PESTICIDES – KNOWN CARCINOGEN (IARC 1)
- A pesticide used in industrial wood preservation
- Associated cancer: Non-Hodgkin lymphoma
- Most important route of exposure: Skin contact
- Uses: Primarily used as a fungicide on utility poles; also registered for use railroad ties, sawn products, plywood, and pilings
- Occupational exposures: Approx. 3,900 workers are exposed at work, primarily in the farming sector where pentachlorophenol is used on fence posts to prevent rot
- Environmental exposures: Via living near hazardous waste sites and older homes that contain pentachlorophenol-treated wood
- Fast fact: Pentachlorophenol is targeted by international environmental agreements (ex. Stockholm Convention) for elimination, except its use on utility poles and cross-arms.
Pure pentachlorophenol is a white crystalline, aromatic compound. Impure pentachlorophenol is dark gray to brown in colour and exists as dust, beads, or flakes. It may also be referred to as PCP or penta. There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.
In 2016, the International Agency for Research on Cancer (IARC) classified pentachlorophenol as Group 1, carcinogenic to humans, based on sufficient evidence that it causes non-Hodgkin lymphoma (NHL) in humans. Exposure to PCP was associated with an increased risk of NHL in all of the available epidemiological studies, including in Canadian sawmill workers and US pesticide manufacturing workers. Several studies also reported an increased risk of multiple myeloma, a subtype of NHL.
Additionally, acute exposure to pentachlorophenol can cause fever and respiratory distress. High levels of exposure to pentachlorophenol over long periods of time can damage the liver and immune system, and cause reproductive and developmental effects. Impurities in the pentachlorophenol, such as dioxins and furans at parts per million levels, may contribute to these
Regulations and Guidelines
|Canadian Jurisdictions||OEL (mg/m3)|
|Canada Labour Code||0.5 [sk, IFV]|
1 [stel, sk, IFV]
|MB, ON, NL, PE, NS||0.5 [sk, IFV]|
1 [stel, sk, IFV]
|BC, AB, NB||0.5 [sk]|
|QC||0.5 [sk; em]|
|SK, YT, NT, NU||0.5 [sk]|
1.5 [sk, stel]
|Other Jurisdiction||OEL (mg/m3)|
|ACGIH 2020 TLV||0.5 [sk, IFV]|
1 [stel, sk, IFV]
mg/m3 = milligrams per cubic meter
sk = easily absorbed through the skin
stel = short term exposure limit (15 min. maximum)
IFV = inhalable fraction and vapour
em = exposure must be reduced to the minimum
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Canadian environmental guidelines and standards*
|Ontario Ambient Air Quality Criteria||24 hour: 20 µg/m3||2016|
|Alberta Ambient Air Quality Objectives & Guidelines||1 hour: 5.0 µg/m3||2017|
|Annual Average: 0.5 µg/m3||2013|
|Quebec’s Clean Air Regulation||1 year limit: 0.001 µg/m3;Prohibited discharge into the air if the concentration of pentachlorophenol exceeds the standard||2011|
|Drinking Water Guidelines (Canada, BC, MB) and Standards (ON, SK)||MAC: 0.06 mg/L||2005-2020|
|Quebec’s Drinking Water Standards||MAC: 0.042 mg/L||2012|
|BC’s Contaminated Sites Regulation, BC Reg 375/96||Sets soil standards for the protection of human health:|
Agricultural and low density residential sites: 90 μg/g
Urban park and high density residential sites: 200 μg/g
Commercial sites: 550 μg/g
Industrial sites: 900 μg/g
Drinking water: 60 µg/L
**Standards are legislated and legally enforceable, while guidelines (including Ontario ambient air quality criteria) describe concentrations of contaminants in the environment (e.g. air, water) that are protective against adverse health, environmental, or aesthetic (e.g. odour) effects
MAC = maximum acceptable concentration
AO = aesthetic objective
µg/m3 = micrograms per cubic meter
μg/g = micrograms per gram
|Health Canada||DSL – high priority substance with intermediate potential for exposure||2006|
|Stockholm Convention on POPs||Annex A: Elimination, with exemptions for use in utility poles and cross-arms||2014|
|Canada-Ontario Agreement on Great Lakes Water Quality and Ecosystem Health||Tier 2 chemical: potential for causing widespread impacts, or that have already caused local adverse impacts on the Great Lakes Basin Ecosystem||2014|
|National Classification System for Contaminated Sites||Rank: “High Hazard”||2008|
DSL = domestic substances list
POPs = persistent organic pollutants
Although pentachlorophenol is persistent and inherently toxic to humans and other organisms, it is not included in the Canadian Environmental Protection Act because it falls under the Pest Control Products Act. Its management is the responsibility of the Pesticides Management Regulatory Agency.
