SUBSTITUTE CHEMICAL PROGRAM
   INITIAL SCIENTIFIC
                  REVIEW
           MSMA/DSMA
               DECEMBER 1975
         U.S. ENVIRONMENTAL PROTECTION AGENCY
             OFFICE OF PESTICIDE PROGRAMS
           CRITERIA AND EVALUATION DIVISION
                 WASHINGTON, D.C. 20460
              i
                    EP/A-540/1-75-020

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This report has been compiled by the
Criteria and Evaluation Division,
Office of Pesticide Programs, EPA, in
conjunction with other sources listed
in the.Preface.  Mention of trade
names or commercial products does not
constitute endorsement or recommendation
for use.

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                                    PREFACE
     The Alternative (Substitute) Chemicals Program was initiated under Public
Law 93-135 of October 24, 1973, to "provide research and testing of substitute
chemicals."  The legislative intent is to prevent using substitutes which in
essence are more deleterious to man and his environment than a "problem" pesti-
cide suspected of causing "unreasonable adverse effects to man or his environ-
ment."  The major objective of the program is to determine the suitability of
potential substitute chemicals which now or in the future may act as replace-
ments for those uses (major or minor) of pesticides that have been cancelled,
suspended, or are in litigation or under internal review for potential unreason-
able adverse effects on man and his environment.

     The substitute chemical is reviewed for suitability considering all appli-
cable scientific factors, such as chemistry, toxicology, pharmacology, environ-
mental fate and movement, use patterns and efficacy.   EPA recognizes the fact
that even though a compound is jjegistered, it still may not be a practical sub-
stitute for a particular use or uses of a problem pesticide.   The utilitarian
value of the "substitute" must be evaluated by reviewing its biological and
economic data.  The reviews of substitute chemicals are carried out in two
phases.  Phase 1 conducts these reviews based on data bases readily accessible
at the present time.  An Initial Scientific Review is conducted to make a
judgment with respect to the "safety and efficacy" of the substitute chemical.
The Phase II Integrated Use Analysis examines the situation resulting from
possible regulatory action against a hazardous pesticide for each of its major
and critical uses.   This Phase II analysis considers  the suitable substitutes
reviewed during Phase I in conjunction with alternative management practices
to evaluate current and projected environmental,  health,  and economic impacts
of potential changes in pest management practices.

     The report summarizes rather than interprets scientific data reviewed
during the course of the studies.   Data is not correlated from different
sources.  Opinions are not given on contradictory findings.

     This report contains the Phase I Initial Scientific Review of MSMA/DSMA.
MSMA/DSMA were identified as registered substitute chemicals for certain
cancelled and suspended uses of 2,4,5-T.  The report covers all uses of MSMA/
DSMA and is intended to be adaptable to future needs.  Should MSMA/DSMA be
identified as substitutes for a problem pesticide other than 2,4,5-T, the
report  can be updated and made readily available for use.  The data contained
in this report was  not intended to be complete in all areas.  Data searches
ended  in January, 1975.

     The review was coordinated by a team of EPA scientists in the Criteria
and Evaluation Division of the Office of Pesticide Programs.  The responsibility
of the  team leader  was to provide guidance and direction and technically re-
view information retrieved during the course of the study.  The  following EPA
scientists were members of the review team:  Fumihiko Hayashi, Ph.D.  (Team
Leader); George Beusch  (Chemistry); William Burnam (Pharmacology and Toxicology);
                                   iii

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 John Bowser (Fate and -Significance in the Environment); Richard Petrie
''Fate and Significance in the Environment) ; Charles Lewis (Registered Uses) ;
and Jeff Conopask, Ph.D. (Economics).

     Data research, abstracting, and collection were primarily performed by
Midwest Research Institute (MRI), Kansas City, Missouri  (EPA Contract
#68-01-2448) under the direction of Mr. Thomas L. Ferguson.  RvR Consultants,
Shawnee Mission, Kansas, under a subcontract to MRI, assisted in data collection.
The following MRI scientists were principal contributors to the report:
James V. Dilley, Ph.D., John Doull, Ph.D., David Hahlen, William B. House, Ph.D.,
Thomas L. Ferguson and Alfred F. Meiners.  Rosemarie von Rumker, Ph.D., (RvR
Consultants) also contributed to the report.

     Draft copies of the report have been reviewed by the scientific staffs
of EPA1s National Environmental Research Centers and their associated labora-
tories.  Comments and supplemental material provided by  the following labora-
tories were greatly appreciated and have been incorporated into this report:
Gulf Breeze Environmental Research Laboratory, Gulf Breeze, Florida, and National
Ecological Research Laboratory, Corvallis, Oregon.  The Ansul Company and Diamond
Shamrock Chemical Company, manufacturers of MSMA/DSMA, reviewed the draft of
this report and made certain comments and additions.
                                    iv

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                               GENERAL CONTENTS
                                                                          Page
List 'of Figures	     vi


List of Tables	    vii


Part   I.     Summary	      1


Part  II.     Initial Scientific Review 	      9


      Subpart A.   Chemistry  	      9
      Subpart B.   Pharmacology and Toxicology  	     35
      Subpart C.   Fate and Significance in the Environment	     49
      Subpart D.   Production and Use	     81


Part III.     Efficacy and Performance Review	    107

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                                   FIGURES






o-                                                                      Page






1     Production Schematic for MSMA and DSMA	    12






2     Titration of Hethylarsonic Acid with  Sodium Hydroxide	    24
                                      vi

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                                      TABLES


 No.                                                                       Page

 1  Arsenic in Total Diet Samples	28

 2  Daily Intake of Arsenic Residues 	  30

 3  Exposure of Tree-Thinning Crews to MSMA	45

 4  Toxicity of MSMA and DSMA to Fish	51

 5  MSMA 6 Lb/Gal (47.74%)  Liquid Concentrate Speciman Label 	  85

 6  DSMA Soluble Powder (63%) Specimen Label 	  86

 7  Weed Control Profile of MSMA	87

 8  Estimated Uses of MSMA and DSMA in the United  States by Regions
      and Categories, 1972	94

 9  Farm Uses of Organic Arsenical Herbicides in the United States
      in 1964, 1966, 1971 and 1972	95

10  MSMA and DSMA Uses in California by Major Crops  and Other Uses,
      1970-1973	99

11  Use of MSMA in California in 1972,  by  Major  Crops  and Other Uses,
      Applications,  Quantities,  and Acres  Treated	100

12  Use of MSMA in California in 1973,  by  Major  Crops  and Other Uses,
      Applications,  Quantities,  and Acres  Treated	101

L3  Use of DAMA in California in 1972,  by  Crops  and  Other Uses,
      Applications,  Quantities,  and Acres  Treated	102

L4  Use of DSMA in California in 1973,  by  Crops  and  Other Uses,
      Applications,  Quantities,  and Acres  Treated	103
                                    vii

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                                PART I.  SUMMARY









                                     CONTENTS






                                                                             Page




Production and Use	      2
Toxicity and Physiological Effects. .






Food Tolerances and Acceptable Intake
Environmental Effects
Efficacy and Performance Review 	     105

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     This section contains a summary of the "Initial Scientific Review"
conducted on MSMA (monosodium methanearsonate) and DSMA  (disodium methane-
arsonate) .  The section summarizes rather than interprets data reviewed.


Production and Use

     DSMA (disodium methanearsonate) is manufactured by a synthesis process
involving two reactions:

           AS203 + 6NaOH - ^ 2Na3As(>3 + 3H20

           Na3As03 + CH3C1 - ^ CH3AsO(ONa)2 + NaCl

                                        DSMA

     MSMA (monosodium methanearsonate) is then made from DSMA by treatment
with sulfuric acid:

                                                   ONa
           2CH3AsO(ONa)2
                  DMSA                       MSMA

DSMA is also an intermediate used in the production of various other salts of
me thy lar sonic acid (MAA) .

     MSMA and DSMA undergo few chemical reactions.  These compounds are in a
stable oxidation state; strong oxidizing or reducing agents are required for
chemical decomposition.  However, there is disagreement over whether mixing
MSMA or DSMA with "hard" water {i.e., water containing relatively high concen-
trations of calcium) could cause precipitation of insoluble calcium methane-
arsonate.

     DSMA readily absorbs water from the air to form a crystalline hexahydrate,
one form in which it is marketed.  Both DSMA and MSMA are also sold as solu-
tions of various strengths and combinations with other herbicides.

     MSMA and DSMA are used mainly as contact herbicides to control a number
of hard-to-control weeds including Johnson grass, nutsedge, dallisgrass, and
crabgrass, as well as several other weeds.  The herbicides are also used for
directed application (having no contact with crop plants) on citrus fruits
(bearing and non-bearing) and on cotton.  DSMA is also registered for use as
a topical application (allowing for contact with crop plants) on cotton.  MSMA
is registered for use as a directed application in non-bearing deciduous fruit
and nut orchards.  MSMA and DSMA are both used on lawns, ornamental grass and
certain noncrop areas, as well.  Tolerances for MSMA and DSMA have been estab-
lished for citrus fruits and cottonseed and are pending for grapes and sugar-
cane.

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     According to the U.S. Tariff Commission, the production of all MAA salts
was almost 30.7 million Ib in 1972.  Of this amount, 24.0 million Ib  (78%)
were estimated to have been MSMA and 6.0 million Ib (19%), DSMA.  An  estimated
7 uillion Ib of the total were exported; negligible amounts, if any,  were
imported.

     In 1972, an estimated 23 million Ib of MSMA and DSMA were used in  the
United States.  Midwest Research Institute (MRI) estimates that this  total
consisted of about 19 million Ib of MSMA and 4 million Ib of DSMA.  About 15.5
million Ib of MSMA and DSMA (about two-thirds of the total domestic consump-
tion) were used by farmers, primarily for preplant and postemergence weed
control on cotton.  The remaining 7.5 million Ib of MSMA and DSMA were  used in
industrial and commercial weed control by governmental agencies and for
residential and home garden weed control.

     By geographic regions, MRI estimates that about 70% of the total 1972
usage of MSMA and DSMA was in the South Central states, followed (in decreas-
ing order of use) by the Southeastern, North Central,  Southwestern, North-
western, and Northeastern states.


Toxicity and Physiological Effects

     Limited data was found on the toxicity and physiological effects of MSMA
and DSMA.  Background material is provided on closely  related compounds, such as
MAA (an equilibrium form of MSMA at low pH) and other  possible metabolic products.

     Reports on the toxicity of MSMA and DSMA to animals indicate that  the com-
pounds are low to moderately toxic.  LD5Q values obtained with rats for MSMA,
DSMA, and related arsenicals are as follows:

           Compound          Concentration (%)*             LD50 (g/kg)

     MSMA                           25,1                        2.6
     MSMA                           51.55                       1.8
     MSMA                           35.21                       1.8
     DSMA                           65.66                       2.8
     MAA                            98.8                        1.4
*  Concentrations tested have been included because available data did not
     always specify whether the LD5Q was expressed in terms of the amount
     of arsenic, DSMA or MSMA, or formulation tested.

In most of the acute toxicity studies, gross pathological changes in tissues
and organs were not observed in the survivors.  However, moderate to severe
gastroenteritis was noted in the animals that died.

     Definitive acute toxicity data for laboratory animals other than the rat
has not been reported.

     In tests on rabbits MSMA and DSMA were reported to be mildly irritating
to the skin.

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     The acute U)$Q for MSMA (22.6 to 29.0%) in cattle was reported to be
1.7 g/kg body weight in 400-lb animals and 1.2 g/kg in calves.

     Heifers (400 Ib) were killed by a total dose of 78.7 oz of MSMA  (21%
arsenic) administered over 9 days or by 47.6 oz administered over 5 days.
One heifer that was treated with MSMA (2 oz per day) died after 23 daily
exposures.

     No subacute toxicological effects were observed in rats fed MAA  (52.3%
arsenic) at dietary levels of 100 ppm for 90 days.  In addition, the  compound
had no effect on dogs when fed at 90 ppm in the diet for 90 days.

     The results of most studies indicate that, in the rat, a cumulative
effect is evident from repeated dosing.

     Although there is limited available data on animal metabolism of MSMA and
DSMA, significant data has been reported on the metabolism of several related
arsenical compounds.  This data is presented as background information on arsen-
icals and does not necessarily apply to MSMA/DSMA:

      1.  Arsenic acid  (H3As04) is excreted rapidly in the urine in man and
          cattle; there is little storage in tissues.  The residue levels
          present in tissues rapidly decrease after the arsenicals are no
          longer fed or other exposure is stopped.

      2.  Some arsenic metabolites are not excreted in milk of cattle.

      3.  The extent of MSMA and DSMA concentration in tissues differs among
          rats, guinea pigs, rabbits, and hamsters.  The rat is the only
          laboratory animal tested in which high concentrations of arsenic
          accumulated.

      4.  Some arsenic compounds do not accumulate in hens' eggs.

      5.  Pentavalent arsenic compounds appear  to be more completely  excreted
          than trivalent  compounds.

      6.  Certain organic arsenicals, bound in  animal tissues, are not released
          from these  tissues to any great extent or stored in animals.

      Effects of MSMA  and DSMA on reproduction and teratogenic effects have
not been studied.   Sodium arsenate  (a microbial metabolite of MSMA and DSMA)
has been found to affect  both resorption and malformation in the hamster.

      Studies have not been  reported on  the  oncogenic effects of MSMA  and  DSMA
in rats or  mice.

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     In field operations involving MSMA and DSMA, the arsenic levels  in  the
urine of applicators have been shown to increase.  However, the level decreases
upon removal from source of application.


Food Tolerances and Acceptable Intake

     Analytical methods which distinguish residues of specific arsenical
compounds in plant materials are not presently being used.  Foods and feed
are analyzed for total arsenic (as As203>; results, therefore, include
naturally occurring arsenic levels in addition to pesticide residues.

     There are currently tolerances for MSMA and DSMA on citrus fruits and
cottonseed.  Tolerances on grapes and sugarcane products are pending.

     Investigators who have monitored the levels of arsenic in food and feed
for a 6-yr period have concluded that the dietary intake of arsenic from
pesticide residues is not significant.

     Acceptable daily intakes (ADI) have not been established for MSMA or
DSMA.
Environmental Effects

     The data available concerning MSMA and DSMA's effects on fish is limited
to toxicity studies.  Only 6 species have been subjected to controlled study,
and the number of replicate tests on these species is small.  No reports were
found on the effects of MSMA or DSMA to fish under field conditions.  Published
data on toxicity to fish is summarized as follows:
                                                           LC5Q
                                                           96-hr
     Species                        Herbicide               ppm

Bluegill                              MSMA                 49.2*
   (Lepomis macrochirus)                               > 1,000

Channel catfish                       MSMA                 26.8
   (Ictalurus punctatus)

Fathead minnow                        MSMA                 13.3
   (Pimephales promelas)

Goldfish                              MSMA                 31.1
   (Carassius auratus)

Rainbow trout                         MSMA                 96.0
   (Salmo gairdneri)
*  Results from two separate investigations.

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     As with all 'pesticides having acute toxicity values for fish of greater
than 1.0 ppm, commercial labels of MSMA and DSMA formulations do not carry any
specific warnings regarding fish toxicity.

     MSMA or DSMA (1.0 ppm in seawater) had no effect on pink shrimp
(Penaeus duorarum) or Eastern oyster (Crassostrea virginica) after 48- and
24-hr exposures, respectively.  A 96-hr exposure to 100 ppm of MSMA was not
toxic to scud (Gammarus fasciatus) .

     Data on the effect of MSMA and DSMA on wildlife is also limited.
Controlled studies have apparently been limited to 2 avian species.

     The acute oral toxicities of DSMA to mallard ducks (Anas platyrhynchos)
and bobwhite quail (Colinus virginianus) are >10,000 mg/kg and 3,160 mg/kg,
respectively .

     Subacute toxicity studies indicate that 10- to 15-day-old ducklings are
not affected by dietary levels of 5,000 ppm MSMA.  The dietary median lethal
concentration (LCso) for bobwhite quail was calculated to be 3,300 ppm of MSMA.
     Studies have been made of the fate and environmental impact of organic
arsenical herbicides  (including MSMA) used in the forest environments of the
Pacific Northwest.  More than 400 determinations were made of arsenic residues
in specific tissue and whole body samples from animals trapped at various
intervals after use of the arsenicals.  About 50% of the animals captured
between 2 and 30 days following treatment contained arsenic residues between
0.5 and 9.8 ppm.  One animal after 1 day of treatment contained arsenic
residues ranging from 17 to 30 ppm in various body parts.  Few animals
collected more than 30 days after treatment contained detectable arsenic
residues.

     Both MSMA and DSMA have been classed as  "relatively nontoxic"  to honey-
bees  (Apis mellifera) , based on U>50 values determined from their contact
effect when  applied in the  dust form.   However,  spraying with MSMA  in aqueous
solutions  (equivalent to  4  Ib  active ingredient  (AI)  in 20 gal of water per
acre)  was reported to be "extremely toxic" to bees;  mortality was about  70%
3 days after spraying.  Oral ingestion  of 100 and  1,000 ppm of MSMA and DSMA
in  sucrose syrup  is also  reported to be "extremely toxic" to the honeybee.

      Soil microorganisms  appear to be capable of degrading organic  arsenical
herbicides,  including MSMA  and DSMA.  Penicillium  brevicaule and Methano-
bacterium have been shown to produce methylarsines from methylarsonates .
Studies  using ^C-labeled MSMA in 4  types of  soil  indicate a 2.4- to 14-fold
increase in  the degradation of MSMA  (based  on ^C02 evolution) when nonsterile
soils  are  compared to steam-sterilized  controls.

      Tests have shown that  soil concentrations of  50 ppm MSMA have  no apparent
toxicity to  soil  microbes.

     Application  of DSMA  at an inordinate rate  (9,992 Ib/acre) apparently
inhibits C02 evolution and  bacterial  growth,  stimulates the growth  of

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 Streptomyces, and  inhibits somewhat the growth of soil fungi.   The  amount of
 organic matter available for microbial activity apparently has  a  direct
 effect on  the rate of decomposition of these compounds in the soil.

     Available data indicates that herbicidally-effective concentrations  of
 MSMA and DSMA "disappear" rather rapidly from field soils after application.
 Microbial  activity appears to some extent  to contribute to their degradation;
 several different chemical reactions also appear to be involved.  There is
 some disagreement among investigators concerning the relative importance  of
 different  chemical pathways, including reduction of the methylarsonates to
 form volatile methylarsines that escape in the atmosphere, and the formation
 of inorganic arsenates.  Leaching of MSMA and DSMA through soil profiles
 appears to be inversely related to the soil clay content.

     Numerous tests have reported the apparent tolerance of important crops
 to MSMA and DSMA residues in soils.  DSMA at a rate of 120 Ib Al/acre had no
visible effect on barley, safflower, cotton, and sorghum for 3 successive
years.  MSMA at a rate of 256 Ib Al/acre had no phytotoxic effect on lettuce,
 sugar beets, broccoli, or tomatoes planted 4 months after application; how-
ever, barley was affected.

     Regarding MSMA and DSMA tests in water, one study reported the effect
 on stream water of MSMA use for forest thinning.   No detectable residues
were found in the water samples using an analytical technique sensitive to
 0.01 ppm arsenic.  Analysis of water following application of MSMA to
 irrigation-system ditch banks showed arsenic levels as high as 0.86 ppm
 immediately after application.  Arsenic concentrations in the water, however,
 decreased as time progressed.

     In bioaccumulation and biomagnification tests,  one ongoing study has been
reported concerning the effect of MSMA on a model micro-ecosystem containing
daphnids (Daphnia magna), crayfish (Procambarus species), algae (Oedogonium
cardiacum), and a channel catfish (Ictalurus punctatus).   The crayfish in this
system were reported to have bioconcentrated arsenic up to 10-fold from water
containing 1 ppm MSMA.  The single arsenical compound present in the crayfish
 (not MSMA) has not yet been identified.

     Specific data on the environmental transport mechanisms for MSMA and DSMA
was not found.
Efficacy and Performance Review

     MSMA and DSMA are widely used for control of Johnson grass, nutsedge,
dallisgrass, sandbur, and a wide variety of weedy grasses and broadleafed weeds.
Although primarily used on cotton, the herbicides are also applied to weeds in
citrus orchards, drainage ditches, rights of way, fence rows, storage yards,
and other similar noncrop areas.

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     The efficacy and effectiveness of MSMA and DSMA vary with the weed being
controlled.  Generally, the rate and number of applications are the most impor-
tant factors.  With Johnson grass and nutsedge, single applications will give
only temporary control and significant regrowth can be expected.  Low tempera-
tures appear to decrease the effectiveness of MSMA and DSMA, while sunlight and
hot temperatures increase the rate of control.

     At least 2 applications of DSMA are needed for good control of Johnson
grass and a single application in the following season can provide up to 99%
control.  At least 2 Ib/acre are needed per application.  Control of Johnson
grass often results in a regrowth of Bermuda grass which is not affected by
DSMA or MSMA.

     MSMA was found to give better control of nutsedge than DSMA.  In comparable
tests, regrowth was 89% in 3 weeks after application of DSMA and was 11% with
MSMA.  It was also found that purple nutsedge is more difficult to control than
yellow nutsedge.  Control is directly related to the number of applications and
good control is achieved when applications are made at 2- to 4-week intervals
during the season.

     Close to 100% seasonal control of broadleaf weeds in cotton and better than
90% control of grasses was achieved with 3 to 4 direct applications of DSMA or
MSMA.

     A single directed application of MSMA or DSMA on cotton weeds can result in
over 50% control of grasses, broadleaf weeds, and morning glory.  This applica-
tion reduces hoe labor by 60%.

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                       PART II.  INITIAL SCIENTIFIC REVIEW


                              SUBPART A.  CHEMISTRY


                                    CONTENTS

                                                                           Page

Synthesis and Production Technology	     10

Physical Properties	     14

Analytical Methods 	     16

  Information Sources	     16
  Multi-Residue Methods	     16
  Residue Analysis 	     16
  Formulation Analysis 	     21

Composition and Formulation	     22

Chemical Properties and Reactions	     23

Alkylation and Dealkylation	     26

Occurrence of Residues in Food and Feed Commodities	     27

Acceptable Daily Intake	     29

Tolerances	     29

References	     31

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     This section reviews available data on the chemistry of MSMA and
DSMA and their presence in foods.  Eight subject areas have been examined:
Synthesis and Production Technology; Physical Properties; Analytical
Methods; Composition and Formulation; Chemical Properties and Reactions;
Occurence of Residues in Food and Feed Commodities; Acceptable Daily
Intake, and Tolerances.  The section summarizes rather than interprets
data reviewed.
Synthesis and Production Technology

     Methylarsonic Acid (MAA) and its salts have been known for over 90 years,
having been first prepared by Meyer  (1883).i/  However, the compounds were not
used commercially until about 1956.
     The original patent for use of sodium salts of various alkylarsonic
acids as herbicides was issued to Arthur Schwerdle (1959).'  Since then he
has been issued patents for various other salts of MAA  (Schwerdle  19623,.3-/
1962b,A/ 1962C,-5-/), but the sodium salts are the most frequently used.
     MSMA  (Monosodium methanearsonate)  is  the most widely used  of  a  group of
organoarsenic herbicides introduced  in  the 1950's that  also  includes the octyl-
and docecylammonium salts,  the disodium salt (DSMA),  and cacodylic acid  (di-
methylarsinic acid).  The 2 major domestic manufacturers, The Ansul  Company
(Marinette, Wisconsin) and  Diamond Shamrock Chemical  Company (Green  Bayou,
Texas), as well as Vineland Chemical Company (Vineland, New  Jersey)  and W. A.
deary Corporation (New Brunswick, New  Jersey) all produce DSMA.   DSMA can
apparently serve as an intermediate  in  the manufacture  of other organoarsenic
herbicides.

     Diamond Shamrock provided details  on  MSMA production  (von  Riimker et al.
1974).Of  The process is believed to be approximately as shown  by  the follow-
ing reaction equations and  by the production schematic  shown in Figure 1:
 I/  Meyer,  G.,  Berichte der Deutsche Gesellschaft,  Berlin,  16:1440 (1883).
 21  Schwerdle,  A.,  U.S. Patent No.  2,889,347  (2 June 1959).
 3/  Schwerdle,  A.  (to Vineland Chemical Company), U.S.  Patent No.  3,030,199
       (17 April 1962a).
 4/  Schwerdle,  A.  (to Vineland Chemical Company), U.S.  Patent No.  3,056,821
       (2 October 1962b).
 5/  Schwerdle,  A.  (to Vineland Chemical Company), U.S.  Patent No.  3,068,088
       (11 December 1962c).
 6/  von Riimker, R., E. W.  Lawless,  and A.  F.  Meiners, Production,  Distribu-
       tion, Use, and Environmental  Impact  Potential of Selected Pesticides,
       for Council of Environmental  Quality,  Contract No.  EQC-311 (15 March
       1974).
                                      10

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             6NaOH 	2Na3AsC>3 + 3H20                       (1)
     Arsenic                     Sodium
     Trioxide                    Arsenite

     Na3As03 + CH3C1	^ CH3AsO(ONa)2 + NaCl                 (2)

               Methyl                     DSMA
               Chloride

                                               x-ONa
     2CH3AsO(ONa)2 + H2S04	^-2CH3As<^       +Na2SC>4          (3)
                                           "  ^OH
             DSMA                               MSMA
     In the first step of the process, drums of arsenic trioxide are opened
in an air-evacuated chamber and automatically dumped into the 50% caustic.
A dust collection system is employed.  The drums are washed carefully with
water, the wash water is added to the reaction mixture, and the drums are
crushed and are sold as scrap steel.  The intermediate sodium arsenite is
obtained as a 25% solution and is stored in large tanks prior to further
reaction.  In the next step, the 25% solution of sodium arsenite is treated
with methyl chloride to give the disodium salt, DSMA.

     In order to obtain MSMA, the solution is partially acidified with
sulfuric acid and the resulting solution is concentrated by evaporation.  The
active ingredient is sold at a number of concentrations, but approximately 58%
is the maximum concentration that can be prepared without encountering an
undesirable increase in viscosity.

     As the aqueous solution is being concentrated, a mixture of sodium
sulfate and sodium chloride precipitates out, about 0.5 lb/100 Ib AI.  These
salts, a troublesome disposal problem because they are contaminated with
arsenic, are removed by centrifugation, washed in a 5-stage counter-current
washing cycle, and then disposed of in a dump situated on nearly impermeable
Beaumont clay which has no aqueous runoff.

     Diamond Shamrock'.s plant is a "low effluent" plant, although aqueous
waste is not discharged.  Methanol, a side product of methyl chloride hydrolysis,
is recovered and used elsewhere in the plant, and recovered water is recycled.
Two equalization ponds are used and the discharge of arsenic averages about 0.7
to 0.8 ppm.  The total amount of arsenic discharged amounts to only about 1/2
Ib/day.
                                      11

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N>
             NaOH
             H2SO4

1




















Dust ,
Collector
t
^ ^ Sodium
^k Ani.nStn '



















^Vent

25% Na3AsO3
Storage

1

** Methylarsonic
*" Acid Unit
{
Crude fc PurifirntJnn "^ IT? MA *;nl*
I .- -.i._
1


^"^
1 1
StrioDer ^ Aqueous By-Product
rr ^" CH3OH Saltsi
1 ^2^ 1 X X
CH3OH Washer  ^.Na2SO4
Recovered and NaCI
used elsewhere 1 1
1 	 Liquid To APP>ved
| Land Fill
                           Figure 1.  Production schematic for MSMA and DSMA



    Source:  von Rximker et al., op. cit. (1974).

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     Other conditions and methods of manufacture are described  in  a U.S.
patent by Urbanowski and Steinkoenig (1969) . '

     According to Urbanowski and Steinkoenig (1969) , the reaction  of  sodium
hydroxide with arsenic trioxide (Equation 1, p. 17) is not initially  sent  to
completion with a stoichiometric ratio of sodium to arsenic  (3.1:1);  a  lower
sodium to arsenic ratio is used initially, and the balance of the  sodium
hydroxide is gradually added to the reaction in proportion to a gradual addi-
tion of methyl chloride (Equation 2, p. 17).  This is done to minimize  the
hydrolysis of methyl chloride to methanol and thus maximize yield.

     The methyl chloride is generally pumped to the reactor as a liquid and
flashes to the gaseous state upon entering the reactor.  The pressure (60  to
120 psig) is regulated by methyl chloride addition.  Temperature is maintained
at 60 to 90 C, because a temperature below 50 C can impair formation of DSMA,
and a temperature above 100C will cause product degradation.  A slight excess
of CH3C1 is used to assure virtually complete conversion of the sodium  arsenite.
Schanhals (1967)' contends that the preferred pressure is 175 psig.

     Following the addition of all reactants, the contents are allowed  to
"digest" until the reaction ceases,  during which time the pressure drops to  5
to 10 psig.  The reaction medium can also contain small amounts of catalysts
or promoters, for example,  a mixture of a saturated aliphatic ketone with
high-boiling mineral spirits.

     Following digestion,  the medium is allowed to cool,  and the DSMA is
precipitated and filtered.   Precipitation is augmented by the addition of a
suitable liquid, such as isopropyl alcohol.
     Yields through the DSMA reaction may be 97% or more based upon
With proper digestion, residual inorganic arsenic (as As203) is under 0.8%
(Urbanowski and Steinkoenig  1969).

     Most of the sodium chloride and sodium sulfate remain in solution.
Stoichiometrically, 36.1 Ib of NaCl and 43.8 Ib of NaS04 would be produced
per 100 Ib of MSMA.  But according to Schwerdle (1959) the NaCl and Na2S04
are simply diluents which do not affect the herbicidal properties.

     DSMA may also be produced with methyl iodide, CH3I, or methyl sulfate,
(CH3)2S04, as the methylating agent (Schwerdle  1959).
I/  Urbanowski, R. L.,  and R.  P.  Steinkoenig (to Diamond Shamrock Corporation),
      U.S. Patent No.  3,440,258 (22 April 1969).
2J  Schanhals, L. R. (to 0. M. Scott & Sons),  "Process for the Manufacture of
      Lower Alkyl Arsinic Acids and Alkali Metal Salts Thereof," U.S. Patent
      No. .3,322,805 (1967).
                                     13

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Physical Properties

Chemical Name;  MSMA, Monosodium methanearsonate
                DSMA, Disodium methanearsonate

Common Name;  MSMA, DSMA.

MSMA Trade Names;  Ansar 170 H.C., Ansar 529 H.C., Bueno, Daconate, Phyban
                   H.C., Silvisar 550, Weed-E-Rad, Weed-Hoe.

DSMA Trade Names;  Ansar 8100, Ansar DSMA Liquid, Arrhenal, Arsinyl, Chipco
                   Crab Kleen, Crab-E-Rad, Dal-E-Rad 100, Di-Tac, DMA, DMA-100,
                   Methar, Sodar, Weed Broom, Weed-E-Rad, Weed-Hoe.
Pesticide Class;  Herbicide; arsenical

                      MSMA

Empirical Formula;  CH^AsC^Na
Structural Formula;  CH3


Molecular Weight:  161.94
ONa

OH
Physical State:  White to faint yellow
                 liquid aqueous solution.
                 Odorless (Vineland)

Specific Gravity;  1.56 at 20C (Vineland)*!/

Density;           13 Ib/gal  (Vineland)*

Bulk Density;
                             DSMA
                               (pure)
                                                                  (hexahydrate)
                                                         ONa
                    183.93 (pure)
                    292.03 (hexahydrate)

                    DSMA hexahydrate
                    White, fine crystalline
                    powder.  Odorless (Vineland)
                    Approximately 63
                    (Vineland)
 *   Figures  for Vineland MSMA refer to  a 51.2%  solution  of MSMA with  3%  sodium
       chloride.
 I/   Vineland Chemical Company,  "MSMA-DSMA Weed  Control," Vineland, New Jersey
       (undated).
                                      '14

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                      MSMA
                                                           DSMA
Melt '.ng Point;
            Below 10F (Vineland)*
            115-119 C (von Riimker et al.
            1974)**
Boiling Point;  112 C (Vineland)*

               Nonflammable
Solubility;  57% w/w at 25 C (Ansul
             19 71)!/
             195.5 g/100 g H20 at 25'
             (Vineland)
pH:
Corrosivity;
          Noncorrosive to stainless
          steel, rubber, alloys and
          plastics.
132-139C, slowly  decomposes
at elevated temperatures
(Martin  1971)I/ 132-139C
(Frear  1969)-?/.   May  sinter
if enclosed in its water  of
crystallization.   Decomposes
at very high temperature
(Vineland).
Nonflammable

28% w/w at 25C  (Ansul  1971)
36% w/w at 20C  (Diamond
Shamrock  1970) A/.
25.4% w/w at 25C  (Martin
1971).
Very soluble in water.  Mod-
erately soluble in low molec-
ular weight alcohol  (Frear
1969) .
Soluble in methanol but
practically insoluble in
other organic solvents
(Martin  1971).

11.2 (5% solution)(Vineland)
10.5 (no concentration given)
(Ansul  1971).

