Nitrapyrin - Chemical Fact Sheet 6/85
CHEMICAL FACT SHEET FOR:
FACT SHEET NUMBER: 54
DATE ISSUED: JUNE 28, 1985
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
2. USE PATTERNS AND FORMULATIONS
- 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
- 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.
- 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
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.
- 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.
- 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
- 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.
- 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
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
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
- 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.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
- 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
- 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
DISCLAIMER: THE INFORMATION PRESENTED IN THIS CHEMICAL INFORMATION FACT
SHEET IS FOR INFORMATIONAL PURPOSES ONLY AND NOT TO BE USED TO FULFILL
DATA REQUIREMENTS FOR PESTICIDE REGISTRATION AND REREGISTRATION.