Pentachlorophenol was not included in other Canadian government guidelines, standards, or chemical listings reviewed.
In 2011, the Pest Management Regulatory Agency (PMRA) re-evaluated pentachlorophenol and approved its registration as a fungicide for industrial wood preservation. Pentachlorophenol is registered for use on utility poles, railroad ties, sawn products, plywood, and pilings. The primary use of PCP is on utility poles. In 2014, PCP was added to the List of Persistent Organic Pollutants (POPs) under the Stockholm Convention, with an ultimate goal of elimination except for use on utility poles and crossarms. The effects of this new designation on PCP use in Canada is not known, but is likely to be minimal since PCP is primarily used on utility poles. Pentachlorophenol is currently registered for use by the PMRA in three formulations.
PCP can be applied to wood via pressure-treating or by thermal impregnation, where PCP is applied by spraying, dipping, brushing, or soaking the wood.
Pentachlorophenol was formerly used in agriculture as an herbicide, defoliant, bactericide, and molluscicide.
Canadian Production and Trade
According to a 1995 report, pentachlorophenol has not been produced in Canada since the early 1980s.
In 2000, between 100 and 1,000 tonnes of PCP (concentration >1%) were imported into Canada for use as a wood preservative. TradeMap lists pentachlorophenol export and import data; however, reporting for pesticides is not standardized and the data is incomplete.
Production and trade
|Canadian Production||2,200 t in 1981 (last year produced)||1997 (forecasted)|
|Domestic Demand||1,100 t||1997 (forecasted)|
t = tonne
Environmental Exposures Overview
Pentachlorophenol can enter the environment (in air, water, and soil) via evaporation from treated woods, industrial spills, and disposal at hazardous waste sites. The general population is most likely exposed to PCP in the vicinity of hazardous waste sites, as well as in older homes that may contain PCP-treated wood. Therefore, low level exposure to PCP may occur by ingesting contaminated indoor or outdoor air, ground water, and food, or via dermal contact with contaminated wood and soil.
People who work or live near a wood treatment facility or where utility poles, railroad ties, or wharf pilings are produced may be exposed to PCP.
Data on Canadian environmental PCP concentration and exposure are limited. Based on the very low data quality available, CAREX Canada developed environmental exposure estimates to pentachlorophenol through various exposure pathways. CAREX Canada’s environmental exposure estimates suggest that PCP concentrations in outdoor air, indoor air, indoor dust, drinking water, and food or beverages do not result in an increased risk of cancer in Canada (very low data quality).
Pentachlorophenol was one of the substances selected for Cycle 2 of the Canadian Health Measures Survey (CHMS), an ongoing joint project of Statistics Canada and Health Canada to establish the current level of exposure to environmental contaminants. Biomonitoring data from the CHMS on Canadians was released in 2013 in the Second Report on Human Biomonitoring of Environmental Chemicals in Canada.
Occupational Exposures Overview
Occupational exposure to pentachlorophenol occurs via dermal contact with the compound while treating wood products, or by inhaling contaminated workplace air (i.e. during production or use of PCP).[1,3] One study found that dermal contact accounted for 95% of total worker exposure in sawmills.
CAREX Canada estimates that approximately 3,900 Canadians are exposed to PCP in their workplaces. The largest industrial groups exposed are farms, electrical power generation (transmission and distribution), and sawmills and wood preservation. The largest occupational groups exposed to pentachlorophenol are electrical power line and cable workers, managers in agriculture, general farm workers, and agriculture service contractors, farm supervisors, and specialized livestock workers.
For more information, see the occupational exposure estimate for PCP.
- Agency for Toxic Substances and Disease Registry (ATSDR). ToxFAQs Sheet for Pentachlorophenol (2001) (PDF)
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