Noncorrosive to stainless
steel, rubber, alloys and
plastics.
**
I/
4/
Figures for Vineland MSMA refer to a 51.2% solution of MSMA with 3%
  sodium chloride.
This melting point range is for the 1.5 hydrated formthe anhydrous
  MSMA decomposes and does not yield a melting point.
Martin, H., Pesticide Manual, British Crop Protection Council, 2nd ed.
  (1971).
Frear, D. E. H., Pesticide Index, 4th ed., College Science
  Publishers, State College, Pennsylvania (1969).
The Ansul Company, Comments in Support of Continued Registration of
  Organic Arsenical Herbicides, Marinette, Wisconsin (31 August 1971).
Diamond Shamrock Chemical Company, DSMA - MSMA Herbicides (bulletin)
  Cleveland, Ohio (1970).
                                       15

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Arsglytical Methods

     This subsection reviews analytical methods for MSMA and DSMA.  The
review describes multi-residue methods, residue analyses, and formulation
analyses.  Information on the sensitivity and selectivity of the methods is
also presented.
Information Sources - The primary  information  sources  for  the  analytical
methods are as follows:   (1) The Pesticide Analytical  Manual  (PAM) ,.!/  published
by the Food and Drug Administration  (FDA) , is  designed to  bring  together
procedures and methods used by  the FDA laboratories  to examine food  samples
for the presence of pesticide residues.   PAM is  published  in  2 volumes.
Volume I contains procedures for multi-residue methods (for samples  of unknown
history which may contain more  than  one pesticide) .  Volume II contains
analytical methods used  for specific pesticide residues and for  specific  foods.
(2) Official Methods of  Analysis of  the Association  of Official  Analytical
Chemists  (AOAC) .j-/ is a  methods manual published about every  5 yr.   The
reliability of the methods must be demonstrated  by a published study showing
the reproducibility of the method  by professional analysts. Methods and
collaborative studies are published  in the Journal of  the  Association of
Official Analytical Chemists.


Multi-Residue Methods -  There are  no multi-residue methods which specifically
detect MSMA and DSMA.  The residue analyses  performed  by FDA  do  not  detect
MSMA  and DSMA as an individual  chemical; all forms of  arsenic  are converted
to arsenic trioxide
 Residue Analysis - The Diamond Shamrock Chemical Company (1970) I/  explains
 the  difficulty in detecting residues of arsenical pesticides as  follows:

         Analytical methods which can distinguish residues of specific
         arsenical compounds in plant materials are not available.   Gas
         chromatography and thin-layer chromatography methods do  not
         have sufficient sensitivity to quantitatively analyze methane-
         arsonate herbicides .... In addition,  no method is available  for
         extracting DSMA or MSMA from plant tissue without altering  the
         chemical composition of the methanearsonate ion.  Therefore,
         all quantitative analyses of methanearsonate residues employ
         the total arsenic method.
 JL/  U.S.  Department of Health,  Education,  and Welfare;  Food and Drug Administra-
       tion,  Pesticide Analytical Manual, 2 vols.  (1971).
 21  Association of Official Analytical Chemists,  Official Methods of Analysis
       of  the Association of Official Analytical Chemists, llth ed.,  Washington,
       D.C.  (1970).
 3/  Diamond  Shamrock Chemical Company, op. cit.  (1970).
                                       16

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     There have been some recent developments which may lead to practical,
specific methods for the determination of MSMA and DSMA residues.

     Sachs et al. (1971)-=.' developed a paper chromatographic separation
method for cacodylic acid, MSMA, sodium arsenate and sodium arsenite.  Four
solvent elution systems were employed.  Aqueous extraction of plant tissues
removed essentially all of the arsenicals applied.  The paper chromatographic
procedures were followed by colorimetric determinations of the separated
arsenicals.  The silver diethyldithiocarbamate colorimetric method was useful
for detecting as little as 0.6 to 20 yg of arsenic (the color is caused by
the formation of an arsine-silver diethyldithiocarbamate complex).

     Braman and Foreback (1973)' developed a method for analyzing various
forms of methylated arsenic acids in the environment at low concentration.
This method depends upon reduction of cacodylic acid to dimethylarsine,
(CH3)2AsH, by sodium borohydride at pH 1 to 2.   This volatile arsine is then
scrubbed out with helium gas and frozen in a liquid nitrogen trap.  The
arsine gas is then volatilized from the trap and a recording is made of the
intensity of arsenic emission lines (234.9 nm or 228.8 nm) produced by an
electrical discharge in the carrier gas.  The limit of detection is very low,
0.5 ng.  Braman and Foreback's method is also applicable to arsenite ion,
arsenate ion, and MAA.  Since arsine, methylarsine and dimethylarsine will
volatilize from the trap in the order of their boiling points,  the compounds
pass through the detector at different times and the analysis readout is
similar in appearance to a gas chromatogram.  Thus, the two methylated
arsenic acids can be distinguished from one another and from inorganic
arsenic.  The authors applied this method to the analysis of water samples,
bird eggshells, seashells and limestone, and adapted this method to the
analysis of urine samples.

     MAA can be treated with ethylene glycol to produce a derivative:
                                   CH3
                            CHo-0.  |  ^0-CH
                                           o
                                           
                            CH2-0
I/  Sachs, R. M.,  J. L. Michael, F.  B.  Anastasia,  and W.  A.  Wells, "Determina-
      tion of Arsenical Herbicide Residues in Plant Tissues," Weed Sci.,
      19(4):412-416 (1971).
2]  Braman, R. S., and C.  C.  Foreback,  "Methylated Forms  of Arsenic in the
      Environment." Science,  182(4118):1247-1249 (December 21, 1973).
                                      17

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     Johnson et al. (1972)!/ observed that this derivative  (which can also
be prepared from MSMA or DSMA) produces acceptable peaks when chromatographed
on a variety of substrates such as 10% OV-17 on Chromosorb W.  Helium or
argon was used as a carrier gas; a flame-ionization detector was employed.
The minimum detectable amount was 1 ng.

     There are, however,  specific analytical methods  which  can  distinguish
residues of MSMA or DSMA  from  inorganic arsenicals.   The method of  Peoples
et al.  (1971).?-' determines MAA and inorganic arsenic  in urine.   Methylarsine
and arsine are evolved from MAA and  inorganic  arsenicals, respectively,  in a
stream  of nitrogen, and absorbed in  silver diethyldithiocarbamate solution.
These compounds absorb at different  wavelengths;  the  absorbances are read and
the residues are calculated.   The sensitivity  is  about 0.2  ppm.

     Specific residue methods  are outlined below:


     Gutzeit Method - ' (Official Final Action)  - In the Gutzeit  method  (AOAC
1970) arsenic  (or  any arsenic  compound)  is converted  to arsine  (a  gas) which
is allowed to interact with strips of paper  treated with mercuric bromide.
The amount of arsenic present  is determined by the length of  the brown color
which develops on  the strip.   The arsine  generator apparatus  is calibrated
using known quantitites of arsenic trioxide  (AS203) .

     Samples  of  fresh fruits,  dried  fruit products, vegetables  or  other
materials  are treated with nitric and sulfuric acids to convert arsenic
compounds  to  arsenic pentoxide
      PAM (Vol II 1970)  cites the sensitivity of the method as 0.01 to
 0.03 mg or about 0.01 ppm.  The method, however, has been superceded by
 colorimetric methods.
      Colorimetric Methods - (Official Final Action) - For each of 2 colori-
 metric methods, the arsenic compound in the sample is converted to arsine (by
 reduction with zinc) and the arsine is absorbed in a reagent which produces a
 color (AOAC 1970).
 I/  Johnson, L. D., K. 0. Gerhardt, and W. A. Aue, "Determination of Methane
       Arsonic Acid By Gas-Liquid Chromatography," Sci. Total Environ., 1(1):
       108-113 (1972).
 21  Peoples, S. A., J. Lakso, and T. Lais, "Simultaneous Determination of
       Methyl Arsonic Acid and Inorganic Arsenic in Urine," Proc. West
       Pharmacol. Soc. 14:178-182 (1971).
                                        18

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     Buttrill (1973)i/ described a coloriraetric method for determining
arsenic residues that has been adopted by AOAC as "official first action"
for arsenic in meat and poultry.  The method uses the molybdenum blue complex
for a spectrophotometric readout and involves ashing with magnesium nitrate
at 600C.  Six groups of 4 samples were analyzed.  The average recoveries for
0.28 to 2.41 ppm arsenic were 87.6 to 109.3%; the standard deviations ranged
from 0.037 to 0.225.  The method is based on the work of Kingsley and Schaffert
(1951),2J whose glassware design is used, and on the sample preparation tech-
niques of Evans and Bandemer (1954) ../

     Molybdenum Blue Method - In this method the arsine is absorbed in a
solution of ammonium molybdate.  The color produced is determined spectro-
photometrically (at 845 nm), and is compared to a series of blanks prepared
similarly.  PAM (Vol II 1970) reports that the molybdenum blue method has a
working range between 0.01 and 0.06 ng of arsenic; the sensitivity of the
procedure is 0.1 ppm.

     Diethyldithiocarbamate Method - With this method, the arsine is absorbed
in a solution of silver diethyldithiocarbamate.  Potassium iodide and stannous
chloride are added, and the color is allowed to develop.   The color intensity
is determined spectrophotometrically (at 522 nm) and the concentration of
arsenic is determined from a standard curve.  According to PAM (Vol II 1970),
the silver diethyldithiocarbamate procedure has a working range of between 1
and 15 mg of AS203.  The sensitivity of the method is estimated to be 0.01 ppm
AS203-

     Dry Ash Methods - Evans and Bandemer (1954) have demonstrated that bio-
logical materials with magnesium nitrate can be ashed in an electric furnace
without loss of arsenic.  Stone (1967)A/ modified this procedure to enable
arsenic analysis in animal tissues at a sensitivity of less than 0.1 ppm.

     Hundley and Underwood (1970)^ investigated a simple, sensitive, and
reproducible procedure for the determination of total arsenic in composite
food samples.  The samples are dry-ashed in the presence of magnesium oxide
I/  Buttrill, W. H., "Collaborative Study of Colorimetric Method for
      Determining Arsenic Residues in Red Meat and Poultry," J. Ass. Offie.
      Anal. Chem.. 56(5):1144-1148 (1973).
2J  Kingsley, G. R., and R. R. Schaffert, "Microdetermination of Arsenic
      and Its Application to Biological Material," Anal. Chem., 23(6):
      914-919 (1951).
3/  Evans, R. J., and S. L. Bandemer, "Determination of Arsenic in Bio-
      logical Materials," Ana]U_Chem., 26(3):595-598 (1954).
4/  Stone, L. R., "Note on the Determination of Arsenic in Animal Tissues,
      Using a Dry Ashing Procedure," J. Ass. Offic. Anal. Chem., 50(6):
      1361-1362 (1967).
5_/  Hundley, H. K. , and J. C. Underwood, "Determination of Total.Arsenic in
      Total Diet Samples," J. Ass. Offic. Anal. Chem., 53(6):1176-1178
      (1970).
                                      19

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and magnesium nitrate.  Arsenic is then evolved from an acid solution as its
hydride.  The arsine is reacted with silver diethyldithiocarbamate to give a
red complex that is measured spectrophotometrically.  The absorbance of this
complex is proportional to arsenic over a wide range of concentrations  (1 to
20 yg arsenic).  The method is sensitive to 0.05 ppm arsenic.  The procedure
of Hundley and Underwood  (1970) utilized the dry-ash procedure of Stone  (1967).
According to Hundley and Underwood, their method is comparable to the wet-ash
procedure and colorimetric determination used as the "official method."  How-
ever, they note that the  official method requires an average of  80 hr for the
analysis of the 12 food categories specified in the total diet program while
the same number of analyses may be accomplished in 20 to 24 hr using the
method of Hundley and Underwood.  Furthermore, a substantial improvement in
recovery is obtained by this method.

     Atomic Absorption Methods - There have been significant recent develop-
ments in the analysis of  arsenic by atomic absorption methods.   The basis for
the new method is the generation of arsine by treatment of the arsenic  sample
with sodium borohydride.  The arsine generated is introduced directly into the
flame.  The method has been recently described by Thompson and Thomerson
(1974).!/ and by Duncan and Parker  (undated),2J  The method apparently has not
yet been used for organo-arsenic pesticides, but it would appear suitable for
both formulation and specific residue analyses.  The organo-arsenic pesticides
would require initial conversion into arsenic oxide by conventional wet diges-
tion or dry-ashing procedures, then by reduction to arsine by aqueous sodium
borohydride.

     Thompson and Thomerson  (1974) report  that the detection limit for  arsenic
is 0.8 mg/ml.  In precision studies, these investigators observed that  a con-
centration of 100 ng/ml in 10 separate measurements produced a relative
standard deviation of 5.7%.

     Duncan and Parker  (undated) reported  an arsenic sensitivity of 0.1 ng/ml
and an  absolute sensitivity of 2 ng in the sample used.  The authors found
that the sample, which was certified by  the National Bureau of Standards to
contain 14  2 yg/g  of arsenic, contained  14.9  0.4 yg/g of arsenic with a
relative standard deviation  (based on 5  determinations) of 2.6%.

     Another atomic  absorption method, investigated by Hoover et al.  (1974)
is intended for the  analysis of food and feed.  It has a sensitivity of about
 I/   Thompson,  K.  C.,  and D.  R.  Thomerson,  "Atomic-Absorption Studies  on the
       Determination of Antimony,  Arsenic,  Bismuth,  Germanium,  Lead, Selenium,
       Tellurium and Tin by Utilizing the Generation of Covalent Hydrides,"
       Analyst, 99:595-601 (1974).
 2J   Duncan,  L., and C. R. Parker, "Applications of  Sodium Borohydride for
       Atomic Absorption Determination of Volatile Hydrides," Technical Topics,
       Varian Associates, Palo Alto,  California (undated).
 3/   Hoover,  W. L.,  J. R. Melton,  P.  A. Haward, and  J.  W.  Bassett,  Jr., "Atomic
       Absorption Spectrometric Determination of Arsenic," J. Ass.  Offie.  Anal.
       Chem., 57(1):18-21 (1974).
                                        20

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0.05 ppm.  A modification of the method, which involves collecting arsine
in a plastic bag, has a sensitivity of 0.1 ppm.


Formulation Analysis - Carey (1968)-i/ proposed a method for formulation
analysis involving a fusion procedure in which the arsonate is decomposed  to
pentavalent arsenic by a potassium bromate-nitric acid solution.  The author
tested the method on MSMA (commercial formulation), DSMA and MAA  (technical
grades), and several other arsenicals.  The fusion temperatures preferably
are kept below 300C.  Color in the fusion mass indicated interferences,
which can be removed by using an ion exchange procedure.  Carey (1968)
presented actual results for each compound, but did not comment on the over-
all accuracy of the method.

     AOAC (1970) lists 4 methods, with official final action status, for
analysis of total arsenic.in formulations.  However, the methods either
specify that they are used for inorganic arsenate or arsenites, or only
mention inorganic arsenicals.  These methods are the hydrazine sulfate distil-
lation method, the iodometric method, an ion exchange method, and a water-
soluble arsenic method.

     The Technical Service Division of EPA recommends an iodometric method
for the determination of DSMA, which involves an initial conversion of DSMA
to As205 (Bontoyan 1970).2-/.  The EPA method is as follows:

             Weigh accurately the sample of approximately 0.25 g into
        the 500 ml long neck Kjeldahl flask, taking care that none of
        the sample adheres to the neck of the flask.  Cover the sample
        with 5.5 ml of concentrated H2S04.  After sample is dissolved
        or thoroughly wetted, add 1 to 2 ml of fuming nitric acid.
        Place on the digestion rack, with the cold finger in place;
        adjust so that the bottom of the flask is 1 in. above the burner
        surface.  Digest for 55 min.  There will be a copious evolution
        of nitrogen oxides which will escape past the cold finger.  If
        the evolution of these fumes ceases before the end of the diges-
        tion period, a few more drops of HN03 should be added very
        cautiously.  After 55-min digestion, remove the cold finger
        and continue digestion to white fumes.  Remove flask from heat
        and cool (to where further additions of chemicals to reaction
        mixture do not splatter badly).  Add 1.5 g ammonium sulfate by
        funnel directly onto the reaction mixture in bottom of flask.
        Shake vigorously for 1 min, then cool under cold water tap.
_!/  Carey, W. F., "Determination of Arsenic in Organic Arsonates," J. Ass.
      Offie. Anal. Chem., 51(6):1300-1301 (1968).
2J  Bontoyan, Warren R., (Technical Services Division, Office of Pesticide
      Programs, EPA), Personal communication to Dr. Alfred Meiners, Midwest
      Research Institute, Kansas City, Missouri  (November 1970).
                                       21

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             Add 60 ml distilled water and 10 ml of KI solution.
        Place over burner without cold finger and boil until solu-
        tion is straw-colored (12 vapors are evolved).  (If boiling
        is continued too long after proper color is reached, solu-
        tion will darken again and assay is ruined.)

             Remove flask and add sodium thiosulfate solutions,
        several drops at a time, shaking until the solution is.
        colorless.  Have 70 ml water ready and add immediately.
        Pour this solution into 50 ml of Na2C03 solution contained
        in a 500-ml Erlenmeyer flask, taking care so as not to
        lose solution by vigorous evolution of C02-  Rinse Kjeldahl
        thoroughly, add to solution in Erlenmeyer flask.  Finish
        neutralizing with Na2C03, add a slight excess.  Add starch
        solution and titrate to a blue end point with standard
        iodine solution.
Composition and Formulation

     MSMA and DSMA are generally sold as aqueous solutions which would contain
most of the water-soluble salts.and by-products produced in the manufacturing
process.  Little information is available concerning the kinds and amounts of
these materials, but sodium sulfate and sodium chloride are the major consti-
tuents.  Surfactants are added to many of the formulations, but no information
is available concerning the nature of these additives.

     The Diamond Shamrock Chemical Company produces methylarsonate herbicides
to suit a variety of customer needs.  There are 3 basic formulations:

      1.  DSMA PowderA dry, crystalline, water-soluble powder suitable for
          field-mixing with surfactants or manufacturing of wettable powder
          combination herbicide products.

      2.  Arsonate LiquidA concentrated water solution containing 6.6 Ib
          of MSMA/gal which is especially suited for manufacture of premixed
          MSMA-surfactant formulations or combination herbicide products.

      3.  MSMA-Surfactant BlendsDiamond Shamrock offers four MSMA-surfactant
          blends to fit a wide range of usage requirements.  Two of these are
          heavy-duty herbicides.

     The Ansul Company also offers a variety of formulations; some representa-
tive examples are shown below:
                                      22

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                                    MSMA
       Percent
       51.3  (ANSAR 170)
       47.8  (PHYBAN HC)
       47.8  (ANSAR 529 HC)
       35.8  (ANSAR 529)
                         Usage
                         For use in formulating herbicides
                         Railroad and industrial use
                         Cotton
                         Cotton, Noncrop
                                    DSMA
       Percent
       81.0  (ANSAR 8100)
       21.8  (ANSAR DSMA Liquid)
                         Usage
                         Cotton
                         Cotton, Noncrop
     Representative formulations offered by Vineland Chemical Company are
shown below:
                                    MSMA
       Percent
       44.92
       51.19
       35.33
                         Usage
                         Cotton, general weed control
                         Cotton, general weed control
                         Cotton, general weed control
                                    DSMA
       Percent
       63.00
                         Usage
                         General weed control, cotton
Chemical Properties and Reactions

     Methylarsonic acid (MAA) is a strong acid which forms two sodium salts,
menosodium methanearsonate (MSMA) and disodium methanearsonate (DSMA) .
CH3
   -As/
        ,OH
NaOH
         n
NaOH
                                            CH3-
Methylarsonic
     acid
     (MAA)
               Monosodium
               methanearsonate
                    (MSMA)
            Disodium
            methanearsonate
                 (DSMA)
The reaction of MAA with sodium hydroxide (NaOH) first forms the monosubstituted
product, MSMA, and then at higher concentrations of NaOH, the disubstituted
product, DSMA.  Figure 2 is a titration curve of MAA with NaOH.  The inflection
points at pH 6.5 and 10.5 indicate the formation of MSMA and DSMA, respectively
(Vineland Chemical Company  undated).  Since the reaction is reversible, DSMA
will revert to MSMA at pH 6 to 7.  DSMA is stable to alkaline hydrolysis
(Martin  1971).

     MSMA and DSMA are highly stable substances and undergo few chemical
reactions.  Limited information is available concerning oxidation or reduction
reactions, and no information is available concerning the effect of ultraviolet
                                      23

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                  12
                  10
                  8
                   0
                     20ml 0.1 N Methylarsonic Acid
                     Titrated with 0.1N NaOH.MSMA
                     is  Formed at the First  Inflection
                     of the  Curve (pH=6.5); DSMA is
                     Formed at pH 10.5
                              i  i  i
                    02468 101214161820222426
                            ml of 0.IN NaOH
Figure 2.   Titration of methylarsonic acid with sodium hydroxide
Source:   Vineland  Chemical Company, op. cit.  (undated).
                                    -24

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radiation  on  these  compounds.  MAA and  its  salts  are the most stable oxidation
state  of monomethylated  arsenic  (Vineland Chemical Company  undated) .   The
salts  (MSMA and  DSMA)  cannot be  oxidized further  except by oxidative degrada-
tion of the methyl  group.   The salts  are very resistant to this oxidation
(Vineland  Chemical  Company  undated) .   MAA  can be reduced .with sulf urous
acid.  Iodine is useful  in  this  as a  catalyst (Melnikov 1971, Noller 1957) :-^-'


       CH3As(OH)2 +  H2S03 -- >  CH3AsO + H2S04
                            cat.
                                    methyl arsenoxide,

Furthermore,  according to Moyerman and  Ehman  (1965),'
      3CH3AsO - >As203 +  (CH3)3As
                OH"              trimethylarsine
                in air

or    4CH3AsO -- } (CH3)2AsOAs(CH3)2 + As203 ,
                OH"      cacodyl oxide
                in air

if pH is 10.5 or greater.

     Anhydrous DSMA  is hygroscopic and will become hexahydrated at ambient
humidities  (Vineland Chemical Company  undated) .  DSMA is sold in the hexa-
hydrated form.

     As explained in the Herbicide Handbook (1970)' water, high in calcium,
magnesium,  and iron, tends to precipitate the water-insoluble MAA salts of
these ions.  Vineland Chemical Company (undated) partially confirms this by
stating that ions, such as calcium and magnesium, in concentrated solution,
can precipitate the  corresponding salts of MAA, which are fairly insoluble.
However, they then qualify the statement by saying that calcium methanearson
ate is more soluble  in cold than hot water.  Under normal usage, with even
the hardest water in the spray tank, no precipitation may be expected since
calcium methanearsonate is water soluble to the extent of about 1,000 ppm at
ambient temperatures.  Barium, strontium and iron salts are also soluble;
magnesium salts have about the same solubility as the calcium salts.
JY  Melnikov, N. N.., Chemistry of Pesticides, Vol. 36 of Residue Rev..
      480 pp. (1971).
2J  Noller, C. R., Chemistry of Organic Compounds, 2nd ed., W. B. Saunders Co.,
      Philadelphia, Pa., 978 pp. (1957).
_3_/  Moyerman, R. M., and P. J. Ehman, (to Ansul Company), "Manufacture of
      Arsinic Acids," U.S. Patent No. 3,173,937 (1965).
4/  Weed Society of America, Herbicide Handbook, 2nd ed.  W. F. Humphrey
      Press, Inc., Geneva, New York  (1970).
                                       25

-------
     DSMA reacts with various  salts  to  form other salts of MAA.   The calcium
salt, CH3As03Ca*H20, is made by warming together a solution of MSMA and
calcium chloride.  The reaction proceeds according to the following equation:

                             H20
                               - - ^ CH3As03Ca*H20 + 2NaCl
The magnesium salt, CH3As03Mg-5H20, is  similarly made  (Raiziss  and Gavron
1923). A'  The silver salt, CH3As03Ag2, may be  prepared  by  treating MSMA with
AgN03 (Pozzi-Escot  1943) .2.7


Alkylation and Dealkylation

     Agar cultures of soil bacteria (unspecified), an actinomycete,  and a
fungus were found to convert 100 ppm i^C-MSMA  to arsenate  (and (X>2) ,  in an
agar culture, to the extent of up  to 10% in 3  days and  19%  in  7 days  (Von Endt
et al. 1968) .!/  (A more detailed  discussion of microbial degradation is
presented in the section of this report entitled "Interactions with Lower
Terrestrial Organisms.")  Noller (1957) reports that chemical  elevation may  be
carried out as :

       CH3As(ONa)2 + (CH3)2S04 - > (CH3)2As(0)ONa  + CH3 NaS04

Another reaction involves an excess alkylating agent:

       (CH3)2 AsONa(CH3)2 S04 - ^ (CH3)AsO  + CH3NaS04
                                      trimethylarsine
                                      oxide

      Sachs  and Michael  (1971)i/  reported  that  MSMA gave no indication of
being demethylated  to form inorganic arsenicals, or reduced to trivalent
arsenic  compounds.  DSMA,  however, is  reported to  be  decomposed by a strong
oxidizing and reducing  agent  (Martin 1971), but no products were  reported.
One method  of analysis  involves  digestion of the salts  with perchloric acid
 (HC10, ) ,  a  strong oxidizing agent, followed by reduction  to arsine and
colorimetric determination (Johnson and Hiltbold 1969) ;!/  no specific products
were  reported.
J./  Raiziss, G. W. , and J. L. Gavron, Organic  Arsenical Compounds, The
      Chemical Catalog Company, New York  (1923).
21  Pozzi-Escot, E., "Reaction for the Differentiation  of Na Methanearsonate
      and Na Cacodylate," Revista  de Ciencias  (Peru)  45:379-380  (1943).
3f  Von Endt, D. W. , P. C. Kearney,  and D. D.  Kaufman,  "Degradation of Mono-
      sodium Methanearsonic Acid by Soil Microorganisms," Agr. Food Chem. ,
      16(1): 17-20 (1968).
4/  Sachs, R. M. , and J. L. Michael, "Comparative Phytotoxicity Among Four
      Arsenical Herbicides," Weed  Sci.. 19(5) : 558-564 (September  1971).
5/  Johnson, L. R. , and A. E. Hiltbold, "Arsenic Content of Soil  and Crops
      Following Use of Methanearsenate Herbicides," Proc. Soil Sci. Soc. Am.,
      33 (2): 279-282 (1969).
                                       26

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Occurrence of Residues in Food and Feed Commodities

     The FDA, Department of Health, Education, and Welfare, monitors
pesticide residues in the nation's food supply through 2 programs.  One
program, commonly known as the "total diet program," involves the examina-
tion of food ready to be eaten.  This investigation measures the amount of
pesticide chemicals found in a high-consumption varied diet.  The samples
are collected in retail markets and prepared for consumption before analysis.
The other program involves the examination of large numbers of samples,
obtained when lots are shipped in interstate commerce, to determine compli-
ance with tolerances.  These analyses are complemented by observation and
investigations in the growing areas to determine the actual practices being
followed in the use of pesticide chemicals.

     A majority of the samples collected in these programs are categorized
as "objective" samples.  Objective samples are those collected where there
is no suspicion of excessive residues or misuse of the pesticide chemicals.
All samples of imported food's" and fish are categorized as "objective" samples
even though there may be reason to believe excessive residues may be found on
successive lots of these food categories.

     Market-basket samples for the total diet studies are purchased from
retail stores, bimonthly, in five regions of the United States.   A shopping
guide with 117 foods for the different regions is used, but not all foods
are represented in all regions because of differences in regional dietary
patterns.  The food items are separated into 12 classes of similar foods
(e.g., dairy products; meat, fish and poultry; legume vegetables; and garden
fruits) for more reliable analysis and to minimize the dilution factor.
Each class in each sample is a "composite."  The food items and the proportion
of each used in the study were developed in cooperation with the Household
Economics Research Division, USDA, and represents the high consumption level
of a 16- to 19-year old male.  Each sample represents a 2-week supply of food.

     Surveillance samples are generally collected at major harvesting and
distribution centers throughout the United States and examined in 16 FDA
district laboratories.  Some samples may be collected in the fields immediately
prior to harvest.  Surveillance samples are not obtained in retail markets.
Samples of imported foods are collected when offered for entry into the
United States.

     The residue analyses performed by the FDA do not detect MSMA and DSMA as
individual chemicals.  Residue analyses are made for total arsenic in the form
of As203, but the analytical method does not distinguish between naturally
occurring arsenic or arsenic resulting from the presence of any of the arsenical
pesticides.

     Table 1 presents the results of total diet program for a 6-yr period.  The
table shows the number of composites which were found to contain arsenic and
the concentration ranges (ppm).  Although the FDA has continued the analytical
program, the results were not published at the time of review.
                                      27

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                                                Table  1.  ARSENIC IN TOTAL DIET SAMPLES!/
oo

Year of study
Date of study!!/
Number of composites
Dairy products
Meat, fish and poultry
Grain and cereal products
Potatoes
Leafy vegetables
Legume vegetables
Root vegetables
Garden fruits
Fruits
Oils, fats and shortening
Sugar and adjuncts
Beverages
Totals (concentration
li/
1964-1965
18

1
1
1

1
1

1



6
 *
(0.12)
(0.10)
(4.7)

(0.11)
(0.10)

(0.18)
--

--
(0.1-4.7)
2S/
1965-1966
28

5 (0.
1 (0.



1 (0.
1 (0.


1 (0.

10 (0.

1-0.5)
1)



1)
1)
--

1)
--
1-0.5)
3i/
1966-1967
30
i/
9 (0.1-0.5)
i/
--
1
2 
-------
      The information in Table 1 was used to calculate the daily intake of
 arsenic shown in Table 2.   Duggan and Corneliussen (1972)!/ drew the fol-
 lowing conclusion for the  6-yr period:

              The incidence and levels of As203 have remained low during
         the 6 years of this study.   While there is a wide variation in
         the actual annual  range, the differences generally are due to
         higher values for  a few samples examined during a particular
         year.  There is a  natural low-level background of arsenic in
         foods, and the values reported  during this period are within
         or slightly above  the natural background.   The dietary intake
         of arsenic from pesticide use does not appear to be significant.


 Acceptable Daily Intake

      The acceptable daily  intake (ADI)  is defined  as the daily intake which,
 during an entire lifetime,  appears  to be without appreciable risk on the
 basis of all known facts at the time of evaluation (Lu  1973).   It is
 expressed in milligrams of  the chemical per kilogram of body weight (mg/kg).

      The ADI for pesticides is established jointly by the FAO  Committee on
 Pesticides in Agriculture  and the WHO Expert Committee on Pesticide Residues.
 However,  an ADI for arsenic has not yet been established.
Tolerances

     Section  408  of  the  Food, Drug and Cosmetic Act, as amended,  gives
procedures  for  establishing  tolerances for pesticide chemicals on raw
agricultural  commodities.  Section 409 applies to food additives, including
pesticide chemicals  on processed  foods.  Tolerances for residues  of MAA,
including MSMA  and DSMA, on  raw agricultural commodities are cited in the
Code of Federal Regulations.j/ They are 0.7 ppm for cottonseed and 0.35 ppm
for citrus  fruit.  Pending tolerances are 0.33 ppm for grapes and 0.39 for
sugarcane (U.S. Environmental Protection Agency 1973)A' Regarding food
additive tolerances,  a tolerance  of 0.9 ppm is established for MAA in or on
cottonseed  hulls  from application of MSMA and DSMA salts of MAA  in the
production  of cotton.JL'
I/  Duggan, R. E., and P. E. Corneliussen, "Dietary Intake of Pesticide
      Chemicals in the United States  (III), June 1968-April 1970," Pest..
      Monit. J.,  5(4):331-341 (March  1972).
21  Lu, F. C., "Toxicological Evaluation of Food Additives and Pesticide
      Residues and Their  'Acceptable Daily Intakes' for Man:  The Role of
      WHO in Conjunction with FAO," Residue Rev., 45:81-93 (1973).
_3_/  Code of Federal Regulations, Title 40, Chapter 1, Subchapter E, Subpart
      C, Section  180.289.
f\J  U.S. Environmental Protection Agency, EPA Compendium of Registered
      Pesticides.. Vol. I  (1973).
5/  Code of Federal Regulations. Title 21, Chapter 1, Subchapter E,
      Section 561.280.
                                      29

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                                   Table 2.  DAILY INTAKE OF ARSENIC RESIDUES^/

Date of studyk/
Dairy products
Meat, fish and poultry
Grains and cereals
Potatoes
Leafy vegetables
Legume vegetables
Root vegetables
Garden fruits
Fruits
Oils, fats and shortening
Sugar and adjuncts
Beverages
Total daily intake
1964-1965/
~ <*
< .001
0.002
0.063

0.001
0.001
_.
0.002

. 
--
--
1965-1966/
 <>
0.003
0.001
_-


< .001
0.001

--
0.001
--
--
1966-19674/
< .001
0.004
0.004
0.003
0.001
0.001
0.001
< .001
0.004
0.004
0.001
0.010
0.033
a/ Expressed in milligrams of As20^/day. Includes naturally occurring
class contained no detectable quantities of arsenic.
b/ Samples collected from
June of first
/ Duggan, R. E., and J. R; Weatherwax,
1967-19681/
0.008
0.045
0.029
0.007
0.002
0.001
0.001
0.004
0.012
0.002
0.002
0.024
0.137
amounts . A
1968-1969S/
0.005
0.034
0.011
0.002
0.001
0.001
< .001
0.001
0.004
< .001
0.001
0.015
0.075
1969-1970S/
0.006
0.048

0.001
--

< .001
0.001
0.001
--
"
--
0.057
dash indicates that the food
year to April of second year.
'Dietary Intake
of Pesticide Chemicals," Sci.. 157:1006-1010 (1 Septembei
      1967).
d_/  Duggan, R. E., and G. Q. Lipscomb, "Dietary Intake of Pesticide Chemicals in the United States (II), June 1966-
      April 1968," Pest. Monit. J.. 2(4):153-162 (March 1969).
e/  Duggan and Corneliussen, op. cit. (1972).               ':

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References

The Ansul Company,  Comments  in  Support of Continued Registration  of  Organic
  Arsenical Herbicides. Marinette, Wisconsin  (31 August 1971).

