

\*\*\* Record 20

102 0 0 0 0 0 0 0 0 0

\*\*\* Record 26

0 0 0

\*\*\* Record 33

4

1 2 0.37 0.47 0 0 0

0.0028880.002888 0

0.1 0.47 0.27 7.5 11.4

2 10 1.44 0.086 0 0 0

0.0028880.002888 0

0.1 0.086 0.036 0.58 11.4

3 10 1.44 0.086 0 0 0

0.0028880.002888 0

0.1 0.086 0.036 0.58 11.4

4 80 1.58 0.03 0 0 0

0.0028880.002888 0

5 0.03 0.023 0.116 11.4

\*\*\*Record 40

0

YEAR 10 YEAR 10 YEAR 10 1

1

1 \-\-\-\--

7 YEAR

PRCP TCUM 0 0

RUNF TCUM 0 0

INFL TCUM 1 1

ESLS TCUM 0 0 1.0E3

RFLX TCUM 0 0 1.0E5

EFLX TCUM 0 0 1.0E5

RZFX TCUM 0 0 1.0E5

**DMA on Turf; *Metabolite of Parent MMA***

FL Turf 8/09/2001

Osceola County; Representation of the Lake Kissimmee/Indian River
Region; MLRA 156A; Metfile: W12834.dvf \[Daytona Beach\] (old:
Met156A.met)

\*\*\* Record 3:

0.78 0 0 25 1 3

\*\*\* Record 6 \-- ERFLAG

4

\*\*\* Record 7:

