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The information in this profile may be out-of-date.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

Pentachlorophenol (PCP)

Trade and Other Names: Trade names for pentachlorophenol include Dowicide, PCP, Penchlorol, Penta, Penta Plus, Pentachloral, Pentacon, Penwar, Priltox, Santobrite, Santophen, Sinituho, and Weedone.

Regulatory Status: Pentachlorophenol is a moderately toxic compound in EPA toxicity class II. It is a Restricted Use Pesticide (RUP) in its formulations as a wood preservative, but a General Use Pesticide (GUP) for other purposes; labels for products containing it must bear the Signal Word DANGER.

Chemical Class: chlorinated hydrocarbon

Introduction: Pentachlorophenol (PCP) is a chlorinated hydrocarbon insecticide and fungicide. It is primarily used to protect timber from fungal rot and wood-boring insects, but may also be used as a preharvest defoliant in cotton, a general pre-emergence herbicide, and as a biocide in industrial water systems. It is available in blocks, flakes, granules, liquid concentrates, wettable powders, or ready-to-use petroleum solutions.

Data presented in this profile are for technical grade pentachlorophenol, unless otherwise stated. Technical grade PCP has historically contained dioxins (e.g. tetra-, hexa- and octochlorodibenzo-p-dioxin) and hexachlorobenzene as manufacturing by-products. Technical grade PCP is typically about 86% pure. The discovery of these compounds in technical grade PCP may be one reason for its being phased out of use. Pentachlorophenol is also a major product of the metabolism of hexachlorobenzene in mammals.

Formulation: It is available in blocks, flakes, granules, liquid concentrates, wettable powders, or ready-to-use petroleum solutions.

Toxicological Effects:

• Acute toxicity: Pentachlorophenol is moderately toxic via the oral route, with reported oral LD50 values for various formulations ranging from 27 to 211 mg/kg in rats [69,70]. In mice the oral LD50 is 74 to 130 mg/kg, and in rabbits 70 to 300 mg/kg [69,70[. It is moderately toxic via inhalation as well, with a reported inhalation LC50 of 0.2 to 2.1 mg/L in rats [17]. The time frame for this LC50 (e.g., 4-hour, 1-hour, etc.) was not given. Inhalation LD50 values (i.e., the median lethal doses, not concentrations, via the inhalation route) of 225 mg/kg in rats and 355 mg/kg in mice are reported, also without a time frame [70]. Another calculated LD50 in rats via the inhalation route is 11.7 mg/kg for 28 to 44 minutes of exposure, assuming a breathing rate of 80 mL/minute [69]. Pentachlorophenol causes irritation to the mucous membranes, skin, and eyes of test animals [9]. Via the dermal route, it is moderately toxic, with reported dermal LD50 values ranging from 96-330 mg/kg in the rat, and 40 to greater than 1000 mg/kg in the rabbit (depending on formulation) [69]. Skin penetration may be the most dangerous route of exposure, being responsible for about 50 known cases of PCP poisoning, 30 of which have resulted in death. Immersion of a human hand in a 0.4 percent PCP solution for 10 minutes caused pain and inflammation. Technical PCP resulted in chloracne on the ears of rabbits, and edema in chicks, but pure PCP did not [70]. High acute exposure to PCP can cause elevated temperature, profuse sweating, dehydration, loss of appetite, decreased body weight, nausea, and neurological effects such as tremors, uncoordinated movement, leg pain, muscle twitching, and coma [69,70]. Some of the symptoms may be due to the impurities in the formulation, rather than the pentachlorophenol itself [69].
• Chronic toxicity: Much research on PCP has been performed with poorly characterized technical material, and the chronic toxicity observed may depend in large measure on the proportion of chlorodibenzo-p-dioxins present in the mixture [69]. In a 90-day feeding trial in rats, 30 mg/kg/day produced depressed red blood cell and hemoglobin levels as well as liver degeneration, and even lower doses resulted in irregular blood chemistry and enzyme levels, along with increased liver and kidney weights [69,71]. Pure PCP, and also technical PCP without dioxin contamination, produced only slight enlargement of livers and kidneys [69]. Purified PCP also did not produce toxic effects such as liver damage and immune system alterations, which had previously been reported for the technical product [69,71]. In humans, the most common exposure to PCP is inhalation in the workplace. Abdominal pain, nausea, fever, and respiratory irritation, as well as eye, skin, and throat irritation, may result from such exposure [70], while very high levels may cause obstruction of the circulatory system in the lungs and cause heart failure [70]. Survivors of toxic exposures may suffer permanent visual and central nervous system damage [70]. Persons regularly exposed to PCP tend to tolerate higher levels of PCP vapors than persons having little contact with these vapors [70,71].
• Reproductive effects: Rats fed PCP at doses of 30 mg/kg/day for 62 days before mating and during lactation showed weight loss, but no decreases in fecundity and fertility [69]. Sperm of male mice given technical or purified PCP for 5 days at 50 mg/kg/day showed no abnormalities within 35 days of treatment [69]. The evidence indicates that PCP does not cause reproductive effects.
• Teratogenic effects: Offspring of rats fed PCP at doses of 30 mg/kg/day for 62 days before mating and during lactation showed lowered survival and growth rates [69]; 3 mg/kg/day did not have any effects [69]. Maternal doses of 5 mg/kg/day of technical PCP in rats produced toxicity to the fetus or embryo, and 50 mg/kg/day on days 6 to 15, 8 to 11 or 12 to 15 of gestation produced increases resorptions, swelling, dilated ureters, and skeletal anomalies [69]. It is unlikely that PCP has teratogenic effects in humans at normal exposure levels.
• Mutagenic effects: PCP is not mutagenic in bacteria or houseflies, but is weakly mutagenic in mice and may be mutagenic in yeast [71]. One study of chromosomal aberrations in occupationally exposed workers showed no increased incidence of sister-chromatid exchanges, while another did find increases [71]. Weak mutagenic effects were seen in human lymphocyte cultures exposed to PCP [71]. The evidence suggests that PCP is nonmutagenic or weakly mutagenic.
• Carcinogenic effects: Studies of two formulated PCP products (Dowcide and Penta) showed increases in cancers of the spleen, liver, and adrenal gland in test mice or rats at doses of about 17 to 18 mg/kg/day [71]. These findings were not replicated for Dowcide in mice in a second study [71]. There have been reports of a possible association between occupational exposures to technical PCP and Hodgkin's disease, acute leukemia, and soft-tissue sarcoma, but confounding factors such as concurrent exposure to other substances makes interpretation of these data problematic [71]. No convincing evidence of PCP's caricinogenic effects in humans is available [71]. Current evidence is not sufficient to assess the potential of PCP to cause carcinogenic effects in humans.
• Organ toxicity: Data from animal studies indicate that the major target organs for PCP are the liver, kidneys, and central nervous system.