Association of Official Analytical Chemists, Official Methods of  Analysis  of
  the Association of Official Analytical Chemists, llth ed., Washington, D.C.
  (1970).~'

Bontoyan, Warren R., (Technical Services Division, Office of Pesticide Programs,
  EPA), Personal communication to Dr. Alfred Meiners, Midwest Research Insti-
  tute, Kansas City, Missouri (November 1970).

Braman, R. S., and  C. C. Foreback, "Methylated Forms of Arsenic in the Environ-
  ment," .Science, 182(4118):1247-1249 (December 21, 1973).

Buttrill, W. H., "Collaborative Study of Colorimetric Method for  Determining
  Arsenic Residues  in Red Meat and Poultry," J. Ass. Offie. Anal. Chem.,
  56(5):1144-1148 (1973).

Carey, W. F., "Determination of Arsenic in Organic Arsonates," J. Ass. Offie.
  Anal. Chem.. 51(6):1300-1301  (1968).

Code of Federal Regulations, Title 40, Chapter 1, Subchapter E, Subpart C,
  Section 180.289.

Code of Federal Regulations. Title 21, Chapter 1, Subchapter E,
  Section 561.280.

Corneliussen, P. E., "Residues in Food and Feed:  Pesticide Residues in Total
  Diet Samples (IV)." Pest. Monit. J., 2(4):140-150 (March 1969).

Corneliussen, P. E., "Residues in Food and Feed:  Pesticide Residues in Total
  Diet Samples (V)." Pest Monit. J.. 4(3):89-104 (December 1970).

Corneliussen, P. E., "Residues in Food and Feed:  Pesticide Residues in Total
  Diet Samples (VI)." Pest. Monit. J. 5(4):313-329 (March 1972).

Diamond Shamrock Corporation, DSMA - MSMA Herbicides (bulletin) Cleveland, Ohio
  (1970).

Duggan, R. E., H. C. Barry,  and L. Y. Johnson, "Pesticide Residues in Total
  Diet Samples," Sci., 151(3706):101-104 (7 January 1966).

Duggan, R. E., H. C. Barry,  and L. Y. Johnson, "Residues in Food  and Feed:
  Pesticide Residues in Total Diet Samples (II), Pest. Monit. J.. 1(2):2-12
  (September 1967).

Duggan, R. E., and P. E. Corneliussen, "Dietary Intake of Pesticide Chemicals
  in the United States (III), June 1968-April 1970," Pest. Monit. J.. 5(4):
  331-341 (March 1972).
                                       31

-------
Duggan, R. E.,and G. Q. Lipscomb, "Dietary Intake of Pesticide Chemicals  in  the
  United States (II), June 1966-April 1968," Pest. Monit. J.  2(4): 153-162
  (March 1969).

Duggan, R. E., and J. R. Weatherwax, "Dietary Intake of Pesticide Chemicals,"
  Sci., 157:1006-1010  (1 September 1967).

Duncan, L., and C. R. Parker,  "Applications of  Sodium  Borohydride for Atomic
  Absorption Determination of  Volatile Hydrides," Technical  Topics,  Varian
  Associates, Palo Alto, California  (undated).

Evans, R. J., and S. L. Bandemer, "Determination of Arsenic  in Biological
  Materials." Anal. Chem.. 26(3):595-598  (1954).

Frear, D. E. H., Pesticide Index. 4th ed., College Science Publishers,  State
  College, Pennsylvania (1969).

Hoover, H. L., J. R. Melton', P.  A. Haward, and  J. W. Bassett, Jr.,  "Atomic
  Absorption Spectrometric Determination  of Arsenic,"  J.  Ass. Offie. Anal. Chem.,
  57(1):18-21  (1974).

Hundley, H. K., and J. C. Underwood, "Determination of Total Arsenic in Total
  Diet Samples," J. Ass. Offic.  Anal. Chem.. 53(6):1176-1178 (1970).

Johnson, L. D., K. 0.  Gerhardt,  and W. A. Ave,  "Determination of Methane
  Arsonic Acid by Gas  Liquid Chromatography," Sci. Total  Environ.,  1(1):108-
  113  (1972).

Johnson, L. R., and A. E. Hiltbold,  "Arsenic Content of Soil and Crops  Follow-
  ing Use of Methanearsonate Herbicides," Proc.  Soil Sci. Soc. Am.,  33(2):
  279-282  (1969).

Kingsley, G. R., and R. R. Schaffert, "Microdetermination of Arsenic and  its
  Application  to Biological Material," Anal. Chem.. 23(6):914-919  (1951).

Lu,  F. C.,  "Toxicological Evaluation of Food Additives and Pesticide Residues
  and  Their 'Acceptable Daily  Intakes' for Man:  The Role of WHO, in Conjunction
  with FAO," Residue Rev.. 45:81-93  (1973).

Martin, H., Pesticide  Manual.  British Crop Protection  Council, 2nd  ed.  (1971).

Martin, R.  J., and R.  E. Duggan, "Pesticide Residues in Total Diet  Samples  (III),"
  Pest. Monit. J.. 1(4):11-20  (March 1968).

Melnikov, N. N., Chemistry of  Pesticides. Vol.  36 of Residue Rev.,  480  pp.  (1971).

Meyer, G.,  Berichte der Deutsche Gesellschaft,  Berlin  16:1440 (1883).

Moyerman, R. M., and P- J. Ehman (to Ansul Company), "Manufacture of Arsinic
  Acids," U.S. Patent  No. 3,173,937  (1965).
                                       32

-------
Noller, C. R., Chemistry of Organic Compounds,  2nd ed.,  W.  B.  Saunders Co.,
  Philadelphia, Pa., 978 pp.  (1957).

Peoples, S. A., J. Lakso, and T. Lais, "Simultaneous Determination of Methyl
  Arsonic Acid and Inorganic Arsenic in Urine," Proc. West. Pharmacol.  Soc.,
  14:178-182  (1971).

Pozzi-Escot,  E., "Reaction for the Differentiation of Na Methanearsonate and
  Na Cacodylate," Revista de Ciencias  (Peru) 45:379-380  (1943).

Raiziss, G. W., and J. L. Gavron, Organic Arsenical Compounds, The Chemical
  Catalog Company, New York (1923).

Sachs, R. M., and J. L. Michael, "Comparative Phytotoxicity Among  Four
  Arsenical Herbicides." Weed Sci., 19(5):558-564 (September 1971).

Sachs, R. M. , J. L. Michael, F. B. Anastasia, and W. A.  Wells, "Determination  of
  Arsenical Herbicide Residues in Plant Tissues," Weed Sci., 19(4):412-416  (1971)

Schanhals, L. R. (to 0. M. Scott & Sons), "Process for the Manufacture  of Lower
  Alkyl Arsinic Acids and Alkali Metal Salts Thereof," U.S. Patent No.  3,322,805
  (1967).

Schwerdle, A., U.S. Patent No. 2,889,347 (2 June 1959).

Schwerdle, A. (to Vineland Chemical Company), U.S. Patent No. 3,030,199
  (17 April 1962a).

Schwerdle, A., (to Vineland Chemical Company), U.S.  Patent No. 3,056,821
  (2 October 1962b).

Schwerdle, A., (to Vineland Chemical Company), U.S.  Patent No. 3,068,088
  (11 December 1962c).

Stone, L. R., "Note on the Determination of Arsenic in Animal Tissues, Using
  a Dry Ashing Procedure," J.  Ass.  Offic. Anal.  Chem.. 50(6):1361-1362  (1967).

Thompson, K. C., and D. R. Thomerson,  "Atomic-Absorption Studies on the
  Determination of Antimony Arsenic, Bismuth, Germanium,  Lead, Selenium,
  Tellurium and Tin by Utilizing the Generation of Covalent Hydrides," Analyst ,
  99:595-601  (1974).

Urbanowski, R. L.,  and R. P.  Steinkoenig (to Diamond Shamrock Chemical Company)
  U.S. Patent No.  3,440,258 (22 April 1969).

U.S. Department of Health, Education,  and Welfare, Food and Drug Administration
  Pesticide Analytical Manual. 2 vols. (1971).

U.S. Environmental Protection Agency,  EPA Compendium of Registered Pesticides,
  Vol. I (1973).
                                      33

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Vineland Chemical Company, MSMA-DSMA Weed Control. Vineland, New Jersey  (undated).

Von Endt, D. W., P. C. Kearney, and D. D. Kaufman, "Degradation of Monosodium
  Methanearsonic Acid by Soil Micro-organisms," Agr. Food Chem.. 16(1):17-20
  (1968).

von Riimker, R., E. W. Lawless, and A. F. Meiners, Production Distribution, Use,
  and Environmental Impact Potential of Selected Pesticides, for Council of
  Environmental Quality, Contract No. EQC-311  (15 March 1974).

Weed Society of America, Herbicide. Handbook,  2nd ed.,  W. F. Humphrey Press,  Inc.,
  Geneva, New York  (1970).
                                        34.

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                      PART II.  INITIAL SCIENTIFIC REVIEW


                    SUBPART B.  PHARMACOLOGY AND TOXICOLOGY


                                   CONTENTS


                                                                          Page

Acute, Subacute and Chronic Toxicity 	  36

  Toxicity to Laboratory Animals 	  36

    Acute Oral Toxicity - Rats	36
    Acute Inhalation Toxicity - Rats	  37
    Subacute Toxicity - Rats	37
    Dermal Toxicity - Rabbits  	  37
    Eye Irritation - Rabbits	38
    Subacute Toxicity - Dogs	38

  Toxicity to Domestic Animals 	  38

    Acute Oral Toxicity - Cattle	38
    Subacute Oral Toxicity - Cattle  .	  38
    Subacute Oral Toxicity - Chickens  	  40

Metabolism	40

  Accumulation and Excretion	40
  Compound Valence vs. Excretion 	  41
  Utilization of Tissue-Bound Arsenic  	  41

Teratogenic Effects  	  42

Mutagenic Effects  	  43

Oncogenic Effects  	  43

Effects on Humans	43

  Manufacturing Exposure 	  43
  Field Exposure   	44

References	46
                                        35

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     This section reviews data on the acute, subacute, and chronic  toxicities
of MSMA and DSMA and other closely related compounds.  Mutagenic effects of
MSMA are also considered.  Where specific data was not found on MSMA and DSMA
metabolic, teratogenic and oncogenic effects, available data on related
arsenicals was reported.  Studies are also reviewed on occupational and
exposure hazards of MSMA and DSMA.  This section  summarizes rather  than inter-
prets data reviewed.
Acute,  Subacute  and  Chronic Toxicity


Toxicity  to  Laboratory Animals -


      Acute Oral  Toxicity - Rats - The acute oral toxicity to the rat of Ansar
170,  a formulation of MSMA (51.55%), was studied  using 120 g Sprague-Dawley
albino rats  weighing 120 g (Palazzolo 1964a).l/  The rats were divided into
8 groups  of  8 animals each (4 males and 4 females) .   The test animals were
intubated with previously determined doses as a 10% aqueous solution.  The
rats  were observed for 14 days.  The acute LD5Q was calculated to be 1.8 g/kg
with  95%  confidence limits of 1.5 to 2.2 g/kg.  The acute oral LDi was 0.6
g/kg  and  the LDgg was 5.3 g/kg.  Necropsy of animals that died during the
study did not reveal any gross pathologic changes in tissues and organs.
 LD5Q
A formulation (Ansar 529) containing MSMA (35.21%) was found to have an
of 1.8 g/kg to albino rats weighing 120 g.  The dead animals exhibited
at   astroeneitis  Palazzolo 14c . '
 moderate gastroenteritis (Palazzolo 1964c) . '
      The acute oral LDso of DSMA (65.66% DSMA, Ansar 184) to albino rats was
 calculated to be 2.8 g/kg, with 95% confidence limits of 2.2 to 3.7 g/kg.  The
 animals used in the test were Sprague-Dawley strain albinos of approximately
 120 g body weight.  The animals were divided into groups of 8 rats each (4
 males and 4 females) and were dosed directly into their stomachs with predeter-
 mined quantities of test material as a 10% solution.  They were observed for
 14 days after treatment.  Necropsy of those that died during the study showed
 only moderate to severe gastroenteritis  (Palazzolo  1964b)..5/
 I/  Palazzolo, R. J., "Acute Oral Toxicity of Ansar 170," unpublished report,
       Industrial Bio-Test Laboratories, Northbrook, Illinois, EPA Pesticide
       Petition No. 9F0794 (1964a).
 2J  Palazzolo, R. J., "Acute Toxicity of Ansar 529 Herbicide," unpublished
       report, Industrial Bio-Test Laboratories, Northbrook, Illinois, EPA
       Pesticide Petition No. 9F0794 (1964c).
 _3/  Palazzolo, R. J., "Acute Oral Toxicity of Ansar 184 Herbicides," unpub-
       lished report, Industrial Bio-Test Laboratories, Northbrook, Illinois,
       EPA Pesticide Petition No. 9F0794 (1964b).
                                        36

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     The acute oral U>50 of MAA, the parent compound of MSMA and DSMA,  (98.8%)
to albino rats weighing 200 to 300 g was determined using Sprague-Dawley
strain animals.  The material was administered as an aqueous solution with  a
dosing syringe.  Three levels of test material were used (0.5, 1.0, and 2.0
g/kg) and untreated controls were included.  The oral LD5Q was calculated to
be 1.4 g/kg, a value considered by the author to be slightly toxic  (Powers
1963).17


     Acute Inhalation Toxicity - Rats - Inhalation tests (Nees  1969a).?/ were
conducted using 10 Sprague-Dawley strain albino rats.

     The rats were placed in a 6 cu ft test chamber and exposed to an
atmosphere containing an average dose of 11.6 g of Ansar 529.  The rats were
exposed for 15 min in the chamber followed by an exposure to fresh air for
15 min.  The procedure was repeated until a total of 10 successive exposures
had been completed.  Rats sacrificed immediately after exposure had minimal
chronic pneumonitis or bronchitis.  Only 1 of the 5 animals sacrificed on
the fourteenth day of the observation period had developed moderate chronic
bronchitis.  No adverse histological effects were noted.


     Subacute Toxicity - Rats - The subacute toxicity of MAA (52.3% arsenic)
to weanling rats (Sprague-Dawley strain) was determined over a 90-day feeding
period (Derse 1968b) .'   The arsenic compound was fed at dietary levels of  3,
15, 30, and 100 ppm.  The results of these tests indicated that there were  no
significant differences between the untreated controls and the animals in any
of the treated groups when body weights, food consumption,  hematology, urinaly-
sis, organ  weights, or gross and histologic observations were compared.


     Dermal Toxicity - Rabbits - A dermal toxicity study for Ansar 529 was
conducted on 6 adult male rabbits (Nees 1969b).'   The clipped skin areas of
the rabbits were exposed to doses of Ansar 529 for a 24-hr  period.   The
animals were observed for signs of toxicity during the 2 weeks following
treatment.  The LD5Q value was found to be between 2 and 4 g/kg.
I/  Powers, M. B., "Methanearsonic AcidAcute Oral Toxicity; Primary Skin
      Irritation," unpublished report, WARF Laboratories, Madison, Wisconsin,
      EPA Pesticide Petition No.  9F0794 (1963).
2J  Nees, Paul 0., WARF Institute report (No.  9031917) submitted to The Ansul
      Company, Marinette, Wisconsin (April 11, 1969a).
3/  Derse, P. H., "Methane Arsenic Acid 90-Day Feeding Study - Rats," unpub-
      lished report, WARF Laboratories, Madison, Wisconsin, EPA Pesticide
      Petition No. 9F0794 (1968b).
j4/  Nees, Paul 0., WARF Institute report (No.  9031917) submitted to The Ansul
      Company,.Marinette, Wisconsin,  (May 15,  1969b).
                                      37

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     Eye Irritation - -Rabbits - An eye irritation study was conducted using
adult albino rabbits of the New Zealand strain.  One-tenth of a ml of Ansar
529 was instilled in one eye of each animal; the other untreated eye served
as a control.  After treatment the material had eye irritation scores of 0.67,
0, and 0 at 24, 48, and 72 hr, respectively, indicating very minimal irritation
only at 24 hr (Nees 1969a).


     Subacute Toxicity - Dogs - Five-month-old beagle puppies were fed MAA  (an
equilibrium form of MSMA at low pH) in a 90-day feeding test  (Derse 1968a) .I/
The arsenic compound was fed at dietary levels of 0, 3, 15, and 30 ppm by
supplementing dry commercial dog  food.  Each treatment group contained 4 female
and 4 male animals.

     Data on body weight and  food consumption  appears  to  indicate  that MAA  in
the diet at  the highest level  (30 ppm) had little effect  on performance of  the
animals.  Statistical analysis confirmed that  there was no significance in  the
differences  in body weights between the treated animals and untreated controls.
Hematological examination did not reveal any effect of  treatment nor did clini-
cal data on  kidney and liver  function.  Organ  weights  of  treated animals were
within  normal ranges  and variations could  not  be attributed to  treatment with
the arsenic  compound.  Histological examinations revealed slight alterations
in some tissues, but  these  occurred randomly in both  treated  and control animals.
Brain,  thyroid, parathyroid,  heart, liver, gall bladder,  kidney, urinary bladder,
spleen, pancreas,  lung, adrenals, gonads,  submaxillary gland,  lymph nodes,  muscle,
stomach, bone,  intestine,  and mesenteric lymph nodes were examined.


Toxicity  to  Domestic  Animals  -


      Acute Oral Toxicity - Cattle - Dairy  calves  with an average body weight of
 400 Ib were used to determine the acute oral toxicity of Ansar 529 (24.8% MSMA)
 and Ansar 170 (51.3% MSMA).  The LD$Q for  Ansar 529 was calculated to be 250
 mg/kg; for Ansar 170 it was calculated to  be 230  mg/kg (Varnell 1965) .-?/


      Subacute Oral Toxicity - Cattle - Two MSMA formulations were used by
 Dickinson (1972)-2/ to determine  the toxicity of the herbicide to cattle.   One
 formulation contained 44.9% MSMA and the  other contained 59% MSMA, although
 in both preparations the total arsenic content was reported to be 21%.
 _!/  Derse, P. H., "Methane Arsonic Acid 90-Day Feeding Study - Dog,"
       unpublished report, WARF Laboratories, Madison, Wisconsin, EPA
       Pesticide  Petition No.  9F0794  (1968a).
 2J  Varnell, T.  R., "Acute Toxicity  - Dairy Cattle," unpublished report,
       E. S. Erwin Associates, Inc.,  Tolleson, Ariz., EPA Pesticide
       Petition No. 9F0794  (1965).
 _3_/  Dickinson, J. 0.,  "Toxicity  of the Arsenical Herbicide Monosodium Acid
       Methanearsonate  in Cattle," Am. J. Vet. Res., 33:1889-1892 (1972).


                                        38

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     The materials were administered orally to the test animals  in  gelatin
capsules.  Yearling white-faced cattle were used:  2 for controls,  3  for  the
44.9% MSMA preparation and 2 with the 59% MSMA preparation.

     Of the 5 cattle treated, 4 succumbed to the toxic effects of the compounds
after they were given a total dosage of 100 mg of MSMA per kilogram body  weight
(10 mg/kg/day for 10 days).  Arsenic residues as high as 64 ppm  were  found in
the kidney.  Toxic nephrosis and hemorrhagic gastritis were observed  in all
test animals.

     In another test, Libke et al. (1971)  reported a combination  of herbi-
cides, including 2/3 gal MSMA, was applied to pasture land at a  recommended rate
of 24 gal/acre.  Each liquid oz contained 657 mg MSMA.

     Two-year-old crossbred beef heifers (597 Ib average body weight)  were
divided into 4 groups of 3 animals each and pastured on 3-acre lots for 3  weeks.
The cattle were turned into the lots within 1 hr of spraying.  Group  I was
placed on pasture sprayed at the recommended level, Group II on  pasture sprayed
at 4 times the recommended level, and Group III (controls) on untreated pasture.
Group IV was confined and fed hay and grain.  Using a dosing syringe,  one  animal
was given 14.7 oz of the mixture; another was given 16 oz.  The  following  day
the dose was reduced to 8 oz/day.  The third animal was treated with  2 oz  of the
mixture applied to a 225 sq in area of clipped skin.  All 3 of the  animals in
Group IV were treated daily until they died.

     The results of this study were summarized by the authors (Libke  et al.
1971).  They reported no significant adverse effects in the cattle grazing
on pasture, even on the pasture which was treated with 4 times the recommended
application rate.

     In the Group IV animals,  the heifer exposed by contact became diarrheic
and refused feed for 10 days prior to death.  She lost 124 Ib during  the 23-
day exposure period.

     One heifer died after a total dose of 78.7 oz (ninth day) and the other
after a total of 47.6 oz (fifth day).

     Attempts to relate toxicity to the various ingredients in the mixture
were not made.

     In another test (Varnell undated b) .'dietary levels of 40, 80.1  and  240.2
mg of Ansar 529 per kg body weight were fed daily to 2 Holstein  calves per
dosage group for 7 days.  A reduction in feed consumption was observed for all
animals, but only one calf at the highest dosage level exhibited the diarrhea
 I/  Libke, K. G., D. F. Watson, and T. L. Bibb, "Effects of a Brushwood Killer
       on  Cattle," Mod. Vet. Prac., 52:37-40  (1971).
 2j  Varnell, T. R., "One Week Feeding of Ansar 529 and  560 to Calves," E.  S.
       Erwin and Associates, Inc., report submitted to The Ansul Company,
       Marinette, Wisconsin  (undated b).
                                      39

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which is a characteristic symptom of Ansar 529 poisoning.  The  investigators
speculated that calves could consume approximately 5% of the acute  lethal dose
of Ansar 529 without interfering with their  feed consumption.

      In a separate test  (Varnell undated a),  plots of Johnson  grass were
sprayed with MSMA in the  form of Ansar 529 or Ansar  170 at a rate of  6.93 Ib
MSMA/acre.  Holstein dairy calves were confined to these plots  for  24 hr; after
this exposure they were removed and observed for 2 weeks.  No signs of toxicity
were observed in the animals other than mild diarrhea which persisted for
approximately 2 days.

      Another study is considered in the Fate and Significance  in the Environ-
ment section on the exposure of cattle grazing in forest areas  treated with
MSMA and other arsenical  herbicides.

      Subacute Toxicity - Chickens - The subacute toxicity of DSMA  in chickens
(Rock Cornish) was evaluated by Hamada and Kobayashi (1968).2J  The amount of
DSMA added to the diet, starting with day-old chicks, was equivalent  to  5 ppm
AS205-  The quantity of DSMA in the diet was increased so that  by the eighth
week the chickens were receiving 10 to 15 ppm as As20s  (5 ppm up  to 2 weeks,
10 ppm  from 2 to 3 weeks, and 15 ppm from 3  to 8 weeks) .  The presence of DSMA
did not result in any signs of toxicity.  The treated chickens  exhibited statis-
tically significant increases in growth and  were found to have  achieved  a better
feed conversion ratio than  the untreated controls.
 Metabolism

 Accumulation and Excretion - Peoples  (1964),'  in an article on inorganic
 arsenical  compounds,  reported on toxicity to cows as compared to the toxicity
 to  laboratory animals.   The ppm's for tissue concentration of a trivalent  arsenic
 compound in treated rats fed a diet containing  50 ppm arsenic trioxide for 21 days
 are as  follows:   blood  (125.0), liver (20.0), heart (43.0), kidney (25.0), spleen
 (60.0), fat (12.0), gastrointestinal  tract (15.0), and skin (27.0).   The treated
 guinea  pigs had  the following ppm's:   blood  (4.0), liver (1.0), heart (20.0),
 kidney  (1.0), spleen (15.0), fat (0.8),  and  gastrointestinal tract (2.0).   The
 following  are ppm's recorded for the  rabbits used in the study:  blood (1.5),
 liver (1.0), heart (0.2),  kidney (1.5),  spleen  (0.2), fat (0.2), gastrointestinal
 tract (1.5), and skin (2.5).  The ppm's  for  hamsters are as follows:  blood (2.5),
 liver (15.0), heart (7.0), kidney (5.0), spleen (2.0), fat (0.7), gastrointestinal
 tract (30.0), and skin  (38.0).  When  fed a control diet, some animals, especially
 rats, still had  measurable levels of  arsenic in various tissues.

 "_!/ Varnell, T. R., "Johnsongrass Treated with High Levels of Ansar 529 and 170,"
      E. S. Erwin and Associates, Inc.,  report to  The Ansul Company, Marinette,
      Wisconsin  (undated a).
 2j Hamada, S., and K. Kobayashi, "Studies on the  Influence of Arsenicals  on  the
      Growth of the Domestic Fowl (Part  I) Effect  of Methane Arsonic Acid,"
      J. Jap. Soc. Food and Nutr..  21:64-66  (1968).
 _3/ Peoples, S. A., "Arsenic Toxicity in Cattle,"  Annal. N. Y. Acad. Sci.,
      111:644-649  (1964).

                                         40

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      In tests on cows, a pentavalent compound was excreted  rapidly in the
urine.  Consequently, there was little storage in tissues, and  the residues
that were present were rapidly depleted in a feed-off period.   Therefore,  the
arsenic levels that occurred represented "transit" rather than  true storage.
In tests with 2 other arsenic compounds, arsenic was not excreted  in the milk
of the cows.

      According to Peoples (1964), the rat is unique among the  various  laboratory
animals in its propensity to accumulate arsenic residues, although its  sensi-
tivity to the toxic effects of arsenic is comparable to other animals.  Accumu-
lation of large amounts of arsenic in the rat was especially noticeable in the
blood levels.

      Similar studies have shown that chickens fed either trivalent  or  pentava-
lent arsenical compounds do not accumulate arsenic in eggs or in tissues
(Peoples 1971) .I/


Compound Valence vs. Excretion - Schreiber and Brouwer (1964).?/ studied the
relationship of arsenic valence to metabolism and toxicity in the  rat.  They
reported that from 21 to 64% of 2 pentavalent arsenicals were excreted  by  rats,
predominately in the urine.  Under identical test conditions, only 9  to 24% of
a trivalent arsenical compound was excreted and this was excreted primarily in
bile.  No valence pattern was noted for arsenic residues in the heart,  red blood
cells and (nonfasted) spleen.


Utilization of Tissue-Bound Arsenic - A study by Winkler (1962)3/ concluded
that trivalent inorganic arsenic is largely changed to the pentavalent  form
in the rat.   Pentavalent arsenic is not reduced.

     Coulson et al. (1935)A/ reported that, when rats were fed shrimp-
supplemented diets which contained high levels of arsenic (17.7 mg/kg)
for 1 year,  only a very small amount (2.82 mg/kg tissue) of the arsenic
obtained from the shrimp was stored in the liver of the rat.   When inorganic
arsenic was fed at the same level, arsenic accumulated to 55 to 65 times
normal concentration in the body tissues and over 100 times normal concentra-
tion (49.1 mg/kg) in livers.
I/  Peoples, S. A., "Health Aspects of Arsenic Herbicides," in Proc. 23rd
      Annual Calif. Weed Conf., pp. 115-116 (1971).
2J  Schreiber, M., and E. A. Brouwer, "Metabolism and Toxicity of Arsenicals.
      I.  Excretion and Distribution Patterns in Rats," Abstract 589, in Fedn.
      Proc.. 23:199 (1964).
3/  Winkler, W. 0., "Identification and Estimation of the Arsenic Residue in
      Liver of Rats Ingesting Arsenicals, J. Ass. Offie. Anal. Chem. 45:80-91
      (1962).
4/  Coulson, E. J., R. E. Remington, and K. M. Lynch, "Metabolism in the Rat
      of the Naturally Occurring Arsenic of Shrimp as Compared with Arsenic
      Trioxide."  J. of Nutr., 10:255-270 (1935).
                                       41

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     During the first 3 months  of  feeding,  18%  of  the  inorganic  arsenic
was stored in the bodies of  the rats, while only 0.7%  of  arsenic from shrimp-
supplemented diets was stored.   The  total quantity stored within the first 3
months was not significantly increased  by feeding  for  an  additional 9 months.

     Rats fed arsenic from shrimp-supplemented  diets for  12 months did not
exhibit any evidence of toxicity in  their growth,  physical appearance or
activity.  Arsenic which occurs in shrimp is apparently bound in an organic
complex and, as such, cannot be liberated in the rat.

     In tests with another compound  on  pigs (Winkler 1962), livers from the
treated animals contained  5.85  ppm (range 3.9 to 8.4 ppm) arsenic, compared
to 0.1 ppm from livers of  control  pigs. Acetone powders  were then made from
the livers and these were  fed to rats at a  level of 30% of the diet.  The
daily feces and urine collections  were  analyzed for total arsenic.  The
average value for 4 rats fed on the  acetone powders indicated that all of the
organic arsenic compounds  were  eliminated in the urine and feces; however,
only 51% of the inorganic  arsenic  was recovered during the 7-day test.

     The results of this study  parallel those of Coulson  et al.  (1935) in
that they appear to show metabolic inertness of tissue-bound arsenic.  The
results seem to indicate that food chain magnification of arsenicals does not
occur.
Teratogenlc  Effects

       Specific  data  on the teratogenic  effects  of MSMA and DSMA on mammals was
not  found.   However,  one study indicated  that sodium arsenate  is teratogenic
to golden hamsters  (Perm et al.  1971) .I/   Arsenic acid (the  free acid  equivalent
-of sodium arsenate)  is one of the probable terminal degradation products  of MSMA
and  DSMA.

       On the eighth  day of gestation, pregnant  female hamsters were  injected
intraveneously  with  sodium arsenate (15 and 25  mg/kg body weight).   Control
animals were injected with demineralized  water. The animals were killed  and
examined on  the 15th day of gestation.  Determinations were  made of  the number
of embryos and  the number of resorptions  (Ferm  et al. 1971).

       Sodium arsenate affected both resorption  and  malformation in the hamster;
the  rates increased  with increasing concentration.   Malformations of the  cranium
were the most common developmental anomaly found.   The authors concluded  that
arsenic has  a profound effect upon reproduction in  the golden  hamster  and that
other animals might  be more or less sensitive.
 _!/  Ferm, V. H., A. Saxon, and B. M. Smith, "The Teratogenic Profile of Sodium
       Arsenate in the Golden Hamster, Arch. Environ. Health, 22:557-560 (1971).
                                       42

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Mutagenic Effects

     MSMA was one of several herbicides evaluated for an ability to induce
point mutations in one or more of 4 different microbial systems.  The mutagenic
rates of MSMA-treated organisms did not differ from spontaneous rates (Anderson
et al. 1972) .I/
Oncogenic Effects

     There are no reported studies on the oncogenic effects of MSMA and DSMA
in animals.  A few studies with mice and rats have been reported in which the
oncogenicity of inorganic arsenicals was considered.  However, studies of the
oncogenic effects of inorganic arsenicals on animals and humans are beyond
the scope of this review.
Effects on Humans

     Two studies were reported concerning the occupational hazards associated
with MSMA and DSMA.  One of these was related to a field exposure and the other
to a hazard arising out of the manufacturing process.


Manufacturing Exposure - DePalma (1969).-/ reported the following case histories
which indicate the danger to which workers in plants manufacturing MSMA and
DSMA may be inadvertently exposed.

     MSMA was being synthesized in a plant by reacting methyl chloride with
sodium arsenite.  The reaction took place under pressure in a closed, 10 by
12 ft, 600 gal stainless steel tank.  Because of a mechanical failure in the
apparatus, the operation was stopped before the reaction was completed.  The
tank was drained, but a solid residue was left on the floor.  An aluminum
ladder was then placed in the tank to enable the workers to repair the
mechanism.
I/  Anderson, K. J.,  E. G.  Leighty,  and M.  T.  Takahashi,  "Evaluation of
      Herbicides for Possible Mutagenic Properties," J. Agr.  Food Chem.,
      20:649-656 (1972).
2J  DePalma, A. G., "Arsine Intoxication in a Chemical Plant," J. Occup.
      Med., 11:582-587 (1969).
                                       43

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     With the aluminum ladder in the vat, the necessary ingredients for the
evolution of arsine gas (AsH3> were present:  (1) arsenic,:(2) water and/or
acid, and (3) aluminum or another base metal such as zinc or tin.

     Five men were exposed to the arsine gas during the repair work.  The
first 2 men entered the vat, inspected the mixer briefly and exited without
experiencing any ill effects.

     Approximately 30 min later another man entered the tank without wearing
a mask or respirator.  He noticed gas bubbling at the foot of the ladder.  He
felt a chill immediately which was later followed by a burning sensation
throughout his body.  When the symptoms persisted, he was hospitalized the
following day.  He was discharged from the hospital 44 days after exposure
still suffering from anemia and peripheral neuropathy.

     A fourth worker entered the tank without a mask or respirator and
remained for approximately 3 min.  He removed a sample of the dark, tarry
substance at the foot of the ladder.  Several hours later he noticed his
urine was a dark orange color.  He experienced chills, nausea, vomiting, and
malaise and was hospitalized the following day.