0.04 0.303 1 172.8 4 2 600

\*\*\* Record 8

1

\*\*\* Record 9

1 0.1 10 100 3 74 74 74 0 5

\*\*\* Record 9a-d

1 25

0101 1601 0102 1602 0103 1603 0104 1604 0105 1605 0106 1606 0107 1507
1607 0108

.023 .026 .030 .035 .042 .050 .056 .060 .063 .068 .074 .079 .082 .125
.148 .189

.023 .023 .023 .023 .023 .023 .023 .023 .023 .023 .023 .023 .023 .023
.023 .023

1608 0109 1609 0110 1610 0111 1611 0112 1612

.229 .265 .294 .314 .326 .017 .018 .019 .021

.023 .023 .023 .023 .023 .023 .023 .023 .023

\*\*\* Record 10 \-- NCPDS, the number of cropping periods

30

\*\*\* Record 11

010261 150261 151261 1

010262 150262 151262 1

010263 150263 151263 1

010264 150264 151264 1

010265 150265 151265 1

010266 150266 151266 1

010267 150267 151267 1

010268 150268 151268 1

010269 150269 151269 1

010270 150270 151270 1

010271 150271 151271 1

010272 150272 151272 1

010273 150273 151273 1

010274 150274 151274 1

010275 150275 151275 1

010276 150276 151276 1

010277 150277 151277 1

010278 150278 151278 1

010279 150279 151279 1

010280 150280 151280 1

010281 150281 151281 1

010282 150282 151282 1

010283 150283 151283 1

010284 150284 151284 1

010285 150285 151285 1

010286 150286 151286 1

010287 150287 151287 1

010288 150288 151288 1

010289 150289 151289 1

010290 150290 151290 1

\*\*\* Record 12 \-- PTITLE

DMA - 4 applications @ 1.53 kg/ha

\*\*\* Record 13

120 1 0 0

\*\*\* Record 15 \-- PSTNAM

DMA

\*\*\* Record 16

140361 0 2 0.0 1.53 0.990.064

240361 0 2 0.0 1.53 0.990.064

030461 0 2 0.0 1.53 0.990.064

130461 0 2 0.0 1.53 0.990.064

140362 0 2 0.0 1.53 0.990.064

240362 0 2 0.0 1.53 0.990.064

030462 0 2 0.0 1.53 0.990.064

130462 0 2 0.0 1.53 0.990.064

140363 0 2 0.0 1.53 0.990.064

240363 0 2 0.0 1.53 0.990.064

030463 0 2 0.0 1.53 0.990.064

130463 0 2 0.0 1.53 0.990.064

140364 0 2 0.0 1.53 0.990.064

240364 0 2 0.0 1.53 0.990.064

030464 0 2 0.0 1.53 0.990.064

130464 0 2 0.0 1.53 0.990.064

140365 0 2 0.0 1.53 0.990.064

240365 0 2 0.0 1.53 0.990.064

030465 0 2 0.0 1.53 0.990.064

130465 0 2 0.0 1.53 0.990.064

140366 0 2 0.0 1.53 0.990.064

240366 0 2 0.0 1.53 0.990.064

030466 0 2 0.0 1.53 0.990.064

130466 0 2 0.0 1.53 0.990.064

140367 0 2 0.0 1.53 0.990.064

240367 0 2 0.0 1.53 0.990.064

030467 0 2 0.0 1.53 0.990.064

130467 0 2 0.0 1.53 0.990.064

140368 0 2 0.0 1.53 0.990.064

240368 0 2 0.0 1.53 0.990.064

030468 0 2 0.0 1.53 0.990.064

130468 0 2 0.0 1.53 0.990.064

140369 0 2 0.0 1.53 0.990.064

240369 0 2 0.0 1.53 0.990.064

030469 0 2 0.0 1.53 0.990.064

130469 0 2 0.0 1.53 0.990.064

140370 0 2 0.0 1.53 0.990.064

240370 0 2 0.0 1.53 0.990.064

030470 0 2 0.0 1.53 0.990.064

130470 0 2 0.0 1.53 0.990.064

140371 0 2 0.0 1.53 0.990.064

240371 0 2 0.0 1.53 0.990.064

030471 0 2 0.0 1.53 0.990.064

130471 0 2 0.0 1.53 0.990.064

140372 0 2 0.0 1.53 0.990.064

240372 0 2 0.0 1.53 0.990.064

030472 0 2 0.0 1.53 0.990.064

130472 0 2 0.0 1.53 0.990.064

140373 0 2 0.0 1.53 0.990.064

240373 0 2 0.0 1.53 0.990.064

030473 0 2 0.0 1.53 0.990.064

130473 0 2 0.0 1.53 0.990.064

140374 0 2 0.0 1.53 0.990.064

240374 0 2 0.0 1.53 0.990.064

030474 0 2 0.0 1.53 0.990.064

130474 0 2 0.0 1.53 0.990.064

140375 0 2 0.0 1.53 0.990.064

240375 0 2 0.0 1.53 0.990.064

030475 0 2 0.0 1.53 0.990.064

130475 0 2 0.0 1.53 0.990.064

140376 0 2 0.0 1.53 0.990.064

240376 0 2 0.0 1.53 0.990.064

030476 0 2 0.0 1.53 0.990.064

130476 0 2 0.0 1.53 0.990.064

140377 0 2 0.0 1.53 0.990.064

240377 0 2 0.0 1.53 0.990.064

030477 0 2 0.0 1.53 0.990.064

130477 0 2 0.0 1.53 0.990.064

140378 0 2 0.0 1.53 0.990.064

240378 0 2 0.0 1.53 0.990.064

030478 0 2 0.0 1.53 0.990.064

130478 0 2 0.0 1.53 0.990.064

140379 0 2 0.0 1.53 0.990.064

240379 0 2 0.0 1.53 0.990.064

030479 0 2 0.0 1.53 0.990.064

130479 0 2 0.0 1.53 0.990.064

140380 0 2 0.0 1.53 0.990.064

