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paraquat; Herbicide Profile 2/85

      CHEMICAL NAME:      1,1'-dimethyl-4,4'-bipyridinium ion; present as the
                          dichloride salt (ICI/Chevron) or dimethyl sulfate
                          salt (56).
      TRADE NAME(S):      Ortho Paraquat, Gramoxone (58).
      FORMULATION(S):     Only available as an aqueous solution containing
                          0.24 kg (2 lb) paraquat cation per L (gal) as the
                          dichloride salt (58).
      TYPE:               Dipyridyl herbicide
      BASIC PRODUCER(S):  Chevron Chemical Co.
                          575 Market St.
                          San Francisco, CA 94105
      STATUS:  Restricted use.  RPAR:  criteria possibly met or
      exceeded:  emergency treatment, chronic effects.  Decision document
      returning paraquat to the Registration Process was signed on 6/29/82.
      Decision Document outlines data gaps and voluntary cancellation of
      certain noncrop use sites (22).
      PRINCIPAL USES:  For desiccation of seed crops, for noncrop and
      industrial weed control in bearing and nonbearing fruit orchards, shade
      trees and ornamentals, for defoliation and desiccation of cotton, for
      harvest aid in soybeans, sugarcane, guar and sunflowers, for pasture
      renovation, for use in "No-Til' or before planting or crop emergence,
      dormant alfalfa and clover, directed spray and for killing potato
      vines.  Paraquat is also effective for eradication of weeds in rubber
      plantations, coffee plantations, and paddy bund (56).
      APPLICATION METHOD(S): Ground or air foliar spray - contact activity
      mainly (58).
                                   I.  EFFICACY
      Important Weeds Controlled: Most annual weeds and grasses (8b).
           Regrowth may occur in perennials with large underground root
      systems.  Rainfall after application has little bearing on effectiveness
                             II.  PHYSICAL PROPERTIES
      MOLECULAR FORMULA:  C12 H14 N2 (cation only) (62); C12 H14 N2 Cl2
                          (dichloride salt) (58).
      MOLECULAR WEIGHT:   186.2 (cation only); 257.2 (dichloride salt) (58).
      PHYSICAL STATE:     White crystalline solid (pure salt); dark red
                          solution (technical product) (58).
                          Technical product > 95% pure (62).
      ODOR:               Faint ammoniacal odor (pure compound) (58).
      DECOMPOSITION TEMPERATURE:  approximately 300c (pure compound) (58).
      BOILING POINT:      Salts decompose at high temperatures, charring
                          rather than melting or boiling (58).
      VAPOR PRESSURE:     Nonvolatile.  Vapor pressure of salts is very low,
                          below 1 x 10-7 mmHg (pure compound) (58).
      SOLUBILITY:         Completely soluble in water (pure compound) (58).
                          III.  HEALTH HAZARD INFORMATION
      OSHA STANDARD:  0.5 mg/m3 averaged over an eight-hour work shift (14).
      ACGIH RECOMMENDED LIMIT:  TWA (Time Weighted Average) = 0.1 mg/m3
                                (respirable sizes) (15c).
           A.  ACUTE TOXICITY
               DERMAL:  LD50 = >480 mg paraquat ion (rabbit).  The
                          concentrate is irritant to skin.  Absorption through
                          intact skin is minimal, but may be facilitated if the
                          skin is damaged (58).
                        LD50 = c. 236 mg/kg (rabbit) (62).
               ORAL:    LD50 = 120 mg parathion ion /kg (58).
                        LD50 = 150 mg paraquat ion/kg (rat); 104 mg/kg (mouse);
                          25-50 mg/kg (dog); 262 mg/kg (Rhode Island hen); 70
                          mg/kg (sheep) (62).
               INHALATION:  As paraquat has no appreciable vapor pressure,
                            there is no hazard from inhalation.  Prolonged,
                            direct contact with the spray mist may cause oral
                            and nasal irritation, and should be avoided (58).
               EYES:    The concentrate is irritating to the eye (58).
           Subacute percutaneous LD50 (20 applications), greater than 24 mg
      paraquat ion/kg (rabbit).
           Rats:  2-year feeding studies did not reveal significant
      abnormalities at dietary levels up to 170 ppm paraquat ion.
           Dogs:  No significant abnormalities were seen after feeding a diet
      containing 34 ppm paraquat ion for 27 months.  Effects were apparent at
      dietary levels of 85 and 170 ppm (58).
                        IV.  ENVIRONMENTAL  CONSIDERATIONS
           Paraquat has a wide margin of safety between recommended dosages
      and rates necessary to cause toxic symptoms to fish and wildlife
      species (58).