     A fifth worker was exposed to the substance while cleaning the tank.  At
the same time, steam was piped up through the main drain in the center of the
tank in order to melt the solid material.  The hose operator was in contact
with the rising steam for approximately 15 min.  Within 30 min he noticed his
urine was unusually dark.  He later developed hot and cold flashes, abdominal
cramps, nausea and vomiting.


Field Exposure - A study was carried out over a 9-week period to determine the
potential occupational hazard of MSMA to tree-thinning crews (Tarrant and
Allard 1972) .JL/

     Urine samples were collected from each worker in the test on Monday
mornings before work was begun and on the following Friday at the end of
the working day.  Subjects were chosen so that the effect of 4 different
methods used to apply MSMA to trees could be studied.

     The method of application did not appear to affect the arsenic level
in urine, although, after a week of exposure, the concentration of total
arsenic was elevated in all of the workers.  The higher levels detected on
Friday were in most instances near normal by the following Monday.

     The data in Table 3 summarizes the arsenic values observed on Mondays
and Fridays  for the various application techniques.
I/  Tarrant, R- F., and J. A. Allard, "Arsenic Levels in Urine of Forest
      Workers Applying Silvicides," Arch. Environ. Health, 24:277-280
      (1972).


                                      44

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     Health problems that could be attributed to arsenic poisoning were not
encountered in the study group.  Arsenic levels did not  accumulate and there
was no increase in the arsenic levels in the urine  after the  first week.
               Table 3.  EXPOSURE OF TREE-THINNING CREWS TO MSMA
                                          Arsenic In urine (ppm)
     Treatment                         Monday                  Friday

     Control (no exposure)          0.04  0.01              0.07  0.03
     Injection operator             0.10  0.01              0.36  0.07
     Hack-squirt operator           0.07  0.01              0.26  0.05
     Injection hatchet operator     0.10  0.01              0.50  0.12
     Source:   Tarrant and Allard, op. cit. (1972).
                                     45

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References

Anderson, K. J., E. G. Leighty, and M. T. Takahashi,  "Evaluation of Herbi-
  cides for Possible Mutagenic Properties,"  J. Agr. Food Chem., 20:649-
  656  (1972).

Coulson, E. J., R.  E.  Remington,  and  K.  M. Lynch,  "Metabolism in  the  Rat
  of the Naturally  Occurring Arsenic  of  Shrimp as  Compared  With Arsenic
  Trioxide," J. of  Nutr.,  10:255-270  (1935).

DePalma, A. G., "Arsine  Intoxication  in  a Chemical Plant,"  J.  Occup.  Med.,
  11:582-587  (1969).

Derse,  P. H.,  "Methane Arsonic Acid 90-Day Feeding Study -  Dog," unpublished
  report, WARE Laboratories,  Madison, Wisconsin, EPA  Pesticide Petition
  No.  9F0794  (1968a).

Derse,  P. H.,  "Methane Arsonic Acid 90-Day Feeding Study -  Rats,"  unpublished
   report, WARF Laboratories, Madison, Wisconsin,  EPA Pesticide Petition
   No.  9F0794 (1968b).

Dickinson,  J.  0.,  "Toxicity of  the Arsenical Herbicide Monosodium Acid
  Methanearsonate  in Cattle," Am. J.  Vet. Res.,  33:188901892 (1972).

Ferm,  V.  H.,  A. Saxon, and B. M.  Smith,  "The Teratogenic Profile  of Sodium
   Arsenate  in the  Golden Hamster," Arch. Environ.  Health,  22:557-560 (1971).

Furst, A.,  and R.  T.  Haro, "A Survey  of Metal Carcinogenesis," Prog.  Exp.
   Tumor Res.,  12:102-133 (1969).

Hamada, S.,  and K.  Kobayashi, "Studies on the Influence of  Arsenicals on the
   Growth of the Domestic Fowl (Part  I) Effect of Methane Arsonic  Acid,"
   J.  Jap.  Soc. Food and Nutr..  21:64-66 (1968).

Hwang, S. W.,  and  L.  S.  Schanker, "Absorption of Organic Arsenical Compounds
   From the  Rat Small Intestine,"  Xenobiotica, 3:351-355 (1973).

Libke, K.  G.,  D. F. Watson, and T. L. Bibb,  "Effects  of a Brushwood Killer on
   Cattle,"  Mod. Vet.  Prac.. 52:37-40  (1971).

Maycumber,  H.  C.,  "Arsenic Residues  in Cattle Grazed in Treated Areas,"
  Contained in L. A. Norris (ed.), "The Behavior and Impact  of Organic
  Arsenical Herbicides in the Forest Environment:   An Interim Report on
  Cooperative Studies," Pacific Northwest Forest and Range  Experiment Station,
  Corvallis, Oregon (unpublished report 1971).

Nees,  Paul 0.,  WARF Institute report   (No. 9031917)  submitted to The Ansul
  Company, Marinette, Wisconsin (April 11, 1969a).


Nees, Paul 0., WARF Institute report  (No. 9031917)  submitted to The Ansul
  Company, Marinette, Wisconsin (May  15, 1969b).


                                       46

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Norris, L. A. (ed.), "The Behavior and Impact of Organic Arsenical Herbicides
  in the Forest Environment:  An Interim Report on Cooperative  Studies,"
  Pacific Northwest Forest and Range Experiment Station, Corvallis,  Oregon
  (ui published report 1971).

Palazzolo, R. J., "Acute Oral Toxicity of Ansar 170," unpublished  report,
  Industrial Bio-Test Laboratories, Northbrook, Illinois,  EPA Pesticide
  Petition No. 9F0794 (1964a).

Palazzolo, R. J., "Acute Oral Toxicity of Ancar 184 Herbicides," unpublished
  report, Industrial Bio-Test Laboratories, Northbrook, Illinois,  EPA
  Pesticide Petition No. 9F0794 (1964b).

Palazzolo, R. J., "Acute Toxicity of Ansar 529 Herbicide," unpublished  report,
  Industrial Bio-Test Laboratories, Northbrook, Illinois,  EPA Pesticide
  Petition No. 9F0794 (1964c).

Peoples, S. A., "Arsenic Toxicity in Cattle," N. Y. Acad.  Sci.  Annals,
  111:644-649 (1964).

Peoples, S. A., "Health Aspects of Arsenic Herbicides," Proc. 23rd Annual
  Calif. Weed Conf.. pp. 115-116 (1971).

Powers, M. B., "Methanearsonic AcidAcute Oral Toxicity;  Primary  Skin  Irritation,"
  unpublished report, WARF Laboratories, Madison, Wisconsin,  EPA Pesticide
  Petition No. 9F0794 (1963).

Schreiber, M., and E. A. Brouwer, "Metabolism and Toxicity of Arsenicals.  I.
  Excretion and Distribution Patterns in Rats," Abstract 589, in Federation of
  American Societies for Experimental Biology , 23:199 (1964).

Tarrant, R. F., and J. A. Allard, "Arsenic Levels in Urine of Forest Workers
  Applying Silvicides," Arch. Environ. Health, 24:277-280  (1972).


Varnell, T. R., "Acute Toxicity - Dairy Cattle," unpublished  report, E. S.
  Erwin Associates, Inc., Tolleson, Arizona, EPA Pesticide Petition No.
  9F0794 (1965).

Varnell, T. R., "Johnsongrass Treated with High Levels of Ansar 529 and 170,"
  E. S. Erwin and Associates, Inc., report submitted to The Ansul  Company,
  Marinette, Wisconsin (undated a).

Varnell, T. R.,  "One Week Feeding on Ansar 529 and 560 to Calves," E. S. Erwin
  and Associates,  Inc.,  report submitted to The Ansul Company, Marinette,
  Wisconsin (undated b).

Winkler, W. 0.,  "Identification and Estimation of the Arsenic Residue in Liver
  of Rats Ingesting Arsenicals," J.  Ass.  Offie.  Anal.  Chem. 45:80-91 (1962).
                                       47

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                     PART II.   INITIAL SCIENTIFIC REVIEW

           SUBPART C.   FATE AND SIGNIFICANCE IN THE ENVIRONMENT

                                  CONTENTS

                                                                          Page

Effects on Aquatic Species 	    50

  Fish	    50

  Lower Aquatic Organisms	    50

    Laboratory Studies 	    50
    Field Studies	    53

Effects on Wildlife	    54

  Laboratory Studies 	    54
  Field Studies	    55

Effects on Beneficial Insects	    57

Interactions with Lower Terrestrial Organisms	    59

Residues in Soil	    62

  Laboratory and Field Studies 	    62
  Monitoring Studies 	    69

Residues in Water	    70

Residues in Air	    71

Bioaccumulation, Biomagnification	    72

Environmental Transport Mechanisms 	    73

References	    75
                                      49

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     This section contains data on the environmental effects of MSMA and DSMA,
including effects on aquatic species, wildlife, and beneficial insects and
interactions with lower terrestrial organisms.  Residues in soil, water and
air are also discussed.  The section summarizes rather than interprets data
reviewed.
Effects on Aquatic Species
Fish - The data available on the effect of MSMA and DSMA on fish is limited to
acute toxicity studies.  In laboratory studies 6 species were tested; the number
of replicate tests on each species tested was small.

     Table 4 shows the low toxicity of MSMA  (and DSMA) to fish; the 96-hr LC$Q
ranges from 13.3 to 96.0 ppm, depending on species, test conditions, and the
amount of active ingredient in the formulation tested.  One report gives a
48-hr LC5Q of greater than 1,000 ppm  (Hughes 1966) .I/


Lower Aquatic Organisms -


     Laboratory Studies - The toxicity of MSMA and DSMA to estuarine animals
was studied in the mid-1960's at the  then existing Bureau of Commercial
Fisheries Biological Laboratory at Gulf Breeze, Florida (Miller and Lowe
1966).I/  Test organisms were exposed for 24 or 48 hr  to MSMA and DSMA con-
centrations of 1.0 ppm in natural flowing seawater at  temperatures ranging
from 15 to 19C, salinity of 29% parts per thousand.   There were no effects
from MSMA or DSMA on pink shrimp (Penaeus duorarum) after 48 hr exposure, nor
on Eastern oyster (Crassostrea virginica) after 24 hr  exposure.  Effects on
shrimp were determined by the percentage of  the population exhibiting paralysis
or loss of equilibrium; effects on oysters were determined by percent decrease
in shell deposition.

     Sanders  (1970)J/ studied the toxicity of a number of herbicides, including
MSMA, to freshwater crustaceans.  MSMA was one of  several herbicides that were
not toxic to scud (Gammarus fasciatus) after 96 hr exposure at a concentration
of 100 ppm.
 I/  Hughes, J. S., Toxicity of Pesticides to Bluegill Sunfish Treated During
       1961-1966,  report  of the Louisiana Wildlife and Fisheries Commission,
       New Orleans, Louisiana  (1966).
 2J  Miller, C. W., and J. I.  Lowe,  "Toxicity of Herbicides to Estuarine
       Animals," U.S. Bureau of Commercial Fisheries Biological Laboratory,
       Gulf Breeze, Florida, unpublished report  (1966).
 3_/  Sanders, H. 0., "Toxicities of  Some Herbicides to Six Species of Freshwater
       Crustaceans," J. Water  Pol. Cont. Fed., 42(8), Part 1:1543-1550 (1970)'.
                                       50

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                            Table 4.  TOXICITY OF MSMA AND DSMA TO FISH
Species Herbicide
Bluegill MSMA
(Lepomis macrochirus)
Channel catfish MSMA
* (Ictalurus purictatus)
Fathead minnow MSMA
(Pimephales promelas)
Goldfish MSMA
(Carassius auratus)
Longnose killifish DSMA
(Fundulus similis)
Rainbow trout MSMA
Concentration ^50 (PPm)
of formulation (95% confidence
(% AI)* limits)
34.7
34.8
34.7
100
100
25.65
22.6
49.2
>
26.8
13.3
31.1
(25.3 - 95.8)
1,000
(20.0 - 35.9)
( 5.06- 35.8)
(24.4 - 38.8)
No effect at 40.0
96.0

Exposure
(hr)
96
48
96
96
96
48
96
Reference
a/
w
a/
sJ
/
I/
e/
  (Salmo gairdneri)
*   AI = Active ingredient.
a./  Schoettger, R. A., Annual Progress Report, 1971, U.S. Department of the Interior, Fish-
      Pesticide Laboratory, Fish and Wildlife Service, Columbia, Missouri (1971).
b/  Hughes, op. .cit.  (1966).
C/  U.S. Department of Interior, Fish and Wildlife Service, unpublished data from Fish-Pesticide
      'Laboratory, Columbia, Missouri (1968).
d/  Lowe, J. I., unpublished data from Bureau of Commercial Fisheries Biological Laboratory, Gulf
      Breeze, Florida (1966).
e/  McCann, J. A., (Chemical and Biological Investigation Branch, Office of Pesticide Programs, EPA),
      "Fish Toxicity Lab Report," EPA Pesticide Petition No. 9F0794 (1969).

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     Blythe (1973)!/ -studied the effects of MSMA on the unicellular green alga
(Chlorella pyrenoidosa).   Autotropic and heterotrophic growth of the organism
in the presence of MSMA was determined by counting cell numbers and measuring
chlorophyll absorption at different times during the life of a culture.
Oxygen evolution in the light and oxygen consumption in the dark at different
herbicide levels were also studied.  MSMA concentrations ranging from 2.5 to
3,000 ppm were used in growth and respirometer experiments.  In almost all of
the growth experiments, MSMA resulted in a stimulation above the check level.
There was no significant effect of MSMA on oxygen evolution and only a slight
effect on oxygen uptake.  The average uptake was 56 ml oxygen/100 min, adjusted
to 100 mg dry weight.  Oxygen uptake was slightly reduced (9%) at an MSMA con-
centration of 20 ppm.  Stimulation of oxygen uptake (18%) was observed at a
MSMA dosage of 3,000 ppm.

     Cox and Alexander (1973).?/ investigated the production of trimethyl-
arsine gas from various arsenic compounds including monomethylarsonic acid
by 3 sewage fungi isolated from raw sewage, for example, Candida humicola,
Gliocladium roseum and P'enicillium species.  Aliquots of raw sewage were added
to culture media and exposed to successively higher concentrations of MAA,
ranging from 100 to 2,000 Vg/ml.  The enrichment cultures obtained in this
manner were incubated for 1 month at room temperature, and the headspace gas
of each incubation bottle was tested for the presence of trimethylarsine by
odor analysis and gas chromatography.  In addition to MAA, 3 other arsenic
compounds were tested in the same manner, each at pH 5, 6, and 7.  The
typical garlic odor of trimethylarsine was detected in cultures containing
MAA at pH 5, but not at pH 6 or 7.  In studies with pure cultures of sewage
fungi, 
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     Field Studies - Edwards (1973)!/ studied the effects of MSMA on a salt
marsh ecosystem in a series of field experiments conducted in 1971 and 1972.
During the summer of 1971, 3 by 6 meter plots of a Spartina alterniflora
salt marsh were treated with MSMA by foliar application at different rates
and frequencies, including 3 applications at 9,000 ppm once weekly for 3
weeks, and 5 applications of 100, 10, and 1 ppm, respectively, once weekly for
5 weeks.  Each treatment and the corresponding controls were replicated 4
times.  Symptoms of MSMA damage to Spartina observed in the 9,000 and 100 ppm
treatments included necrosis of leaf tips and slight curling and necrosis of
leaf margins.  MSMA applied 5 times at the rate of 100 ppm decreased the dry
matter of living Spartina, while 3 applications at the rate of 9,000 ppm did
not noticeably affect it.  (The author has no explanation for this seeming
inconsistency.)  None of the treatments significantly affected the density
of Spartina shoots, flowering of Spartina, nor the dry matter of dead
Spartina.  Three MSMA applications at 9,000 ppm reduced the numbers and dry
weight of Littorina irrorata, a mollusk associated with Spartina by 45%,  but
this decrease was not statistically significant because of the large variation
in the spatial distribution of the Littorina population in the area.

     In 1972 a second set of plots of the same size (3 by 6 m) was estab-
lished in another area of a similar marsh and treated with MSMA by spray
applications once at 90,000 ppm; 30 times (twice each day for 5 consecutive
days at monthly intervals for 3 consecutive months) at 10,000, 1,000,  100,
and 10 ppm; and by flooding twice daily for 5 consecutive days each month for
3 consecutive months with either 100 or 0 ppm in seawater.  The spray treat-
ments were randomized and replicated 4 times.  The flooding experiment was
duplicated.  None of these treatments altered the number of Spartina shoots.
Thirty applications of MSMA at 10,000 ppm decreased the standing crop of
living Spartina, increased the standing crop of dead Spartina, and reduced
the number of flowering shoots.  These applications, as well as the single
application at 90,000 ppm increased the percent of dead and necrotic tissue on
living shoots of Spartina.  Thirty applications of MSMA at 10,000 ppm reduced
the numbers and dry matter of Littorina by 68%.  None of the other spray
treatments affected Littorina adversely.
I/  Edwards, A. C., "The Effects of an Organic Arsenical Herbicide on a
      Salt Marsh Ecosystem," M.S. thesis, Auburn University, Auburn,
      Alabama (1973).
                                       53

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     Observations from the flooding experiment suggested that flooding with
100 upm of MSMA in seawater is no more deleterious to Spartiria than spraying
at the same concentration.  Littorina were adversely affected by (unspecified)
environmental conditions in the flooding experiments.  Their numbers were
reduced in the treated as well as the untreated plots.  However, Edwards (1973)
concluded that the test results were insufficient to assess their significance.

     Thirty foliar applications of 10,000 ppm MSMA and 30 flooding applications
of 100 ppm MSMA in seawater resulted in arsenic levels of 26 and 28 ppm in
Spartina, and of 26 and 33 ppm in the soil.  Littorina contained 100 ppm of
arsenic after completion of 30 foliar applications of MSMA at 10,000 ppm.  This
level declined to 11 ppm within 1 month.  Upon completion of the 30 floodings
with 100 ppm MSMA in seawater, another mollusk, Modiolus demissus, contained
20 ppm of arsenic, and 16 ppm 1 month later.  Edwards does not report arsenic
residues in Littorina from the flooding tests, nor in Modiolus from spray tests.

     The primary objective of the studies was to determine whether MSMA at
concentrations which might conceivably be in tide water as a result of runoff
from agricultural land could cause damage to a salt marsh ecosystem.  Because
most organic arsenicals are tightly bound to soil colloids, and since herbi-
cides are greatly diluted in runoff water, it is highly unlikely that
concentrations in tide water would even approach 1 ppm, according to Edwards.
He concluded that MSMA would have negligible effects on the parameters studied
at pollution concentrations and that high rates of application, equal to or
above those recommended for noncrop use, would likely have only limited,
short-term effects.
Effects  on Wildlife


     Data on  the  effects  of MSMA and DSMA on wildlife are also limited.  Con-
trolled  studies have  apparently  been limited to  2  species.

Laboratory Studies  -  Subacute  toxicity  studies were  conducted on mallard duck-
lings  and bobwhite  quail, using  a technical grade  MSMA  (51.3%).  The ducklings
were 10- to 15-day-old pen-reared birds that were  in good physical  condition
at  the start  of the feeding period.  The animals were divided as follows:  5
control  groups of 10  birds each; 5 toxic groups  of 10 birds  each which were
given  a  toxic pesticide in the diet at  levels of 68  to  464 ppm; and one test
group  which was fed at a single  dietary level of 5,000  ppm MSMA.  The MSMA group
was fed  for 5 days  with treated  ration  and then  for  3 days on untreated.  The
controls received a standard laboratory diet for the 8-day test period.  No signs
of  systemic toxicity or any abnormal behavioral  reaction were observed in the
MSMA-treated  birds.  The dietary median lethal concentration (LCso). of MSMA for
ducks  was determined to be greater than 5,000 ppm  (Fletcher  1973a).!/
 I/  Fletcher,  D., "8-Day Dietary LC5q Study with Monosodium Acid Menthane-
       arsonate in Mallard Ducklings,  unpublished report of Industrial
       Bio-Test Laboratories, Northbrook, Illinois (1973).
                                         54

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     In studies on bobwhite quail, multiple doses of technical grade MSMA
(51.3%) were given at dietary levels of 312.5, 625, 1,250, 2,500, and
5,000 ppm.  The birds were fed treated ration for 5 days, followed by 3 days
of untreated ration.  The dietary median lethal concentration  (LC^p) was
calculated to be 3,300 ppm with 95% confidence limits of 1,941 to 5,610 ppm.
Necropsy did not reveal any characteristic gross pathology  (Fletcher et al.
1973b) .1

     A formulation containing 81% DSMA was administered to mallard ducks at
a level of 10,000 mg/kg of body weight.  Both male and female birds were
tested.  None of the ducks died.  All birds were sacrificed, but an exami-
nation for gross pathological conditions of tissues failed to detect any
abnormalities (Industrial Bio-Test Laboratory 1973a) .!/

     In a similar study, acute oral LD5Q of DSMA to bobwhite quail was
established as 3,160 mg/kg body weight.  Gross pathological examination
failed to reveal any abnormalities in any organ or tissue as a result of
treatment (Industrial Bio-Test Laboratory 1973b).-i'


Field Studies - Norris (1971)A/ presented an interim report on comprehensive,
cooperative studies among scientists, forest land managers, and several
Pacific Northwest organizations on the fate and environmental impact of organic
arsenical herbicides including MSMA and DSMA, in the forest environment.  The
studies were initiated following the death of 8 range cattle in forest areas
where organic arsenical herbicides had been used.  Arsenic residues had been
found in hair and tissue from 4 of the dead cattle.

     Schroedel et al. (1971V5-/ studied the effects on wildlife of arsenical
herbicides, including MSMA and DSMA, used in forest management.  Animals
(numbers not specified) were trapped at various intervals after the use of
arsenical herbicides, and arsenic residues were determined in specific tissues
or whole bodies.  More than 400 determinations of arsenic residues were made
on samples collected from 3 treatment areas in western Washington, and 4 in
eastern Washington.
17  Fletcher, D., D. H. Jenkens, and M. L. Keplinger, "8-Day Dietary
      Study with Monosadium Acid Methanearsenate in Bobwhite Quail," unpub-
      lished report of Industrial Bio-Test Laboratories, Northbrook, Illinois
      (1973).
2J  Industrial Bio-Test Laboratories, "Acute Oral LDso for Mallard Ducks
      (Ansar 8100)," unpublished report to The Ansul Company, Inc., Marinette,
      Wisconsin (1973a).
$1  Industrial Bio-Test Laboratories, "Acute Oral LDso for Bobwhite Quail
      (Ansar 8100)," unpublished report to The Ansul Company, Inc., Marinette,
      Wisconsin (1973b).
47  Norris, L. A.,  ed., "The Behavior and Impact of Organic Arsenical Herbicides
      in the Forest Environment:  An Interim Report on Cooperative Studies,"
      unpublished report,  Pacific Northwest Forest and Range Experiment Station,
      Corvallis, Oregon (1971).
5/  Schroedel T., H. JIartwell,  L. Norris, and J. Allard, "Arsenical Silvicide
      Effects on Wildlife," contained in Norris, op.  cit.  (1971).


                                       55

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     Several species .of birds, mountain beaver and porcupines did not
contain detectable arsenic residues.  A single deer which was recognized by
applicators as a long-time resident of one of the treated areas was also
collected.  Histopathologic examinations on this animal showed no arsenic-
induced lesions, and chemical analysis revealed no arsenic residues.  Voles,
shrews, mice, and chipmunks contained low levels of arsenic shortly after
thinning with arsenical herbicides commenced.  About 50% of these animals
had arsenic residues between 0.5 and 9.8 ppm arsenic between 2 and 30 days
following treatment.  Most of the residues were less than 5.0 ppm.  Few
animals (number not specified) that were collected more than 30 days after
treatment contained detectable residues.  Most ground squirrels that were
collected contained arsenic residues similar to those found in voles, shrews,
mice, and chipmunks, but one squirrel collected 1 day after treatment contained
residues ranging from 17 to 30 ppm arsenic in various body parts.  No further
details on numbers of animals, types of tissues analyzed, or other study
parameters were given.

     A total of 11 dead -snowshoe hares was found in one treatment area near
Colville, Washington, between June of 1970 and February of 1971.  High levels
of arsenic in tissues from the hares indicated arsenic poisoning, although
postmortem degeneration prevented more detailed studies.  Most of the dead
hares were found within a few hundred yards of "wash areas," locations where
crews disposed of remaining herbicide at the end of the working day and where
they washed their equipment and hands.  The normal procedure was to empty the
remaining contents of "squirt cans" and all wash water on the ground.  Severe
damage to vegetation at these sites suggested high concentrations of the
herbicide.  When this method of disposal of excess pesticide and wash water
was discontinued, no further mortality of hares was observed in this area.
Samples of soil, forest floor material and vegetation from the "wash areas"
contained high levels of arsenic.

     Two hares were collected 2 and 42 days following treatment with arsenical
herbicide in another area in eastern Washington.  They did not contain
detectable arsenic residues.  Five other hares collected in western Washington
232 days after treatment contained either extremely low or nondetectable
arsenic residues.

     In a comparison test, Harr  (1971)i/ studied the effects of a diet
containing 50 ppm MSMA on rabbits.  This study was still in progress at the
time of Norris1 report.  Early observations indicated a 35% reduction in food
intake in rabbits exposed for 14 days.  The animals showed considerable
intestinal inflammation and congestion, indicating that this level of MSMA
produces  considerable sublethal chronic toxicity.

     In another related study, Maycumber  (1971)' evaluated the exposure of
cattle grazing in areas treated with arsenical herbicides including MSMA.
 I/  Harr,  J.  R.,  "Functional,  Histologic,  and Residue Effects  of MSMA  in
       Rabbits," contained in Norris,  op.  cit. (1971).
 2J  Maycumber,  H. C.,  "Arsenic Residues in Cattle Grazed  in Treated Areas,"
       contained in Norris, op. cit.  (1971).
                                        56

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Pre- and post-exposure samples of hair were collected from 37 head of  adult
cattle grazing in 1970 in a forest area treated with an .arsenical herbicide
which was also the same area where cattle mortality had been observed  in  1969.
Similar samples were collected from 28 other head of cattle which grazed  in
another forest area treated with a commercial formulation of MSMA (48.47%
purity; 6 Ib/gal).  There was no cattle mortality reported in either of the  2
test areas.  There was a statistically significant (at the 5% level) increase
in arsenic concentrations between pre- and post-exposure samples at both  sites.
There was no significant difference in arsenic levels between the 2 sites in
samples collected at a given time.

     Two cows from the MSMA-exposed group and one female deer trapped  in  the
test area were sacrificed for examination of tissues for arsenic residues and
arsenic-induced lesions.   There was no cow mortality in either of the  2 test
areas.  No arsenic-induced lesions, and no detectable arsenic residues were
found in samples of blood, liver, kidney, lungs, heart,  muscle, spleen, tongue,
brain, paunch content, or udder of the 2 sacrificed cows.   The analytical
method used was sensitive to arsenic residues as low as  0.2 ppm.  Hard tissues
(bone, hair, skin)  were apparently not analyzed (Maycumber 1971).

     As with all pesticides having wildlife dietary toxicity values greater  than
500 ppm, registered labels of MSMA- and DSMA-containing pesticides do not carry
specific warning or caution statements in regard to wildlife toxicity.  They do
include the general statement: "Do not feed treated forage to livestock or graze
treated areas."

     Data from laboratory investigations on the toxicity of methanearsonates
to laboratory animals indicates that their acute oral toxicity is relatively low.
However, observations from field studies conducted in the Pacific Northwest,  as
reported by Norris (1971), indicate misuse of these herbicides or careless
dumping of excess spray mixture must be avoided.

Effects on Beneficial Insects

     In toxicity tests on honeybees (Apis mellifera),  Atkins  et al.  (1973)i'
summarized the effects of a large number of pesticides and other agricultural
chemicals.   Using a laboratory procedure which primarily measures a pesticide's
contact effect, pesticides were applied in dust form to  groups of 25 bees
per test level, 3 replicates per each of 3 colonies,  for a total of 9 repli-
cates per test level.   The procedure permits determination of an LD^Q value
for each pesticide in micrograms of chemical per bee.

      Both MSMA and DSMA were  classified in  a category of pesticides considered
relatively nontoxic to honeybees.  Pesticides in this category, after  exposure
to honeybees  for 48 hr at 80F and a  65%  relative humidity, were found to be
nontoxic at equal to  or  greater  than  11 ug/bee.  DSMA produced  9,8% bee
mortality at  the rate of  217.55  ug/bee.
 17  Atkins,  E.  L.,  E. A.  Greywood,  and R. L, Macdonald,  "Toxicity  of  Pesticides
       and Other -Agricultural  Chemicals to Honey Bees," University  of
       California, Agricultural Extension  Report M-16, 37 pages  (1973),

                                      57

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     Moffett et al. (1972)!/ studied the effect of MSMA and several other
herbicides on honeybees.  About 50 bees were collected, caged in a 2 x 2 x 6 in.
wire pen, and fed 60% sucrose syrup and distilled water.  The next day  dead
bees were removed from the cage, and the remaining live bees were sprayed with
MSMA in aqueous solution at a rate equivalent to 4 Ib in 20 gal/acre.  Dead
bees were counted daily for 14 days after spraying.  Each treatment was
replicated 5 times.  MSMA was "extremely toxic to sprayed bees."  Bee mortality
was about 70% 3 days after spraying.

     Morton et al.  (1972)1/ and Morton and Moffett (1972)!/ studied the toxicity
of herbicides, including MSMA and DSMA, fed orally to honeybees.  The test
herbicides were fed to newly emerged worker honeybees in 60% sucrose syrup at
concentrations of 0, 10, 100, and 1,000 ppm by weight.  MSMA and DSMA were
found to be extremely toxic at 100 and 1,000 ppm by weight concentrations.
MAA, MSMA and DSMA were among the most toxic of all compounds tested; toxicity
increased with increasing concentration.  At the rate of 1,000 ppm by weight,
50% of the test bees were killed in 2.5 days by MSMA; 1.2 days by DSMA; and 1.5
days by MAA.

     The findings of Moffett et al. (1972), Morton et al. (1972) and
Morton and Moffett  (1972) regarding the bee toxicity of MSMA and DSMA appear
to be at variance with those of Atkins et al.  (1973).  Atkins et al. (1973)
applied pesticides  to honeybees in dust form, whereas Moffett et al. (1972)
applied aqueous sprays, and Morton et al. (1972) and Morton and Moffett (1972)
applied the herbicides orally in sucrose syrup.  MSMA and DSMA appear to be
more toxic when applied to honeybees topically in aqueous solution (Moffett
et al. 1972) and orally in sucrose syrup (Morton and Moffett 1972) than when
applied topically in a dry dust form (Atkins et al. 1973).

     Newton and Holt (1971)' reported an interesting observation on the
mortality of 2 species of Coleoptera in Ponderosa pines injected with MSMA
and other arsenical herbicides.  The 2 insects involved were pests, rather
than beneficial insects.

     Treatments consisted of MSMA at 6.67 Ib Al/gal, applied by injection
with a "Hypo-Hatchet" tree injector at waist height.  A volume of about 1.3 ml
of undiluted material was applied in each injection.  In the treatment area,
the presence of all insects under observation was confirmed in scattered dead
or dying trees.  For the control, plots were thinned with other treatments,
including felling and nonarsenical injection.
I/  Moffett, J. 0., H. L. Morton, and R. H. Macdonald, "Toxicity of Some
      Herbicidal Sprays to Honey Bees," J. Econ. Entomol., 65(l):32-36 (1972).
2/  Morton, H. L., J. 0. Moffett, and R. H. Macdonald, "Toxicity of Herbicides
      to Newly Emerged Honey Bees," Environ. Entomol., 1(1):102-104 (1972).
_3/  Morton, H. L., and J. 0. Moffett, "Effects of Herbicides on Honey Bees,"
      Proc. West. Soc. Weed Sci.. 25:15-16 (1972).
4/  Newton, M., and H. A. Holt, "Scolytid and Buprestid Mortality in
      Ponderosa Pines Injected with Organic Arsenicals," J. Econ. Entomol.,
      64(4):952-958 (1971).
                                        58

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     All organic arsenical treatments resulted in lower attack levels on  the
treated trees than on the control trees by the insects studied, including the
mountain pine beetle (Dendroctonus ponderosae) and the pine engraver (Ips pini).
No larvae of these species were found alive.  There was much evidence of  larval
mortality and hatch failure.  The authors speculate that an endometatoxic
reaction involving reduction of the organic arsenicals to arsines may be  a
possible explanation for the insecticidal effectiveness observed.

     However, the controls in the experiment consisted only of untreated
felled trees, which beetles preferentially attack, even over dead  standing
trees (Nagel et al. 1957) .I/


Interactions with Lower Terrestrial Organisms

     Studies on the interactions between arsenicals and microorganisms date
back to the early nineteenth century.  Gosio, an Italian researcher, stated
that certain fungi including Aspergillus glaucus, Aspergillus virens,
Mucor mucedo, Mucor ramosus, and Penicillium brevicaule produce a
poisonous gas from moldy wallpaper caused by arsenic in the pigment.  This
gas became known in the literature as "Gosio-gas"; Gosio himself believed
it to be an alkyl arsine.  Challenger et al.  (1933)2.7 and Challenger and
Higginbottom (1935)1'  were the first to identify "Gosio-gas" correctly
as trimethylarsine.  They demonstrated that a strain of Penicillium
brevicaule added to culture media containing sodium methylarsonate produced
trimethylarsine.  A large number of experiments was conducted in an effort
to classify the mechanism of this biological methylation.   Results were
inconclusive.  In the course of the studies,  it was found that three
bacterial species, Bacterium mesentericus vulgatis, Bacterium mesentericus
ruber,  and Bacterium subtilis, did not give off the typical garlic odor of
trimethylarsine when added to glucose-meat extracts (at 37C)  that were tested
separately with several organic and inorganic arsenical compounds.

