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Nitrapyrin - Chemical Fact Sheet 6/85

                       CHEMICAL FACT SHEET FOR:



                 1.  DESCRIPTION OF CHEMICAL

- Generic Name:  2-chloro-6-(trichloromethyl)pyridine
- Common Name:  nitrapyrin
- Trade Name:  N-Serve
- EPA Shaughnessy Code:  069203
- Chemical Abstracts Service (CAS) Number:  1929-82-4
- Year of Initial Registration:  1974
- Pesticide Type:  Bacteriostat

- Chemical Family:  pyridines
- U.S. and Foreign Producers:  Dow Chemical Company


- Application sites:  Nitrapyrin is registered for use as a nitrogen
  stabilizer in corn, cotton, rice, sorghum, strawberries, and wheat.
- Types of formulations:  Emulsifiable concentrate and soluble
- Types and methods of application:  Broadcast or band with soil
  injection or incorporation during or immediately after application.
- Application rates:  0.25 lb. a.i./A to 1.0 lb. a.i./A.
- Usual carriers:  Water and/or fertilizer

                   3.  SCIENCE FINDINGS

Chemical Characteristics

- Nitrapyrin is a white crystalline solid with a mildly sweet odor.
  The melting point is 62-63 degrees C.  The vapor pressure of
  nitrapyrin is 2.8 x 10(-3) mm Hg at 23 degrees C, and its solubility
  is 0.004 grams (g)/100 g in water.

Toxicological Characteristics

- Acute toxicology
  - Nitrapyrin has moderate oral toxicity (Toxicity Category III) and
    is a moderate dermal irritant (Toxicity Category III).
- Chronic toxicology
  - Chronic feeding/oncogenicity, teratogenicity, and reproduction
    testing using nitrapyrin TGAI have been identified as data gaps.
    Previous chronic testing was conducted using 6-chloropicolinic
    acid (6-CPA), a major metabolite which was initially identified as
    the residue of concern.  A chronic feeding/oncogenicity study in
    the rat using 6-CPA, although considered supplementary data,
    indicated (upon reevaluation) significant compound related micro-
    scopic changes (biliary hyperplasia) occurred in female rat livers
    at all doses tested.
  - Nitrapyrin did not demonstrate an increase in unscheduled rat
    hepatocyte DNA synthesis and was not genotoxic in mutagenicity
    tests.  Gene mutation (Ames) and chromosomal aberration tests are
    data gaps.

Physiological and Biochemical Behavioral Characteristics

- Mechanism of action:  Nitrapyrin is an ammoniacal nitrogen
  stabilizer which inhibits the nitrification of ammoniacal and urea
  nitrogen fertilizer in the soil by selectively and temporarily
  inhibiting <<Nitrosomonas spp.>>  These bacteria convert ammonium
  nitrogen to nitrite nitrogen, which in turn is converted to nitrate
  nitrogen by other bacteria, e.g. Nitrobacter.

Environmental Characteristics

- Degradation:  Preliminary data indicate that hydrolysis of
  nitrapyrin is rapid, the rate increasing with increasing temperature.
  It is not affected by pH, and degrades more rapidly in the light than
  in the dark.
- Persistence:  In soil, nitrapyrin has a half-life of <3 to 35 days,
  depending on soil type.
- Bioaccumulation:  Nitrapyrin accumulates in the edible and visceral
  tissues of bluegill sunfish with maximum bioconcentration factors of
  33 X and 60 X, respectively.  The residues depurate rapidly.

Ecological Characteristics

- Avian studies:  Acute oral (mallard duck), >2708 mg/kg (slightly
  toxic); avian dietary (Japanese quail), >820 ppm (slightly toxic).
- Aquatic species studies:  <<Daphnia magna>> 48-hour acute, 5.8 mg/l
  (moderately toxic); bluegill sunfish 96-hour acute, 7.876 mg/l
  (moderately toxic); rainbow trout 96-hour acute, 9.191 mg/l
  (moderately toxic).
- Potential problems for endangered species:  Based on an estimated
  environmental concentration (EEC) of 0.1 ppm in water (due to
  runoff), the expected hazard to aquatic organisms is expected to be
  minimal.  However, use in rice, although estimated to be negligible,
  may result in an EEC in floodwater of 0.4 ppm.  This level may
  impact on endangered or threatened species, such as the Fat Pocket-
  book Pearly Mussel, which is a bottom dweller. and as such would be
  exposed to nitrapyrin in both the water and sediments.  The aquatic
  invertebrate toxicity test data are not appropriate in assessing
  hazard to bivalves.  Therefore, marine mollusk shell deposition
  testing is required.  Formal consultation with the Office of
  Endangered Species, USFWS, will be considered after these data are
  received and evaluated.

