Pentachlorophenol (PCP)

Pentachlorophenol was first synthesized in the 1930s and became widely used as a wood preservative and biocide [1]. In the mid-20th century it was used in termite treatments, wood preservatives for log homes and structural lumber, wood bleaching, and as a general biocide. PCP was manufactured with dioxin impurities (particularly hexachlorodibenzo-p-dioxin), which complicated the health analysis in studies of PCP-exposed populations. EPA began restricting uses in the 1980s, and residential uses were largely cancelled [2]. Today PCP use in the US is restricted to industrial applications — utility poles and railroad ties treated with PCP are ubiquitous in the infrastructure landscape. The EPA classifies PCP as a restricted-use pesticide, but enormous volumes of treated wood remain in service and in landfills [3]. Leaching of PCP from treated wood into soil and groundwater around utility poles, power lines, and railroad rights-of-way creates extensive low-level community contamination.

Living near utility poles, railroad ties, or former wood treatment facilities is the most common pathway for community exposure [1]. PCP leaches from treated wood into surrounding soil and groundwater, and can be detected in water near railroad rights-of-way and utility corridors. Dietary exposure comes from contaminated water and from food grown in PCP-contaminated soil near treatment sites [2]. Occupational exposure occurs in wood treatment facilities, utility line maintenance, and railroad maintenance of way work. Some log home residents may have elevated indoor air PCP from treated structural wood, particularly in older structures treated in the 1970s–1980s [3].

PCP is a probable human carcinogen (IARC Group 2B), with evidence for non-Hodgkin lymphoma and soft tissue sarcoma in occupationally exposed workers [1]. It acts as an uncoupler of oxidative phosphorylation — it disrupts the mitochondrial energy production process, causing excessive heat generation and metabolic collapse. Acute high-level poisoning causes high fever, profuse sweating, rapid heart rate, and can be fatal. Chronic lower-level exposure causes chloracne, liver damage, neurological effects, and immune dysfunction [2]. PCP-associated dioxin impurities from older industrial formulations added additional carcinogenicity to occupational exposures studied before modern purification methods [3].

Workers in wood preservation facilities, utility line maintenance, and railroad maintenance face the highest occupational exposures [1]. People who live near creosote and PCP wood treatment operations, or near railroad rights-of-way and utility corridors with heavy treated wood infrastructure, face environmental exposures [2]. People who use private well water near such corridors should test for PCP and related compounds.

Test your private well water if you live near railroad tracks or utility corridors with treated wood — PCP can leach into shallow groundwater [1]. Avoid burning treated wood in fireplaces or wood stoves — incineration of PCP-treated wood releases highly toxic chlorinated dioxins and dibenzofurans [2]. If you work in wood preservation or railroad maintenance, use PPE including impermeable gloves, chemical splash goggles, and NIOSH-approved respiratory protection for operations generating dust or mist. Liver function tests and CBC should be part of occupational health monitoring [3]. Before purchasing rural property, check for proximity to railroad lines, former wood treatment facilities, and utility rights-of-way that may indicate PCP soil contamination.