           Toxicity to fish depends on the formulation and wetter used, LC50
      (96-hr) is:  for rainbow trout 32 mg/l; for brown trout 2.5-13 mg/l
      Behavior In Or On Soils
      1.  Adsorption and leaching characteristics in basic soil types:  An
            important and unique property of paraquat is its very rapid
            and complete inactivation by soil.  This results from
            reaction between the double positively charged paraquat
            cation and clay minerals present in soils to form complexes
            with the negatively charged sites on the clay minerals (and
            even insertion into the layer planes of such minerals as
            Paraquat cannot be removed from such sites by washing, even
            with saturated solutions of salts, and can only be
            regenerated by breaking down the clay mineral with 18 N
            sulfuric acid.  Most soils have sufficient capacity in the
            top inch of soil alone to bind many hundred times the normal
            field rates of application of paraquat in this form.  There
            are also other forms of binding of paraquat in soils -- e.g.,
            by reaction with humic acids and by normal Langmuir type
            adsorption onto organic matter and soil particles.  In the
            case of this rather weaker binding there is a true
            equilibrium between the quantity adsorbed and free paraquat
            in an aqueous phase in contact with the soil.  However, even
            in this case, fairly high concentrtions in the soil are
            required to give phytotoxic concentrations of paraquat in the
            soil water.
      2.  Microbial breakdown:  Experiments with micoorganisms in culture
            media have shown that certain of these are capable of
            decomposing paraquat in the absence of soil.  However, they
            degrade bound paraquat with difficulty or not at all.
      3.  Loss from photodecomposition and/or volatilization:  Loss of
            paraquat can occur by photochemical decomposition on sprayed
            leaf surfaces and on dead and decaying vegetation.
            Photochemical decomposition of paraquat has also been shown
            in the laboratory by irradiating thin layers of soil, but
            such decomposition on the soil has not been unequivocally
            demonstrated under field conditions.
      4.  Resultant average persistence at recommended rates:  When bound to
            soil is very persistent but biologically unavailable (58).
           The chemical information provided below has been condensed
      from original source documents, primarily from "Recognition and
      Management of Pesticide Poisonings", 3rd ed. by Donald P.  Morgan,
      which have been footnoted.  This information has been provided in
      this form for your convenience and general guidance only.  In
      specific cases, further consultation and reference may be required
      and is recommended.  This information is not intended as a sub-
      stitute for a more exhaustive review of the literature nor for the
      judgement of a physician or other trained professional.
           If poisoning is suspected, do not wait for symptoms to develop.
      Contact a physician, the nearest hospital, or the nearest Poison
      Control Center.
           FREQUENT SYMPTOMS AND SIGNS OF POISONING:  Exposure to paraquat
      may cause irritation of the eyes, nose, throat, and skin.  It may also
      cause nose bleeding and abnormalities or loss of fingernails.  Exposure
      to mixtures of paraquat and a related compound, diquat, may cause
      serious and permanent injury to the eyes (14).
           The earliest (1-4 days) symptoms of injury and signs following
      ingestion of a toxic dose of PARAQUAT are burning PAIN (oral,
      substernal, abdominal), NAUSEA, VOMITING, DIARRHEA, and sometimes
      melena.  Early symptoms are sometimes so mild that vigorous treatment
      is improperly delayed.
           From 24-74 hours, indications of renal and hepatic insult appear.
      Albuminuria, hematuria, pyuria, and ELEVATED BUN and CREATININE may
      occur.  OLIGURIA may develop, and this signals severe poisoning.
      JAUNDICE and elevations of serum GOT, GPT, LDH, and alkaline
      phosphatase reflect hepatocellular injury.  These injuries are usually
      reversible, although severe renal tubular damage may require
      extracorporeal hemodialysis.
           A progressive decline in arterial oxygen tension and CO diffusion
      capacity commonly precedes the appearance of pulmonary symptomatology.
      COUGH, DYSPNEA, and TACHYPNEA usually appear 72-96 hours after paraquat
      ingestion, but may be delayed as long as 14 days.  Progressive CYANOSIS
      reflects deteriorating gas exchange caused by the fibrogenic reaction
      in the alveolar sacs.  In a few cases, the production of COPIOUS WATERY
      SPUTUM (pulmonary edema) has followed ingestions of large amounts (200
      ml) of paraquat or diquat concentrate (25).
           SKIN CONTACT:  If paraquat or solutions containing paraquat get on
      the skin, immediately flush the contaminated skin with water.  If
      paraquat or solutions containing paraquat soak through the clothing,
      remove the clothing immediately and flush the skin with water.  If
      irritation persists after washing, get medical attention (14).
           INGESTION:  Induce vomiting and send to a hospital as quickly as
      possible (58).
           INHALATION:  If a person breathes in large amounts of paraquat,
      move the exposed person to fresh air at once.  If breathing has
      stopped, perform artificial respiration.  Keep the affected person warm
      and at rest.  Get medical attention as soon as possible (14).