Tolerance Assessment

- U.S. tolerances for residues of nitrapyrin (2-chloro-6-(trichloro-
  methyl)pyridine) and its metabolite, 6-chloropicolinic acid, in or
  on raw agricultural commodities, are as follows (40 CFR 180.350):

  Commodities                                Tolerance (ppm)

  Cattle, fat                                      0.05
  Cattle, mbyp                                     0.05
  Cattle, meat                                     0.05
  Corn, fodder                                     1.0
  Corn, forage                                     1.0
  Corn, grain                                      0.1
  Corn, fresh                                      0 1
  Cottonseed                                       1.0
  Goats, fat                                       0.05
  Goats, mbyp                                      0.05
  Goats, meat                                      0.05
  Hogs, fat                                        0.05
  Hogs, mbyp                                       0.05
  Hogs, meat                                       0.05
  Horses, fat                                      0.05
  Horses, mbyp                                     0.05
  Horses, meat                                     0.05
  Poultry, fat                                     0.05
  Poultry, mbyp                                    0.05
  Poultry, meat                                    0.05
  Rice, grain                                      0.2
  Rice, straw                                      2.0
  Sheep, fat                                       0.05
  Sheep, mbyp                                      0.05
  Sheep, meat                                      0.05
  Sorghum, fodder                                  0.5
  Sorghum, forage                                  0.1
  Sorghum, grain                                   0.1
  Strawberries                                     0.2
  Wheat, forage                                    0.5
  Wheat, grain                                     0.1
  Wheat, straw                                     0.5

- No Mexican tolerances or Codex MRL's have been established for
  residues of nitrapyrin.  A Canadian tolerance of 0.1 ppm exists
  for, presumably, residues of nitrapyrin <<per se>> in or on corn.
- Residue studies are not adequate to support existing tolerances.
  The plant and animal metabolisms of nitrapyrin are not adequately
  understood, and analytical methodology may need to be revised when
  required data are evaluated.  Storage stability data and additional,
  more geographically representative residue data are required for
  most commodities.
- Tolerances have been proposed for residues of nitrapyrin and its
  metabolite, 6-CPA, in or on the crop group cereal grains, lettuce,
  potatoes, soybeans, and soybean forage and hay.  The Agency has
  decided, however, that no new tolerances or exemptions will be
  established until all major toxicology and residue chemistry data
  requirements have been satisfied.

Summary Science Statement

- The existing data base is insufficient to fully assess the toxicology,
  residue chemistry, environmental fate, or ecological effects of
  nitrapyrin.  Previous toxicity testing had been conducted using the
  major metabolite 6-chloropicolinic acid, and in most areas previous
  testing was found, upon reevaluation, to be supplementary or invalid
  according to current testing guidelines.


- Risk/benefit review:  None of the risk criteria set forth in Title
  40 Code of Federal Regulations 162.11 for commencing a special review
  have been met or exceeded by nitrapyrin.
- Groundwater potential:  Nitrapyrin <<per se>> has not been previously
  identified as a potential groundwater contaminant, and in monitoring
  studies conducted to date, nitrapyrin residues have not been found in
  groundwater.  However, one study using the 6-CPA metabolite indicated
  a moderate potential for 6-CPA to leach in loam soil.  Therefore,
  environmental chemistry studies are being required in the minimum
  times necessary to conduct the tests, and will be evaluated on an
  expedited basis when received.

                   5.  SUMMARY OF MAJOR DATA GAPS

- 6 months:  product identity and composition, physical and chemical
  characteristics, avian subacute dietary and freshwater fish toxicity,
  acute freshwater invertebrate toxicity.
- 9 months:  hydrolysis, photodegradation, acute dermal and inhalation
  toxicity, primary eye irritation and dermal sensitization, gene
  mutation (Ames).
- 12 months:  preliminary analysis of product samples, leaching and
  adsorption/desorption, structural chromosomal aberration, acute
  toxicity to estuarine and marine organisms.
- 15 months:  teratology (2 species).
- 18 months:  animal metabolism and residues.
- 24 months:  plant metabolism, storage stability, analytical methods
  and stability of residues under storage, crop residue studies for
  corn, sorghum, strawberries, wheat, and cottonseed, general
- 27 months:  aerobic aquatic metabolism, field dissipation (soil) and
  dissipation aquatic (sediment).
- 39 months:  rotational crops (confined), irrigated crops, reproduction
- 50 months:  chronic feeding (2 species), oncogenicity (2 species),
  rotational crops (field).

                    6.  CONTACT PERSON AT EPA

Richard F. Mountfort
Product Manager (23)
Environmental Protection Agency (TS-767C)
401 M Street S.W.
Washington, DC  20460
(703) 557-1830