     More recently, McBride and Wolfe (1971)' showed that cell extracts  and
whole cells of a strain of Methanobacterium methylate and reduce arsenate
to dimethylarsine under anaerobic conditions.  These preparations produced
dimethylarsine from arsenate, arsenite, and methylarsonic acid.   The process
involves a series of methylations and reductions and requires adenosine
triphosphate, hydrogen, and a methyl donor (l^C-methylcobalamin).   in the
pathway, arsenate is reduced to arsenite which is methylated to form MAA.
Dimethylarsinic acid,  formed by the reductive methylation of MAA,  is reduced
_!/  Nagel, R. H., D. McComb, and F. B. Knight, "Trap Tree Method for Controlling
      the Engelmann Spruce Beetle in Colorado," J. Forestry. 55(12):894-898 (1957)
2/  Challenger, F., C. Higginbottom, and L. Ellis, "The Formation of Organometal-
      loidal Compounds by Microorganisms, Part 1.  Trimethylarsine and Dimethyl-
      ethylarsine," J. Chem. Soc. Trans., pp. 95-101 (1933).
3/  Challenger, F., and C. Higginbottom, "The Production of Trimethylarsine by
      Penicillium brevicaule (Scopulariopsis brevicaulis)," Biochem. J.,
      29:1757-1778 (1935).
47  McBride, B. C.,, and R. S. Wolfe, "Biosynthesis of Dimethylarsine by
      Methanobacterium," Biochemistry, 10(23):4312-4317 (1971).

                                       59

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to dimethylarsine.  The authors point out that pollution hazards exist when
arscaic and its derivatives are introduced into an environment where anaerobic
organisms are growing.

     Von Endt et al.  (1968)i/ studied the degradation of MSMA by soil
microorganisms.  Four types of soil  (Sharkey clay, Hagerstown silty clay
loam, Cecil sandy loam, and Dundee silty clay loam) were treated with
^C-labeled MSMA at 10 and 100 ppm.  All soils were initially adjusted to
field capacity and incubated for  21  to 60 days at 28 to 30C.  Steam-sterilized
soils served as controls.  Measurement of evolved l^cc^ indicated that from
1.7 to 10.0% of the MSMA was degraded in nonsterile soil, as compared to 0.7%
in steam-sterilized controls.  The rate of C02 evolution was proportional to
the organic matter content of the soils studied.  The authors concluded that
soil microorganisms appear to play some role in the decomposition of MSMA.
In additional tests,  4 soil microorganisms  (1 fungus, 2 actinomycetes, and
1 bacterium not further identified), isolated in pure culture degraded from
3 to 20% of the MSMA  to C02 when  grown in liquid culture containing 10 ppm
of MSMA and 1 g/liter of yeast extract.  Thin-layer chromatographic analysis
(capable of separating MSMA, arsenate, and  arsenite) discovered only arsenate
and MSMA in extracts  from the soil and from the microbial cultures examined.
This data  supports the assumption that soil microorganisms  are at least
partly responsible for MSMA degradation in  the soil.  The authors pointed out
that the metabolism of most organic  herbicides leads to the formation of less
toxic products.   By contrast, they reported that the metabolism of DSMA in
soils yields the  inorganic arsenate, a compound that is 10  to 25 times more
toxic than the parent herbicide.

     Newton  (1971)-2-/  also studied the microbial degradation of MSMA.  In the
introduction to his paper, Newton presents  an excellent overview of previous
work, including a comment on possible sources of errors in  the conclusion
reached by Von Endt et al.  (1968) as reported in the preceding paragraph.
Newton points out that the chromatographic  techniques used  by Von Endt et al.
would not  have registered the presence of arsines, and that they may have
overlooked the possibility that  some of the radioactivity may have been lost
through volatilization of arsines.

     Newton  inoculated Czapek-Dox agar containing various levels of arsenicals
with molds cultured  from wood.   Glucose was added as an energy source to some
cultures,  while others were glucose-free.   After 2 weeks incubation, it was
observed  that cultures supporting colonies  of molds and containing glucose
were producing the characteristic garlic odor from substrates containing up
to  50,000  ppm MSMA.   Further tests were then set up to investigate the
 I/  Von Endt,  D.  W.,  P.  C.  Kearney,  and D.  D.  Kaufman,  "Degradation of Mono-
       sodium Methanearsonic Acid by  Soil Microorganisms," Agr.  Food Chem.,
       16(1):17-20 (1968).
 2J  Newton,  M.,  "Organic Arsenicals:  Breakdown in Forest Trees and in Media
       Containing Energy Sources - A  Progress Report," Oregon State University,
       Corvallis,  Oregon, unpublished report, submitted to Environmental
       Protection Agency (1971).
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relationship between the energy source in the substrate and the ability of
molds to produce arsine from MSMA at concentrations of 100, 1,000, and 10,000
ppm.  Substantial losses of arsenic occurred at all levels of glucose, and at
all 3 concentrations of MSMA.  These losses occurred through volatilization
at temperatures below 70C.  It was concluded that high concentrations of
organic arsenicals are subject to attack by molds and perhaps other micro-
organisms.  Arsines appear to be the principal metabolites responsible for
escape of arsenic from the cultures.  The findings indicate that there may be
substantial losses of arsenic through volatilization following applications
of organic arsenical herbicides.  The author suggests that the role of organic
arsenical herbicides as persistent compounds needs to be reexamined.

     May (1974)i/ conducted a series of tests to determine if soil
microorganisms contribute to the degradation of arsenical herbicides,
including MSMA.  The test herbicides were added to soil samples collected
in 4 areas of the country:  California, Alabama, Central Plains of Texas,
and the Rio Grande Valley of Texas.  MSMA was added to the soil samples at
a concentration of about 50 ppm (27.0 ppm of elemental arsenic).  One-half
of the soil samples were-sterilized by autoclaving prior to addition of the
herbicides.  Finally, all samples were again subdivided, and about 1 g of
corn syrup was added to one-half of the samples to evaluate the effect of
an energy source.  All samples were exposed to sunshine.  The weight of each
sample was checked periodically, and water was added to bring the sample
back to its original weight if a loss had occurred.  Periodically, aliquots
were analyzed for arsenic residues and evaluated for the microbial population.
The isolations indicated that there was no apparent toxicity to the soil
microbes due to the presence of the arsenical herbicides.  Analysis of soil
samples for elemental arsenic after 60 days showed considerable variations.

     Stojanovic et al. (1972)-2./ studied the biodegradation  and the effects
on the soil microflora of a number of pesticides, including DSMA, with a
view to the disposal of large quantities of pesticides in the soil.  A
calcareous West Point loam soil was amended with 5 tons/acre of DSMA AI
and subsequently incubated for 56 days.  The extent of biodegradation was
estimated from the quantity of C02 evolved during the incubation period.  The
effects on microbial populations were determined from plate counts of the
incubated samples.  Based on the rate of C0 evolution, DSMA was not
appreciably degraded under these conditions; it inhibited the C02 evolution
rate by about 9% when compared to the control (soil alone).  -When a DSMA
liquid formulation was incubated with soil in the same manner, there was a
23% inhibition of C02 evolution compared to the control.  In comparison to
soil alone, DSMA inhibited bacterial growth, stimulated the growth of
Streptomyces, and somewhat inhibited the growth of soil fungi.  The findings
indicate that excessive concentrations of DSMA in edaphic environments are
 .!/  May,  K J.,  Microbial Degradation of  Organic  Arsenicals,  The Ansul Company,
       Agrichemical Development Center,  Weslaco, Texas,  Project  No.  32531-71208,
       Report (1974).
 2J  Stojanovic,  B. J.,  M. V.  Kennedy,  and F.  L. Shuman,  Jr.,  "Edaphic Aspects
       of  the Disposal of Unused Pesticides, Pesticide Wastes,  and Pesticide
       Containers," 3. Environ. Qual.,  1(1)^54-62  (1972).


                                        61

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likely to produce shifts in microbial populations and temporarily to favor
microorganisms which may overpopulate the soil and thus create a condition
which in some respects is comparable to partial sterilization.

     Khurana and Singh (1972)!/ investigated the growth response of
Curvularia lunata to 11 herbicides in liquid culture.  MSMA stimulated the
growth of the fungus, whereas several other herbicides caused inhibition.

     Laird and Newton  (1973)2/  studied  the effects of MSMA. and other
herbicides on invasion of western hemlock by the  fungus Fomes annosus.
The herbicides were  used as  chemical thinning  agents by waist-high 'injections
into the trees.  Six months  later,  injection wounds of trees  treated with
MSMA. were not infected.
Residues  in Soil

      Laboratory and Field "Studies  - The degradation of  organoarsenicals
in soil is  complex.  In its  fullest sense,  degradation  is  the  complete
mineralization of the herbicide molecule (Woolson 1974).$/ Arsenic
compounds are normal soil components and arsenic contributes about 4
ppm (dry  weight) to most plants.  Consequently,  most plants are not
adversely affected until high arsenic concentrations are reached  in
soils.  According to Woolson et al. (1970a) ,A/ arsenic  concentrations
of about  250 ppm in the upper 6 in of soil  reduced the  growth  of  4-week-
old corn  by about 50%.  Under these conditions,  dry plant  material contained
about 10  ppm arsenic (dry weight).  Generally, the arsenic level  required
for phytotoxicity is variable, and is influenced by the chemical  form
of the arsenic residues, soil fertility level, iron and arsenic in the
soil, and plant vigor.

      The  organic portion of  organoarsenicals can be metabolized.  Metabolism
may include reduction in a volatile compound, which then escapes  to
 the air (Woolson 1974).
 If   Khurana, S.M.P.A., and S. Singh, "Growth Response of Curvularia
        lunata to Various Herbicides in Liquid Culture, "Chem.  Mikrobiol.
        Technol. Lebensm.t 2:63-65 (1972).
 2j   Laird, P.P., and M. Newton, "Contrasting Effects of Two Herbicides  on
        Invasion by Fomes annosus in Tree-Injector Wounds on Western Hemlock,"
        Plant Pis. Rep., 57(1):94-96 (1973).
 3/   Woolson, E.A., "Organoarsenical Herbicides."  Contained in:  P.C.  Kearney
        and D.D. Kaufman, eds., Degradation of Herbicides, 2nd  ed., Marcel
        Dekker, Inc., New York, New York, in press (1974).
 47   Woolson, E.A., J.H. Axley, and P.C. Kearney, "Arsenic Research Summary,"
        U.S. Department of Agriculture, Agricultural Research Service,  Crops
        Protection Research Branch, Pesticide Investigations, unpublished
        report (1970a).
                                        62'

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     Schweizer (1967a, 1967b)il/ studied the toxicity of DSMA soil residues
on cotton, rice, soybeans, oats, corn, and wheat.  Soils studied included
Bosket silt loam (pH 7.9), collected from an undisturbed "creek bank, and
Dubbs silt loam (pH 6.4) and Sharkey clay (pH 6.3) collected from fallowed
fields.  The Bosket and Dubbs silt loams were low-phosphorus soils, the
Sharkey clay a high-phosphorus soil.  Growth of cotton planted immediately
after incorporation of DSMA in Bosket silt loam was reduced significantly
by DSMA concentrations of 50 to 80 ppm by weight.  This phytotoxicity
decreased with time, particularly during the first 16 weeks.  DSMA incor-
porated into the same silt loam at 120 ppm by weight did not significantly
inhibit the growth of cotton planted 32 weeks later.  The addition of
phosphorus (40 to 320 ppm by weight) increased the toxicity of DSMA to
cotton, while added phosphorus increased cotton growth in the absence of
DSMA.  This effect of phosphorus on the phytotoxicity of DSMA was much more
pronounced in the low-phosphorus than in the high-phosphorus silt loam.

     Schweizer also investigated the effect of 50 ppm by weight of DSMA on
corn, oats, rice, soybeans, and wheat, when incorporated into the Bosket silt
loam.  Rice was the most susceptible crop; wheat was the most tolerant.
Growth of rice in the DSMA-treated soil was inhibited by 75%; soybeans by
39%; oats by 12%; corn and cotton by 10%; and wheat by 0%.  In a further
study, the growth of rice planted in Bosket silt loam 4 weeks after treatment
was significantly inhibited at concentrations of DSMA of 5 ppm by weight
or more.  However, in rice planted 12 weeks after treatment, no toxic residues
of DSMA from an initial application as high as 50 ppm by weight were detected.
There was no effect on the growth of rice planted in the other two soils 4
weeks after application of DSMA at concentrations as high as 100 ppm by
weight.

     It is noteworthy that in Schweizer's tests, DSMA was thoroughly incor-
porated into the soil, whereas under field use conditions, the herbicide is
applied to the surfaces of target plants and soil.

     Johnson and Hiltbold (1969)'  studied the arsenic content of soil and
crops following use of MSMA and DSMA.  The distribution of arsenic at
different soil depths was determined after 4 years of repeated applications
of these herbicides to turf (established common Bermuda grass,  Cynodon
dactylon) on Chesterfield sandy loam, pH about 5.5.  MSMA and DSMA were
applied as sprays at the rates of 2, 4, and 8 Ib Al/acre four times each
summer during the 1962-1965 period.  Soil was not disturbed.  The Bermuda
grass was mowed as needed and clippings removed.  Fertilization adequate
for good turf growth was maintained, but there was no irrigation.  Over
I/  Schweizer, E. E., Effects of Residues of DSMA in Soils on Cotton,
      Soybeans, and Cereal Crops, Mississippi State University, Agricultural
      Experiment Station, State College, Mississippi, Bulletin 736 (1967a).
2/  Schweizer, E. E., "Toxicity of DSMA Soil Residues to Cotton and
      Rotational Crops." Weeds, 15(1):72-76 (1967b).
,3/  Johnson, L. R., and A. E. Hiltbold, "Arsenic Content of Soil and Crops
      Following Use of Methanearsonate Herbicides," Soil Sci. Soc. Amer.
      Proc.. 33(2):279-282 (1969).
                                       63

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the 4-yr treatment period, the total arsenic applied as MSMA was equivalent
to 14.7, 29.4, and 58.7 Ib arsenic/acre, respectively.  DSMA provided 12.9,
25.8, and 51.6 Ib arsenic/acre.

     When soil samples were analyzed for arsenic content at the end of this
4-yr treatment regimen, arsenic concentrations were highest in the upper 2 in
of soil; they decreased with increasing depth.  There was little difference
in the soil arsenic content between the methanearsonates at similar application
rates.  The arsenic content of soils in the check plots was then subtracted
from that found in the treated plots to provide an estimate of the distribution
of the applied arsenic.  Essentially all of the arsenic applied at the rate of
2 Ib/acre was accounted for within the upper 12 in of soil.  Recovery decreased
to about 75% at the 4 Ib Al/acre rate, and to about 50% at the 8 Ib Al/acre
rate.  Yields of cotton, soybeans, sorghum, corn, oats, vetch, and crimson
clover planted in the treated plots in the fifth year were not affected by any
of the organoarsenical treatments.

     About 90% of the soil arsenic content occurred in the clay fraction,
associated with aluminum.  By contrast, most of the soil phosphorus was
associated with iron minerals and organic matter.  These results indicate a
considerable difference between arsenic and phosphorus distribution among
chemical and mineral forms in the soil.  Arsenic is much more extractable by
mild salt solutions, suggesting a greater water solubility and lower extent of
adsorption, precipitation, or occlusion.  Organic forms of arsenic were not
found in appreciable concentrations.  The authors attribute the incomplete
recoveries of arsenic from the high-rate treatments to removal in the form of
residues in harvested crops or leaching below the root zone.  Regarding the
possible development of arsenic toxicity in soils from the continued use of
organoarsenicals, the authors suggest that erosion, leaching, and crop removal
probably preclude hazardous accumulations of arsenic in most soils treated with
normal  rates of methylarsenates for weed control.

     Hamilton and Arle  (1968)1/ studied the effects of herbicide residues in
irrigated soils in Arizona on crops planted in fields that had been treated the
previous year.  In field  tests at Mesa, Arizona, herbicides were applied to a
soil containing 42% sand, 37% silt, and 21% clay, and disk-incorporated.
Barley  and safflower were planted each winter, and cotton and sorghum each
summer  for 3  successive years following the original application.  DSMA,
applied at the unusually  high rate of 120 Ib Al/acre, had no visible effect on
any  crop in any year.   It was the least phytotoxic of all herbicides studied
under these conditions.

                          7/
     Baker et al.  (1969),' in field experiments, investigated the effects of
organic arsenical herbicides on cotton and on the arsenic content of soils in
California, Arizona, and  Mississippi.  Among the methods of application
 I/  Hamilton,  K.  C.,  and H.  F.  Arle,  "Herbicide Residues in Irrigated Soils,"
       Progr.  Agr. in Arizona,  21(2):16-17 (1968).
 2J  Baker, R.  S., H.  F.  Arle,  J.  H. Miller,  and J.  T.  Holstun,  Jr.,  "Effects
       of Organic  Arsenical Herbicides on Cotton Response and Chemical
       Residues,"  Weed Sci.,  17(1):37-40 (1969).
                                       64

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 studied were  1)  application  of  directed  sprays  to  cover small weeds in the
 drill  row having minimal  contact  on  cotton leaves  more  than 2 to 3 in above
 the  ground, and  2) the application,  by nozzle,  of  topical  sprays which covered
 the  entire cotton plant.  MSMA  and DSMA  were  applied  at 2  or 3 Ib/acre in 2 or
 3 applications on different  plots.   Cotton was  highly tolerant to directed
 applications.  Topical applications  to young  cotton  (2  to  4 in high)  reduced
 yields slightly, but topical applications  at  later stages  of growth caused
 progressively severe yield reductions and  delayed  maturity.   The effect of
 the  treatments on the arsenic contents of  soils was relatively small  in
 comparison to naturally occurring arsenic  levels.

     Lange and Fischer (1971)-=-' investigated  the residual  characteristics of
 a number of herbicides including  MSMA in California for more than 7 yr at
 various locations throughout the  State,  from  Tulelake in the north to El
 Centro in the south.  MSMA was  studied in  one test at the  West Side Field
 Station near  Five Points, California.  The soil consisted  of 2.8% organic
 matter, 24% sand, 44% silt^  and 31%  clay.   Irrigation and  rainfall water over
 a 12-month period was 69  in.  MSMA. was applied  to  the soil surface at the rates
 of 16, 64, and 256 Ib Al/acre,  followed  by sprinkler  irrigation,  without
 incorporation.   Four months  after application,  6 crops  (barley,  milo,  lettuce,
 sugar  beets,  broccoli, tomatoes)  were planted and  evaluated  for  symptoms of
 phytotoxicity.   Eight months after treatment, 4 new crops  (barley,  milo,
 cotton, and tomatoes) were seeded and allowed to grow for  about  1 month.
 They were then evaluated  and burned  down.   One  yr  after the  initial appli-
 cation, another  6 crops (barley,  canary  grass,  safflower,  sugar  beets,  lettuce,
 and  carrots)  were planted and evaluated.   MSMA  at  the unusually  high  rate of
 256  Ib/acre was  slightly  phytotoxic  to barley at 4 months, but virtually non-
 phytotoxic at 8  months.   No  phytotoxicity  to  any crop at any time was observed
 at the 16 and 64 Ib/acre  rates, nor  to crops  other than barley at the 256
 Ib/acre rate.

     Sandberg et al. (1973).?-/ studied the  effects  of  6  annual  applications  of
 MSMA on arsenic  residues  in  soil.  MSMA was applied near Weslaco,  Texas,  for
 6 consecutive years at the rates  of  2.0  and 6.0 Ib Al/acre per year.   Soil
 cores  were collected at the  end of each  growing season  at  3  different  depths
 ranging from  0 to 18 in.  After 6 annual applications,  both  rates  of MSMA
 resulted in statistically significant buildup of arsenic in  the upper  6  in  of
 soil (3.3 to  4.5 ppm arsenic above an average background of  11.0  ppm arsenic).
 Arsenic residues in the 6- to 12-in  soil layer were increased  only by  the
 higher rate of MSMA, and the arsenic residue  levels at  the depths  of 12  to
 18 in were not affected by any of the MSMA treatments.

     During the  study period, a total of 4.9 and 16.6 Ib of  elemental  arsenic
 were applied  in  the form of MSMA  at  the  2  treatment levels.  These  figures
_!/  Lange, A. H., and B. B. Fischer, Studies of Herbicide Residues and
      Various Cultural Practices, University of California, Agricultural
      Extension, MA-35, 16 p. (1971).
2J  Sandberg, G. R., I. K. Allen, and E. A. Dietz, Jr., Arsenic Residues in
      Soils Treated with Six Annual Applications of MSMA and Cacodylic
      Acid (CA), The Ansul Company, Marinette, Wisconsin, Report 73 Wes
      8-9-10, Project No. 32532-73312, 82 p. (1973).

                                        65

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were converted to parts per million of arsenic in the soil and added to the
measured average background arsenic levels to arrive at the total arsenic
level what would be expected in the soil after 6 yr of treatment.  For the
2.0 Ib/acre MSMA rate, the total added arsenic was 2.4 ppm.  When added
to the 11.0 ppm background, the total arsenic level should have equaled
13.4 ppm; 13.3 ppm of arsenic were actually found.  For .the 6.0 Ib/acre
MSMA treatment series, the calculated level of arsenic was 19.3 ppm;
however, 16.1 ppm arsenic were found, a deficient equivalent to 16.5% of
the predicted concentration.

     Speculating about possible reasons for these deficits, the authors
reject leaching losses because throughout the entire 6-year test period,
there was no significant accumulation of arsenic residues in the 12- to
18-in soil horizon.  Microbial reduction of organic arsenicals to gaseous
methyl arsines appears to be a more plausible loss mechanism.  They further
suggest that the rate of reduction depends on the amount of organic
arsenicals applied to the soil; the amount of arsenic "lost" from the soil
in this study was proportional to the amount of organic arsenic added.  Less
than 1% of the added arsenic was not recovered at the lowest rate of arsenic
applied, while 28% of the applied arsenic was not recoverable in the plots
treated at the highest rate of arsenic.  The authors hypothesize that if
their assumptions are correct, an equilibrium will eventually be reached in
which loss mechanisms would remove arsenic from the soil at the same rate as
it is applied.   (The question of the fate of the "escaping" quantities of
arsenicals was not reported.)

     The  treatment rates  of MSMA selected  for  this  study  are  equivalent  to  the
 recommended,  and 3 times  the  recommended,  single  treatment  dose.  Two Ib MSMA/
 acre is  the  recommended rate  for a  single  application;  the  6  Ib/acre rate
 corresponds  to  the cumulative  seasonal  dose  of  3  separate applications.

     In a companion  study reported by Raab  (1970),' MSMA was applied to
 Texas sandy  clay loam plots with an organic matter content  of 1.5% near
Weslaco,  Texas.  Treatment rates were 2.0 and  6.0 Ib Al/acre annually, and
 20  to 60  Ib  Al/acre  applied the first year only.  In each case, the
 herbicide was applied in  a water solution directly  to the soil surface.  On
 the day  of treatment  agronomic crops,  including  corn,  sorghum, cotton, soy-
beans, sugar beets,  and wheat  were planted.  At  the appropriate stage of
 growth,  corn and sorghum  fodder samples were harvested  for  forage.  The corn,
 sorghum,  seed cotton, soybean, wheat, and  sugar beets were  harvested at
 maturity  for yields.  Samples  of all harvested products were analyzed for
 arsenic residues.  The yield  of soybeans planted  immediately after the
 highest application  rate  of MSMA  (60 Ib/acre) was reduced to about 25% of
 the untreated control.   There were  no  significant adverse effects  on the
 yields  of any of the other crops  from any  of the  single MSMA treatments  in
 the first year,  nor  from the  repeat  treatments at the  lower 2  rates  (2.0
 and 6.0  Ib Al/acre)  the  following year.
 _!/  Raab,  H.,  MSMA Museum Plots,  Ansul Test Station,  Weslaco,  Texas,
       The Ansul Company Report,  (1970).
                                        66

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     In an earlier study reported by Ehman (1967),  plots of loamy fine sand
in Fairfax, South Carolina, were sprayed in 1964 with DSMA at 15, 50, and 100
Ib Al/acre.  On the same day, cotton, soybeans, sorghum, and peanuts were
planted in these plots.  Because of stunting, the initial peanuts had to be
replanted one month later.   Cotton, soybeans, and sorghum grew normally at
the 15 Ib/acre rate.   There was some stunting at the 2 higher rates.  This
abated somewhat as the season progressed, especially in the plots treated at
50 Ib Al/acre.  The same plots, without retreatment, were planted to cotton,
soybeans, sorghum, peanuts, oats, corn, and tobacco the following year.  There
were no apparent adverse effects on these crops from the DSMA treatments
applied the previous year.

     Norris (1971) summarized the results of extensive studies in the Pacific
Northwest in which a number of different investigators participated.  The
objective of these investigations was to evaluate the behavior and impact of
organic arsenical herbicides in the forest environment.  One of the tests
(Canutt et al. 1971)!/ studied the contribution of single-tree treatment with
organic arsenical herbicides (as is customary in commercial thinning practices)
to arsenic residues in the forest floor, soil, and vegetation.  Five trees of
each of 3 timber types were treated with MSMA in line with operational
practices.  Samples of forest floor material, soil, and vegetation were
collected at points one-half, 2 and 4 times the crown radius at 0, 6, and 40
weeks after treatment.  Analytical data at the first sampling after treatment
indicated a rise in the concentration of arsenic in forest floor material from
one treatment area.  Most of the remaining analytical values showed only small
changes in arsenic content.  Norris concluded:  "Injection of trees with MSMA
increased the arsenic level of forest floor material but not soil collected
6 weeks after treatment."
                                3 /
     Dickens and Hiltbold (1967)  studied the movement and persistence of
methylarsonates in soil, including soil adsorption from solutions of DSMA,
effects of soil type and pH on the leaching of surface-applied DSMA, and
effects of soil type and added organic matter on the oxidation of methylear-
sonates.  Soils studied included Norfolk loamy sand, Augusta silt loam, Decatur
clay loam, and Vaiden clay.  Soil pH ranged from 6.0 to 6.2 in the first 3
soils, and was 5.3 in the Vaiden clay.  Reference clay minerals that were also
studied included montmorillonite, kaolinite, litnonite, and vermiculite.
Adsorption on the natural soils and on the reference materials was determined
at initial DSMA concentrations equivalent to 0 to 25 ppm arsenic.  Kaolinite
removed much more DSMA from solution than did vermiculite.  Different size
fractions of Augusta silt loam adsorbed different percentages of DSMA, ranging
from 11 and 12% of the DSMA quantity applied for the silt and sand fractions,
I/  Ehman, P. J., Museum Plots - 1964, 1965, and 1967, The Ansul Company,
      Marinette, Wisconsin, Report, (1967).
2J  Canutt, P. R., L. Norris, and J. Allard, "Arsenic Residues in Forest
      Floor, Soil, Vegetation, and Water After Injecting Conifers with MSMA,'
      contained in Norris, op. cit. (1971).
31  Dickens, R., and A. E. Hiltbold, "Movement and Persistence of Methane-
      arsonates in Soil," Weeds, 15(4)=299-304 (1967).
                                        67

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respectively, to 100% of the applied concentrations for the clay fraction.
Adsorption by whole soils was generally related to their clay contents.

     In a leaching study in the laboratory, DSMA was applied to the surface
of Norfolk loamy sand and Decatur clay loam in columns 9 in long by 3.8 mm
internal diameter at a rate equivalent to 100 Ib of DSMA hexahydrate per
acre, or 3,287 mg arsenic per column.  Leaching with 20 successive 1-in
(30 ml) increments of water removed 52% of the applied DSMA from Norfolk
loamy sand.  Rates of movement of DSMA in this soil did not differ at 3 pH
levels (5.5, 6.1, and 6.5).  In the Decatur clay loam, about one-half of
the applied DSMA remained in the top 1 in of the column, and none was leached
below 6 in.  These widely differing leaching rates of DSMA in the 2 soils are
consistent with their respective adsorption capacities for DSMA.

     The rate of DSMA decomposition in the 4 soils mentioned above was deter-
mined in an additional laboratory experiment in which treated soil samples
were incubated for periods of time during which respiration and release of
C02 derived from l^C-labeled DSMA were measured.  After incubation of the
soils containing 210 ppm of the radio-labeled DSMA at 30C for 30 days, the
pattern of evolution of l^CC^ from Decatur, Augusta and Vaiden soils was
similar to that for total C02-  At 30 days, 0.7, 1.8 and 5.5% of the DSMA-
carbon in the soils, respectively, was evolved as CC^.  In the investigators'
opinions, this indicated that the oxidation of DSMA occurred coincidentally
with the metabolism of soil organic matter.  There was no indication of any
adaptive oxidation of DSMA in the soils with time.  In the Norfolk loamy sand,
there was increased decomposition of DSMA relative to soil organic matter at
the end of 30 days, suggesting an adaptation of the microbial population to
metabolize DSMA.  Decomposition of added ryegrass enhanced this process to the
extent that  16% of the methylcarbon was recovered as CC^.  The investigators
concluded that DSMA is decomposed under aerobic soil conditions and that the
'amount of organic matter available for microbial activity has a direct effect
on the rate of decomposition.

     Hiltbold et al.  (1974)i' investigated the distribution of arsenic in soil
profiles after repeated applications of MSMA in field and laboratory experiments.

     Field plots were set up at 3 locations in Alabama on level areas of Dothan
loamy sand,  Hartsells fine sandy loam, and Decatur silt 3oam.  Beginning in 1966,
MSMA was applied to these plots as broadcast spray prior to the planting of
cotton at  the rates of 8.9, 17.8 and 35.6 Ib Al/acre annually, corresponding to
2.5, 5, and  10 times normal use rates, for 6 consecutive seasons  (1966 to 1971).
Cumulative amounts of elemental arsenic applied amounted to 24, 49, and 98 Ib/
acre at the  end of the sixth year.  A soil core to a 35 in depth was obtained
from each  plot and sectioned into 6-in increments for analysis.  Residual
arsenic from MSMA was obtained as the difference between arsenic contents of
treated and  control samples.  Arsenic occurred throughout the sampling depth of
the untreated plots, ranging from 2.4 to 12.6 ppm.  Percentage recovery of
 I/   Hiltbold,  A.  E.,  B.  F.  Hajek,  and  G.  A.  Buchanan,  "Distribution of Arsenic
       in Soil  Profiles After Repeated  Applications  of  MSMA," Weed  Sci.,
       22(3):272-275 (1974).
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applied arsenic averaged 67% in Hartsells fine sandy loam; 57% in Decatur
silt loam; and 39% in Dothan loamy sand.  Essentially all of the arsenic
recovered in the soils occurred in the plow layer, with no evidence of
leaching into deeper zones.

     Batch equilibrium and soil column studies in the laboratory indicated
that the rate of MSMA movement through the surface horizon would be fastest
in Dothan loamy sand and slowest in Decatur silt loam.  The arsenic distri-
bution with depth measured in the field samples showed that movement of MSMA
was less in Decatur than in the other 2 soils.  In all soils, leaching in
the field was considerably less than adsorption coefficients for MSMA would
predict.  The authors suggest that this is probably due to MSMA decomposition
yielding an inorganic arsenate of lower mobility than MSMA.

     The reports reviewed in this subsection indicate that herbicidally
effective concentrations of MSMA and DSMA "disappear" rather rapidly from
field soils after application.  Microbial activity appears to contribute to
this degradation, at least to some extent.  Several different chemical
reactions seem to be involved.  There is some disagreement among different
investigators concerning the relative importance of different chemical
pathways, including reduction of the methanearsonate molecule to form volatile
methyl arsines that escape to the air; formation of inorganic arsenate;
formation of insoluble salts; adsorption on soil colloids; and ion exchange
reactions within the soil.

     A very informative tabular summary on the chemical and biological
transformations of arsenicals in soil has been prepared by Woolson (1974).

     Leaching of MSMA and DSMA through soil profiles appears to be inversely
related to the soil clay content.  The data reviewed indicates that under field
use conditions, leaching of these herbicides below the plow level is not likely
to occur to any appreciable extent, with the possible exception of very sandy
soils.

     A number of agronomic crops appear to be highly tolerant to MSMA or DSMA
residues in the soil, even at concentrations many times higher than those that
might result from the use of the contact herbicides in accordance with label
directions.

Monitoring Studies - In the 1969 National Soils Monitoring Program for pesti-
cides (Wiersma et al. 1972) ,i/ 1,729 samples of cropland soils from 43 states,
and 199 samples of nonpropland soils from 11 states, were collected.   All
samples were analyzed for arsenic residues by atomic absorption spectro-
photometry.  The minimum detection limit was 0.1 ppm, and the recovery value
for arsenic averaged 70%.  Results were corrected for percent recovery.   More
I/  Wiersma, G.  B.,  H.  Tai,  and P.  F.  Sand,  "Pesticide Residue Levels in
      Soils, FY 1969-National Soils Monitoring Program,"  Pest. Monit. J.,
      6(3):194-201 (1972).
                                       69

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elemental arsenic than other pesticide residues were found.  For example,
1,713 of the 1,726 sites sampled (99.3%) had detectable residues of arsenic,
ranging from 0.25 to 107.45 ppm, with a mean level of 6.43 ppm.  The authors
suggest that most of this arsenic was from natural sources, although
agricultural sources cannot be ruled out.  In the noncropland soil samples,
detectable arsenic residues were found in 195 of 198 sites sampled (98.5%),
ranging from 0.33 to 54.17 ppm; the mean level was 5.01 ppm.