240380 0 2 0.0 1.53 0.990.064

030480 0 2 0.0 1.53 0.990.064

130480 0 2 0.0 1.53 0.990.064

140381 0 2 0.0 1.53 0.990.064

240381 0 2 0.0 1.53 0.990.064

030481 0 2 0.0 1.53 0.990.064

130481 0 2 0.0 1.53 0.990.064

140382 0 2 0.0 1.53 0.990.064

240382 0 2 0.0 1.53 0.990.064

030482 0 2 0.0 1.53 0.990.064

130482 0 2 0.0 1.53 0.990.064

140383 0 2 0.0 1.53 0.990.064

240383 0 2 0.0 1.53 0.990.064

030483 0 2 0.0 1.53 0.990.064

130483 0 2 0.0 1.53 0.990.064

140384 0 2 0.0 1.53 0.990.064

240384 0 2 0.0 1.53 0.990.064

030484 0 2 0.0 1.53 0.990.064

130484 0 2 0.0 1.53 0.990.064

140385 0 2 0.0 1.53 0.990.064

240385 0 2 0.0 1.53 0.990.064

030485 0 2 0.0 1.53 0.990.064

130485 0 2 0.0 1.53 0.990.064

140386 0 2 0.0 1.53 0.990.064

240386 0 2 0.0 1.53 0.990.064

030486 0 2 0.0 1.53 0.990.064

130486 0 2 0.0 1.53 0.990.064

140387 0 2 0.0 1.53 0.990.064

240387 0 2 0.0 1.53 0.990.064

030487 0 2 0.0 1.53 0.990.064

130487 0 2 0.0 1.53 0.990.064

140388 0 2 0.0 1.53 0.990.064

240388 0 2 0.0 1.53 0.990.064

030488 0 2 0.0 1.53 0.990.064

130488 0 2 0.0 1.53 0.990.064

140389 0 2 0.0 1.53 0.990.064

240389 0 2 0.0 1.53 0.990.064

030489 0 2 0.0 1.53 0.990.064

130489 0 2 0.0 1.53 0.990.064

140390 0 2 0.0 1.53 0.990.064

240390 0 2 0.0 1.53 0.990.064

030490 0 2 0.0 1.53 0.990.064

130490 0 2 0.0 1.53 0.990.064

\*\*\* Record 17

0 2 0

\*\*\* Record 18

0 0 0.5

\*\*\* Record 19 \-- STITLE

Adamsville Sand; Hydrologic Group C

\*\*\* Record 20

102 0 0 0 0 0 0 0 0 0

\*\*\* Record 26

0 0 0

\*\*\* Record 33

4

1 2 0.37 0.47 0 0 0

0.0028880.002888 0

0.1 0.47 0.27 7.5 8.2

2 10 1.44 0.086 0 0 0

0.0028880.002888 0

0.1 0.086 0.036 0.58 8.2

3 10 1.44 0.086 0 0 0

0.0028880.002888 0

0.1 0.086 0.036 0.58 8.2

4 80 1.58 0.03 0 0 0

0.0028880.002888 0

5 0.03 0.023 0.116 8.2

\*\*\*Record 40

0

YEAR 10 YEAR 10 YEAR 10 1

1

1 \-\-\-\--

7 YEAR

PRCP TCUM 0 0

RUNF TCUM 0 0

INFL TCUM 1 1

ESLS TCUM 0 0 1.0E3

RFLX TCUM 0 0 1.0E5

EFLX TCUM 0 0 1.0E5

RZFX TCUM 0 0 1.0E5

Number range CHAPTER**Appendix B: PRZM/EXAMS Output
Files**[]{#__RefHeading___Toc126565973 .anchor}

**MMA on Cotton; *Parent Compound***

  -------------------- ---------- --------- --------- -------- ----------- ----------
  stored as                                                                
  MAActMX1.out                                                             

  Chemical: MAA                                                            

  PRZM environment:    modified                                            
  MScottonC.txt        Wedday, 22                                          
                       January                                             
                       2003 at                                             
                       10:52:38                                            

  EXAMS environment:   modified                                            
  ir298.exv            Thuday, 29                                          
                       August                                              
                       2002 at                                             
                       14:34:12                                            

  Metfile: w03940.dvf  modified                                            
                       Wedday, 3                                           
                       July 2002                                           
                       at                                                  
                       08:05:46                                            

  Water segment                                                            
  concentrations (ppb)                                                     

                                                                           

