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Aldicarb (Temik) - Chemical Fact Sheet 6/88

                          CHEMICAL FACT SHEET FOR




1.  Description of Chemical

   - Common Name:   Aldicarb
   - Generic Name:  2-methyl-2-(methylthio) proprionaldehyde
                    0-(methylcarbamoyl) oxime
   - Trade Name:    Temik
   - EPA Shaughnessy Code: 098301
   - Chemical Abstracts Service (CAS) Number:  116-06-3
   - Year of Initial Registration:  1970
   - Pesticide Type:  Insecticide, acaricide, nematicide
   - Chemical Family:  Carbamate
   - U.S. and Foreign Producers:  Rhone-Poulenc (formerly Union Carbide
                                  Agricultural Chemical Co.)
2.  Use Patterns and Formulations

   - Aldicarb is currently registered for use only on cotton, potatoes,
     citrus, peanuts, soybeans, sugar beets, pecans, tobacco, sweet
     potatoes, ornamentals, seed alfalfa, grain sorghum, dry beans, and
     sugar cane.
   - Types and Methods of Application:  Soil incorporated.
   - Application Rates:  0.3 - 10.0 lbs. active ingredient.
   - Types of Formulation:  Granular formulation (15%, 10%, and 5%).  Also
     as a granular in a mixture with the fungicides pentachloronitrobenzene
     and 5-ethoxy-3-(trichloromethyl)-1,2,4-thiadiazole.
3.  Science Findings

   Chemical Characteristics
   - Technical aldicarb is a white crystalline solid with a melting point
     of 98-100 C (pure material).  Under normal conditions, aldicarb is a
     heat-sensitive, inherently unstable chemical and must be stabilized to
     obtain a practical shelf-life.
   Toxicological Characteristics
   - Aldicarb is a carbamate insecticide which causes cholinesterase
     inhibition (ChE) at very low exposure levels.  It is highly toxic by
     the oral, dermal and inhalation routes of exposure (Toxicity Category
     I).  The oral LD50 value for technical aldicarb is 0.9 mg/kg and 1.0
     mg/kg for male and female rats, respectively. The acute dermal LD50
     for aldicarb in rats is 3.0 mg for males and 2.5 mg for females.
     Rats, mice and guinea pigs were exposed to aldicarb, finely ground,
     mixed with talc, and dispersed in the air at a concentration of 200
     mg/m^3 for five minutes; all animals died.  At a lower concentration
     (6.7 mg/M^3), a 15 minute exposure was not lethal;  however, 5 of 6
     animals died during a 30 minute exposure.  Exposure of rats for eight
     hours to air that had passed over technical aldicarb or granular
     aldicarb produced no mortality.  Aldicarb applied to the eyes of
     rabbits at 100 mg of dry powder caused ChE effects and lethality.
   - The toxicity data base for aldicarb is complete.   The toxicity data
     base includes a 2-year rat feeding/oncogenicity study which was
     negative for oncogenic effects at the no-observed effect level (NOEL)
     of 0.3 mg/kg bw/day; a 100-day dog feeding study and a 2-year dog
     feeding study with NOELs of 0.7 and 0.1 mg/kg bw/day, respectively,
     for effects other than cholinesterase inhibition (highest levels
     tested (HLT)); an 18-month mouse feeding/oncogenicity study with a
     NOEL of 0.7 mg/kg bw/day and was negative for oncogenic effects at the
     levels tested (0.1, 0.3 and 0.7 mg/kg bw/day);a 2-year mouse
     oncogenicity study which was negative for oncogenic effects; a 6-month
     rat feeding study using aldicarb sulfoxide with a NOEL of 0.125 mg/kg
     bw/day for ChE inhibition; a 3-generation rat reproduction study with
     a 0.7 mg/kg bw/day NOEL; a rat teratology study, which was negative
     for teratogenic effects at 0.5 mg/kg bw/day (HLT);  a hen
     neurotoxicity study which was negative at up to 4.5 mg/kg bw/day; a
     mutagenicity study utilizing the rat hepatocyte primary culture/DNA
     repair test which was negative for mutagenic effects at 10,000
     ug/well; and a mutagenicity test utilizing an in vivo chromosome
     aberration analysis in Chinese hamster ovary cells which was negative
     for mutagenic effects at 500 ug/ml.

