What is Pentachlorophenol?

Pentachlorophenol is a manufactured chemical with the molecular formula C₆HCl₅O.

It does not occur naturally.

Pure form: Colourless crystals

Impure form (technical grade, most common at hazardous waste sites): Dark grey to brown dust, beads, or flakes.

Humans are most often exposed to the impure form.

What is Pentachlorophenol used for?

• Formerly used as a biocide to kill small organisms.
• Currently used as a wood preservative to protect wood from decay and insect damage.
• Since 1984, purchase and use have been restricted to certified applicators—no longer available to the general public.
• Commercial applications include:
  • Treatment of utility poles, fences, shingles, walkways, building components, piers, docks, porches, flooring, and laminated beams
  • Agricultural uses such as wood protection for buildings/products and fencerows/hedgerows

In the Environment

• Found in air, water, and soil.
• Enters the environment via:
  • Evaporation from treated wood
  • Industrial spills
  • Disposal at uncontrolled hazardous waste sites
• Degraded by sunlight, other chemicals, and microorganisms within days to months.
• Present in fish and other foods, though tissue levels are typically low.

Sources & Routes of Exposure

Sources of Exposure

• Indoor air:
  • Pressure-treated log homes brushed with pentachlorophenol: 0.0005–0.01 ppb
  • Industrially dipped, non-pressure-treated log homes: 0.034–0.0104 ppb

• Outdoor air:
  • Much lower concentrations; general population breathes ~0.063 mg/day

• Occupational exposure:
  • Workers in wood treatment facilities/lumber mills: 10.5–154 mg/day (inhalation)
  • Handling treated lumber: ~35 mg/day (skin absorption)

• Detected at low levels in drinking water and food.
• Additional exposure from dermal contact with pentachlorophenol or treated wood products.

Routes of Exposure

• Inhalation: Primary exposure route (contaminated air)
• Ingestion: Contaminated food or water
• Dermal contact: Direct skin exposure to chemical or treated materials
• Excretion: Primarily via urine

Health Effects

Acute Effects

• Highly toxic when ingested by humans.
• Acute inhalation exposure in humans may cause:
  • Cardiovascular and blood effects
  • Liver damage (including jaundice)
  • Eye irritation and visual damage
  • Neurological effects: lethargy, tachypnoea, tachycardia, delirium, convulsions

• Animal studies report acute oral exposure effects on:
  • Cardiovascular system, blood, liver, immune system, CNS

• Acute inhalation: High toxicity in rats and mice
• Acute oral: Extreme toxicity in rats and mice

Chronic Effects

• Long-term inhalation exposure in humans can cause:
  • Upper respiratory tract inflammation, bronchitis
  • Blood disorders (e.g., aplastic anaemia)
  • Kidney and liver effects
  • Immune system impacts
  • Eye, nose, and skin irritation

• Chronic oral exposure in animals: Effects on liver, kidney, blood, endocrine system, immune system, CNS
• EPA: No RfC established
• EPA RfD: 0.03 mg/kg/day (liver and kidney pathology in rats)
• CalEPA: Chronic inhalation reference exposure level of 0.1 mg/m³ (based on EPA’s RfD)

Reproductive and Developmental Effects

• One study found 22 of 90 women with histories of spontaneous abortions, unexplained infertility, or menstrual disorders had elevated pentachlorophenol and/or lindane blood levels.
  • No direct causal link to pentachlorophenol due to lindane presence and other confounding factors.

• Oral animal studies indicate:
  • Decreased offspring survival in rats
  • Maternal toxicity (reduced maternal body weight)
  • No evidence of birth defects

Cancer Risk

• Case reports suggest possible associations between inhalation exposure and:
  • Hodgkin’s disease
  • Soft tissue sarcoma
  • Acute leukaemia
  • However, co-exposure to other toxic substances complicates conclusions.

• Oral animal studies show:
  • Increased liver tumours (hepatocellular adenomas and carcinomas)
  • Uncommon tumours: adrenal medulla pheochromocytomas, hemangiosarcomas, hemangiomas

• EPA classification: Group B2 – Probable human carcinogen

Safety

First Aid Measures

• Eye Contact: Remove contact lenses; flush eyes with running water for at least 15 minutes (cold water may be used); avoid eye ointments; seek medical attention.
• Skin Contact: Wash immediately with plenty of water and non-abrasive soap; clean skin folds/creases thoroughly; cover irritated skin with an emollient; seek medical advice if irritation persists.
• Serious Skin Contact: Wash with disinfectant soap; apply antibacterial cream; seek immediate medical attention.
• Inhalation: Rest in a well-ventilated area; seek immediate medical attention.
• Serious Inhalation: Move victim to safe area; loosen tight clothing; give oxygen if breathing is difficult; perform mouth-to-mouth resuscitation if not breathing; seek medical attention.
• Ingestion: Do not induce vomiting; check mouth/lips for tissue damage; loosen tight clothing; perform mouth-to-mouth resuscitation if not breathing; seek immediate medical attention.

Exposure Controls and Personal Protection

Engineering Controls

• Use process enclosures, local exhaust ventilation, or other engineering controls to maintain airborne concentrations below recommended limits.
• If operations generate dust, fumes, or mist, ensure adequate ventilation to keep exposure within safe limits.

Personal Protective Equipment

The following personal protective equipment is recommended when handling pentachlorophenol:

• Splash goggles
• Lab coat
• Dust respirator (approved/certified)
• Gloves

PPE for Large Spills:

• Splash goggles
• Full protective suit
• Dust respirator
• Boots
• Gloves
• Self-contained breathing apparatus to avoid inhalation
• Consult a safety specialist before handling, as suggested PPE may not be sufficient

Regulation

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).

Australia

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