  Year                 Peak       96 hr     21 Day    60 Day   90 Day      Yearly

  1961                 65.09      62.95     58.61     55.19    49.39       21.69

  1962                 11.76      11.51     10.55     8.766    7.704       5.322

  1963                 39.1       37.74     32.69     24.42    20.28       8.135

  1964                 39.24      38.21     35.12     33.3     30.67       15.94

  1965                 24.54      23.7      20.69     15.77    13.14       7.627

  1966                 53.72      52.96     48        36.46    30.86       12.39

  1967                 79.49      76.86     70.48     63.01    56.87       23.95

  1968                 32.32      31.29     29.01     24.31    20.64       10.02

  1969                 8.928      8.628     7.512     5.693    5.159       3.291

  1970                 41.59      40.26     37.83     33.71    30.94       13.87

  1971                 55.31      53.5      46.74     36.49    31.1        14.29

  1972                 12.54      12.14     10.91     9.013    7.794       4.129

  1973                 50.35      49.42     45.43     38.9     33.64       15.21

  1974                 20.38      19.72     17.22     13.07    11.55       7.581

  1975                 18.72      18.32     17.09     14.53    13.64       6.486

  1976                 108        104       96.52     84.24    75.78       30.98

  1977                 18.52      17.93     15.72     13.82    12.86       8.962

  1978                 45.52      44.07     39.88     32.76    28.01       11.07

  1979                 114        111       102       86.49    77.08       34.07

  1980                 36.1       34.97     32.37     25.62    21.9        11.78

  1981                 32.85      31.96     29.2      27.15    24.76       9.833

  1982                 92.91      89.77     82.39     72.41    67.74       27.25

  1983                 83.45      80.74     71.43     55.14    46.57       20.21

  1984                 10.25      9.927     8.799     8.587    8.277       5.447

  1985                 52.59      50.76     44.34     35.22    31.06       13.37

  1986                 50.6       48.88     43.71     34.32    29.2        12.58

  1987                 29.07      28.1      25.2      19.43    16.51       7.632

  1988                 33.78      32.72     29.22     26.81    24.77       11.24

  1989                 46.29      44.76     40.74     35.72    31.46       14.67

  1990                 31.71      30.68     27.61     22.76    19.2        8.016

                                                                           

  Sorted results                                                           

  Prob.                Peak       96 hr     21 Day    60 Day   90 Day      Yearly

  0.032258             114        111       102       86.49    77.08       34.07

  0.064516             108        104       96.52     84.24    75.78       30.98

  0.096774             92.91      89.77     82.39     72.41    67.74       27.25

  0.129032             83.45      80.74     71.43     63.01    56.87       23.95

  0.16129              79.49      76.86     70.48     55.19    49.39       21.69

  0.193548             65.09      62.95     58.61     55.14    46.57       20.21

  0.225806             55.31      53.5      48        38.9     33.64       15.94

  0.258065             53.72      52.96     46.74     36.49    31.46       15.21

  0.290323             52.59      50.76     45.43     36.46    31.1        14.67

  0.322581             50.6       49.42     44.34     35.72    31.06       14.29

  0.354839             50.35      48.88     43.71     35.22    30.94       13.87

  0.387097             46.29      44.76     40.74     34.32    30.86       13.37

  0.419355             45.52      44.07     39.88     33.71    30.67       12.58

  0.451613             41.59      40.26     37.83     33.3     29.2        12.39

  0.483871             39.24      38.21     35.12     32.76    28.01       11.78

  0.516129             39.1       37.74     32.69     27.15    24.77       11.24

  0.548387             36.1       34.97     32.37     26.81    24.76       11.07

  0.580645             33.78      32.72     29.22     25.62    21.9        10.02

  0.612903             32.85      31.96     29.2      24.42    20.64       9.833

  0.645161             32.32      31.29     29.01     24.31    20.28       8.962

  0.677419             31.71      30.68     27.61     22.76    19.2        8.135

  0.709677             29.07      28.1      25.2      19.43    16.51       8.016

  0.741935             24.54      23.7      20.69     15.77    13.64       7.632

  0.774194             20.38      19.72     17.22     14.53    13.14       7.627

  0.806452             18.72      18.32     17.09     13.82    12.86       7.581

  0.83871              18.52      17.93     15.72     13.07    11.55       6.486

  0.870968             12.54      12.14     10.91     9.013    8.277       5.447

  0.903226             11.76      11.51     10.55     8.766    7.794       5.322

  0.935484             10.25      9.927     8.799     8.587    7.704       4.129

  0.967742             8.928      8.628     7.512     5.693    5.159       3.291

                                                                           

  0.1                  91.964     88.867    81.294    71.47    66.653      26.92

                                                               Average of  13.2347
                                                               yearly      
                                                               averages:   

                       with 20%                                            
                       PCA                                                 
                       applied                                             

                       18.3928    17.7734   16.2588   14.294   13.3306     5.384

                                                                           2.64694

  Inputs generated by                                                      
  pe4.pl -                                                                 
  8-August-2003                                                            
  -------------------- ---------- --------- --------- -------- ----------- ----------

**DMA on Cotton; *Sum of Parent Compound and Metabolite of MMA***

Note: This table was generated by adding together the time series
produced by the DMA on Cotton (Parent) input file and the DMA on Cotton
(Metabolite of MMA) input file. The resulting time series was sorted to
determine the annual peak and averages and the upper 90^th^ percentile
values were established.