   Physiological and Biochemical Behavioral Characteristics
   - Aldicarb and its metabolites are absorbed by plants from the soil and
     translocated into the roots, stems, leaves, and fruit.  The available
     data indicate that the metabolism of aldicarb in plants and small
     animals is similar.
   - Aldicarb is metabolized rapidly by oxidation to the sulfoxide
     metabolite, followed by slower oxidation to the sulfone metabolite,
     which is 25 times less acutely toxic than aldicarb. Both metabolites
     are subsequently hydrolyzed and degraded further to yield less toxic
     entities.  Available studies demonstrate that the administration of
     aldicarb to a lactating ruminant results in the rapid metabolism and
     elimination of the material.  No residues of the parent compound and
     little, if any, residues of aldicarb sulfoxide or aldicarb sulfone are
     found in the tissues and milk.  the predominant residue detected in
     tissues and milk is aldicarb sulfone nitrile.

   Environmental Characteristics
   - Sufficient data are available to fully assess the environmental fate
     of aldicarb.  From the available data, aldicarb has been determined to
     be mobile in fine to coarse textured soils, even including those soils
     with high organic matter content, and has been found to reach ground
     water.  Aldicarb is not expected to move horizontally from a bare,
     sloping field.  Therefore, accumulation of aldicarb in aquatic
     nontarget organisms is expected to be minimal.  This is further
     supported by an octanol/water partition coefficient of 5 and an
     ecological magnification value of 42.

   Ecological Characteristics
   - Aldicarb is highly toxic to mammals, birds, estuarine/marine
     organisms, and freshwater organisms.  LC50 values for the bluegill
     sunfish and rainbow trout have been reported as 50 ug/liter and 560
     ug/liter, respectively.  An LC50 of 410.7 ug/liter was reported for
     the Daphnia magna.  Studies on the toxicity of aldicarb to the mallard
     duck and bobwhite quail indicate LD50 values of 1.0 and 2.0 mg/kg,
   - Limited exposure to mammals is expected from a dietary standpoint.
     However, data from field studies and the use history of aldicarb
     provide sufficient information to suggest that application of this
     pesticide may result in some mortality, with possible local population
     reductions of some avian species.  Whether these effects are
     excessive, long-lasting, or likely to diminish wildlife resources
     cannot be stated with any degree of certainty.  Therefore, additional
     field studies have been required to further quantify the impact on
     avian and small mammal populations.  Field study results will be
     submitted in April 1988.
   - Aldicarb has also been found to pose a threat to the endangered
     Attwater's Greater Prairie Chicken, living in or near aldicarb-treated
     fields.  Accordingly, all aldicarb products are required to bear
     labeling restrictions prohibiting the use of the product in the Texas
     counties of Aransas, Austin, Brazoria, Colorado, Galveston, Goliad,
     Harris, Refugio, and Victoria if this species is located in or
     immediately adjacent to the treatment area.

   Tolerance Assessment
   - The Agency is in the process of reassessing the existing tolerances
     for aldicarb.  Processing studies for coffee and potatoes have been
     submitted and are acceptable.  A large animal metabolism study has
     been submitted to the Agency and satisfies the data requirement.  A
     completed study of aldicarb residues on soybean processing fractions
     is to be submitted by August, 1988.  The requirement to submit a study
     analyzing aldicarb residues on treated cotton forage has been
     satisfied with a label restriction prohibiting the feeding of treated
     forage to livestock.

   Problems known to Have Occurred with Use of the Chemical
   - In 1979 aldicarb residues were found in drinking water wells located
     near aldicarb treated potato fields in Suffolk County, Long Island,
     New York, at levels greater than 200 parts per billion (ppb).
     Subsequently, aldicarb has been detected in ground water in 48
     counties within 15 other States at levels up to 515 ppb.  In all, the
     Agency has evaluated over 35,000 ground water samples of which 32%
     were positive for residues of aldicarb.  The Agency's Office of
     Drinking Water (ODW) has established a Health Advisory level (HA) of
     10 ppb for residues of aldicarb in drinking water.
   - The Pesticide Incident Monitoring System (PIMS) reports on aldicarb
     from 1966 through 1982 contained 165 incidents associated with human
     injury.   Most of the human incidents alleged that aldicarb was the
     cause of the problem, but there was insufficient evidence to support
     such a conclusion.  Those incidents involving confirmed aldicarb
     poisonings appeared to be the result of failure to use label
     recommended safety equipment while applying aldicarb.  Other incidents
     resulted from accidental spillage, ingestion of aldicarb, or
     consumption of food commodities improperly treated with aldicarb.
   - The largest document episode of foodborne pesticide poisoning in North
     American history occurred in July 1985 from aldicarb-contaminated
     California watermelons.  More than a thousand probable causes were
     reported from California, Oregon, Washington, Alaska, Idaho, Nevada,
     Arizona and Canada.  The spectrum of illness attributed to aldicarb
     ranged from mild to severe and included cases of grand mal seizures,
     cardiac arrhythmias, severe dehydration, bronchospasms, and at least
     two stillbirths occurring shortly after maternal illness.  The prompt
     embargo of watermelons on July 4, 1985 abruptly terminated the major
     portion of the outbreak and reported illnesses occurring after the
     implementation of the watermelon certification program were far fewer
     and milder in comparison to earlier cases.  Contamination of the
     watermelons ranged up to 3.3 ppm of aldicarb sulfoxide (ASO), a
     metabolite of aldicarb.  Clinical signs occurred from exposures to
     dosages estimated to be as low as 0.0026 mg/kg ASO.