• Fate in humans and animals: PCP is rapidly absorbed through the gastrointestinal tract following ingestion [71]. Accumulation is not common, but if it does occur, the major sites are the liver, kidneys, plasma protein, brain, spleen, and fat [69,71]. Unless kidney and liver functions are impaired, PCP is rapidly eliminated from blood and tissues, and is excreted, mainly unchanged or in conjugated form, via the urine [71]. Single doses of PCP have half-lives in blood of 15 hours in rats, 78 hours in monkeys, and 30 to 50 hours in humans [69].

Ecological Effects:

• Effects on birds: The compound is slightly toxic to practically nontoxic to bird species. The reported 5-day dietary LC50 value in Japanese quail is greater than 5139 ppm [54]. Reported acute oral LD50 values for PCP are 380 mg/kg in mallard duck and 504 mg/kg in pheasant [55].
• Effects on aquatic organisms: PCP may be highly to very highly toxic to many species of fish; reported 96-hour LC50 values are 68 ug/L in chinook salmon, 52 ug/L in rainbow trout, 205 ug/L in fathead minnow, 68 ug/L in channel catfish, and 32 ug/L in bluegill sunfish [55]. Several species of fish, invertebrates, and algae have had levels of PCP that were significantly higher (up to 10,000 times) than the concentration in the surrounding waters [71]. Once absorbed by fish, pure PCP is rapidly excreted as is its metabolite, with a biological half-life of only 10 hours [71]. Biomagnification, that is the progressively higher concentration of a compound as it passes up the food chain, is not thought to be significant because of PCP's rapid break down in living organisms [70].
• Effects on other organisms: Cattle and other farm animals have ingested PCP by chewing and licking outdoor wood structures, or from being housed in wooden pens that were treated with PCP solutions. This has caused sickness and death in some of these animals [17].

Environmental Fate:

• Breakdown in soil and groundwater: PCP is moderately persistent in the soil environment, with a reported field half-life of 45 days [15]. PCP degrades most rapidly in flooded or anaerobic (airless) soils, at higher temperatures and in the presence of organic matter in the soil [12,15]. Breakdown is mainly by anaerobic biodegradation; breakdown by sunlight and hydrolysis do not appear to be significant processes [15]. It is poorly sorbed at neutral and alkaline conditions, and may be mobile in many soils [12,15]. Sorption will be slightly greater (and mobility slightly lesser) in soils with higher proportions of soil organic matter [12]. The compound has been found in groundwater in California, Oregon, and Minnesota at very low concentrations ranging from 0.06 ppt to 0.64 ppb [15].
• Breakdown in water: In the water environment, PCP is mainly bound to sediments and suspended particles in water [12]. PCP will dissociate by releasing a hydrogen ion and may then be more readily degraded by sunlight or microorganisms [12]. In water, biodegradation occurs, mainly at the surface, with a half-life ranging from hours to days [12]. It does not evaporate to a significant degree. PCP has been detected at very low levels in rivers and streams (0.01 to 16 ug/L), surface water systems (1.3 to 12 ug/L), and seawater (0.02 to 11 ug/L) [12].
• Breakdown in vegetation: PCP may be taken up by plants; lettuce grown on soil containing PCP contained low levels of PCP residues [12]. Uptake and accumulation varies according to plant species. PCP is strongly toxic to plants [9].

Physical Properties:

• Appearance: At room temperature, pentachlorophenol is a colorless crystalline solid with a phenolic odor [9]. Color may vary from white to dark grayish brown, depending on the purity of the compound [9].
• Chemical Name: pentachlorophenol [9]
• CAS Number: 87-86-5
• Molecular Weight: 266.34
• Water Solubility: 80 mg/L @ 20 C [9]
• Solubility in Other Solvents: v.s. in acetone, alcohols, ether, and benzene; s. in petroleum ether, carbon tetrachloride, and paraffins [9]
• Melting Point: 191 C [9]
• Vapor Pressure: 16,000 mPa @ 20 C [9]
• Partition Coefficient: 5.12 [17]
• Adsorption Coefficient: 30 (at pH 7) (estimated) [15]

Exposure Guidelines:

• ADI: Not Available
• MCL: 0.001 mg/L [67]
• RfD: 0.03 mg/kg/day [8]
• PEL: 0.5 mg/m3 (8-hour) [28]
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

ISK Biosciences
5966 Heisley Road
P.O. Box 8000
Mentor, OH 44061-8000

• Phone: 216-357-4100
• Emergency: 216-357-7070
  

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.