  ------------------ ---------------- ------------------ ------------------
                     ppb                                 

  year               Peak             Average            

  1961               89.5             28.16038           

  1962               69.42            17.99364           

  1963               40.051           12.09472           

  1964               73               23.41964           

  1965               60.7             17.7723            

  1966               61.01            16.63727           

  1967               87.76            31.17746           

  1968               43.38            17.07995           

  1969               16.2             6.104696           

  1970               138.9            30.85104           

  1971               57.7             22.94463           

  1972               25.57            9.780566           

  1973               50               20.20716           

  1974               42.84            16.23299           

  1975               97.82            20.10098           

  1976               121.86           41.19082           

  1977               37.18            17.25269           

  1978               38.75            14.82005           

  1979               118.76           44.91417           

  1980               65.2             24.9073            

  1981               37.39            15.14247           

  1982               110.6            37.03625           

  1983               95.8             36.35403           

  1984               50.3             14.68191           

  1985               68               22.61434           

  1986               55.92            21.73297           

  1987               33.68            12.55942           

  1988               64.7             19.76704           

  1989               51.72            24.68408           

  1990               22.88            11.99881           

                                                         

  Sorted                                                 

  ppb                Peak             Average            

  0.032258           138.9            44.91417           

  0.064516           121.86           41.19082           

  0.096774           118.76           37.03625           

  0.129032           110.6            36.35403           

  0.16129            97.82            31.17746           

  0.193548           95.8             30.85104           

  0.225806           89.5             28.16038           

  0.258065           87.76            24.9073            

  0.290323           73               24.68408           

  0.322581           69.42            23.41964           

  0.354839           68               22.94463           

  0.387097           65.2             22.61434           

  0.419355           64.7             21.73297           

  0.451613           61.01            20.20716           

  0.483871           60.7             20.10098           

  0.516129           57.7             19.76704           

  0.548387           55.92            17.99364           

  0.580645           51.72            17.7723            

  0.612903           50.3             17.25269           

  0.645161           50               17.07995           

  0.677419           43.38            16.63727           

  0.709677           42.84            16.23299           

  0.741935           40.051           15.14247           

  0.774194           38.75            14.82005           

  0.806452           37.39            14.68191           

  0.83871            37.18            12.55942           

  0.870968           33.68            12.09472           

  0.903226           25.57            11.99881           

  0.935484           22.88            9.780566           

  0.967742           16.2             6.104696           

                                                         

                     peak             yearly             average

  0.1                117.944          36.96803           21.67379

  with 20%           PCA                                 

                     23.6             7.4                4.3
  ------------------ ---------------- ------------------ ------------------

**MMA on Turf; *Parent Compound***

  -------------------- ---------- -- ------- ------- ------- ----------- ---------
  stored as                                                              
  MAAtfKG.out                                                            

  Chemical: MAA                                                          

  PRZM environment:    modified                                          
  FLturfC.txt          Monday, 16                                        
                       June 2003                                         
                       at                                                
                       13:48:06                                          

  EXAMS environment:   modified                                          
  ir298.exv            Thuday, 29                                        
                       August                                            
                       2002 at                                           
                       14:34:12                                          

  Metfile: w12834.dvf  modified                                          
                       Wedday, 3                                         
                       July 2002                                         
                       at                                                
                       08:04:28                                          

  Water segment                                                          
  concentrations (ppb)                                                   

                                                                         