4.  Summary of Regulatory Position and Rationale:

   - Dietary Exposure to Treated Food Commodities
     - The Agency has recently received the final results of a National
       Food Survey which monitored raw agricultural commodities for
       residues of aldicarb in the market place.  After these data have
       been evaluated, the dietary exposure from consuming treated food
       commodities will be estimated, and a risk assessment will be
       conducted.  The Agency may propose further regulatory action
       depending on the results of this study.
   - Dietary Exposure to Contaminated Ground Water
     - The Agency has concluded that there are unacceptable risks to
       persons consuming drinking water that is contaminated with aldicarb
       at levels greater than the HA of 10 ppb due to a reduced margin of
       safety for ChE inhibition.
     - The Agency cannot identify all specific areas of the nation where
       aldicarb residues exceed the HA, or the number of people who would
       be exposed to these high levels of contamination.  However, the
       Agency can predict certain areas of the nation where the ground
       water supplies have a relatively high vulnerability to aldicarb
       contamination due to the hydrogeology and/or agronomic practices
       found in that area.  Additionally, the Agency can predict certain
       areas which would have a medium vulnerability to contamination,
       although the vulnerability within some of these areas could vary
       greatly with some areas being much more vulnerable.
     - It is the Agency's presumption that the risks posed by aldicarb
       contamination of ground water above the HA in current or potential
       drinking waters will likely be more significant, in almost all
       cases, than any local benefit derived from aldicarbs continued use.
       Consequently, the Agency is proposing to regulate the use of
       aldicarb in order to eliminate or prevent contamination of ground
       water at levels above the HA.  As a basic level of protection for
       all areas where aldicarb is used, the Agency is proposing a number
       of restrictions on the label.  Specifically, no use of aldicarb
       would be permitted within 300 feet of a drinking water well, and
       aldicarb would be classified as a restricted use pesticide due to
       ground water concerns.  (Aldicarb is already classified as a
       restricted use pesticide due to its acute toxicity.)  Additionally,
       the Agency is seeking public comment as to what, if any, additional
       measures should be considered regarding the use of aldicarb and
       site-conditional restrictions.
     - The Agency will also require monitoring in those areas classified as
       having a medium tendency to leach.  The data generated will be used
       to determine whether further regulatory action is required in these
     - Finally, for those areas where there is the greatest likelihood of
       ground water contamination, states will need to implement, either
       for the entire state or for a county(ies) within the state, State
       Pesticide Ground Water Management Plans (MPs).  Briefly, MPs are
       comprehensive plans which describe the measures states will impose
       to prevent ground water contamination.  The Agency believes that MPs
       provide the best method of protection ground water pesticide
     - The Agency is soliciting public comment on a number of issues
       regarding its preliminary determination for aldicarb.  Included are
       questions regarding the components of an MP, which assessment
       (hydrogeologic region or county) should be used in identifying those
       areas where contamination is most likely to occur, how should a
       localized risk/benefit analysis be performed and who should conduct
       it, and who is responsible for the costs associated with cleaning up
       ground water contamination

5.  Summary of Major Data Gaps

6.  Contact Person at EPA

   Bruce Kapner
   Special Review Branch, Registration Division
   Office of Pesticide Programs (TS-767C)
   401 M St., SW.
   Washington, D.C.  20460
   Phone:  (703) 557-1170