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Pesticide
Information
Profile
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PCNB
Publication Date: 9/93
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TRADE OR OTHER NAMES
Trade names for products containing PCNB include Avicol, Botrilex,
Folsan, Saniclor, Terraclor, Tubergran and Turcide. The fungicide is often
used in combination with insecticides and fungicides including carbaryl,
imazalil, tridimenol, etridiazole and fuberidazole.
INTRODUCTION
PCNB is a organochlorine fungicide used for seed and soil treatments at
planting. It is also know as quintozene. It is used on a variety of
vegetable and field crops including lettuce, cotton, brassicas, tomatoes,
flowers and bulbs and on turf grass. Depending on the producer and the
manufacturing procedure, PCNB impurities can include hexachlorobenzene,
pentachlorobenzene and tetrachloronitro-benzene.
Most products containing PCNB have been cancelled for use in the United
States.
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Depending on the formulation PCNB carries the signal word WARNING or
CAUTION on the label. The WARNING signal word denotes a moderately toxic
compound and the CAUTION signal word denotes a slightly toxic compound.
The lethal dose for humans is between 500 to 5,000 mg/kg (2). PCNB has a
rat oral LD50 of around 1,500 mg/kg when fed in oil, but when administered in
water, the LD50 was significantly higher (greater than 12,000 mg/kg) (9).
Humans exhibited no skin irritation after a 48-hour, contact but a
sensitivity reaction occurred in 20% of the subjects after a second skin
exposure. This indicates that allergic reactions to repeated exposure may
occur (7).
CHRONIC TOXICITY
Rats fed diets containing PCNB over a wide range of doses (3 mg/kg to 150
mg/kg) for three months had elevated liver to body weight ratios in all groups
except in females at the low dose (9). No blood chemistry changes were seen.
In another experiment, rats fed diets containing high levels (250 mg/kg) of
the fungicide in their food for 90 days showed decreased growth (7).
Dogs fed diets containing relatively low doses for two years showed no
growth related effects or blood changes. Microscopic structural changes were
confined to liver-cell enlargement (7).
Reproductive Effects
A three-generation study of rats fed small amounts of PCNB showed no
effects from the treatment. To produce reproductive effects in mice and rats
required doses close to the lethal levels (2). It is unlikely that this
compound would present a significant reproductive risk to humans chronically
exposed.
Teratogenic Effects
Early studies showed defects in kidney formation in offspring when PCNB
products containing hexachlorobenzene were administered to pregnant mice. In
a later study, feeding pregnant rats moderate doses (125 mg/kg) of pure PCNB
during active organ formation did not result in fetal toxicity or birth
defects. At very high doses (500 mg/kg) female mice produced offspring with
missing kidneys and cleft palate (2). Several of the other products found in
the PCNB fomulation are not teratogenic in rats or mice.
Mutagenic Effects
It appears from limited test information that PCNB is either not
mutagenic or weakly mutagenic (2).
Carcinogenic Effects
As with the teratogenic data, early cancer studies were performed with
PCNB that contained hexachlorobenzene. These studies showed that mice given
very high dose of 464 mg/kg by stomach tube from days 7 to 28 and then placed
on diets of about 50 mg/kg for 18 months, developed liver tumors (2).
Organ Toxicity
Cats given very high oral doses of 1,600 mg/kg showed some blood
chemistry changes (methemoglobin formation) after 24 hours. There was slight
recovery after 48 hours. This condition changes the bloods ability to bind
and carry oxygen throughout the body (7).
Fate in Humans and Animals
In mammals PCNB is eliminated unchanged in the feces or as metabolites in
urine. The speed and thoroughness of absorption varies among species.
Eggs from chickens fed low doses of PCNB in their diets were considered
safe for human consumption. Only trace amounts were found in the milk of cows
fed 25 mg/day.
Storage in the tissues did not occur in rats, dogs, or cows. The major
metabolites are the aniline (PCA) and sulfide (MPCPS) and are found primarily
in the body fat, with minimal amounts in the muscles. Impurities account for
the prominent persistent residues. There is some evidence that
pentachlorphenol is formed directly from PCNB (2).