  Year                 Peak          96 hr   21 Day  60 Day  90 Day      Yearly

  1961                 35.05         34.56   32.64   30.57   30.08       17.63

  1962                 95.81         94.98   90.32   81.15   74.69       41.93

  1963                 102           101     98.16   89.8    83.47       54.22

  1964                 251           248     237     211     193         106

  1965                 161           159     152     137     128         86.19

  1966                 246           243     230     208     203         123

  1967                 163           160     152     138     128         88.32

  1968                 150           148     141     126     116         77.03

  1969                 131           129     126     117     109         70.91

  1970                 101           99.32   95.67   88.69   84.05       55.32

  1971                 139           137     130     125     121         74.93

  1972                 227           224     218     201     191         111

  1973                 108           107     103     95.21   89.06       62.47

  1974                 88.47         87.39   83.96   79.21   77.31       51.76

  1975                 102           101     96.52   86.52   80.16       48.8

  1976                 358           353     338     313     292         154

  1977                 135           134     129     116     109         88.19

  1978                 313           309     291     262     247         138

  1979                 135           133     127     116     110         81.84

  1980                 99.32         98.1    94.06   85.59   82.1        56.64

  1981                 73.58         72.69   68.99   63.6    62.01       46.41

  1982                 227           223     216     195     183         103

  1983                 160           158     153     142     137         90.96

  1984                 246           243     235     220     216         128

  1985                 135           133     127     115     107         76.08

  1986                 61.87         61.22   58.59   54.48   51.79       39.7

  1987                 113           111     108     102     96.25       56.06

  1988                 56.32         55.69   53.79   51.32   51.05       37.19

  1989                 97.04         95.68   90.59   80.42   73.87       43.78

  1990                 52.06         51.46   49.05   45.18   42.62       29.24

                                                                         

  Sorted results                                                         

  Prob.                Peak          96 hr   21 Day  60 Day  90 Day      Yearly

  0.032258065          358           353     338     313     292         154

  0.064516129          313           309     291     262     247         138

  0.096774194          251           248     237     220     216         128

  0.129032258          246           243     235     211     203         123

  0.161290323          246           243     230     208     193         111

  0.193548387          227           224     218     201     191         106

  0.225806452          227           223     216     195     183         103

  0.258064516          163           160     153     142     137         90.96

  0.290322581          161           159     152     138     128         88.32

  0.322580645          160           158     152     137     128         88.19

  0.35483871           150           148     141     126     121         86.19

  0.387096774          139           137     130     125     116         81.84

  0.419354839          135           134     129     117     110         77.03

  0.451612903          135           133     127     116     109         76.08

  0.483870968          135           133     127     116     109         74.93

  0.516129032          131           129     126     115     107         70.91

  0.548387097          113           111     108     102     96.25       62.47

  0.580645161          108           107     103     95.21   89.06       56.64

  0.612903226          102           101     98.16   89.8    84.05       56.06

  0.64516129           102           101     96.52   88.69   83.47       55.32

  0.677419355          101           99.32   95.67   86.52   82.1        54.22

  0.709677419          99.32         98.1    94.06   85.59   80.16       51.76

  0.741935484          97.04         95.68   90.59   81.15   77.31       48.8

  0.774193548          95.81         94.98   90.32   80.42   74.69       46.41

  0.806451613          88.47         87.39   83.96   79.21   73.87       43.78

  0.838709677          73.58         72.69   68.99   63.6    62.01       41.93

  0.870967742          61.87         61.22   58.59   54.48   51.79       39.7

  0.903225806          56.32         55.69   53.79   51.32   51.05       37.19

  0.935483871          52.06         51.46   49.05   45.18   42.62       29.24

  0.967741935          35.05         34.56   32.64   30.57   30.08       17.63

                                                                         

  0.1                  250.5         247.5   236.8   219.1   214.7       127.5

                                                             Average of  74.62
                                                             yearly      
                                                             averages:   

                                                                         

  Inputs generated by                                                    
  pe4.pl -                                                               
  8-August-2003                                                          

                                                                         
  -------------------- ---------- -- ------- ------- ------- ----------- ---------

**DMA on Turf; *Metabolite of MMA***

  ------------------ ---------- ------- -------- -------- ----------- ----------
  stored as                                                           
  DMAhikMX.out                                                        

  Chemical: DMA                                                       

  PRZM environment:  modified                                         
  FLturfC.txt        Monday, 16                                       
                     June 2003                                        
                     at                                               
                     13:48:06                                         

  EXAMS environment: modified                                         
  ir298.exv          Thuday, 29                                       
                     August                                           
                     2002 at                                          
                     14:34:12                                         

  Metfile:           modified                                         
  w12834.dvf         Wedday, 3                                        
                     July 2002                                        
                     at                                               
                     08:04:28                                         

  Water segment                                                       
  concentrations                                                      
  (ppb)                                                               

                                                                      

