Pentachlorophenol [factsheet]

PENTACHLOROPHENOL

Please Note: The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS), which contains information on oral chronic toxicity of pentachlorophenol and the RfD and the carcinogenic effects of pentachlorophenol including the unit cancer risk for oral exposure, and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile for Pentachlorophenol. Other secondary sources include the Hazardous Substances Data Bank (HSDB), a database of summaries of peer-reviewed literature, and the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.

Environmental/Occupational Exposure

* Exposure to pentachlorophenol in the indoor air of pressure-treated log homes brushed with pentachlorophenol has been measured at 0.0005 ppb to 0.01 ppb, and levels in the air of industrially dipped, non-pressure-treated log homes have been measured at 0.034 to 0.0104 ppb. Levels in outdoor air are much lower, and the general population is estimated to breathe in about 0.0009 mg/kg/d. (1)

* Workers at wood treatment facilities and lumber mills are estimated to breathe in about 0.15 to 2.2 mg/kg/d, and workers who handle treated lumber can absorb about 0.5 mg/d through the skin. (1)

* Pentachlorophenol has been detected at low levels in drinking water and food. (1)

* Exposure may also occur through dermal contact with pentachlorophenol or with wood products treated with pentachlorophenol. (1)

Assessing Personal Exposure

* Pentachlorophenol and its breakdown products can be measured in blood, urine, and tissues. (1)

Health Hazard Information

Acute Effects:

* Pentachlorophenol is extremely toxic when ingested by humans; the probable oral lethal dose is 50 to 500 mg/kg (1 teaspoon to 1 ounce) for a 70-kg person. (2)

* Acute (short-term) inhalation exposure to pentachlorophenol in humans may result in death from effects on the circulatory system and accompanying heart failure. (3)

* Other effects noted from acute inhalation exposure in humans include effects on the cardiovascular system, blood, liver (jaundice), and eyes (visual damage and irritation). (1,3)

* Animal studies have reported effects on the cardiovascular system, blood, liver, immune system, and central nervous system (CNS) from acute oral exposure to pentachlorophenol. (1)

* Tests involving acute exposure of animals, such as the LC₅₀ and LD₅₀ tests in rats and mice, have shown pentachlorophenol to have high toxicity from inhalation exposure and extreme toxicity from oral exposure. (1,4)

Chronic Effects (Noncancer):

* Chronic (long-term) exposure by inhalation to pentachlorophenol in humans has resulted in inflammation of the upper respiratory tract and bronchitis, blood effects such as aplastic anemia, effects on the kidney and liver, and irritation of the eyes, nose, and skin. (1,3)

* Chronic oral exposure to pentachlorophenol in animals has resulted in effects on the liver, kidney, and immune system. (1,5)

* The RfC for pentachlorophenol is under review by EPA. (2)

* The RfD for pentachlorophenol is 0.03 mg/kg/d based on liver and kidney pathology in rats. (2)

* EPA has high confidence in the study on which the RfD is based because a moderate number of animals/sex were used in each of three doses, a comprehensive analysis of parameters was conducted, and a reproductive study was also run; medium confidence in the supporting database because only one chronic study is available; and, consequently, medium confidence in the RfD.

Reproductive/Developmental Effects:

* One study reported that 22 out of 90 women with histories of spontaneous abortions, unexplained infertility, or menstrual disorders were found to have elevated blood levels of pentachlorophenol and/or lindane. However, a direct causal relationship with pentachlorophenol exposure cannot be inferred from this study due to the presence of lindane in the blood and other possible confounding factors. (1)

* Oral animal studies suggest that exposure to pentachlorophenol decreases the survival of the offspring in rats. Other oral animal studies have found evidence that pentachlorophenol produces maternal toxicity (depressed maternal body weight), but does not cause birth defects. (1,2)

Cancer Risk:

* Epidemiologic studies have not reported an association between inhalation pentachlorophenol exposure and cancer; however the available studies are considered inadequate due to possible observation bias of the study participants and other factors. (1,2)

* Oral animal studies have reported increases in liver tumors and two uncommon tumors (adrenal medulla pheochromocytomas and hemangiomas) in mice. (1,2)

* EPA has classified pentachlorophenol as a Group B2, probable human carcinogen. (2)

* EPA uses mathematical models, based on animal studies, to estimate the probability of a person developing cancer from ingesting water containing a specified concentration of a chemical. EPA calculated an oral unit risk estimate of 3 H 10^-6 (m g/L)^-1. EPA estimates that, if an individual were to ingest water containing pentachlorophenol at 0.3 Fg/L* over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of ingesting water containing this chemical. Similarly, EPA estimates that ingesting water containing 3.0 Fg/L would result in not greater than a one-in-hundred thousand increased chance of developing cancer, and water containing 30 Fg/L would result in not greater than a one-in-ten thousand increased chance of developing cancer. (2)

Physical Properties

* Pentachlorophenol exists as colorless crystals with a sharp, phenolic odor when hot, but very little odor at room temperature. (1)

* The odor threshold for pentachlorophenol is approximately 12 ppm. (1)

* Impure pentachlorophenol is dark gray to brown and exists as dust, beads, or flakes. (1)

* The chemical formula for pentachlorophenol is C₆HCl₅O, and its molecular weight is 266.35 g/mol. (1)

* The vapor pressure for pentachlorophenol is 0.00011 mm Hg at 25 EC, and it has a log octanol/water partition coefficient (Log K_ow) of 5.01. (1)

Uses

* Pentachlorophenol was once one of the most widely used biocides in the United States, but it is now a restricted use pesticide and is no longer available to the general public. (1)

* The principal use for pentachlorophenol is as a wood preservative; it is also used for the formulation of fungicidal and insecticidal solutions and for incorporation into other pesticide products. (1)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
1,000.0
_ _ _ _ 100.0	* LC₅₀ (rats) (355 mg/m³) * LC₅₀(mice) (225 mg/m³)		4 4
_ _ _ _ 10.0
_ _ _ _ 1.0
_ _ _ _ 0.1		* OSHA PEL, ACGIH TLV, and NIOSH REL (0.5 mg/m³)	1

ACGIH TLVCAmerican Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.

LC₅₀ (Lethal Concentration₅₀)CA calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined experimental animal population.

NIOSH RELCNational Institute of Occupational Safety and Health recommended exposure limit; NIOSH-recommended exposure limit for an 8- or 10-h time-weighted-average exposure and/or ceiling.

OSHA PELCOccupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.

^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.

References

1. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Pentachlorophenol (Draft). U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1992.

2. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Pentachlorophenol. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.

3. U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

4. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

5. U.S. Environmental Protection Agency. Health Effects Assessment for Pentachlorophenol. EPA/540/1-86/043. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1988.