     The highest arsenic residues in cropland soil across the United States
were found in the New England states and in New York, Pennsylvania, Ohio,
Kentucky, Arkansas, and North Dakota.  Among these states, only one,
Arkansas, is a cotton-growing state.  Thus, there were no correlations between
high soil residue levels of arsenic and the growing of cotton, the crop that
receives by far the greatest share of methanearsonate herbicide applications.
In a breakdown of arsenic residues by cropping regions, the mean arsenic
residues found in cotton regions were lower than those found in corn or
vegetable growing regions,, but higher than those found in general farming
or small grain farming regions, or regions with predominantly irrigated land.
Pesticide use records indicated that MSMA and DSMA were used at fewer than
0.5% of all sites sampled.

     In the National Soils Monitoring Program for pesticides in 1970 (Crockett
et al. 1970),  soil and crop samples were collected from 1,506 cropland sites
in 35 states,  ^esticide use records indicated that MSMA was used at 13 of
1,346 sites sampled, 0.97% of all sites.  DSMA was reportedly used at 6 sites,
0.45% of all 1,346 sites sampled.  The mean application rate of DSMA was 2.02
Ib Al/acre.  Eleven of the 13 reported MSMA uses were on cotton; all of the 6
DSMA uses were on cotton.  No analyses of soil or crop samples for arsenic
were performed in the 1970 program.

     The National Soils Monitoring Program did not collect samples in 1971,
but sampling was done in 1972.  Data from the 1972 program was not included in
this review since results were not available.
Residues  in Water

     Hartley  (1970)A/ reported on the monitoring of 7 canals in the Rio Grande
Area for  arsenic in  irrigation water following treatment of ditchbanks with
MSMA.  The canals were dewatered prior to the treatment, and the initial water
over the  treated area was  sampled for the first 4 hr and then analyzed for
arsenic content.  The maximum arsenic concentrations found were 0 ppm in 1
canal, less than 0.01 ppm  in 2 canals, 0.01 ppm in 3 canals, and 0.48 ppm in
1  canal.
 I/   Crockett, A.  B.,  G.  B. Wiersma, H. Tai, W. G. Mitchell, and P. J. Sand,
       "National  Soils Monitoring Program  for Pesticide Residues - FY 1970,"
       U.S.  Environmental Protection Agency, Technical Services Division,
       unpublished manuscript  (1970).
 21   Bartley, T.  R.,  "Abstract  of Progress Report on Herbicide Monitoring,"
       Proc. West. Soc. Weed Sci.,  23:65-66  (1970).
                                       70

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     In a study of a Bureau of Reclamation project on the Rio Grande, Salman
et al. (1972)i/ analyzed arsenic concentrations in irrigation water following
application of MSMA to ditchbanks of irrigation systems while ditches were
dewatered or full.  Samples of treated and untreated water were collected to
determine any increase in arsenic residues in the irrigation water following
herbicide applications.  The soil irrigated by these waters is estimated to
possibly contain anywhere from 1 to 70 ppm of naturally occurring arsenic.
MSMA was applied at rates ranging from 2.4 to 5.0 Ib Al/acre.  Three dewatered
laterals were treated by spraying both banks of the dry laterals.  One full
irrigation system was treated by spraying in a downstream direction during
application to both banks and the complete water surface.  Two other full
irrigation systems were treated by spraying downstream on one bank for about
2 miles and then spraying the other bank upstream for the same distance.
Maximum arsenic concentrations found in the first water released through 3
MSMA-treated ditchbank sections of dewatered laterals were 0.54, 0.12, and
0.29 ppm.  In all 3 laterals, arsenic concentrations dropped to 0.06 ppm or
less within 10 min.  The maximum arsenic concentration found in water in the
lateral in which the entire water surface along with the 2 banks was sprayed
was 0.86 ppm.  In the other 2 full laterals in which only the banks, but not
the water was treated, maximum arsenic concentration was 0.16 and 0.17 ppm
arsenic.  In all 3 instances, the arsenic concentration decreased rapidly
with time.

     Laterals treated while full showed lower maximum arsenic concentration
in the water than those treated while dewatered, except the one lateral where
the entire water surface was (inadvertently) sprayed.  Apparently, a greater
dilution of the herbicide is obtained when applied to a full system.
Calculations from the data collected indicate that from 0.002 to 0.04 Ib of
arsenic per acre treatment could reach farmland from a 24-hr, 6-in irrigation.

     When MSMA was used for forest thinning, in accordance with commercial
thinning practice in the studies reported by Norris (1971), an effort was made
to determine if any arsenic would be detectable in stream water collected
downstream from treated units (Canutt et al. 1971).  Five trees in each of
3 different timber types were treated with MSMA, according to commercial
practice, and water samples from a nearby stream were taken periodically at
points above and below treated areas.  No detectable arsenic residues were
found in stream water samples using an analytical technique sensitive to
0.01 ppm of arsenic.


Residues in Air

     There is some evidence that methanearsonates may be reduced and
methylated to form volatile methylarsines which escape to the air from
treated soil surfaces.  However, no data was found on the possible presence
I/  Salman, H. A., T. R. Hartley, and A. D. Summers, Progress Report of
      Residue Studies on Organic Arsenicals Used for Ditchbank Weed Control,
      U. S. Department of the Interior, Bureau of Reclamation, Report REC-
      ERC-72-37, 8 p. (1972).
                                       71

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and fate of such MSMA or DSMA degradation products in air.

     The Ansul Company (1971)i/ suggested that the degradation of MSMA and
DSMA via trimethylarsine is of a low order of magnitude since trimethylarsine
is rapidly oxidized in air to a non-volatile, pentavelent arsenical.
Trimethylarsine is spontaneously flammable in air.

     Newton (1971), based on studies reviewed in the subsection on lower
terrestrial organisms, reported the presence of high concentrations of organic
arsenicals, especially MAA, which are subject to attack by molds, and perhaps
other organisms.  According to Newton, "The disappearance of substantial
amounts of arsenic during an experiment procedure in which there were no
opportunities for los.s is conclusive evidence for loss by volatilization."
Because the boiling points of the organic arsines are 52.7*0 (for trimethyl-
arsine) or lower, and because the other volatile arsenic compounds implicated
have boiling points ranging above 150C, the conclusion is drawn that the arsines
are the principal metabolites responsible for escape of arsenic from these cul-
tures  (Lange 1956).!/ in consideration of the analogy to Challenger's work
(1951) ,.i' it is likely that trimethylarsine constitutes an important fraction
of the lost arsenic.
Bioaccumulation, Biomagnification

     Woolson et al.  (1974)A/ studied the accumulation of 14C-MSMA in a model
micro-ecosystem containing daphnids (Daphnia magna), crayfish  (Procambarus sp.),
algae (Oedogonium cardiacum), catfish  (Ictalurus punctatus), 10 kg of soil,
and 80 liters of water.  Crayfish bioconcentrated MSMA up to tenfold from
water containing 1 ppm of MSMA.  Homogenized crayfish were  fractionated in
order to isolate and identify the arsenical compounds present.  A single
compound (not MSMA)  was observed in the MSMA-treated crayfish.  Work is in
progress to identify these arsenic containing compounds.
_!/  The Ansul  Company,  "Comments  in  Support  of  Continued Registration of
      Organic  Arsenical Herbicides,  in Response to  the  Federal Register Arsenic
      and Lead Notice 36  FR 12079,"  unpublished report, Marinette, Wisconsin,
      55 pages (1971).
21  Lange, N.  A., Handbook of  Chemistry, Handbook Publishers, Inc.,  Sandusky,
      Ohio,  1,969 pages (1956).
_3/  Challenger,  F.,  "Biological Methylation," contained in:  F. F. Nord  (ed.),
      Advances in Enzymology,  Vol. 12, pp. 429-491,  Interscience Publisher,
      New York,  New  York  (1951).
4/  Woolson, E.  A.,  P.  C.  Kearney, A.  R. Isensee, W.  G. McShane, K.  J.  Irgolic,
      and R. A.  Zingaro,  "Bound Arsenic Fractions in a  Crustacean,"  American
      Chemical Soc., Division  of  Pesticide Chemistry, 168th  National Meeting,
      Atlantic City, New  Jersey  (1974).
                                      72

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     However, Isensee et al. (1973)i/ studied the distribution of 2 related
organic arsenicals among aquatic organisms in a model ecosystem, including
mosquitofish (Gambusia affinis), daphnids (Daphnia magna), snails (Physa sp.),
and algae (Oedogonium cardiacum).  These organisms were exposed to the arsenicals
for 3, 29, 32, and 33 days, respectively.  Algae and Daphnia bioaccumulated more
arsenicals than did the 2 higher food chain organisms, snails and fish.  The
amount of arsenicals accumulated indicates that they do not have a high potential
to biomagnify in the environment.  Daphnia magna concentrated the arsenicals
by about 2,000 times the water content at the time of sampling.  An increase in the
biomass in the system, primarily algae, over 32 days largely accounted for a
gradual loss of the test compounds from solution.

     These observations indicate that some aquatic organisms can accumulate
organic arsenicals to high levels.  However, organisms representing the higher
links in the food chain (snails and fish) had smaller bioaccumulation ratios
than lower link organisms (algae and Daphnia).
Environmental Transport Mechanisms

     Woolson (1974) proposed an environmental cycle for arsenic.  Major inputs
into the system come from air and water pollution and from pesticide usage.
Soil is the sink where arsenic ultimately returns.  Arsenic reaches man through
air, water and food.  Ingested arsenic is eliminated and returns to the water
or soil portions of the environment.  Plants and animals receive arsenic from
air or water pollution, from the soil, or from pesticide usage.  Arsenic
reaching the soil may begin the cycle of chemical transformation, precipita-
tion, and/or uptake once again.

     According to McBride and Wolfe(1971), arsenate may be converted to
dimethylarsine by a series of reduction and methylation steps in which MAA is
an intermediate.  Woolson(1974) suggests that the arsines produced are likely
oxidized back to MAA or cacodylic acid, or demethylated and returned to the
arsenate form in the soil.  Methylation as well as demethylation can occur in
the soil medium.
if  Isensee, A. R., P. C. Kearney, E. A. Woolson, G. E. Jones, and V. P.
      Williams, "Distribution of Alkyl Arsenicals in Model Ecosystems,"
      Environ. Sci. Technol., 7(9):841-845 (1973).
                                       73

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     Braman and Foreback (1973)i' analyzed environmental samples for arsenate
and arsenite ions and methylarsenic acids in nanogram amounts.  They detected
dimethylarsinic acid and MM in natural waters, bird eggshells, seashells, and
human urine.  According to the authors, the continued introduction of arsenic
compounds into the environment may eventually result in a general increase in
their concentrations in water and air due to the bacterial mobilization of all
forms of arsenic.  They further emphasized the need for information on the
effect of all forms of arsenic and ecological systems.

     Woolson et al. (1970b)^./ reported that the organic arsenates have about
the same leaching and fixing characteristics in the soil as shown by Dickens
and Hiltbold (1967) for inorganic arsenates.  Additionally, Von Endt et al.
(1968) have shown that MSMA is degraded to the inorganic arsenates so that,
ultimately, the behavior and fate of inorganic arsenate is of prime importance,
regardless of the source of the arsenic.  Woolson et al. (1970b) pointed out
that arsenic applications to crops by way of pesticides for insect and weed
control and for desiccation may result in arsenic accumulations in the soil
that may ultimately build up to levels toxic to plants, as well as to other
biota.

     Data on the behavior of MSMA and DSMA in soil and water indicates that
movement of these compounds from treated land to water by leaching appears to
be minimal.  Observations from the treatment of irrigation ditchbanks indicate
that surface transfer of MSMA residues from treated land areas to water
likewise appears to be minimal, probably due to fixation phenomena in plants,
soils, and sediments.

     MSMA and DSMA residues in the soil do not appear to be persistent, as
such.  Accumulation of herbicidally effective residue levels of the unchanged
herbicides in the soil, therefore, appears unlikely.  However, gradual
accumulation of arsenic-containing degradation products in treated soils
appears to be possible, and very little information seems to be available on
the possible magnitude and significance of such arsenic buildup.
I/ Braman, R. S., and C. C. Foreback, "Methylated Forms of Arsenic in the
     Environment,"  Sci.. 182:1247-1249  (1973).
2j Woolson, E. A.,  P. C. Kearney, and J.'H. Axley, "Chemical Distribution
     of Arsenic in  Soils," U. S. Department of Agriculture, Agricultural
     Research Service,  Crops Protection Research Branch, Pesticide
     Investigations, unpublished report (1970b).
                                       74

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The Ansul Company, "Comments in Support of Continued Registration of Organic
  Arsenical Herbicides, in Response to the Federal Register Arsenic and Lead
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Atkins, E. L., E. A. Greywood, and R. L. Macdonald,  Toxicity of Pesticides
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Baker, R. S., H. F. Arle, J. H. Miller, and J. T. Holstun, Jr., "Effects of
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Bartley, T. R., "Abstract of Progress Report on Herbicide Monitoring,"
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Blythe, T. 0., "Determination and Characterization of the Effects of Fluometuron
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Braman, R. S., and C. C. Foreback, "Methylated Forms of Arsenic in the
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Canutt, P. R., L. A. Norris, and J. Allard,  "Arsenic Residues in Forest Floor,
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Challenger, F., "Biological Methylation," contained in:  F. F. Nord (ed.),
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Challenger, F., and C. Higginbottom,  "The Production of Trimethylarsine
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Challenger, F., C. Higginbottom, and L.  Ellis, "The Formation of Organo-
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                                      75

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Dickens, R., and A. E. Hiltbold, "Movement and Persistence of Methane-
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Edwards, A. C., "The Effects of an Organic Arsenical Herbicide on a Salt
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Fletcher, D., "8-Day Dietary LC5Q Study with Monosodium Acid Methanearsonate in
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                                      76

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Khurana, S. M. P- A., and S. Singh, "Growth Response of  Curvularia  lunata
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NewtOP, M., "Organic Arsenicals:  Breakdown in Forest Trees and in Media
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Von Endt, D. W., P. C. Kearney, and D. D. Kaufman, "Degradation of Mono-
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  16(1):17-20 (1968).

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  Research Service, Crops Protection Research Branch, Pesticide Investigations,
  unpublished report (1970b).

Woolson, E. A., P. C. Kearney, A. R. Isensee, W. G. McShane, K. J. Irgolic,
  and R. A. Zingaro, "Bound Arsenic Fractions in a Crustacean," American
  Chemical Soc., Division of Pesticide Chemistry, 168th National Meeting,
  Atlantic City, New Jersey (1974).

Zabel, R. A., and F. W. O'Neill, "The Toxicity of Arsenical Compounds to
  Miccroorganisms," TAPPI, 40(11):911-914 (1957).
                                       79

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                    PART II.   INITIAL SCIENTIFIC REVIEW

                       SUBPART D.   PRODUCTION AND USE

                                  CONTENTS


                                                                         Page

Registered Uses of MSMA and DSMA	82

  Federally Registered Uses	82
  State Regulations	84

Production and Domestic Supply 	  91

  Volume of Production 	  91
  Imports	92
  Exports	92
  Formulations	92

Use Patterns of MSMA and DSMA in the United States	93

  General	93
  Agricultural Uses of MSMA and DSMA	95
  Industrial and Commercial Uses of MSMA and DSMA	96
  Government Agencies' Uses of MSMA and DSMA	97
  Home Garden Uses of MSMA and DSMA	97
  MSMA and DSMA Uses in California	97

References	105
                                      81

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     This section contains data on  the  registration  and  on  the production and
uses of MSMA and DSMA.  The  section summarizes  rather  than  interprets  data
reviewed.
 Registered Uses of MSMA and DSMA
 Federally Registered Uses - MSMA is the monosodium salt, and DSMA the disodium
 salt of methylarsonic acid (MAA).   These two closely related methanearsonate
 herbicides provide postemergence control of a number of hard-to-kill grass weeds,
 including Johnson grass, nutsedge, dallisgrass, crabgrass, and several other
 weeds.  MSMA and DSMA are contact herbicides.  They must contact green plant
 tissues to be effective.  Their exact mode of action is not known.

      DSMA was the first methanearsonate to be commercially developed and
 marketed for weed conttol in cotton.   MSMA became available somewhat later,
 but has in the interim achieved far greater volume than DSMA,  especially for
 use on cotton.  MSMA is more effective than DSMA, providing the same degree
 of weed control at somewhat lower  rates.  On the other hand, DSMA is somewhat
 safer to young cotton and is, therefore, preferred by some cotton growers,
- especially for early season applications.

      MSMA and DSMA are currently offered for sale in the United States by
 about 9 different suppliers, in a  variety of formulations, and in several
 combinations with other herbicide  active ingredients (see the subsection on
 Formulations, p. 92).

      MSMA and DSMA are currently registered in the United States for use as
 directed applications*on cotton; for use under bearing or nonbearing citrus
 trees, including grapefruit, oranges, lemons, limes, and tangerines.  DSMA is
 also registered for use as a topical application on cotton (ground equipment
 or aerial application).  MSMA is registered for use as a directed application
 in non-bearing deciduous fruit and nut orchards.  MSMA and DSMA are also
 registered for weed control on drainage ditchbanks; for control of grass weeds
 and certain other weeds in lawn and ornamental turf; and for use on noncrop-
 land for the control of hard-to-kill grass weeds and certain other hardy weedr
 such as cocklebur, sandbur, ragweed, puncturevine, and tules in or along
 rights-of-way, fence rows, storage yards, and similar noncrop areas.'
 * Directed application means that the spray solution is not permitted to
     contact leaves, stems, or bark of the crop in which weeds are to be
     controlled.
 \J  U.S. Environmental Protection Agency, EPA Summary of Registed Pesticides,
       Vol. I, p. D-82, M-27.
                                        82

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     Tolerances established for MAA are recorded in the Code of Federal
Regulations, Title 40, Part 180.289.  They apply to both MSMA and DSMA.   The
only residue tolerances for MSMA and DSMA currently in effect are 0.35 ppm
in or on citrus fruits, 0.7 ppm in or on cottonseed, and 0.9 ppm in cottonseed
hulls.  Tolerances for MSMA and DSMA residues in or on grapes and sugarcane are
currently pending.

     On cotton, MSMA may be used as a preplant and/or postemergence appli-
cation, at the rate of 2.0 Ib Al/acre.  Preplant broadcast applications may
be made if planting of cotton is delayed and weeds have already emerged.
Cotton may be planted immediately following MSMA application.  Applications
after cotton emergence must be directed so as to keep the spray off cotton
foliage.  If needed, a second or repeat application may be made about 1 to 3
weeks after the first application.   Only 1 directed spray should be applied if
following a topical application of DSMA.  MSMA and DSMA should only be applied when
cotton is 3-4 in tall and before first bloom.  The spray must be kept off cotton  foliage.
                                    I
     DSMA is recommended on cotton only as a postemergence application, at the
rate of 2.25 to 3.0 Ib Al/acre.   It can be applied postemergence as a directed
or topical application.  For topical treatments use 2.8 Ib Al/acre at 40 to 50
gpa mixed with 1 or 2 quarts of a mild surfactant suitable for use on cotton
either with ground or aerial equipment.   Apply when cotton has 1-2 true leaves
to first square and do not make topical applications after first square.  One
directed application of DSMA may be made following a topical application to
weeds under the conditions previously mentioned for MSMA.

     For weed control in bearing or nonbearing citrus groves, and in nonbearing
agricultural plantings such as deciduous fruit and nut orchards, MSMA is recom-
mended as a directed application at the rate of 2.0 to 4.0 Ib Al/acre.  For
bearing and nonbearing citrus orchards DSMA is recommended as a directed appli-
cation at the rate of 3 to 6 Ib  Al/acre.

     DSMA is not registered for  use in nonbearing deciduous fruit or nut
orchards.

     For weed control on noncropland,  MSMA is registered and recommended at
2.25 to 4.5 Ib Al/acre, or 4.5 to 9.0  Ib AI/100 gal.   DSMA is recommended for
use on noncropland at 4.7 to 5.5 Ib AI/100 gal.

     For use on lawn and ornamental turf grass,  both MSMA and DSMA are
recommended at the rate of 1.0 oz AI/1,000 ft^ for smaller areas,  or 2.7 to
6.0 Ib Al/acre.   MSMA and DSMA should  be used only on established lawns and
turf, and not at all on lawns consisting of Saint Augustine,  bahiagrass,  or
centipede grass, or on dichondra lawns.  

     For an overview of these registrations,  including the range of  dosage
rates, general and specific directions for use,  use limitations, caution
statements, and other details pertinent to commercial use, specimen labels
                                        83

-------
for a typical, widely used MSMA liquid formulation (Ansar 529 H.C.
containing 47.74% MSMA, equivalent to 6.0 Ib MSMA/gal, by The Ansul Company,
EPA Registration No. 6308-29) and for DSMA powder (containing 63.0% DSMA
Anhydrous, equivalent to 100% DSMA hexahydrate, by the Diamond Shamrock
Corporation, Agricultural Chemicals Division, EPA Registration No. 677-203-AA)
are included in this section (Tables 5 and 6).

     The MSMA 6 Ib/gal label (Table 5) includes directions for use on cotton,
bearing and nonbearing citrus, agricultural plantings, noncropland, and lawn
and ornamental turf.  The DSMA powder label (Table 6) includes directions
for use on cotton, ornamental turf grass, and noncropland.

     Table 7 presents an activity profile for MSMA on about 120 different
weed species.  Among these, Johnson grass (Sorghum halepense), nutsedge
(Cyperus sp.). dallisgrass  (Paspalum dilatatum). cocklebur (Xanthium sp.),
ragweed  (Ambrosia sp.), sandbur  (Cenchrus sp.), and puncturevine  (Tribulus
terrestris) are economically most important regarding the use of MSMA and
DSMA in the United States.

State Regulations - Toxicity studies indicate that MSMA and DSMA are not
highly toxic  to mammals (see the subsection on Pharmacology and Toxicology,
p. 37).  The  two herbicides are rated "slightly toxic" with regard to mammalian
toxicity.  Some states that regulate the use of pesticides have placed special
restrictions  on pesticides which are highly toxic or otherwise hazardous to
man and/or environmental health.  For instance, in California, 42 pesticides
have been designated as "injurious or restricted materials."  The use of
pesticides in this category is subject to special restrictions under regulations
administered  by the State Department of Agriculture.  The California list of
"injurious materials" includes "certain arsenic compounds," including inorganic
trivalent arsenicals and inorganic pentavalent  arsenates, but not organic
pentavalent arsenicals including MSMA and DSMA.  Thus, these herbicides are
neither  subject to special  regulations in California nor, as far as is known,
in any other  state.

      In  the  Federally  registered labels of MSMA products, directions  for  use  on
cotton do not include  provisions for  aerial  applications, nor do  they specifi-
cally recommend against application by aircraft.   Several cotton  growing  states,
including Arkansas, Louisiana, and Mississippi, permit the application of MSMA
by aircraft  prior  to planting, or up  to the  "cracking" stage  of cotton.   Air-
craft applications may be made to prepared seedbeds when planting of  cotton has
been  delayed  and weeds have emerged,  or as a postplant treatment, but no  later
than  initial  cracking  of  soil  in the  field before  emergence of  cotton, or a
maximum  of  5  days  after planting, whichever  occurs  first.

      Aircraft applications  may be made only  during  these periods, but must not
be made  after emergence of  the cotton.  The  Cooperative  Extension Service recom-
mendations  for cotton  weed  control  in Arkansas, Louisiana and Mississippi do  not
recommend such aerial  applications, but suppliers  of MSMA formulations provide
special  directions for application by aircraft  to  users  in the  states mentioned.
                                         84

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                                         Table  5.    MSMA  6  LB/GAL  (47.74%)   LIQUID CONCENTRATE  SPECIMEN LABEL
00
Ln
               Ansar529H.C
               Herbicide
                iUGH  CONCENTRATE
               MSMA Liquid Plus Surfactant
               For Selective
               Post-Emergent
               Weed Control
               ACTIVE INGREDIENT:
               Monoiodlum Acid
               MtthMiurtonitt*  . . .
               INERT INGREDIENTS: 52.26*

               Toul ArMnic ( elerrwntil)
               II in wattr tolubti
               form	  22.06%

              Product contiini 6.0 Ibi.
               MSMA ptr gallon.
               CAUTION:
               Keep out of  the
               reach of children
               Read entire label
               before using
               this product
CAUTION: Keep Out of the Reach of Children

CAUTION: Harmful if swallowed. Avoid contact with Ik.ft. Avoid brtathing spray mm. Wash hand* after irting. Avoid
storage near feed or food product!. Kttp children and domtilic animals off treated areas until thu matt nil hasbttn
WMhid into the toil.
ANTIDOTE: tf taken internally, induct vomiting and call physician at one*.
READ ENTIRE LABEL BEFORE UUNQ THIS PRODUCT.
WARRANTY - CONDITION OF SALE:  DIRECTIONS FOR USE ol thu product art basad on fiald uia and tens
baliavad reliable and should ba followed carefully. It n however impossible to alimmata all risks attociattd with usa of
ihii product. Becauta luch faetori at weather condition!, foreign materiel and manner of uw for application art all
beyond the control of The Aniul Company or the Seller of thu product, such thingi at crop injury, inelftctiveneu or
other  unintended coniaquencai may refult. ALL SUCH RIS*S ARE ASSUMED BV THE BUYER
Artiul warrant! that thu product conform! to the chemical description on the label and it reasonably '' 'or  the
purposei referred to m the direction! for UM at modified by the above. Anuti makes no other warrantiai. CKP/CU or
implied, including FITNESS or MERCHANTABILITY. In no CJte than Amu I or the Seller be liable for consequential.
special or indirect damages resulting from the UM or handling of thu product. The foregoing u a condition of tale by
The Aniul Company and it accepted at tuch by the Buyer.
GENERAL INFORMATION:  ANSAR 529 H.C. Herbicide n  uteful for .elective pott-emergent weed control.
particularly for grauy weadt. Iti phytotouc propariiai are quickly inactivated on contact with toil, It n a combination
of herbicide  and turfactant. It h unnacttaary to add any other aurfactant to the aprey eolutton. Beit  retuitt are
obtained on young actively growing weedt at air temperature* above 70 F.
MIXING INSTRUCTIONS:  ANSAR 529 H.C. Herbicide it completely water tolubie Fill the tpray equipment tank
about half full with water and add the required amount of herbicide with agitation.  Fimth titling the tank with water
and apply. After ute, clean equipment thoroughly by fluthing with water. Do not itore tpray Million n
interspaces and around bate of trees or vmas. Spray unwanted vegetation 10 iust than of run-off. If regrowth occurs.
rwpply as required, however, do not  eKceed 3 applications par year.
Do not  allow apray solution to contact leave*, stems or  bark. Use a shield, if necessary, for nuneiy planting* or
young trees. Do not apply around treat or vinat from which fruit will be harvaeltd within one ytar of trtftimtnt.
NON-CROP: ANSAR 529 H.C. Herbicide is useful for control of (ohnsongrass, nutsedge, dallitgrass. cockHbur. rag-
weed, sandbur, puncture vine and certain other wttdi on drainage ditchbanki. nghu-ol way. fence rows, storage
yards, and similar  non-crop areas. Mix ANSAR 629 H.C. Herbicide  at a rate of 6  to 12  pmtt in 100 gallons
of water. Spray unwanted vegetation  at a rate of about 50 gallon! of |pray solution per acre  Usa ipray equipment
that gives good low volume coverage. If regrowth occurs, reepply at required.
LAWN AND ORNAMENTAL TURF: ANSAR 629 H.C. Herb-ode is useful for control of daihigrats. tandbur.
bahiagrass, nut sedge, cfabgrats, chick weed and wood sorrel with hula or no injury to tolerant  lawn grams On new
lawns, do not treat until after three mowings. Tolerant grasses may be temporarily discolored Zoyna. blutgresset and
bermuda are qimt tolerant. Do not ute on St. Augustine or centipede
Mow lawns  1 to 1 1/2 mchti high before treatment. Mix 1 1/3 fluid ounce* IB teaspooni)  of ANSAR 529 H.C
Herbicide in 2  1/2 gallons of water and apply to an area of 1,000 tq.  ft Spray thoroughly 10 wet all undesirable
plants. Repeal applications,-10 to 14 days apart, may be needed for good  control.
ANSAR 529 H.C. Herbicide is manufactured by The Aniul Company. Met matte,  Wisconsin

X . *1. ANSAR, ANSUL are registered trademarks of The Ansut Company.


Net Contents  5 Gallons     Form  NO. 0-7392     EPA  Reg.  No. 6308-29
                                                       SPECIMEN  LABEL
 :i
 THE ANSUL COMPANY.
MARINETTE. WISCONSIN

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                                                         Table  6.     DSMA  SOLUBLE  POWDER  (63%)   SPECIMEN  LABEL
I
'..
a
                          IfADMTM IAM&
                      MMtl UMNO IMS MOPUC?

                        OBMU MK*MAT1ON
             DSMA JOWOft  e paimwiQMt*  K**bud. tot tsu in
             <*. iwrf *d non nta.n.ng 3M pewnd. ol DSMA POWDER P*vi I

         *:   iMM  for band OPPIKOSP*,.  appry  I gaflen el abe*a
         T.  dfund tpoy p-f ecrt tor each  l-wh band width l bo
                  ol conen grown on 40-inch re* -pacing A ukend
to 3 woeU afat * lint oppkcehon Keep tptey ell cvtton
W-g.
APPtr ONtf WHtN COTTON IS 3 MCHfS HIGH TO fltST
OOM DO NOT APflT AFTC* FUST UOOM
S-M bwtnimg end ftddnli dncolerehen ol cotion tel.oo may
orrauonoBy b Mrn totttHnng rocomrnvncnld trotmnt. how
OMI. letten planH *it detep nermatly and yield *-B not
be.ellemd
OlNAMCNTAl TUVG.USS DSMA POWDC* con be uted lot

upoelti end letgt crabgrtm. dottngra.., nwtttdg*.  tendbwr
and weed tot**l with .Me at ne -H-'r ' -rf'iW'vK.d.
                ,  Mew twtigfOH to htnghi el I to
                                                            KIT   CIITEITS
                                                                                                                       fHIIJ
                                                           **-     _.*       -
                                                           Diamond  Shamrock
                                                           Chemical
                                                                       DSMA  POWDER
                                                                     tot "oUoinonoiKO Wood CoMrol In Cotton. Turf ond Non-Oop AIO.I
                                                                  ACTTVfK
                                                                                                                                               ID inik b.lo-. I,.olr-.nl M.!  !
                                                                                                                                               KIWMI pl J  1 lhl <~>l '
                                                                                                                                              On.. 10 orop.,1, .(*! OiMA K1WH1
                                                                                                                                              if opplMd la tonto'ouot and IKW  DO NOT appiV >
                                                                               nan WMIITCNTS
                                                                                               IBM Anihydroin-
                                                                                                   TOTAL
                                                                                                             U.0%
                                                                                                             "0%
                                                                                                             100.0%
                                                                                          TotW Anotlk. OH In woi-tolUo lo.
                                                                                           OXBIOUod Bt OlOMOIttBl .  . 2S.*5%
                                                                                             to,.1..lint lo 100% Oitodivn
                                                                                                                                                         .        .
                                                                                                                                              DO NOT 'M*od wnM 2 Mh o**' knl o
                                                                                                                                              MON CO DIM* fOWOCI  ttl^a^t
                                                                                                                                                                            l -or
                                                                                                                                                                      ApplMOMn thowld 
                                                                                                                                                     :  
                                                                                                                                                  ta. good od 10-1>I  . 01 o -010 of 1 IB J> po*nd>
                                                                                                                                                  of DSMA POWOI* pklt 1 to Ite OjMMH Of terfOBiO wtoctBM
                                                                                                                                                  in 40 ffodont of won* $pf.y unaow.oblo *oootBtnwi ttwouoh-
                                                                                                                                                  '  to pomt of mn-olf  AovqMtto  to^QMiao Bnd ^loBipl.to

                                                                                                                                                         I May bo nocotjOiy it n

                                                                                                                                                                  CAUTION
                                                                                                                                                  Wai. ttBoh Bftot ta.