  Year               Peak       96 hr   21 Day   60 Day   90 Day      Yearly

  1961               16.97      16.69   15.87    14       12.95       8.062

  1962               41.33      40.87   38.61    36.3     33.46       18.43

  1963               44.22      43.53   41.21    39.63    37.62       23.93

  1964               103        101     95.74    83.25    76.23       41.49

  1965               72.51      71.31   66.86    58.88    54.2        34.64

  1966               91.73      90.25   84.53    77.33    73.65       45.62

  1967               57.18      56.28   52.93    48.2     45.02       31.48

  1968               82.33      80.88   76.01    66.38    60.32       34.97

  1969               55.37      54.52   52.78    49.27    45.69       30.25

  1970               37.82      37.26   35.77    32.7     30.76       20.35

  1971               50.96      50.16   47.07    44.5     43.6        27.89

  1972               87.75      86.23   83.22    75.86    72.3        42.64

  1973               40.1       39.57   37.94    34.81    32.41       22.78

  1974               31.01      30.55   29.16    27.37    27.17       19

  1975               36.12      35.81   33.9     29.85    27.88       17.16

  1976               122        120     113      105      98.21       50.73

  1977               47.97      47.31   45.3     40.19    38.54       30.83

  1978               106        104     96.81    87.36    83.81       46.93

  1979               67.25      66.4    62.34    54.7     50.26       33.62

  1980               37.54      37.01   35.28    32.22    31.21       22.03

  1981               26.13      25.77   24.27    22.45    22.3        17.39

  1982               86.59      85.07   81.68    72.2     68.05       37.94

  1983               57.08      56.28   54.39    50.38    49.44       32.99

  1984               96.51      95      89.08    78.18    78.22       46.59

  1985               48.15      47.49   44.92    40.31    37.88       26.8

  1986               27.12      26.71   25.41    23.37    21.58       16.68

  1987               45.73      45.01   43.9     40.72    37.73       22.03

  1988               23.46      23.13   21.83    19.66    19.78       14.45

  1989               35.62      35.02   32.8     28.55    25.96       15.42

  1990               19.29      19.02   17.94    16.34    15.31       10.34

                                                                      

  Sorted results                                                      

  Prob.              Peak       96 hr   21 Day   60 Day   90 Day      Yearly

  0.032258           122        120     113      105      98.21       50.73

  0.064516           106        104     96.81    87.36    83.81       46.93

  0.096774           103        101     95.74    83.25    78.22       46.59

  0.129032           96.51      95      89.08    78.18    76.23       45.62

  0.16129            91.73      90.25   84.53    77.33    73.65       42.64

  0.193548           87.75      86.23   83.22    75.86    72.3        41.49

  0.225806           86.59      85.07   81.68    72.2     68.05       37.94

  0.258065           82.33      80.88   76.01    66.38    60.32       34.97

  0.290323           72.51      71.31   66.86    58.88    54.2        34.64

  0.322581           67.25      66.4    62.34    54.7     50.26       33.62

  0.354839           57.18      56.28   54.39    50.38    49.44       32.99

  0.387097           57.08      56.28   52.93    49.27    45.69       31.48

  0.419355           55.37      54.52   52.78    48.2     45.02       30.83

  0.451613           50.96      50.16   47.07    44.5     43.6        30.25

  0.483871           48.15      47.49   45.3     40.72    38.54       27.89

  0.516129           47.97      47.31   44.92    40.31    37.88       26.8

  0.548387           45.73      45.01   43.9     40.19    37.73       23.93

  0.580645           44.22      43.53   41.21    39.63    37.62       22.78

  0.612903           41.33      40.87   38.61    36.3     33.46       22.03

  0.645161           40.1       39.57   37.94    34.81    32.41       22.03

  0.677419           37.82      37.26   35.77    32.7     31.21       20.35

  0.709677           37.54      37.01   35.28    32.22    30.76       19

  0.741935           36.12      35.81   33.9     29.85    27.88       18.43

  0.774194           35.62      35.02   32.8     28.55    27.17       17.39

  0.806452           31.01      30.55   29.16    27.37    25.96       17.16

  0.83871            27.12      26.71   25.41    23.37    22.3        16.68

  0.870968           26.13      25.77   24.27    22.45    21.58       15.42

  0.903226           23.46      23.13   21.83    19.66    19.78       14.45

  0.935484           19.29      19.02   17.94    16.34    15.31       10.34

  0.967742           16.97      16.69   15.87    14       12.95       8.062

                                                                      

  0.1                102.351    100.4   95.074   82.743   78.021      46.493

                                                          Average of  28.1154
                                                          yearly      
                                                          averages:   

                                                                      

  Inputs generated                                                    
  by pe4.pl -                                                         
  8-August-2003                                                       
  ------------------ ---------- ------- -------- -------- ----------- ----------