---

The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

---

E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Quintozene, PCNB

Trade and Other Names: The common name for PCNB (Pentachloronitrobenzene) is Quintozene. Trade or other names for PCNB or products containing it include Avicol, Botrilex, Brassicol, Earthcide, Folosan, Kobu, Kobutol, Pentachloronitrobenzene, Pentagen, Saniclor, Terraclor, Terrazan, Tilcarex, Tri-PCNB, Triquintam, Tritisan, Tubergran, and Turfcide.

Regulatory Status: Pentachloronitrobenzene is a slightly toxic compound in EPA toxicity class III. Labels for products containing PCNB must bear the Signal Word CAUTION. Most products containing PCNB have been cancelled for use in the U.S.

Chemical Class: organochlorine

Introduction: PCNB is a organochlorine fungicide used as a seed dressing or soil treatment to control a wide range of fungi species in such crops as potatoes, wheat, onions, lettuce, tomatoes, tulips, garlic, and others. Depending on the producer and the manufacturing procedure, PCNB impurities can include hexachlorobenzene, pentachlorobenzene, and tetrachloronitrobenzene. The fungicide is often used in combination with insecticides and fungicides including carbaryl, imazalil, tridimenol, etridiazole, and fuberidazole. It is available as a dustable or wettable powder, in granular form, emulsifiable concentrate, and seed treatment.

Formulation: The fungicide is often used in combination with insecticides and fungicides, including carbaryl, imazalil, tridimenol, etridiazole, and fuberidazole. It is available as a dustable or wettable powder, in granular form, emulsifiable concentrate, and seed treatment.

Toxicological Effects:

• Acute toxicity: PCNB is a slightly toxic compound via oral administration. The reported oral LD50 values for test animals are 1710 mg/kg in male rats, 1650 mg/kg in female rats, and 800 mg/kg in rabbits [7,9]. A single oral administration of over 2500 mg/kg in dogs reportedly caused no fatal response [7]. It is slightly toxic via inhalation as well, with a reported 4-hour inhalation LC50 of 6.49 mg/L [9]. PCNB is slightly toxic via the dermal route with reported dermal LD50 values of 2000 to 4000 mg/kg in rats [17]. A dermal dose of 4000 mg/kg in rabbits did not result in observable signs of toxicity or skin irritation [7]. Humans exhibited no skin irritation after a single 48-hour contact, but a second exposure (2 weeks later) elicited a sensitivity reaction in 13 of 50 of the test subjects, indicating a potential for skin sensitization [7]. No reports of skin sensitization have been reported from nonexperimental exposures [7]. It has a potential for eye irritation, and has caused a reversible case of conjunctivitis with some corneal injury [7,17]. Administration of 1600 mg/kg to cats caused disruption of normal transport of oxygen by hemoglobin (methemoglobin), as well as changes in red blood cells [7]. If these effects occur in humans as a result of very high acute exposure, the likely effects could include fatigue, possible dizziness, and lethargy. It seems unlikely, based on the reported levels of methemoglobin (a maximum of about 11%), that loss of consciousness or brain anoxia could occur [7,17].
• Chronic toxicity: Rats fed diets of about 275 mg/kg/day PCNB over 3 months experienced reduced body weights and growth rates [7]. These effects were seen in males at only half that dose [7]. At doses of about 35 mg/kg/day, both sexes of rats showed increased relative liver weights, and males had elevated relative liver weights at doses as low as 3.5 mg/kg/day [7]. In a rat study over the course of 2 years, the sex differences in reduced weight gain were reversed, and the females showed reduced weight gain at doses at which males did not [7]. These decreases in either sex were not markedly different at low and high doses, and did not show a strong relationship to PCNB dose [7]. Dogs showed no growth effects at doses of 20 mg/kg/day, but there was some enlargement in liver cells [7]. In another study in dogs, impairment of liver bile production and fat metabolism was observed at doses of slightly more than 3.5 mg/kg/day, but no adverse effects were seen at about 0.6 mg/kg/day [7].
• Reproductive effects: A three-generation study of rats fed PCNB doses of 25 mg/kg/day (and higher for weanlings) showed no effects from the treatment [7]. Between the treatment and control groups of rats, there were no differences in numbers and positions of implantations, dead/resorbed fetuses, litter size or fetal sex ratios at maternal doses as high as 125 mg/kg/day on days 6 to 15 of pregnancy [7]. Similar findings (lack of reproductive effects) were observed in another rat study at doses up to 200 mg/kg/day on unspecified days [7]. PCNB does not appear to cause reproductive effects.
• Teratogenic effects: There were no increases in visceral or skeletal abnormalities or birth weights at maternal doses as high as 125 mg/kg/day on days 6 to 15 of pregnancy [7]. Findings of missing kidneys and cleft palate in mice at maternal doses of 500 mg/kg/day on days 7 to 11 of gestation may have been attributable to the presence of hexachlorobenzene in the test product (at a level of 11%, or approximately 55 mg/kg/day) [7,17]. The data indicate that PCNB is not teratogenic.
• Mutagenic effects: No significant increases in mutation rates were observed in mice following injection of PCNB just underneath the skin [7]. The dominant lethal assay for mutation in mice was also negative. It has been observed to increase frequency of mutation in E. coli, but it is not clear whether the underlying mutation rate changed or PCNB interfered with DNA repair processes in the cells [7]. It appears that PCNB is either nonmutagenic or weakly mutagenic, and it is unlikely that mutagenic effects would be seen in humans under normal circumstances.
• Carcinogenic effects: The maximum tolerated dosage of about 464 mg/kg/day from day 7 to 28 and about 150 mg/kg/day for 78 weeks (when they were sacrificed) resulted in increased production of liver tumors in mice [7]. Under slightly different conditions, the same results were obtained, also in mice [7]. It is possible that these studies were performed with PCNB samples which may have contained hexachlorobenzene, which may have contibuted to the observed increases. There is insufficient information to determine the carcinogenic potential of PCNB.
• Organ toxicity: The main target organ, following chronic exposure to PCNB, is the liver. Acute effects may occur in the red blood cells and hemoblobin in the circulatory system.