                                                                                                                                                  BOt rflOW MlOOTI OB InBt^ OBM MBIil BIBIOIiBl I.M BBOt
                                                                                                                                                  wooSod I>0 tod
                                                                                                                                                  A^id tlliojl BBB* lood BBd lood BIBdoltl-

                                                                                                                                                  OO NOT food tnwtod Inogi to tixitotll of |

                                                                                                                                                  DO NOI
                                                                                                                                                  O.OOSO.
                                                                                                                                                  M NO!
                                                                                                                                                                    I xtod fof d
                                                                                                                                                                   Mm .* not ..iBiitit pwtpt
                                                                                                                                                                   UdMo od OWOM Mo. 01 o<
                                                                                                                                                           DO NOT ~o . OBtMo -* OBtpB/.
                                                                                                                                                                WAJIAMTT AND UoUTATK> O DAMAOB
                                                                                                                                                           UUtt wnwBMft tfMtt thlt
                                                                                                                                                                                        < t
                                                                                                                                                      WO"B1  o l KIBonB OBoi
                                                                                                                                                  doofftption OMrf it HBUIIBf| fit fw Iho jylpMot tOd B

                                                                                                                                                  ,.Bil  inpllod VBftBfilT. MvdtiMj or olhot o.rmrBI
                                                                                                                                                  or lBBod WBB.r, o( BTNH1 v ol MIKMAHIAHITT.
                                                                                                                                                  Bnd no BoiM ol UUR n BHI*iB*ilod to do 01 oitofrt M
                                                                                                                                                  onifMMj vrirti a ipocnV fofonVMO to I*HO BiBMBHtp. lo> no
                                                                                                                                                  ovool >Koll lUlII . lioM.tr to. or BOOBih o
                                                                                                                                                  OOtOod IftO BMfCBBtO priCO Ol tho H*Btol Bt to
                                                                   CAUTION-  KEEP OUT OF REACH OF CHILDREN.
                                                                   v/nu 1 1 vn.                      FQR ADO|TIOMAL CAUTIONS.
                                                         AGRICULTURAL CHEMICALS DIVISION-CLEVELAND,OH.O 441IB
                                                                                    DIAMOND HAMMOCK CORPORATION

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                            Table 7.   WEED CONTROL PROFILE OF MSMA

COMMON NAME
Ageratum, tropic
Amaranth, spiny
Angeltongrass
Aster, whttehcath
Bamboo grass
Barley, little
Barnyardgrass
Beggarweed, Florida
Bermudagrass
Betony. Florida
Bindweed, field
Bitterweed
Blackberry
Blackseedgrass
Bluegrass. annual
Bluegrass, Kentucky
Bracken, Eastern
Brome, downy
Brome grass
Broomsedge
Buckwheat, wild
Buffelgrass
Bulrush
Burcucumber
Bursage, wool y leaf
Buttercup
Camphorweed
Canary grass. Reed
Careless weed
Carpetgrass
Carpetweed
Carrot, wild
Cheatgrass
Chickweed
Chickweed, field
Chickweed, mouseear
Chickweed, sticky
Chompipe
Cocklebur, common
Cockle, corn
Coffee weed
Cogongrass
Copper leaf, Virginia
Cornflower
Crabgrass. hairy
Crabgrass, large
Crabgrass, small
Crabgrass, smooth
Cress, hoary
Crotalaria, showy
Croton. tropic
Croton, wooty
Crowfootgrass
Cucumber, wild
Cudweed
Dallisgrass
Dandelion
Day flower
Dichondra
Dock, broadleaf
Dock, curly
Dodder, field
Dogbane, hemp
Dogfennel
Dropseed. Indian
Dry mar y. heartleaf


LATIN NAME

a
P
P

a
a
a
P
P
P
a
b

a
P
a
a

P
a

P
a

a
a or

a

a
fa

a
P
P


a
a
a

a
a
a
a
a
a
P
a
a
a
a
a
b
P
P
a
P
P
P
a
P
P

a
Ageratum conyzoidas
Amaranthus spinosus
Andropogon annulatus
Aster pilosus
lschamum mulican/l. timorense
Hordeum pusillum
Echinochloa crusgalli
Desmodtum tortuosum
Cynodon dactylon
Stachys Moridana
Convolvulus arvensis
Helenium tanuifolium
Rubus sp.
Spror bolus indicus
Poa annua
Poa pratensis
Pteridium aquilinum
Bromus tectorum
Bromus sp.
Vtndropogon virginicus
Polygonum convolvulus
Pennisatum ciliara
Scirpus sp.
Sicyos angulatus
Franseria tomentosa
Ranunculus sp.
fa Heterotheca subaxillaris
Phalaris arundinacaa
Amaranthus palmeri
Axonopus affinis
Mollugo verticillata
Daucus carota
Bromus secalinus
Stellaria media
Carastium arvense
Cerastium vulgatum
Cerastium visconsum
txuphorus unisatus
Xanthium penrtsylvanicum
Agrostemma githago
Sesbania sp.
Imperata cylindrica
Acalypha virginica
Centaurea cyanus
Digitaria sanguinalis
Digitaria sanguinalis
Digitaria ischaamum
Digitaria ischaemum
Cardaria draba
Crotalaria spactabilis
Croton glandulosus
Croton capitatus
Dactyloctanium aagyptium
Echinocystis lobata
Gnaphalium sp.
Paspalum dilatatum
Taraxacum officinale
Commelina communis
Dichondra rapans
Rumax obfutifolius
Rumax crispus
Cuscuta campastrii
Apocynum cannabinum
Eupatorium capillif olium
Sporobolus diandar
Drymaria cordata
DEGREE OF CONTROL WITH MSMA*
2 - 3 Ibs. 4 - 6 Ibs. / - 9 Ibs.
very good

good

very good
tolerant
fair

tolerant

stunting good at first bloom


fair to good
tolerant
tolerant

fair-late spring
tolerant

fair
good
good




tolerant tolerant tolerant
good
excellent

tolerant
excellent late spring

good
good
good
excellent
good

tolerant
tolerant


good
good
good
good







good
tolerant





t

fair to good

Source:  The Ansul Company, ""Weeds Controlled by MSMA," Marine tie, Wisconsin
          (1972).
                                            87

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                                         Table 7.   (Continued)
COMMON NAME
Eveningptimrose, cutleaf
                                  LATIN NAME
                                                                            DEGREE OF CONTROL WITH MSMA*
                                                                            2  3 Ibs.          4-6 Ibf.          7  9 lb>.
                                        Oanothera laciniata
Falsedandelion. Carolina
Fescus. tall
Fiddleneck
Filaree. redstem
Fingergrass. swollen
Flax, common
Fleabane, annual
Fleabane. daisy
Flixweed
Foxtail, giant
Foxtail, green
Foxtail, yellow
Galinsoga. hairy
Garlic, wild
Geranium, Carolina
German weed
Goldenrod
Goosegrass
Greenbriar. common
Cromwell
Groundcherry. clammy
Groundcherry. longleal
Groundcherry. smooth
Groundsel
Hempweed. climbing
Hen bit
Hilograss
Honeysuckle. Japanese
Horsenettle
Horseweed
Jimsonweed
Johnsongrass
Kikuyu grass
Knapweed. Russian
Knotweed
Kochia
Kudzu
Lallang
Lambsquarter, common
Lettuce, minors
Lettuce, wild
Lovegrass, feather
Mallow, purple poppy
Mayweed
Medusa head
Mriastoma. Banks
Milkweed, butterfly
Milkweed, honeyvine
Morningglorv. annual
Morningglory, bigroot
Morningglory, cypressvine
Morningglory. ivyleat
Morningglory. smallflower
Morningglorv. tall
Morningglorv. wild
Mullein, common
Mullein, Turkey
Mustard, blue
Mustard, tansy
Mustard, tumble
Mustard, wild
Nightshade, black
Nightshade, silverlaaf
a or b


aorb


a or b
a
a
a
a
a
a
P
a or b

P
a
P

P
P
P
P

a

P
P
a
a
P

P
a

P

a

a
a

a
a

P
P
a
P
a
a
a
a
P
b


a

a
a
P
Pyrrhopappus carohnianus
Festuca sp.
Amsinckia douglasiana
Erodium cicutarium
Chloris inflate
Linum usitatissimum
Erigeron annuux
Erigeron strigosus
Descurainia Sophia
Setaria fabarii
Sataria viridis
Setaria glauca
Galinsoga ciliata
Allium vineale
Geranium carolinianum
Borreria latifolia
Solidago sp.
Eleusine indica
Smilax rotundifolia
Lithospermum officinale
Physalis heterophylla
Physalis longifolia
Physalis subglabrata
Senecio sp.
Mikania seandens
Lamium amplexicaule
Paspilum conjugatum
Lonicera japonica
Solanum carolinense
Erigeron canadensb
Datura stramonium
Sorghum halepense
Pannisetum clandestinum
Centaurea repens
Polygonum sp.
Kochia scoparia
Pueraria lobata
Imperata cylindrica
Chenopodium album
Montia perfoliata
Lactuca scarioU
Eragrostis amabilis
Callirhoe involucrata
Anthemis cotula
Taeniatherum asparum
Melastoma malabathricum
Asclepias tubarosa
Ampalamus albidus
Ipomoea purpurea
Ipomoea pandurata
Ipomoea quamoclit
Ipomoea hederacea
Jaquemontia tamnifolia
Ipomoaa purpurea
Convolvulus arvensts
Verbascum thapsus
Eremocarpus setigems
Chorispora tanalla
Descurainia pinnata
Sisymbrium altissimum
Brassica kaber
Solanum nignim
Solanum elaeagnHolium
                                                                             tolerant
                                                                             fair
                                                                             fair in spring
                                                                             good
                                                                             good
                                                                             good
                                                                             good
                                                                             good

                                                                             fair
                                                                             very good on
                                                                              young plants
                                                                             good
                                                                             good
                                                                             excellent
                                                                             tolerant
                                                                             good
                                                                             good
                                                                             tolerant
                                                                             good
                                                                             fair to good
                                                                             good


                                                                             fair


                                                                             good


                                                                             good

                                                                             good
                                                                             good



                                                                             fair to good

                                                                             good
good
 excellent at full bloom


 excellent

 good


 good
                                                      88

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                                                  Table  7.    (Continued)
  COMMON NAME

  Nimblewill
  Nutsedge. purple
  Nunedge. yellow

  Oats, wild
  Onion, wild
  Orchardgrass

  Panicum. fall
  Panicum, Texas
  Partridge pea
  Paspalum. Panama
  Paspalum. sour
  Passionflower, mavpop
  Passionflower, redfruit
  Peppervine
  Pepperweed, Virginia
  Pigweed, redroot
  Pigweed, rough
  Plantain, bracted
  Plantain, broadleaf
  Plantain, buckhorn
  Poison ivy
  Pokaberrv
  Poorjoe
  Prickly pear
  Puncturevine
  Purslane, common
  Purslane. Florida
  Pusley

 Quackgrass

  Ragweed, common
  Ragweed; giant
 Raoulgrast
 Rattlcbox
 Redtop
 Redvine
 Rhodesgrast
 Rice, jungle
 Racket, London
 St. Augustinegrass
 Saltbush. Wright
 Saltorais, desert
 Sandbur. field
 Sandbur. Southern
 Sedge, giant
 Sedgegrast
 Sansitiveplant
 Sensitiveplant, giant
 Sesbania. hemp
 Shepherdspurse
 Siamweed
 Sicklepod
 Sicklepod
 Sida. prickly
 Signalgrass. broadleaf
 Smartweed. Pennsylvania
 Smutgrass
 Sneezeweed. bitter
 Sorrel, red
 Sowthistle. spiny
 Spanish needles
Sprangletop
Sprangletop. red
Spurge, spotted
Starbur, bristly
Stargrais. Australian
  LATIN NAME

  p     Muhlenbergia schreberi
  P     Cyperus rotundus
  P     Cyperus esculemus

  a     Ann. fatua
  p     A Ilium canadema
  p     Dactylis glomerata

  a     Panicum dichotomiflorum
  a     Panicum texanum
  a     Cassia fasciculate
        Paspalum f imbriatum
        Paspalum conjugatum
  p     Passitlora incarnate
        Passiflore foetida
 P     Ampalopsn arboree
 a or b  Lepidium virjinicum
       Amarahthus ratrof laxus
 a     Amaranthus ratrotlaxus
 a     Plantago aristata
 P     Plantago major
 P     Plantago lanceolata
 P     Rhus radicans
 P     Phytolacca americana
 a     Diodia tens
 P     Opuntiasp.
 a     Tribulus tarrestris
 a     Portulac* olaracaa
 a     Richardia ic.br.
 a     Richardia scabra

P    Agropyron repens

a     Ambrosia arumiiiifoli.
a     Ambrosia trifida
      Rottboellia exettata
      Crotalaria sagittalis
      Agrostis alba
P     Brunnkhia ctrrhosa
      Chloris gayana
a     Echinochloaeohmum
      Sitymbrrum irio
p    Stenotephrum  sacundatum
      Atriptax wrightii
      Dtstichlh stricta
a     Canchrui pauciflorus
a     Canchrus achinatus
      Hypolytrum latifolium
      Selena sumatrarais
      Mimosa pudica
      Mimosa invisa
      Sesbania axaliata
      Cacnella bursa-pastoris
      Eupatorium odoratum
      Cassia tore
      Cassia obtusifotia
      Sidaspinosa
      Brachiaria platyphylla
      Polygonum pennsylvarucum
      Sporoboluspoiratii
      Helanium amarum
      Rumax acetosella
      Sonchusasper
      Bidens bipimata
      Leptochloa imbricata
      Laptochloa (iliformis
      Euphorbia maculata
     Acanthosparmum hispidum
     Chloris dtvaricata
   DECREE OF CONTROL WITH MSMA-
   2  3 Ibs.           4 - 6 HM.           7  9 Ibs.
  good
  good

  good to excellent

  tolerant

  good
  good
  excellent
  very good
  good
 good
 fair
 tolerant

 good
 good
 excellent
 fair
 tolerant

 tolerant
 fair
 good
 good
 good
 good
 good
 very good
 fair to good
 good
fair to good
good
poor
fair to good
tolerant
tolerant
                                                                                  good
                   good to excellent
                   good early
                  excellent
                                                             89

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                                        Table  7.    (Continued)
COMMON NAME

Stinkgrass
Stork's bill
Sunflower
Swinecress

Thistle, blessed
Thistle. Canada
Thistle. Russian

Thistle, yellow star
Timothy
Torpedograss
Trumpetcreeper
Tules
Vasey grass
Velveileaf
 Verbena, roadside
 Vervain, blue
 Vervain, prostrate
 Vetch, narrowleaf
 Wallflower. Western
 Watergrass
 Watermelon, wild
 Wheatgrass, crested
 Wildergrass
 Witchgrass
 Witchweed
 Woodsorrel, common yellow
 Woodsorre). creeping
 Yarrow, common
 Yerba-de-tugo
                   LATIN NAME

                         Eragrostis cilianensis
                     or b Erodium cicutarium
                         Hehanthus annum
                     or b Coronopus didymus

                         Cnkus benadictus
                         Ctrsium arvensa
                         Salsola Kali
                         Centauraa solstitialis
                         Phlaum pratense
                         Panicum rapens
                         Campsts radicans
                         Scirpus sp.
                         Paspalum urvillei
                         Abu ti Ion theophrasti
                         Verbena  hastata
                         Verbena hastata
                         Verbena rigida
                         Vicia angustifolia
                         Erysimum asperum
                         Echinochloa crysgalli
                         Citrullus vulgaris
                         Agropyron cristatum
                         Andropogon nodosus
                         Panicum capillare
                         Stria* lutea
                         Oxalis stricta
                         Oxalis comiculata
                         Achiflea millefolium
                         Eclipta alba
                                    DEGREE OF CONTROL WITH MSMA*
                                    2 - 3 IDS.          4 - 6 Ib*.           7 - 9 IDS.

                                    poor
                                    fair in spring
                                    good
                                    fair in spring       good early
                                     on young plants

                                    poor
                                    good

                                    tolerant



                                    good

                                    good
                                    good
                                    good
                                    good
                                          Asystasia coromandetiana
                                          Axonopus compressus
                                          Bulbostylis sp.
                                          Cantrosama pubescent
                                          Cyctosorus gonyloidet
                                          Cyrtoeoccum accrescera
                                          Eragrostis elongata
                                          Lygodium flexuosum
                                          Lygodium scandens
                                          Panicum nodosum
                                          Panicum pitipes
                                          Paspalum commersonii
                                          Paspalum scrobiculatum
                                          Pityrogramma calomelanai
                                          Stenochlaena palustris
                                                                poor
                                                                good
                                                                good
                                                                poor
                                                                good
                                                                good
                                                                tolerant
                                                                good to very good
                                                                good to very good
                                                                fair
                                                                good
                                                                excellent
                                                                excellent
                                                                good to very good
                                                                fair to good
  'Degree of Control
    Tolerant
    Poor
    Fair
    Good
    Excellent
0 - 10S Control
10 - 60% Control
60  75% Control
75  95. Control
95  100". Control
a =  annual  plant
b =  biennial  plant
p =  perennial plant
                                                        90

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In regard to DSMA, at least one formulation has received Federal approval for
aerial application as of July 16, 1975 (Ansar 8100 herbicide-high concentrate
DSMA powder, 81.0% disodium methanearsonate).  For aerial applications of DSMA
formulations, special attention should be given to recommended rates and timing
of application (as related to the growth stage of the cotton), as well as pre-
vailing weather conditions both prior to and at the time of application.


Production and Domestic Supply


Volume of Production - According to the United States Tariff Commission annual
reports (1971, 1972, 1973),!/ there were four basic producers of methylarsonic
acid salts as herbicides in the United States during the 1972-1973 period.
MSMA was produced in each of the 3 years by 2 manufacturers  the Ansul
Company, Marinette, Wisconsin; and Diamond Shamrock Corporation, Cleveland,
Ohio.  DSMA was produced by 4 different companies in 1971 and 1972  Ansul;
Diamond; the W. A. deary Corporation, New Brunswick, New Jersey; and Vineland
Chemical Company, Vineland, New Jersey.  In 1973, 3 companies, Ansul, Cleary
and Vineland, produced DSMA.  In addition to MSMA and DSMA, the category
"methylarsonic acid salts" in the Tariff Commission reports includes the
dodecyl- and octylammonium salts.

     The Tariff Commission reported the following production volumes for MAA
salts for the 1970-1973 period: 1970, 30,454,000 Ib; 1971, 24,476,000 Ib;
1972, 30,698,000 Ib; 1973, 40,126,000 Ib.

     Thus, the total quantity of MAA herbicides produced in the United States
varied from about 24 million Ib in 1971 to 40 million Ib in 1973.

     MSMA was one of 25 selected pesticides whose production, distribution,
use, and environmental impact potential were recently studied by Midwest
Research Institute and RvR Consultants in a project funded jointly by the
Council on Environmental Quality and the Environmental Protection Agency
(von Riimker et al.  1974).'   The base year for production and use estimates
for that study was 1972.  The U.S. production volume of MSMA in 1972 was
estimated at 24 million Ib AI.  Of the remaining 6.7 million Ib of other
methanearsonate (30.7 million Ib total less 24 million Ib MSMA), about 6
million Ib were estimated to be the DSMA; the balance was octyl- and dodecyl-
ammonium salts.
If  U.S. Tariff Commission, Synthetic Organic Chemicals, U.S. Production
      and Sales, TC Publication 681 (1971, 1972, 1973).~
21  von Riimker, R., E. W. Lawless, and A.  F.  Meiners, Production, Distri-
      bution, Use and Environmental Impact Potential of Selected Pesticides,
      Final Report for Council on Environmental Quality, Washington, D.C.,
      Contract No. EQC-311, 439 pp. (1974).
                                       91

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Imports - According-to MRI, the absence of reported MAA imports from U.S.
trade data indicates insignificant quantities imported.


Exports - The Bureau of Census (1972)i/ placed total exports of formulated
herbicides at 38,867,237 Ib, with no specific listing for MAA herbicides.
However, MRI estimates 7 million Ib AI of MSMA was exported.


Formulations - MSMA and DSMA are available to users in the United States in
a number of different concentrates and formulations.  Liquid concentrates
are used most frequently.  DSMA is also available in the form of dry soluble
powders.  MSMA is completely water soluble, and DSMA is highly soluble.
Therefore, water is a very satisfactory solvent for liquid formulations of
both materials, and more expensive organic solvents and emulsifiers are not
required.  However, surfactants are essential for good coverage of, and
efficacy on, target weeds.  Some liquid formulations contain varying amounts
of surfactants, whereas others contain none.  In the latter case, the user
has to add his own surfactant to the spray tank.  This is preferred by some
users because it allows them to use a surfactant which works best with the
local water, and to use just the amount of surfactant needed, based on previous
experience.

     MSMA and DSMA formulations are offered under a variety of different
trade names or lines of trade names.  Three companies offer herbicide
products containing MSMA or DSMA in combination with other herbicides.
These products include one containing MSMA plus sodium cacodylate; combinations
of MSMA with fluometuron and prometryne, respectively; and one containing
DSMA plus 2,4-D.

      The most frequently used formulations are:  1) MSMA liquid concentrates
 containing 4,  6,  or 8 Ib Al/gal.   These formulations are offered without or
 with varying amounts of surfactant(s) added.   There are no significant dry
 powder or granular MSMA formulations on the market at present;  2) DSMA liquid
 concentrates and soluble powders containing from 20 to about 80% AI (DSMA used
 in anhydrous form, or as penta- or hexahydrate).   Low-concentrate DSMA liquid
 or granular formulations (2 to 4% active ingredient) are offered for lawn weed
 control by amateur gardeners.
\J  U.S. Bureau of the Census, U.S. Exports, Schedule B, Commodity by Country,
      Section 599.2080, Report FT 410  (1972).
                                        92

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      About 40  different  MSMA and DSMA herbicide products are listed in the
 Pesticide Handbook (Billings 1974) ..!/  The most popular formulations are
 offered by several suppliers,  under  several different trade names.
 Use Patterns  of MSMA and  DSMA in the  United States
 General -  MSMA and DSMA are  organic  arsenical  herbicides  derived from
 pentavalent arsenic.  DSMA was the first herbicide  in  the group  to be introduced
 commercially,  but  MSMA  has since outpaced DSMA by a considerable margin because
 of  its  somewhat superior herbicidal  effectiveness as compared to DSMA.

     MSMA and DSMA  (along with the other organic arsenical herbicides) are
contact herbicides which are very effective against hard-to-kill  grass weeds
and several species of broadleaf weeds.  They are relatively inexpensive,
compared to many other herbicides recommended for the same weed control
purposes.  No other herbicides are directly comparable to the organic arsenical
herbicides in regard to efficacy, low cost,  and physical and chemical properties,
including ease of formulation and application.

     MRI and RvR Consultants (von Riimker et al. 1974) estimated MSMA and DSMA
use in the United States in 1972 by region and major category.    (See Table 8.)

     They contend that about 23 million Ib of MSMA and DSMA AI were used in
the United States in 1972.   Approximately 19 million Ib, more than 80% of
this total, are believed to have consisted of MSMA.   An estimated 15.5 million
pounds of MSMA and DSMA, about two-thirds of the total domestic consumption,
were used in agriculture, primarily for postemergence weed control on cotton.
Industrial and commercial weed control uses  accounted for an estimated 4.5
million Ib AI; uses by governmental agencies resulted in an additional 1.2
million Ib.  It is further estimated that about 1.8 million Ib  of MSMA and
DSMA were used for residential and home garden weed control purposes.  Geogra-
phically, an estimated 14.7 million Ib of MSMA and DSMA AI were used in the
South Central region in 1972, about 70% of the subtotal, exclusive of home
garden uses for which there were no estimates available.  The largest single
use in the South Central region was weed control on cotton.   About 3 million
Ib of MSMA and DSMA were used in the Southeastern states,  about 1.4 million Ib
in the North Central, and about 1 million Ib in the Southwestern states.  Less
than 1 million Ib each were used in the Northwestern and Northeastern states.
All of the figures are subtotals and do not  include home,  garden, and residential
uses of MSMA and DSMA.
\J  Billings, S. C., ed., Pesticide Handbook-Entoma,  25th ed.,  Entomological
      Soc. of Amer., College Park, Maryland, 312 pp.  (1974).
                                       93

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                        Table  8.   ESTIMATED USES OF MSMA AND DSMA IN THE UNITED STATES
                                              BY REGIONS AND CATEGORIES, 1972
so



Category


Industrial/ Government
Region

Northeast!/
North Central!*/
Southeast^/
South Cent rail/
Northwest!!/
Southwest-
Total
Agriculture

Negl.
500
1,800
12,700
200
300
15,500
commerical
(Thousands
300
700
1,000
1,700
400
400
4,500
agencies
of pounds active
100
200
250
250
100
300
1,200
Subtotal Home garden
ingredient)
400
1,400 Geographic dis-
3,050 tribution not
14, 650 known
700
1,000
21,200 1,800
Total






23,000
     a/  New England States,  New York,  New Jersey,  Pennsylvania.
     b/  Ohio,  Indiana,  Illinois, Michigan, Wisconsin,  Maine,  Iowa,  Missouri, North Dakota, South Dakota,
          Nebraska,  Kansas.
     /  Maryland,  Delaware,  Virginia,  West Virginia, North Carolina, South Carolina, Georgia, Florida.
     df  Kentucky,  Tennessee, Arkansas, Louisiana,  Mississippi,  Alabama, Oklahoma, Texas.
     e/  Montana,  Idaho, Wyoming, Colorado, Utah, Washington,  Oregon, Alaska.
     f/  New Mexico,  Nevada,  Arizona, California, Hawaii.
     Source:  von RUmker, op. cit.(1974).

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Agricultural  Uses  of MSMA and  DSMA -  Surveys  on the use of pesticides by
farmers  in the  United  States were  conducted by the  U.S. Department of
Agriculture (1964,  1966,  and 1971).ill/   Data for 1972 was obtained from
the MRI  and RvR Consultants study  (von RUmker 1974).

     Table 9  summarizes farm uses  of  organic  arsenical herbicides  from
these  surveys for  the  years 1964,  1966, 1971,  and 1972.  USDA data includes
other  arsenical herbicides.
              Table 9.  FARM USES OF ORGANIC ARSENICAL HERBICIDES  IN  THE
                            UNITED STATES IN 1964, 1966, 1971 AND  1972
                                               Year
                                1972      1971      1966      1964
                                RvR/     USDAk/    USDA      USDA

                                     (Thousands of Pounds AI)

     Crops                     15,300    7,837       866     1,006
     Other farm uses*             200      144        15        71

       Total farm uses         15,500    7,981       881     1,077
*  Includes fence rows, ditchbanks and other noncrop farm uses.
a/  von RUmker op. cit. (1974).
b/  U.S. Department of Agriculture Pesticide use reports for 1968, 1970, 1974.


     According to USDA, the use of organic arsenical herbicides by farmers
increased substantially from the mid-1960's to 1971.  Table 9 shows an
additional substantial increase from 1971 to 1972.  USDA data, however, is not
_!/  U.S. Department of Agriculture, "Quantities of Pesticides Used by
      Farmers in 1964," Agricultural Economic Report No. 131, Economic
      Research Service (1968).
21  U.S. Department of Agriculture, "Quantities of Pesticides Used by
      Farmers in 1966," Agricultural Economic Report No. 179, Economic
      Research Service (1970).
3/  U.S. Department of Agriculture, "Farmers' Use of Pesticides in 1971.  .
      Quantities," Agricultural Economic Report No. 252, Economic Research
      Service (1974).
                                        95

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directly comparable to the RvR estimates, which are based on U.S. Tariff
Commission reports.  USDA data is derived from interviews with farmers in
selected counties throughout the United States.  The interviews were conducted
as part of nationwide programs to collect data on farm production expenditures.
Pesticide uses data was a small segment of the overall program.  The raw
pesticide data obtained was expanded and adjusted to apply from the survey
sample to nationwide use.  The USDA reports point out that the reliability of
the data is related to the quantity of pesticides used, the number of acres
treated, and the importance of the crop in the region.  The relative distribu-
tion of pesticides among crops and regions shown in their report is more
reliable than absolute quantities for individual crops and regions.  MRI
believes that the actual farm use was higher than that shown by USDA survey
results, so that actual farm use of MSMA and DSMA did not nearly double from
1971-1972, as Table 9 indicates.

     Weed control on cotton is by far the most important agricultural use
of MSMA and DSMA.  Additional farm uses of the 2 compounds include weed control
in bearing or nonbearing citrus groves (except in Florida).  MSMA can be used
in nonbearing vineyards and nonbearing deciduous fruit and nut orchards, such
as apple, pear, peach, plum, prune, apricot, cherry, almond and walnut.  MSMA
and DSMA are also used on the farm for weed control on fallow land, on drainage
ditchbanks, rights-of-way, storage areas, along fence rows, and in similar
places around the farm requiring weed control.

     Of the total estimated farm use of MSMA and DSMA in the U.S. in 1972,
15.5 million Ib AI (Table 8), 12.7 million Ib, or more than 80%, were used
in the South Central states, the area in which a large share of the U.S. cotton
crop is grown.  An estimated 1.8 million Ib of MSMA and DSMA were used on farms
in the Southeastern states, and 500,000 Ib or less each in the North Central,
Southwestern and Northwestern states.
Industrial and Commercial Uses of MSMA and DSMA - An estimated 4.5 million Ib
of MSMA and DSMA AI were used in 1972 for industrial and commercial weed
control purposes.  In this  field, MSMA and DSMA are used for postemergence
control of hard-to-kill grass and broadleaf weeds, and as a silvicide in
privately owned forests.  Mixed with other herbicide brush killers, MSMA
increases kill or dieback of woody weeds.

     According to MRI and RvR estimates  (von Rumker et al. 1974), about 4
million Ib of MSMA were used domestically for industrial and commercial weed
control purposes  in  1972  and an  additional  500,000 Ib of. DSMA were used
in the same field, resulting in the total of 4.5 million Ib of MSMA and DSMA
shown in Table 8  for industrial  and commercial weed control.  By geographical
region, 1.7 million Ib (slightly more than one-third of the total for this
category) were used in the  South Central states, followed by the Southeastern
states (about 1.0 million Ib) and, in decreasing order of use volume, the North
Central, Northwestern, Southwestern, and Northeastern states.
                                        96

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Government Agencies* Uses of MSMA and DSMA - MRI and RvR also studied  the
uses of selected pesticides, including MSMA, by governmental agencies  and
estimated that these agencies used about 1.0 million pounds of MSMA active
ingreclent in 1972.  An additional 200,000 Ib of DSMA were applied for weed
control purposes by governmental agencies in 1972, thus accounting for the
MSMA and DSMA total of 1.2 million Ib AI indicated in Table 8.   This volume
was distributed relatively evenly throughout the entire country.  The  North-
western and Northeastern states accounted for the smallest shares of the
total (von RUmker et al. 1974).

     Governmental agencies use MSMA or DSMA for the control of weeds along
Federal, state, county or other roads; in flood control, irrigation, recla-
mation, or water districts; in county or city parks; on school and other
premises; as a silvicide in publicly owned forests; and in many other  situa-
tions where postemergent weed control is desired.  Such governmental agencies
often operate on tight budgets.  When this is the case, MSMA and DSMA  are
attractive because of their relatively low cost in comparison to many  other
herbicides.
Home Garden Uses of MSMA and DSMA - MSMA and DSMA are the preferred herbicides
for the selective control of crabgrass, nutsedge, dallisgrass, sandbur,
bahiagrass, chickweed, wood sorrel and similar weeds in established lawns and
turf, except St. Augustine, centipede, or carpetgrass, or dichondra lawns.
Two or more repeat treatments at 14-day intervals may be necessary for
satisfactory lawn weed control.

     It is estimated that about 1.8 million Ib of MSMA and DSMA AI were used
for residential and home garden weed control in 1972.  Since home and garden
pesticide uses were not included in the MRI/RvR study, estimates on the
geographic distribution of residential and home garden could not be made.


MSMA and DSMA Uses in California - California keeps detailed records of
pesticide uses by crops and other uses which are published quarterly and
summarized annually.  Table 10 summarizes the uses of MSMA and DSMA in
California by major crops and other uses for 1970-1973 period.

     In California, organic arsenical herbicides are not subject to the
special restrictions and reporting requirements imposed upon the sale and use
of pesticides designated as "injurious or restricted materials."  For this
reason, the percentage of all MSMA and DSMA uses reported to the State
Department of Agriculture and included in its statistics is probably not as
high as in the case of the restricted pesticides.  However, the California
Department of Agriculture and others familiar with pesticide uses in the
State believe that the Department's statistics do include a high percentage
of the actual uses of nonrestricted pesticides.
                                       97

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     According to these State reports (Table 10), the use of MSMA in California
for all purposes increased from 181,300 Ib in 1970 to 256,000 Ib in 1973, with
the 1971 and 1972 use volumes ranging in between.  Much smaller quantities of
DSMA were used, ranging from 21,800 Ib in 1970 to 90,300 Ib in 1971.  The
quantities of DSMA used in California in 1972 and 1973 were intermediate.

     The combined volume of use of MSMA and DSMA in California, according to
the State pesticide reports, was about 200,000 Ib AI in 1970.  It jumped to
about 300,000 Ib AI in 1971 and remained at about that level during 1972 and
1973.

     The use of MSMA and DSMA on cotton in California declined from 32,400 Ib
in 1970 to around 12,000 Ib in 1971, 1972, and 1973.  The use on citrus
increased steadily, from about 600 Ib in 1970 to 7,700 Ib in 1973.  The
sizable increase in the use of MSMA and DSMA on California citrus from 1972
to 1973 was probably due to the registration of the use of these herbicides
in bearing citrus orchards.

     MSMA and DSMA uses on "other crops" include those for which the herbicides
are registered and recommended, such as nonbearing grape vineyards and
deciduous fruit and nut plantings.  In addition, MSMA and DSMA were used on
a number of crops, including beans, celery, onions, garlic, tomatoes, rice,
safflower, sorghum, sugar beets, and alfalfa, for which they are not registered
or recommended Federally or within the state.

     Other uses of MSMA and DSMA in California include uses in residential
and industrial areas; in flood control, irrigation, and mosquito control
districts; in other water resource areas; and uses by city, county, state, and
Federal government agencies, and.by the University of California.  Some of
these other uses of MSMA and DSMA in California involve applications to farm-
lands.  Therefore, the category "other uses" in Table 10 is not comparable to
the nonagricultural MSMA and DSMA use categories in Table 8.

