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The information in this profile may be out-of-date.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.

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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

Hexachlorobenzene

Trade and Other Names: Trade names for this product include Anticarie, Bent-cure, Bent-No-more, Ceku C.B., Granero, No Bunt, Perchlorobenzene and Res-Q.

NOTE: This compound should not be confused with hexachlorocyclohexane (HCH), which has historically been referred to as benzene hexachloride and is also commonly known as lindane.

Regulatory Status: Hexachlorobenzene is a practically nontoxic compound in EPA toxicity class IV. It has been banned from use in the U.S.

Chemical Class: chlorinated hydrocarbon

Introduction: Hexachlorobenzene is a chlorinated hydrocarbon selective fungicide used as a seed protectant treatment, especially on wheat to control common and dwarf bunt. It may be used with or without other seed treatments, fungicides, and/or insecticides. It has fumigant action on fungal spores and is available as a dry seed treatment or slurry for seed treatment. Unless otherwise stated, the data presented in this profile are for technical hexachlorobenzene.

Formulation: It has fumigant action on fungal spores and is available as a dry seed treatment or slurry for seed treatment.

Toxicological Effects:

• Acute toxicity: Hexachlorobenzene is slightly to practically nontoxic via the oral route of exposure. The reported acute oral LD50 values are 3500 mg/kg in the rat, 4000 mg/kg in the mouse, 2600 mg/kg in the rabbit, and 1700 mg/kg in the cat [7]. Its toxicity via the dermal route has not been determined [7,9,59]. It is reported to be a possible skin irritant [7]. Hexachlorobenzene is slightly to moderately toxic via inhalation, with reported inhalation LC50 values of 1.6 mg/L for the cat, 3.6 mg/L for the rat and 4 mg/L for the mouse [17]. Single doses of HCB are relatively nontoxic though repeated doses, even at small amounts, are toxic [60]. Unlike humans, rodents exhibit neurological symptoms including tremors, paralysis, muscle incoordination, weakness, and convulsions at high single doses [7]. Rats have been observed to withstand an acute subcutaneous (injected just below the skin) dose of 500 mg/kg without detectable injury (including liver injury) [7].
• Chronic toxicity: Dietary doses to rats of approximately 50 mg/kg/day killed 95% of the females and 30% of the males within 4 months [7]. Almost all survived when the dose rate was reduced to approximately 5 mg/kg/day [7]. Rats receiving doses of 25 or 50 mg/kg/day showed nervous system effects such as tremor, hyperexcitablity, and lethargy; skin eruptions; as well as increases in weights of liver, kidneys, spleen and lungs [7]. Those receiving only 5 mg/kg/day remained clinically well (i.e. had no outward manifestations of illness), but blood factors such as total hemoglobin and blood enzymes were decreased in females, and males showed increased liver weight [7,59]. Findings of increased weights of liver, spleen, and kidney were reproduced in a second study in rats with a dose regime of 50 mg/kg/day on alternating days over a period of 53 weeks [7,59]. Increases in weights of the adrenal gland due to HCB exposure were also observed. These increases were reversible within a 38-week period after HCB administration was stopped [59]. A syndrome called "porphyria" is associated with HCB exposure as well [7,59]. HCB is one of the most effective compounds at inducing porphyria in humans and in animals. Approximately 15 mg/kg/day produced porphyria in rabbits (leading to death), and 50 mg/kg/day led to similar effects and fatalities in pigs over 90 days [7,59]. A dose of 5 mg/kg/day did not produce any symptoms [7]. In a Turkish population accidentally exposed to HCB in the 1950s (from eating treated seed grain), estimated total dietary exposure of 50 to 200 mg/person (a different dose to each individual according to body weight) resulted in several thousand cases of porphyria [7]. In this population, recovery usually followed termination of exposure, although many people remain seriously disfigured and at least 10% of those people affected died [7]. Symptoms of HCB-induced porphyria consist of blistering/scarring of the skin, light sensitivity, susceptibility to skin infection, and possibly osteoporosis (decreased bone calcium content) [7]. Pophyria is a general disruption in the normal metabolism of porphyrin compounds (often an overproduction), of which hemoglobin, and its chemical building blocks, are members [7]. It is recognizable by the measurable increases in porphyrin compounds in the body and bodily fluids (e.g., blood, urine, feces, etc.) and increased activity of liver enzymes [7,59].
• Reproductive effects: Doses of 4 mg/kg/day blocked ovulation in one female monkey of four and reduced estrogen levels in all four over an unspecified period [7]. Doses of 10 mg/kg/day did not cause increased fetal mortality or miscarriage in rabbits [7]. In a four-generation reproduction study of rats at doses of approximately 8 mg/kg/day, decreased fertility was observed [7]. It does not appear that exposure to HCB at normal levels will cause reproductive effects in human populations.
• Teratogenic effects: Doses of 80 mg/kg/day for 4 or more days of pregnancy reduced fetal birth weights and caused slight increase in 14th ribs in rats [7]. Mice showed cleft palate and kidney malformations at maternal doses of 100 mg/kg/day on days 7 to 16 of pregnancy [7]. In a four-generation reproduction study of rats at doses of approximately 8 mg/kg/day, high pup mortality was observed [7]. Survival was affected down to doses of approximately 2 mg/kg/day [7]. No gross deformities were noted at any dose level in this study. The potential for the compound to cause birth defects in human populations is likely to be small at common levels of exposure.
• Mutagenic effects: Dominant lethal assays in rats were negative for mutagenicity [7]. HCB was shown to be nonmutagenic in several tests with bacteria and was mutagenic with yeast cells [17]. Available data suggest that it is unlikely that HCB is mutagenic.
• Carcinogenic effects: Hexachlorobenzene caused increased numbers of tumors per animal in a long-term study where the lowest dose tested was 4 mg/kg/day [7]. Increases in tumors of the lung, thyroid, liver, and spleen were noted [7,59]. Mice fed for 2 years had increases in liver tumors at doses of approximately 12 and 24 mg/kg/day [7,59]. The potential for hexachlorobenzene to cause carcinogenic effects in humans at normal levels of exposure is not known.
• Organ toxicity: Available data from animal tests indicates that the nervous system, liver, kidneys, spleen, and lungs are the target organs affected by exposure to HCB [59].