• Fate in humans and animals: PCNB is very rapidly absorbed from the gastrointestinal tract of monkeys [7]. The speed and thoroughness of absorption varies among species. In mammals, PCNB is eliminated unchanged in the feces or as metabolites in urine [7]. While PCNB metabolism may be fairly rapid, the metabolism of the common contaminants of PCNB (hexa- and pentachlorobenzene) may be much slower [7]. The major metabolites are pentachloroaniline, pentachlorophenol, pentachloroanisole, which may be stored in body fat [9]. Storage of PCNB in the tissues did not occur in rats, dogs, or cows. 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 [17].

Ecological Effects:

• Effects on birds: PCNB is practically nontoxic to bird species; the reported acute oral LD50 values were greater than 2000 mg/kg in mallards and pheasants, and 170 mg/kg in bobwhite quail [17,53]. No tissue buildup was observed, and no lesions were found on internal organs [17].
• Effects on aquatic organisms: PCNB is highly toxic to fish, with reported LC50 values of 0.55 mg/L in rainbow trout and 0.1 mg/L in bluegill sunfish [17]. However, other data suggest that it may be less toxic; a water concentration of 1.2 mg/L (its solubility limit in water) reportedly caused no fatalities in rainbow trout and golden orfe [9]. PCNB has been shown to accumulate in aquatic animals and in aquatic plants [68].
• Effects on other organisms: The compound is nontoxic to bees when used as directed [9].

Environmental Fate:

• Breakdown in soil and groundwater: PCNB is of varying persistence in the environment; various half-lives in soil have been reported, ranging from less than 3 weeks to over a year [68]. The soil type is the main source of variation, with more rapid breakdown occurring in sandier soils [68]. Metabolites in the soil include pentachloroaniline, pentachlorobenzene, hexachlorobenzene, and pentochlorothioanisole [12]. These will persist for 2 or 3 years. PCNB is lost mainly through either evaporation or biotransformation [68]. Under oxygenated conditions, many soil bacteria aid in the breakdown of this product [68]. PCNB shows an appreciable capacity for soil binding, and is not expected to be extensively mobile in most soils [12,14]. Even very low mobility of a highly persistent compound, though, can result in appreciable movement over time. PCNB has been found in very low amounts in well water in Ohio and in groundwater in California, Missouri, and Texas, and Ontario, Canada [12].
• Breakdown in water: PCNB is unchanged by sunlight, and is stable in acidic and neutral solutions [9,12]. It is rapidly adsorbed to sediments and suspended solids, absorbed by biota, and volatilized out of the water column, with an estimated half-life of 1.8 to 5 days [12].
• Breakdown in vegetation: Plants take up PCNB from both soil and water, and it may be translocated throughout the plant [17]. Major breakdown products in plants may include pentachloroaniline and methylthiopentachlorobenzene [9]. 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 [17].

Physical Properties:

• Appearance: PCNB is a pale yellow crystalline solid at room temperature [9].
• Chemical Name: pentachloronitrobenzene [9]
• CAS Number: 82-68-8
• Molecular Weight: 295.34
• Water Solubility: 0.44 mg/L @ 20 C [9]
• Solubility in Other Solvents: v.s. in alcohols, benzene, and chloroform [9]
• Melting Point: 144 C [9]
• Vapor Pressure: 6.6 mPa @ 20 C [9]
• Partition Coefficient: 4.46 [17]
• Adsorption Coefficient: 5000 (estimated) [14]

Exposure Guidelines:

• ADI: 0.007 mg/kg/day [8]
• MCL: Not Available
• RFD: 0.003 mg/kg/day [8]
• PEL: Not Available
• HA: Not Available
• TLV: 0.5 mg/m3 (8-hour) [56]

Basic Manufacturer:

Uniroyal Chemical Co., Inc.
Benson Road
Middelbury, CT 06749

• Phone: 203-573-2000
• Emergency: 203-723-3670
  

References:

References for the information in this PIP can be found in Reference List Number 6

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.