           EYE CONTACT:  If paraquat or solutions containing paraquat get
      into the eyes, wash eyes immediately with large amounts of water,
      lifting the lower and upper lids occasionally.  Get medical attention
      immediately.  Contact lenses should not be worn when working with this
      chemical (14).
      1.   After a DIPYRIDYL compound has been INGESTED, EVACUATE the
           STOMACH, then LOAD the gastrointestinal tract with an effective
           ADSORBENT, to minimize toxicant absorption.  These measures must
           be undertaken immediately, even though the patient is free of
           signs of systemic toxicity, and even when, by all accounts, the
           ingested dose was probably small and was taken as long as several
           days prior to treatment.
           INTUBATE the STOMACH, ASPIRATE content, then LAVAGE with at least
           two liters of a slurry of ADSORBENT in normal saline.  Then,
           slowly instill several hundred additional ml of adsorbent slurry,
           allowing the stomach and intestine to accommodate this volume
           without overdistension and vomiting.
           A.   The ideal adsorbent is BENTONITE, administered as a 7 gm per
                100 ml suspension.  If not immediately available, use
                ACTIVATED CHARCOAL, 30-50 gm in 300-400 ml of water, or any
                concentration that will flow through the tube.  As soon as
                bentonite has been obtained, administer it as rapidly as the
                patient will tolerate it.  If patient cannot swallow
                bentonite, administer it by stomach tube at the highest
                concentration that will flow through the tube.
           B.   Initiate SALINE CATHARSIS.  Give SODIUM SULFATE, 0.25 gm/kg,
                and repeat in two hours if no bowel movement has occurred.
                Magnesium salts are probably contraindicated, because of the
                risk of magnesium retention in the presence of impaired renal
           C.   Continue administering bentonite suspension and sodium
                sulfate until the gut has been thoroughly flushed.  This may
                require several days.
      2.   Secure samples of blood and urine for dipyridyl analysis.  (See
           Confirmation of Diagnosis.)
      3.   Commence INTRAVENOUS INFUSIONS of glucose and electrolyte to
           minimize toxicant concentrations in the tissues, and expedite
           excretion of the dipyridyl.  Attempt to establish a diuresis of
           10-15 liters per day.
           CAUTION:  Monitor fluid balance and electrolytes continuously to
                     insure against fluid overload if acute tubular necrosis
      4.   Although cases of paraquat poisoning have been successfully
           managed by forced diuresis regimens alone, it is more effective to
           use extracorporeal HEMODIALYSIS and/or HEMOPERFUSION over
           specially coated charcoal.  This procedure for toxicant removal is
           best executed in tertiary care centers where blood levels of
           paraquat can be monitored regularly, and various complications of
           hemoperfusion can be detected and forestalled.  The prognosis is
           generally good when blood levels do not exceed 0.05 to 0.10 ppm by
           24-48 hours after paraquat ingestion.
      5.   DO NOT ADMINISTER SUPPLEMENTAL OXYGEN in paraquat poisoning.
           Increased levels of alveolar oxygen accelerate the pathologic
           process in the lung caused by paraquat.  Some clinicians recommend
           maintaining the patient in an atmosphere of 15-16% oxygen as soon
           as possible, to retard the fibrogenic process.
      6.   The topical injuries to mucous membranes produced by ingested
           dipyridyls are painful and may require topical local anesthetic.
      7.   The effectiveness of various medicines and procedures in paraquat
           poisoning remains uncertain.  The free-radical scavenger
           superoxide dismutase is theoretically appropriate as an antidote,
           but is unproved.  Corticosteroids are often given, and may be
           helpful.  There is limited laboratory evidence supporting the use
           of propranolol and expectorants:  glyceryl guaicolate, anise oil,
           terpin hydrate, ammonium chloride and potassium iodide.  One
           victim is thought to have benefited from a combination of
           azathioprine and potassium aminobenzoate.  Lung transplant in one
           case of paraquat poisoning was not successful (25).
                        VI.  FIRE AND EXPLOSION INFORMATION
           Commercial formulation is an aqueous salt solution, nonflammable
                                VII.  COMPATIBILITY
           Not compatible with some alkyl sulfonate or alkyl aryl sulfonate
      wetting agents or alkali-metal salts of hormone weed killers.  Liable
      to hydrolysis in the presence of alkaline materials including alkaline
      waters.  At all dilutions generally used, paraquat is virtually
      noncorrosive to materials commonly used in spraying equipment.  It is
      generally not advisable to store undiluted paraquat in contact with
      metals; the undiluted material is best kept in the original container
                            VIII.  PROTECTIVE MEASURES
      STORAGE AND HANDLING:  Under normal storage conditions, in original
      containers, shelf life is indefinitely long.  The dry chemical is
      somewhat sensitive to ultraviolet light.  The product is stable to heat
      beyond the range of ordinary ambient temperatures (58).  Paraquat can
      kill if swallowed.  Do not put in food or drink containers.  Keep out
      of reach of children (56).