ECOLOGICAL EFFECTS
The LD50 of PCNB is greater than 3,700 mg/kg in mallards and 170 mg/kg in
bobwhite quail. No tissue buildup was observed (4). Examination of various
organs failed to reveal lesions. This would indicate that PCNB is either only
slightly toxic or practically non-toxic to birds.
PCNB is highly toxic to fish. Relatively low concentrations in water
(0.3 ppm to 9.0 ppm) caused mortality to bluegills and to trout. PCNB has
been shown to accumulate in aquatic animals and in aquatic plants. Algae
accumulate the greatest amount. The bioconcentration factor for algae was
estimated to be roughly 14,000 times the background water concentration of
PCNB (2, 8).
ENVIRONMENTAL FATE
The amount of time for one half of the PCNB fungicide to be eliminated
from an area of application is between 5 to 10 months. The soil type is the
main source of variation. PCNB is lost largely through evaporation. PCA, one
of the breakdown products of PCNB, is less toxic to microorganisms (4).
Metabolites in the soil include aniline, pentachlorabenzene,
hexachlorabenzene, and sulfide. These will persist for two or three years.
Under oxygenated conditions, many soil bacteria aid in the breakdown of this
product (8).
Plants take up PCNB from both soil and water (4). One week after young
cotton plants were treated with 300 ppm PCNB, they contained 91 ppm of the
parent compound and 2.0 ppm pentachlorobenzene, 2.77 ppm hexachloro-benzene,
0.65 ppm aniline, 1.36 ppm sulfide, and traces of other metabolites.
PCNB is unchanged by sunlight. It is not expected to leach extensively,
but it has been found in drinking water in Ohio and in ground water in
California and Ontario, Canada (8).
PHYSICAL PROPERTIES AND GUIDELINES
Exposure Guidelines:
| NOEL (dog): | 0.75 mg/kg/day |
| ADI: | 0.007 mg/kg/day (EPA) |
| RfD: | 0.003 mg/kg/day |
| LEL: | 4.5 mg/kg/day (dog) |
Physical Properties:
| CAS #: | 82-68-8 |
| Chemical name: | pentachloronitrobenzene |
| Chemical class/use: | nitro aromatic fungicide |
| Solubility in water: | 0.44 mg/l |
| Solubility in other solvents: | slightly soluble in alcohols; freely soluble in benzene and chloroform. |
| Melting Point: | 144 degrees C |
| Vapor Pressure: | 1.1 x 10 to the minus 4 mm Hg |
BASIC MANUFACTURER
Uniroyal Chemical
World Headquarters
Middlebury, CT 06749
Telephone: 203/573-200
Emergency: 209/224-8910
Review by Basic Manufacturer:
Comments solicited: October, 1991
Comments received:
REFERENCES
Shepard, Thomas H. (1986). Catalog of Teratogenic Agents. The John
Hopkins University Press, Baltimore, MD.
National Library of Medicine (1992). Hazardous Substances Databank.
TOXNET, Medlars Management Section, Bethesda, MD.
U. S. Environmental Protection Agency (1976). Initial Scientific
Review of PCNB, Substitute Chemical Program. Office of Pesticide Programs,
Criteria and Evaluation Division.
Scott Products (No date). PCNB. Technical Data, 34 pages.
U. S. Environmental Protection Agency (1968-81). Pesticide Abstracts,
Office of Pesticides and Toxic Substances, Management Support Division, 75-
0098, 78-2944, 79-1635, 80-0246, 81-1983.
Food and Drug Administration (1986). The FDA Surveillance Index.
Bureau of Foods, Dept of Commerce, National Technical Information Service,
Springfield, VA.
Edwards, I. Ralph, Donald G. Ferry, and Wayne A. Temple.
Fungicides an Related Compounds. in Handbook of Pesticide Toxicology, Volume
3 Classes of Pesticides. Wayland J. Hayes and Edward R. Laws Editors.
Academic Press, Inc. NY.
Howard, Philip H. (1991). Handbook of Environmental Fate and
Exposure data for Organic Chemicals, Volume III. Lewis Publishers, Chelsea,
MI.
The Agrochemicals Handbook. 1991. Royal Society of Chemistry.
Cambridge, England.
Disclaimer: Please read
the pesticide label prior to use. The information contained at this web
site is not a substitute for a pesticide label. Trade names used herein
are for convenience only; no endorsement of products is intended, nor is
criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
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