     Tables 11 through 14 present the uses of MSMA and DSMA in California in
detail, by crops and other uses, number of applications, pounds of active
ingredient, and number of acres treated  for 1972 and 1973, the two most
recent years for which such data is available.  These tables expand and
provide further insight into the MSMA and DSMA uses in California in 1972 and
1973 presented in summary form in the left part of Table 10.

     At the present time, no other state records or publishes pesticide use
data in comparable detail.  Limitations of time and resources available for
this task did not permit development of estimates on the uses of MSMA and
DSMA by states, crops, and other uses beyond the detail provided in Table 8.

     By far the largest share of MSMA and DSMA used each year was for indus-
trial, commercial and residential weed control,  and for flood and vector con-
trol.  The arsenicals were also used in irrigation districts and other water re-
source areas and by governmental agencies.  Only about 10% of the MSMA and DSMA
quantities used in recent years in California was applied to cotton, citrus and
other crops.


                                       98

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                 Table 10.  MSMA AND DSMA USES IN CALIFORNIA BY MAJOR CROPS AND OTHER USES, 1970-1973
VO
VO
Year
Crop/use Product

Cotton
Citrus
Other crops*-'
Other uses?.'
Total, all uses
1973
MSMA

11.1
7.7
8.6
228.8
256.2
DSMA

1.1
Negl.
Negl.
38.3
39.4
1972
MSMA
Thousand
10.7
1.4
4.9
228.8
245.8
DSMA
of Pounds
0.2
Negl.
2.9
55.6
58.7
1971
MSMA
of Active
11.3
1.0
4.8
206.9
224.0
DSMA
Ingredients
2.2
Negl.
0.3
87.8
90.3
1970
MSMA
^M^^

28.6
0.6
11.5
140.6
181.3
DSMA

3.8
Negl.
0.1
17.9
21.8
         a./  Including some crops for which MSMA and DSMA are not registered or recommended, e.g., beans,
               celery, onions, garlic, tomatoes, rice, safflower, sorghum, sugar beets, alfalfa.
         t>/  Including residential and industrial areas; flood control, vector control and irrigation districts;
               other water resource areas; uses by city, county, state, and Federal Government agencies, and by
               the University of California.

         Source:  California Department of Agriculture, Pesticide use reports  for 1970,  1971,  1972 and 1973.

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Table U.  USE OF MSMA IN CALIFORNIA IN 1972,  BY CROPS AND
  OTHER USES, APPLICATIONS, QUANTITIES, AND ACRES TREATED
Commodity
Almond
Celery
Citrus
City agency
Cotton
County agricultural commissioner
County or city parks
County road
Federal agency
Fallow (open ground)
Flood control
Flowers
Industrial areas
Irrigation district
Lemon
Lettuce (head)
Nonagricultural areas
Onion (dry)
Orange
Other agencies
Plum
Pomegranate
Reclamation district
Residential control
Rice
Saf flower
School district
Sorghum
State highway
Sugar beet
Turf
University of California
Vector control
Walnut
Water areas
Water resources
Watermelon
Total
Source: California Department of
Applications
5
11
1

61




11

1
4

1
1
180
1
52

1
1


1
1

1

1
10


11
29

1
386
Agriculture ,
Pounds
913.91
111.80
31.19
1,579.98
10,714.08
26,194.49
1,124.71
20,043.89
1,024.17
2,467.51
1,335.83
13.10
32.41
44,662.32
68.27
77.20
16,002.34
202.16
1,332.76
34,853.01
9.35
124.78
1,168.55
3,498.85
20.79
109.96
258.06
1.45
34,784.94
117.65
490.22
944.89
458.50
749.93
14,452.26
25,802.46
1.02
245,778.79
Pesticide Use
Acres
437.00
146.60
10.00

3,557.20




579.00

7.00
2.75

20.00
33.00
3,833.76
14.00
944.00

20.00
40.00


10.00
47.00

34.00

35.00
103.00


308.00
200.00

24.00
10,405.31
Report 1972
    (1972).                100

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            Table 12.  USE OF MSMA IN CALIFORNIA IN  1973, BY CROPS AND
              OTHER USES, APPLICATIONS, QUANTITIES, AND ACRES TREATED
U -
U -
Commodity
Almond
Beans (dry edible)
Celery
Citrus
City agency
Cotton
County agricultural commissioner
County or city parks
County road
Federal agency
Fallow (open ground)
Flood control
Grape
Industrial areas
Irrigation district
Lemon
Lettuce (head)
Nonagricultural areas
Nonagricultural areas
Olive
Orange
Orchard
Ornamentals
Other agencies
Pomegranate
Reclamation district
Residential control
School district
Sorghum
State highway
Structural control
Tomato
Turf
University of California
Vector control
Walnut
Water areas
Water areas
Water resources
Total
U = Miscellaneous units.
Source: California Department of
Applications
9
1
30
1

109




21

9
5

9
2
107
4
6
83
1
1

1



1


2
2


12
23
1

440

Agriculture ,
Pounds
2,063.08
50.61
883.12
15.43
2,712.89
11,115.50
24,120.35
3,162.40
12,518.35
206.74
2,619.54
2,910.95
1,730.27
16.72
40,119.42
579.94
1.49
9,843.22
16.85
111.22
7,121.50
31.19
31.13
34,046.09
20.24
2,568.03
4,510.00
855.25
361.87
66,009.73
2.27
137.81
144.04
230.13
992.50
3,212.06
2,805.93
1.55
18,367.85
256,247.26

Pesticide Use
Acres
605.00
15.00
684.00
4.00

6,499.00




930.25

287.00
9.70

544.00
35.00
2,652.87
4.00
29.00
2,537.00
10.00
10.00

3.00



58.00


82.00
22.00


910.00
207.24
1.00

16,134.06


               Report 1973 (1973).
                                       101

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      Table 13,   USE OF DSMA IN CALIFORNIA IN 1972, BY CROPS AND
       OTHER USES, APPLICATIONS, QUANTITIES, AND ACRES TREATED
Commodity
Almond
City agency
Cotton
Applications
4
4
Pounds
402.20
2,048.51
160.98
Acres
435.00
230.00
County agricultural
  commissioner                             14,310.25
County or city parks                          618.49
County road                                   867.78
Federal agency                              1,109.61
Flood control               ^               8,564.99
Garlic                         2              661.50           75.00
Industrial areas               2                4.82            1.50
Irrigation district                         3,153.44
Nonagricultural areas         23            1,172.56          582.59
Onion (dry)                    8            1,794.24          299.00
Orange                         1                7.39           20.00
Other agencies                              1,928.14
Pasture/rangeland              1                0.02            4.00
Recreational areas             1                1.84            1.00
Residential control                         2,508.90
School district                             3,081.87
State highway                              14,064.75
Structural control                             39.44
University of California                      505.62
Water areas                    4               35.83           32.00
Water resources                             1,624.10        	
   Total                      50           58,667.27        1,680.09
 Source:  California Department of Agriculture, Pesticide Use Report 1972
         (1972).
                                   102

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      Table 14.  USE OF DSMA IN CALIFORNIA IN 1973, BY CROPS AND
       OTHER USES, APPLICATIONS, QUANTITIES, AND ACRES TREATED
     Commodity            Applications        Pounds            Acres

City agency                                 1,238.34
Cotton                         11           1,124.76          867.00
County agricultural
  commissioner                              9,477.26
County or city parks                        1,991.51
County road                                   850.64
Federal agency                                830.31
Fallow (open ground)            4             120.60           45.25
Flood control                               2,107.16
Grape                           1               0.04           86.00
Industrial areas                5              25.20            8.62
Irrigation district                           627.15
Nonagricultural areas          12             230.55           31.60
Other agencies                                910.28
Residential control                         1,518.02
School district                             2,151.91
State highway                              14,965.26
University of California                      355.03
Water resources                __             923.31 .       	

     Total                     33          39,447.33        1,038.47
Source:  California Department  of Agriculture, Pesticide Use Report 1973
           (1973).
                                  103

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References

The Ansul Company, Weeds Controlled by MSMA, Marinette, Wisconsin (1972).

Billings, S. C., ed., Pesticide Handbook-Entoma, 25th ed., Entomological
  Soc. of Amer., College Park, Maryland, 312 pp. (1974).

California Department of Agriculture, Pesticide use reports for 1970, 1971,
  1972 and 1973.

U.S. Bureau of the Census, U.S. Exports, Schedule B, Commodity by Country,
  Section 599, 2080 Report FT410  (1972).

U.S. Department of Agriculture, Farmers' Use of Pesticides in 1971...Quantities,
  Agricultural Economic Report No. 252, Economic Research Service (1974).

U.S. Department of Agriculture, Quantities of Pesticides  Used by Farmers in 1964,
  Agricultural Economic Report No. 131, Economic Research Service (1968).

U.S. Department of Agriculture, Quantities of Pesticides  Used by Farmers in
  1966, Agricultural Economic Report No. 179, Economic Research Service  (1970).

U.S. Environmental Protection Agency, EPA Compendium of Registered  Pesticides,
  Vol. I, p. m - 9.

U.S. Tariff Commission, Synthetic Organic Chemicals, U.S. Production and Sales,
  T.C. Publication 681 (1971, 1972, 1973).

von RUmker, R. E. W. Lawless, and A. F. Meiners, Production, Distribution, Use
  and Environmental Impact Potential of Selected Pesticides, Final  Report for
  Council on Environmental Quality, Washington, D.C., Contract No.  EQC-311
  439 pp. (1974).
                                       104

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                     PART III.  EFFICACY AND PERFORMANCE REVIEW


                                     CONTENTS



                                                                           Page

Introduction	106

Efficacy in Noncrop Uses	107

  Johnson Grass Control	  107
  Nutsedge Control	108

Efficacy in Crop Uses	109

  Weed Control on Cotton	109
  Weed Control on Wheat	112
  Weed Control on Soybeans	112
  Weed Control on Citrus Crops	112
  Weed Control on Sugarcane	113

References	114
                                       105

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     This section- contains a general assessment of the efficacy of MSMA
and DSMA.  Studies on the production of MSMA and DSMA in-the United States,
as well as an analysis of their use patterns at the regional level and by
major crop, were conducted as part of the Scientific Review (Part II) of
this report.  The section summarizes rather than interprets data reviewed.


Introduction

     Efficacy tests are intended to determine a product's ability to actually
control a specified target pest or produce a specified plant action.  Data
on actual usefulness is also evaluated since the effectiveness and usefulness
of a given herbicide can differ.  A herbicide can be effective in controlling
a target weed species, but some adverse effect such as the death of desirable
plants would negate its usefulness.

     The following criteria were used to review efficacy tests: types of crops
involved, target pests and population level, quantitative and qualitative
changes in yields, and rates and time application, in accordance with con-
ditions on the product's label.  Data on higher dosages than recommended was
also reviewed to allow an estimate of safety between effective pesticide levels
and those which injure the crop.  Some of these factors are crop variety,
geographical location of the test, year of the test, methods of application,
numbers of sampling replicates, climatic conditions prior to treatment, at
treatment, and right after treatment, edaphic (soil) factors, and many others.
Statistical validity of tests was also considered.

     This review presents a range of the potential benefits to be derived from
the use of MSMA and DSMA for weed control of specific pests in a specific crop
area.

     The use of the methanearsenates for weed control in both crop and
noncrop areas has been recognized and accepted throughout the agricultural
industry.  Although a considerable number of methanearsonates exist,
DSMA and MSMA are the two most commonly known and widely used.

     DSMA and MSMA are primarily known for control of Johnson grass
in cotton and noncrop areas.  Undoubtedly, Johnson grass is the most
economically important weed controlled by these arsenicals.  Yellow
nutsedge and purple nutsedge are the second most important weeds treated
with these products.  Other important weeds controlled include dallisgrass,
sandbur, and field sandbur.

     In addition to control of many weedy grasses, broad-leaved weeds,
such as cocklebur, pigweed, ragweed, puncturevine, ivy-leaved morning
glory, and annual morning glory may be controlled using DSMA or MSMA.
Best control is obtained on these weeds if the application is made while
the weeds are in an early stage of growth.
                                      106

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     Other familiar weeds susceptible to these herbicides  include  green
foxtail, yellow foxtail, giant foxtail, witchgrass, crotalaria or  rattle-
box, barnyard or watergrass, and tules or bulrush.

     The efficacy of MSMA and DSMA depends on the timing, number of applica-
tions, temperature and type of surfactant used.  Widiger (1966')'  reported
that repeat applications are needed for control of the deep-rooted perennials
and that mature or nearly mature weeds in noncrop areas require increased
spray volumes to obtain adequate coverage.  He also found that temperatures
below 60F appear to decrease the effectiveness of DSMA and MSMA and that
sunlight appears to be as important to the action of these herbicides as
temperature.  The use of a surfactant is recommended also since it increases
the effectiveness of these herbicides.
Efficacy in Noncrop Uses


Johnson Grass Control - Johnson grass is a serious weed problem, particularly
in the southern states.  Both MSMA and DSMA have been found to effectively
control Johnson grass, when used as postemergent herbicides.  Their attractive-
ness is due to their ability to attack and decay the rhizomes of the grass,
preventing regrowth.  The rate and number of applications are important to
control.

     Most tests indicated that single applications of methanearsonates
provide only short-term control.  Williams and Horsnail (1972)2/ evaluated
MSMA along railroads, roadsides, ditchbanks and on waste ground at various
locations in the South.  These tests were conducted with single applications
of 10 Ib/acre MSMA.  The results of three roadside test sites showed
95 to 97% control 31 to 33 days after application, dropping to 17 to 80%
control in 89 to 139 days after application.  Along a ditchbank in Louisiana,
control dropped from 81% in 41 days after application to 4% in 70 days after
application.  Similar results were obtained along railroads and waste ground.

     Millhollon (1970)!/ reported that an initial application of MSMA in the
spring killed the foliage, but many stools survived and produced abundant
new foliage from rhizomes in approximately 4 weeks.  A second application of
MSMA at either 2.5 or 4 Ib/acre destroyed this regrowth and apparently killed
 I/ Widiger,  R.  E.,  "Weeds Controlled by the Methanearsonates,"  Proc.  South.  Weed
      Sci.  Soc.t 19:51-56  (1966).
 2J Williams, D. J.,  and G.  B.  Horsnail, "Asulam for  Johnson  Grass  Control in Non-
      crop  Situations,"  Proc.  South.  Weed Sci.  Soc.,  25:347-353  (1972).
 _3_/ Millhollon,  R. W., "MSMA for Johnson Grass  Control  in  Sugarcane,"  Weed Sci.,
      18:333-336 (1970).
                                     107

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most stools of Johnson grass since the authors observed very little new growth
thereafter.  Roeth (1972)1/ also found that 2 applications of MSMA at 3 Ib/acre
reduced rhizome yield by 76%.

     Sckerl et al. (1966)!/ evaluated the efficacy of these arsenicals at
various rates and number of applications in the greenhouse and in tests along
highway rights-of-way in Arkansas.  The authors reported that poor control was
evidenced when DSMA was applied at a rate of 1 Ib/acre and that rates ranging
from 2 to 5 Ib/acre gave 78 to 80% control with no significant difference among
these rates.  Regardless of the rate, some regrowth occurred.  Another test
showed that 3 applications of DSMA gave 91 to 93% seasonal control at rates of
3 and 4 Ib/acre, whereas MSMA gave 83 to 90% seasonal control with 3 applica-
tions of 2, 3, and 4 Ib/acre.  One application of MSMA or DSMA the following
season controlled 90% of the Johnson grass regrowth.

     Bermuda grass is not affected by the arsenicals and often becomes the
dominant grass upon control of. Johnson grass.  Millhollon  (1969)!/ evaluated
MSMA for control of Jdhnson grass on drainage ditchbanks in Louisiana sugar-
cane in 1965 and 1966.  He found that 3 applications of MSMA in 1965 at rates
varying from 3.6 to 7.2 Ib/acre substantially reduced the stand of Johnson
grass.  Infestation in the following spring varied from 3 to 9%.  Two treat-
ments in 1966 resulted in a reduction to 1 to 2% in the following spring.
Bermuda grass became dominant on the treated plots resulting in a 50%
infestation the following year.


Nutsedge Control - Purple and yellow nutsedge are important perennial
weed species in temperate and tropical areas and are common in many
field crops, orchards and vegetables.  They often benefit from the lack
of competition when other weeds are controlled by herbicides.

     Leyden (1967)A/ evaluated MSMA for control of nutsedge in citrus
orchards in Texas and found that MSMA in 4 applications at 30-day intervals
resulted in complete topkill a few days after application.  However, 60%
regrowth was experienced 30 days after the fourth application.
I/ Roeth, F. W., "Herbicidal Control of Johnson Grass in Noncropland,"
     Proc. North Cent. Weed Control Conf., 27:56-57  (1972).
2J Sckerl, M. M., R. E. Frans, and A. E. Spooner, "Selective Inhibition
     of Johnson Grass with Organic Arsenicals," Proc. South. Weed Sci. Soc.,
     19:351-357 (1966).
3/ Millhollon R. W., "Control of Johnson Grass on Drainage Ditchbanks in
     Sugarcane." Weed Sci.. 17:370-373 (1969).
4/ Leyden, R. F., "Control of Nutsedge in Texas Citrus Orchards,"
     Proc. South. Weed Sci. Soc., 20:130-133  (1967).

                                      108

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     Keeley and Thullen  (1971)i/ found that an application of 3 Ib/acre  of
MSMA provided significantly better control of purple nutsedge than DSMA.
Regrowth was 89% in 3 weeks after application of DSMA and 11% in 3 weeks
afte-r application of MSMA.  Three applications of these herbicides resulted
in a 57% regrowth 1 week after the last application of DSMA and a 9% regrowth
with MSMA.  In another test it was found that purple nutsedge was more diffi-
cult to control than the yellow.

     Jagshitz (1975) ?J found that 2 postemergent treatments of -DSMA at  4 Ib AI/
acre applied in early summer, 1974, provided excellent control (96%) of yellow
nutsedge in Kentucky bluegrass, but only good control (84%) in a soil area.
Three applications at 4 Ib Al/acre gave excellent control in both areas, 96% and
93%, respectively.  Turfgrass injury was slight.  Two or 3 applications of DSMA
in midsummer, 1974, also gave excellent control in Kentucky bluegrass, 99% and
98%, respectively, but turfgrass injury was considered objectionable.


Efficacy in Crop Uses

Weed Control on Cotton - MSMA and DSMA are registered for directed application
on cotton for postemergent control of a variety of broad-leaved weeds,  grasses
and morning glory.  Most topical applications are not Federally registered, but
some states are reported to have registered this method of application.  DSMA
has been the most common arsenical, but the recent trend is toward MSMA use.
One commercial formulation of DSMA is Federally approved and registered for topi-
cal application with either ground or aerial equipment.

                             3/
     Hamilton and Arle (1970)  evaluated directed applications of DSMA and
MSMA on irrigated cotton at University of Arizona experimental stations and
found that broadleaf weed control averaged 100% when 3 to 4 direct applications
of DSMA or MSMA were made.  Grass control averaged 92% with DSMA and 91% with
MSMA.  These tests were averaged for a 3-yr period and included weeds and
grasses such as browntop panicum, junglerice, barnyard grass,  red spangletop,
Wright ground cherry, palmer amaranth and wooly morning glory.   Some localized
foliage chlorosis or burning was evidenced after the first application.
_!/ Keeley, P. E., and R. J. Thullen, "Control of Nutsedge with Organic
     Arsenical Herbicides," Weed Sci.. 19:601-606 (1971).
2J Jagshitz, J. A., "Postemergent Crabgrass and Nutsedge Control in Turfgrass
     with Herbicides." Proc. Northeast Weed Sci. Soc.. 29:376-381 (1975).
_3/ Hamilton, K. C., and H. F. Arle, "Directed Applications of Herbicides in
     Irrigated Cotton." Weed Sci.. 18:85-88 (1970).
                                    109

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     Arle and Hamilt'on (1971)!/ evaluated the effects of single or repeated
topical applications of MSMA and DSMA at rates of 2.2 (the recommended rate),
4.5, 6.7, and 9.0 kg Al/ha on irrigated cotton over a 4-yr period.  In 1966,
1967, 1968, and 1969, single topical applications of MSMA. and DSMA at the
given rates were applied to cotton plants 2, 4, 6 and 8 weeks after emergence
when plants measured 5, 10, 20, and 30 cm high, respectively.  In 1968 and 1969,
MSMA and DSMA, at rates of 2.2 and 6.7 kg Al/ha, were applied as topical sprays
1, 2, 3, or 4 times at 2-week intervals.  In 1967 only DSMA was applied.
Untreated cotton height averaged 20, 30, 46 and 71 cm tall at the 4 times
of application, respectively.  There were no significant differences in yield
among rates and dates with single applications of DSMA.  Single applications
of MSMA reduced cotton yields, but only when applied at later dates or
higher rates than is recommended.  MSMA applied at recommended rates and times
of application did not significantly reduce cotton yield.  All single topical
applications of MSMA and DSMA reddened cotton stems and petioles; these symp-
toms were more noticeable with MSMA than DSMA.  In most cases these symptoms
were only temporary and did not affect plant maturity and cotton yield, except
under the conditions previously mentioned.  Repeated topical applications of MSMA
and DSMA discolored or burned cotton foilage, reddened the stems, and stunted
the plants in varying degrees in relation to the rate and number of applications.
Two or more topical applications of MSMA at the recommended rate of 2.2 kg Al/ha
significantly reduced cotton yields as compared to one application of MSMA.  Re~
peated topical applications of MSMA or DSMA at this rate did not affect length,
strength,or fineness of fiber, boll weight or seed per boll, but did decrease lint
percentage.  Different varieties of cotton were used each year, but DSMA, at the
recommended rate, did not significantly reduce cotton yield within any given year
without 3 or more applications.  Single or repeated applications of MSMA affected
cotton growth more than did DSMA.  Commercial formulations of MSMA and DSMA
(specific formulation not given) were mixed in 374 1/ha of water to which 0.5%
of blended surfactant was added (alkarylpolyoxyethylene glycoles, free fatty
acids, and isopropanol).

     Hogue (1971)-?.' compared directed topical applications for MSMA on cotton
in Mississippi and found that there were no significant differences in weed
control between the 2 application methods of the same treatments when based on
hoe labor requirements.  Weed control of sida, pigweed, purslane, prostrate spurge,
spotted spurge, and morning glory was studied.  An initial topical application
of MSMA at 2 Ib Al/acre applied to cotton plants 3 to 6 in tall and then reapplied
2 weeks later did not significantly reduce cotton height compared to directed appli-
cations of MSMA at the same rates and times of application.  However topical appli-
cations of MSMA significantly decreased cotton yields as compared to directed appli-
cations of the same treatment.  The compounds were mixed in water and applied at a
rate of 20 gal/acre.  The mixture contained 0.25% nonionic surfactant plus an un-
specified formulation of MSMA.
I/ Arle, H. F., and K. C. Hamilton, "Topical Applications of DSMA and MSMA in
     Irrigating Cotton," Weed Sci., 19:545-547  (1971).
2/ Hogue, C. W., "Directed Versus Topical Application of Herbicide Combinations
     in Cotton," Proc. South. Weed Sci. Soc., 24:93-98 (1971).

                                    110

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     Hogue (1973)i/ conducted experiments from 1968 to 1971 to evaluate
postemergent weed control with selected herbicides.  He reported  that 1  direct
application of MSMA per year on 3- to 6-in cotton resulted in an  average reduc-
tion of 29 hr of hoe labor per acre in the 1970 to 1971 season.   A single
application of 2.0 Ib Al/acre MSMA resulted in 54% control of broad-leaved weeds,
grasses and morning glory for the 1969 to 1971 period when applied to 6- to  9-in
cotton.  Under the same conditions DSMA resulted in a 51% control.  Average
yie.tds increased with 2 applications of MSMA but were not significantly  differ-
ent with a single application of MSMA or DSMA.

     Baker et al. (1969)2/ studied the effects of timing and method of applica-
tion of MSMA and DSMA on cotton in field experiments in California, Arizona,
and Mississippi.  Rates of application were either 2 or 3 Ib Al/acre of  the
salts and either 2 or 3 applications were made to treated plots.  Cotton was
highly tolerant of directed spray treatments of MSMA and DSMA, and yields were
not reduced.  A topical application to cotton 2 to 4 in tall slightly reduced
yields, but single topical applications made at later stages of growth to other
plants caused progressively severe reductions in yields and delayed maturity,
especially when cotton plants were in the early square and early  bloom stage.

     Havelka and Merkle (1967)!/ found that lint yields were not  affected by a
topical application of DSMA (3 Ib Al/acre) or MSMA (2 Ib Al/acre) when sprayed
at the early square stage, but were severely reduced by treatment at blooming,
which is a later application time than recommended.

     Jeffery et al. (1972)A/ also found that cotton yields were not reduced by
a topical application of MSMA or DSMA except when applied at the bloom stage.
A rate of 2 Ib Al/acre was used for both chemicals.
_!/  Hogue, C. W., "Postemergence Weed Control in Cotton with Linuron and
      Dinoseb," Proc. South. Weed Sci. Soc., 26:135-141 (1973).
21  Baker, R. S., H. F. Arle, H. J. Miller, and J. T. Holstun, "Effects of
      Organic Arsenical Herbicides on Cotton Response and Chemical Residues"*
      Weed Sci. 17(1):37-40 (1969).
31  Havelka, U. D., and M. G. Merkle, "Arsenic Residues in Cotton and Johnson-
      grass /' P^pc,._S^uth.JJeed_Sci._^oc ., 22:51-57 (1969).
4/  Jeffery, L. S., T. MeCutchen, and P- E. Hoskinson, "Effects of DSMA and
      MSMA on Cotton," Tenn. Farm and Home Sci., Progress Report No. 84, pp.
      19-21 (1972).
                                      Ill

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Weed Control on Wheat - Wild oats are a common weed pest in barley and wheat.
Widiger and Klosterboer (1967)*' conducted several tests to determine the
phytotoxicity of MSMA to wheat and wild oats and to evaluate rates of appli-
cation and their effect; on yields.  The results showed that one application
of MSMA gave good control of wild oats, yellow foxtail, green foxtail and
wild mustard.  Wild buckwheat showed early chlorosis and stunting but re-
covered and was not controlled.  The results of 2 tests showed that MSMA
increased wheat yields by 8.0 and 8.6 bu/acre over the untreated check yield
of 24.6 bu/acre.
Weed Control on Soybeans - Cocklebur, pigweed and Johnson grass are major
weed pests in soybeans, often lowering quality and yield.  MSMA effectively
controls Johnson grass but is highly toxic  to soybeans.

     McWhorter  (1970).2/ evaluated a recirculating spray  system for control
of Johnson grass in  soybeans*  The results  showed between 70 and  75% control
at harvest when 3  tp 4 lb of MSMA were applied per acre.  Some injury  to the
beans was evidenced; however, yields increased when  compared to a cultivated
control by 2.0 to  8.0 bu/acre.

     Connell and Derting  (1973)J/ also evaluated MSMA for control of various
weeds in soybeans*   Results of tests at  Schlater, Mississippi, using MSMA at
6.0 Ib/acre, showed  good control of seedling Johnson grass.


Weed Control on Citrus Crops - Herbicide-treated citrus  orchards  promote
faster tree growth;  offer less mechanical injury to  fruit, branches and
roots; and require less fertilizer and water than cultivated orchards.
Klosterboer  (1974)i/ evaluated several herbicides in grapefruit orchards
for phytotoxicity, defoliation, fruit abscission and yield.  The  results
showed defoliation (6.7%) and fruit abscission  (9.2%) which were  slightly
less than the weeded control.

     MSMA and DSMA are not Federally registered or accepted.  However, the
herbicides are registered for state usage.
 I/ Widiger, R. ., and A.  P.  Klosterboer, "The Use of MSMA to Control Certain
      Problem Weeds in Wheat and Barley," Proc. North Cent. Weed Cont. Conf..
      22:57 (1967).
 2j McWhorter, C. G., "A Recirculating Spray System for Postemergence Weed
      Control in Row Crops." Weed Sci.. 18:285-287 (1970).
 3/ Connell, J. T., and C.  W.  Derting, "Glyphosate Performance on Johnson
      Grass and Associated  Weed Species in No Tillage Soybeans," Proc. South.
      Weed Sci. Sec.. 26:51-56 (1973).
 4/ Klosterboer, A, D., "Phytotoxicity of Glyphosate, MSMA and Paraquat
      to Bearing Citrus," Proc. South. Weed Sci. Soc.. 27:166-169 (1974).

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Weed Control on Sugarcane - Johnson grass is the most troublesome weed in Louisi-
ana sugarcane.  Often a planting must be abandoned at the end of the first ratoon
crop because of the heavy infestation of Johnson grass.

     Millhollon (1970) conducted experiments between 1966 and 1968 to evaluate
the use of MSMA for control, of Johnson grass in sugarcane.  The results showed
that 2 applications of 4 Ib/acre MSMA resulted in 96% control of Johnson grass
over 3 years whereas only one application resulted in 59% control.  Yields of
sugar increased an average of 85% over the untreated check plot.

     The initial application of MSMA was only slightly phytotoxic to sugarcane
with temporary mild leaf chlorosis and stunting as the usual symptoms.  The
second application was more phytotoxic as relatively large areas of many leaves
were necrotic after treatment and sugarcane was moderately stunted for several
weeks.
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References
Arle, H. F., and K. C. Hamilton, "Topical Applications of DSMA and MSMA in
  Irrigating Cotton." Weed Sci., 19:545-547  (1971).

Baker, R. S., H. F. Arle, J. H. Miller, and  J. T. Holstun,  Jr.,  "Effects of
  Organic Arsenical Herbicides on Cotton Response and Chemical Residues,"
  Weed Sci.. 17:37-40  (1969).

Connell, J. T., and C. W. Derting "Glyphosate Performance on  Johnson  Grass
  and Associated Weed  Species in No  Tillage  Soybeans," Proc.  South. Weed Sci.
  Soc.,  26:51-56  (1973).

Hamilton, K. C., and H. F. Arle, "Directed Applications  of  Herbicides in
  Irrigated Cotton." Weed Sci.. 18:85-88  (1970).

Havelka, U. D., and Ml G. Merkle, "Arsenic Residues  in Cotton and Johnson-
  grass," Proc. South. Weed  Sci. Soc..  22:51-57  (1969).

Hogue, C. W., "Directed Versus Topical Application of Herbicide  Combinations
  in Cotton," Proc. South. Weed Sci.  Soc., 24:93-98  (1971).

Hogue, C. W.,  "Postemergence Weed Control in Cotton  with Linuron and  Dinoseb,"
  Proc.  South. Weed Sci.  Soc..  26:135-141  (1973).

Jagshitz, J. A., "Postemergent Crabgrass and Nutsedge Control in Turfgrass
  with Herbicides," Proc. South. Weed Sci. Soc.,  29:376-381 (1975).

Jeffery, L.  S., T. McCutchen, and P.  E. Hoskinson, "Effects of DSMA and MSMA
  on Cotton",  Tenn. Farm  and Home Sci.. Prog. Rept.  No.  84,  pp.  19-21 (1972).

Keeley,  P.  E., and R.  J.  Thullen, "Control of Nutsedge with Organic Arsenical
  Herbicides." Weed Sci.. 19:601-606 (1971).

Kinsella, N. J., "Environmental Impact and Public Response  to an Intensive
  Spraying  Program,"  Proc.  South. Weed Sci.  Soc.,  26:334-338 (1973).

Klosterboer, A. D., "Phytotoxicity  of Glyphosate, MSMA,  and Paraquat  to
  Bearing  Citrus," Proc.  South. Weed Sci.  Soc.,  27:166-169  (1974).

Leyden,  R.  F.  "Control of Nutsedge  in Texas  Citrus Orchards," Proc.  South.
  Weed  Sci.  Soc..  20:130-133 (1967).

McWhorter,  C.  G.,  "A  Recirculating  Spray  System for  Postemergence Weed Control
  in Row Crops," Weed Sci..  18:285-287 (1970).

Millhollon,  R. W., "Control of  Johnson Grass on Drainage Ditchbanks in
  Sugarcane,"  Weed Sci.,  17:370-373 (1969).
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Millhollon, R. W., "MSMA for Johnson Grass Control in Sugarcane," Weed  Sci.,
  18:333-336  (1970).

Offutt, J. R., "Chemical Weed Control Replaces Mechanical Weed Control  in
  Ditch Maintenance." Proc. Calif. Weed Conf.. 19:32-37 (1967).

Roeth, F. W., "Herbicidal Control of Johnson Grass in Noncropland," Proc. North
  Cent. Weed Control Conf.. 28:56-57 (1972).

Sckerl, M. M., R. E. Frans, and A. E. Spooner, "Selective Inhibition of
  Johnson Grass with Organic Arsenicals," Proc. South Weed Sci. Soc.,
  19:351-357  (1966).

Widiger, R. E., "Weeds Controlled by the Methanearsonates," Proc. South. Weed
  Sci. Soc.. 19:51-56 (1966).

Widiger, R. E., and A. D. Klosterboer, "The Use of MSMA to Control Certain
  Problem Weeds in Wheat and Barley," Proc. North Cent. Weed Control Conf.,
  22:55-57 (1967).

Williams, D. J., and G. B. Horsnail, "Asulam for Johnson Grass Control in
  Noncrop Situations," Proc. South. Weed Sci. Soc., 25:347-353 (1972).
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