      PROTECTIVE CLOTHING:  Personnel must wear full protective equipment at
      all times.  This includes:  Neoprene-coated or rubber glvoes, workshoes
      or overshoes, latex rubber apron, goggles to protect eyes, overalls or
      rubber suit (56).
                                         Minimum Respiratory Protection*
         Condition                          Required Above 0.5 mg/m3
         _________                          ________________________
      Particulate Concentration
      1.5 mg/m3 or less            Any chemical cartridge respirator with an
                                   organic vapor cartridge(s) and dust and
                                   mist filter(s), including pesticide
                                   respirators which meet the requirements of
                                   this class.
                                   Any supplied-air respirator.
                                   Any self-contained breathing apparatus.
      Greater than 1.5 mg/m3** or  Self-contained breathing apparatus with a
      entry and escape from        full facepiece operated in pressure-demand
      unknown concentrations       or other positive pressure mode.
                                   A combination respirator which includes a
                                   Type C supplied-air respirator with a full
                                   facepiece operated in pressure-demand or
                                   other positive pressure or continuous-flow
                                   mode and an auxiliary self-contained
                                   breathing apparatus operated in
                                   pressure demand or other positive pressure
      Fire Fighting                Self-contained breathing apparatus with a
                                   full facepiece operated in pressure-demand
                                   or other positive pressure mode.
      Escape                       Any gas mask providing protection against
                                   organic vapors and particulates, including
                                   pesticide respirators which meet the
                                   requirements of this class.
                                   Any escape self-contained breathing
      *   Only NIOSH-approved or MSHA-approved equipment should be used.
      **  Use of supplied-air suits may be necessary to prevent skin contact
          while providing respiratory protection from airborne concentrations
          of paraquat; however, this equipment should be selected, used, and
          maintained under the immediate supervision of trained personnel.
          Where supplied-air suits are used above a concentration of 1.5
          mg/m3, an auxiliary self-contained breathing apparatus operated in
          positive pressure mode should also be worn (14).
                       IX.  PROCEDURES FOR SPILLS AND LEAKS
                                  (800) 424-9300
          Persons not wearing protective equipment and clothing should be
      restricted from areas of spills until cleanup has been completed.
          If paraquat is spilled, the following steps should be taken:
      1.  Ventilate area of spill.
      2.  Collect spilled material in the most convenient and safe manner and
          deposit in sealed containers for reclamation or for disposal in a
          secured sanitary landfill.  Liquid containing paraquat should be
          absorbed in vermiculite, dry sand, earth or a similar material.
      Waste disposal method:
          Paraquat may be disposed of in sealed containers in a secured
      sanitary landfill (14).
                               X.  LITERATURE CITED
       8b. Thomson, W.T.  1981.  Agricultural chemicals - book 2:
               herbicides.  Revised ed.  Thomson Publications, Fresno, CA.
               274 pp.
      14.  U. S. Department of Health and Human Services, National Institute
               for Occuptational Safety and Health.  1981.  Occupational
               health guidelines for chemical hazards.  F. W. Mackinson, R.
               S. Stricoff, L. J. Partridge, Jr., and A. D. Little, Inc.,
               eds.  DHHS (NIOSH) Publ. No. 81-123.  Washington, DC.
      15c. American Conference of Governmental Industrial Hygienists.  1984.
               TLVs:  threshold limit values for chemical substances and
               physical agents in the work environment and biological exposure
               indices with intended changes for 1984-85.  Cincinnati, OH.
               116 pp.
      22.  U.S. Environmental Protection Agency, Office of Pesticide
               Programs.  1983.  June 1983 status report on rebuttable
               presumption against registration (RPAR) or special review
               process, registration standards and the data call in
               programs.  Washington, DC.  45 pp.
      25.  Morgan, D.P.  1982.  Recognition and management of pesticide
               poisonings, 3rd ed.  U.S. Environmental Protection Agency,
               Washington, DC.  120 pp.
      56.  Farm Chemicals Handbook, 70th ed.  1984.  R. T. Meister, G. L.
               Berg, C. Sine, S. Meister, and J. Poplyk, eds.  Meister
               Publishing Co., Willoughby, OH.
      58.  Weed Science Society of America, Herbicide Handbook Committee.
               1983.  Herbicide handbook of the weed science society of
               America, 5th ed.  Weed Science Society of America, Champaign,
               IL.  515 pp.
      62.  The Pesticide Manual:  A World Compendium, 7th ed.  1983.  C.R.
               Worthing, ed.  The British Crop Protection Council, Croydon,
               England.  695 pp.