Pentachlorophenol is a manufactured chemical with the molecular formula C6HCl5O. [1] It does not occur naturally. Pure pentachlorophenol exists as colourless crystals. Impure pentachlorophenol (the form usually found at hazardous waste sites) is dark grey to brown and exists as dust, beads, or flakes. Humans are usually exposed to impure pentachlorophenol (also called technical grade pentachlorophenol). [2]

Uses [3,4,5]

Pentachlorophenol was used as a biocide to kill small organisms and is now used as a wood preservative to protect wood from decay and insect attack. Since 1984, the purchase and use of pentachlorophenol has been restricted to certified applicators. It is no longer available to the general public. Pentachlorophenol is applied commercially in the treatment of utility poles, fences, shingles, walkways, building components, piers, docks and porches, and flooring and laminated beams. It is also used in agricultural purposes such as wood protection treatment to buildings or products, and fencerows or hedgerows.

In the Environment [4]

Pentachlorophenol can be found in the air, water, and soil. It enters the environment through evaporation from treated wood surfaces, industrial spills, and disposal at uncontrolled hazardous waste sites. Pentachlorophenol is broken down by sunlight, other chemicals, and microorganisms to other chemicals within a couple of days to months. Pentachlorophenol is found in fish and other foods, but tissue levels are usually low.

Sources & Routes of Exposure

Sources of Exposure [6]

  • Exposure to pentachlorophenol in the indoor air of pressure-treated log homes brushed with pentachlorophenol has been measured at 0.0005 to 0.01 parts per billion (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 0.063 milligrams per day (mg/day).
  • Workers at wood treatment facilities and lumber mills are estimated to breathe in about 10.5 to 154 mg/day, and workers who handle treated lumber can absorb about 35 mg/day through the skin.
  • Pentachlorophenol has been detected at low levels in drinking water and food.
  • Exposure may also occur through dermal contact with pentachlorophenol or with wood products treated with pentachlorophenol.

Routes of Exposure [3]

The major route of exposure to pentachlorophenol is via inhalation of contaminated air. Exposure may also occur via the ingestion of contaminated food or water. Furthermore, pentachlorophenol can also enter your body through skin contact and can leave your body through urine.

Health Effects [6]

Acute Effects

Pentachlorophenol is extremely toxic when ingested by humans. Acute inhalation exposure to pentachlorophenol in humans may result in effects on the cardiovascular system, blood, liver (jaundice), and eyes (visual damage and irritation). Neurological effects reported following exposure of humans to high levels of pentachlorophenol include lethargy, tachypnea, tachycardia, delirium, and convulsions. Animal studies have reported effects on the cardiovascular system, blood, liver, immune system, and central nervous system (CNS) from acute oral exposure to pentachlorophenol. Tests involving acute exposure of rats and mice have shown pentachlorophenol to have high toxicity from inhalation exposure and extreme toxicity from oral exposure.

Chronic Effects

Chronic exposure by inhalation to pentachlorophenol in humans has resulted in inflammation of the upper respiratory tract and bronchitis, blood effects such as aplastic anaemia, effects on the kidney and liver, immunological effects, and irritation of the eyes, nose, and skin. Chronic oral exposure to pentachlorophenol in animals has resulted in effects on the liver, kidney, blood, endocrine, immune system, and CNS. EPA has not established a Reference Concentration (RfC) for pentachlorophenol. The Reference Dose (RfD) for pentachlorophenol is 0.03 milligrams per kilogram body weight per day (mg/kg/d) based on liver and kidney pathology in rats. The California Environmental Protection Agency (CalEPA) has calculated a chronic inhalation reference exposure level of 0.1 milligrams per cubic metre (mg/m3) based on a route-to-route extrapolation of EPA’s 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. 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.

Cancer Risk

Case reports suggest a possible association between inhalation pentachlorophenol exposure and cancer (Hodgkin’s disease, soft tissue sarcoma, and acute leukaemia); however, concommittent exposure to other toxic substances may have contributed to the reported carcinogenic effects. Oral animal studies have reported increases in liver tumours (hepatocellular adenomas and carcinomas) and two uncommon tumours (adrenal medulla pheochromocytomas, hemangiosarcomas, and hemangiomas) in mice. EPA has classified pentachlorophenol as a Group B2, probable human carcinogen.

Safety [7]

First Aid Measure

  • Eye Contact: Check for and remove any contact lenses. Immediately flush eyes with running water for at least 15 minutes, keeping eyelids open. Cold water may be used. Do not use an eye ointment. Seek medical attention.
  • Skin Contact: After contact with skin, wash immediately with plenty of water. Gently and thoroughly wash the contaminated skin with running water and non-abrasive soap. Be particularly careful to clean folds, crevices, creases and groin. Cover the irritated skin with an emollient. If irritation persists, seek medical attention.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.
  • Inhalation: Allow the victim to rest in a well-ventilated area. Seek immediate medical attention.
  • Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek medical attention.
  • Ingestion: Do not induce vomiting. Examine the lips and mouth to ascertain whether the tissues are damaged, a possible indication that the toxic material was ingested; the absence of such signs, however, is not conclusive. Loosen tight clothing such as a collar, tie, belt or waistband. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek immediate medical attention.

Exposure Controls & Personal Protection

Engineering Controls

It is recommended that process enclosures, local exhaust ventilation, or other engineering controls be used to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.

Personal Protective Equipment

The following personal protective equipment is recommended when handling pentachlorophenol:

  • Splash goggles;
  • Lab coat;
  • Dust respirator (be sure to use an approved/certified respirator or equivalent);
  • Gloves

Personal Protection in Case of a Large Spill:

  • Splash goggles
  • Full suit
  • Dust respirator
  • Boots
  • Gloves
  • A self-contained breathing apparatus should be used to avoid inhalation of the product
  • Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

Regulation [4,8,9]

United States

OSHA: The Occupational Safety & Health Administration has established the following Permissible Exposure Limits (PEL):

  • General Industry: 0.5 mg/m3 (Skin)
  • Construction Industry: 0.5 mg/m3 TWA (Skin)

ACGIH: The American Conference of Governmental Industrial Hygienists has set the following Threshold Limit Value (TLV):

  • 0.5 mg/m3 TWA (Skin)
  • Appendix A3 (Confirmed Animal Carcinogen with Unknown Relevance to Humans)

NIOSH: The National Institute for Occupational Safety and Health has established the following Recommended Exposure Limit (REL):

  • 0.5 mg/m3 TWA (Skin)

EPA: The Environmental Protection Agency has set a limit for drinking water of 1 part of pentachlorophenol per billion parts of water (1 ppb).


Safe Work Australia: Safe Work Australia has established a time weighted average concentration for pentachlorophenol of 0.5mg/m3 for an 8-hour workday.

Australian Drinking Water Guidelines specifies a limit of 0.01 mg/L for pentachlorophenol