• Fate in humans and animals: Animal studies show that absorption of HCB from the gastrointestinal tract following oral administration is variable, depending on the solvent vehicle used [7,59]. Following absorption, HCB may be processed into pentachlorophenol and other more water-soluble compounds (e.g., tetrachlorohydroquinone, pentachlorothiophenol) in the liver and then excreted in the urine, or in some instances it may be excreted intact into the intestine with the bile [59]. Absorption may also occur via lymphatic system uptake and direct deposition into body fat, with no processing in the liver [59]. Movement into body fat may be increased by lack of protein in the diet [7]. In rats, half of a single dose of the product is lost within 3 to 4 months but in monkeys it takes 2 1/2 to 3 years [59].

Ecological Effects:

• Effects on birds: Hexachlorobenzene is slightly to moderately toxic to bird species. In Japanese quail it has a 5-day dietary LC50 of 568 ppm [54]. The reported acute oral LD50 vlaues in bobwhite quail were 575 mg/kg and in mallard duck was 1450 mg/kg [17].
• Effects on aquatic organisms: Hexachlorobenzene is slightly toxic to fish species, with reported 96-hour LD50 values of 11 to 16 mg/L in channel catfish, greater than 50 mg/L in coho salmon, 22 mg/L in fathead minnow, and 12 mg/L in bluegill and large mouth bass [55]. Rainbow trout have been shown to accumulate residues of 3800 to 8900 times the exposure level of 0.1 to 2.0 ug/L (ppb) within 28 days [55]. Likewise, Daphnia accumulated residues nearly 900 times exposure levels of 0.05 to 0.15 ug/L within 48 hours, and neither trout nor Daphnia significantly degraded hexachlorobenzene [55]. The bioaccumulation ratio in algae is 570, and the major proportion of compounds detected is the parent compound, indicating little degradation [61]. These data indicate a significant potential for bioaccumulation.
• Effects on other organisms: The compound is nontoxic to bees [9].

Environmental Fate:

• Breakdown in soil and groundwater: HCB is a highly persistent compound, with reported field half-lives in the soil environment ranging from 2.7 to 7.5 years [15]. Evaporation is rapid while it is on soil surfaces, but considerably less so when it is mixed into the soil [62]. HCB is moderately to strongly bound by most soils [15]. Data from testing on hydrosoils indicate that it may be degraded both aerobically and anaerobically [55]. It has a low water solubility, and thus is likely to show low mobility in the soil environment. Due to its lengthy persistence, however, even low mobility may result in appreciable travel; therefore, HCB may pose some risk of groundwater contamination. Hexachlorobenzene has been found in well water in several states at low concentrations ranging from 1 ppb to 5.6 ppb and only in a very small percentage of all of the wells tested [63].
• Breakdown in water: HCB is of low water solubility, so it would most likely reach surface waters via surface run-off by attachment to soil particles. Once in the aquatic environment, it is likely to be short-lived; HCB underwent very rapid, almost complete (i.e. less than 5 days) degradation to pentachlorophenol and related compounds in innoculated hydrosoil samples under both aerobic and anaerobic conditions [15].
• Breakdown in vegetation: Breakdown in vegetation appears rapid, with residue levels in grass at approximately 1% of the initial amount after 15 days, and at approximately 0.01% after 19 months [62].

Physical Properties:

• Appearance: HCB is a colorless crystalline solid at room temperature [9].
• Chemical Name: hexachlorobenzene [9]
• CAS Number: 118-74-1
• Molecular Weight: 284.81
• Water Solubility: 0.005 mg/L [9]
• Solubility in Other Solvents: i.s. in ethanol; s. in hot benzene, chloroform, and ether [9]
• Melting Point: 226 C [9]
• Vapor Pressure: 1.45 mPa @ 20 C [9]
• Partition Coefficient: Not Available
• Adsorption Coefficient: 50,000 (estimated) [15]

Exposure Guidelines:

• ADI: Not Available
• MCL: 0.001 mg/L [8]
• RfD: 0.0008 mg/kg/day [8]
• PEL: 0.025 mg/m3 (8-hour) [28]
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Atomergic Chemetals Corp.
222 Sherwood Avenue
Farmingdale, NY 11735-1718

• Phone: 516-694-9000
• Emergency: 800-424-9300
  

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.