Pentachlorophenol (PCP) is an
organochlorine compound
Organochlorine chemistry is concerned with the properties of organochlorine compounds, or organochlorides, organic compounds that contain one or more carbon–chlorine bonds. The chloroalkane class (alkanes with one or more hydrogens substituted ...
used as a
pesticide
Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...
and a
disinfectant
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
. First produced in the 1930s, it is marketed under many trade names.
It can be found as pure PCP, or as the sodium salt of PCP, the latter of which dissolves easily in water. It can be biodegraded by some bacteria, including ''
Sphingobium chlorophenolicum''.
Uses
PCP has been used as a
herbicide
Herbicides (, ), also commonly known as weed killers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...
,
insecticide
Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...
,
fungicide
Fungicides are pesticides used to kill parasitic fungi or their spores. Fungi can cause serious damage in agriculture, resulting in losses of yield and quality. Fungicides are used both in agriculture and to fight fungal infections in animals, ...
,
algaecide, and
disinfectant
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
and as an ingredient in
antifouling paint.
Some applications were in agricultural seeds (for nonfood uses), leather, masonry,
wood preservation
Wood preservation refers to any method or process, or even technique, used to protect the wood and extend its service life.
Most wood species are susceptible to both biological (''biotic'') and non-biological (''abiotic'') factors that cause d ...
, cooling-tower water, rope, and paper. It has previously been used in the manufacture of food packaging materials. Its use has declined due to its high toxicity and slow biodegradation.
Two general methods are used for preserving wood. The pressure process method involves placing wood in a pressure-treating vessel, where it is immersed in PCP and then subjected to applied pressure. In the nonpressure process method, PCP is applied by spraying, brushing, dipping, or soaking.
Pentachlorophenol esters can be used as active esters in
peptide synthesis
In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl ...
, much like more popular
pentafluorophenyl esters.
Exposure
People may be exposed to PCP in occupational settings through the inhalation of contaminated workplace air and dermal contact with wood products treated with PCP. Also, general population exposure may occur through contact with contaminated environment media, particularly in the vicinity of wood-treatment facilities and hazardous-waste sites. In addition, some other important routes of exposure seem to be the inhalation of contaminated air, ingestion of contaminated ground water used as a source of drinking water, ingestion of contaminated food, and dermal contact with soils or products treated with the chemical.
Toxicity
Short-term exposure to large amounts of PCP can cause harmful effects on the liver, kidneys, blood, lungs, nervous system,
immune system, and gastrointestinal tract. Elevated temperature, profuse sweating, uncoordinated movement, muscle twitching, and coma are additional side effects.
Contact with PCP (particularly in the form of vapor) can irritate the skin, eyes, and mouth. Long-term exposure to low levels, such as those that occur in the workplace, can cause damage to the liver, kidneys, blood, and nervous system.
Finally, exposure to PCP is also associated with carcinogenic, renal, and neurological effects. The
U.S. Environmental Protection Agency toxicity class classifies PCP in group B2 (probable human
carcinogen
A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...
).
Monitoring of human exposure
Pentachlorophenol may be measured in plasma or urine as an index of excessive exposure. This is usually performed by
gas chromatography
Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for Separation process, separating and analyzing compounds that can be vaporized without Chemical decomposition, decomposition. Typical uses of GC include t ...
with electron-capture or
mass-spectrometric detection. Since urine contains predominantly conjugated PCP in chronic exposure situations, prior
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
of specimens is recommended. The current ACGIH biological exposure limits for occupational exposure to PCP are 5 mg/L in an end-of-shift
plasma specimen and 2 mg/g creatinine in an end-of-shift
urine
Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...
specimen.
Absorption in humans and animals
PCP is quickly absorbed through the
gastrointestinal tract
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...
following ingestion. Accumulation is not common, but if it does occur, the major sites are the liver, kidneys,
plasma protein
Plasma proteins, sometimes referred to as blood proteins, are proteins present in blood plasma. They perform many different functions, including transport of hormones, vitamins and minerals in activity and functioning of the immune system. Other b ...
,
spleen
The spleen (, from Ancient Greek '' σπλήν'', splḗn) is an organ (biology), organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter.
The spleen plays important roles in reg ...
, and
fat
In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food.
The term often refers specif ...
. Unless kidney and liver functions are impaired, PCP is quickly eliminated from tissues and blood, and is excreted, mainly unchanged or in conjugated form, via the urine. Single doses of PCP have half-lives in blood of 30 to 50 hours in humans.
Biomagnification
Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance, e.g a pesticide, in the tissue (biology), tissues of organisms at successively higher levels in a food chain. This inc ...
of PCP in the food chain is not thought to be significant due to the fairly rapid metabolism of the compound by exposed organisms.
Releases to the environment
PCP has been detected in surface waters and sediments, rainwater, drinking water, aquatic organisms, soil, and food, as well as in human milk,
adipose tissue
Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, Blood vessel, vascular endothel ...
, and urine. As PCP is generally used for its properties as a biocidal agent, considerable concern exists about adverse ecosystem effects in areas of PCP contamination.
Releases to the environment are decreasing as a result of declining consumption and changing use methods. However, PCP is still released to surface waters from the atmosphere by
wet deposition, from soil by run off and leaching, and from manufacturing and processing facilities. PCP is released directly into the atmosphere via volatilization from
treated wood products and during production. Finally, releases to the soil can be by leaching from treated wood products, atmospheric deposition in precipitation (such as rain and snow), spills at industrial facilities, and at
hazardous waste
Hazardous waste is waste that must be handled properly to avoid damaging human health or the environment. Waste can be hazardous because it is Toxicity, toxic, Chemical reaction, reacts violently with other chemicals, or is Corrosion, corrosive, ...
sites.
After PCP is released into the atmosphere, it decomposes through
photolysis
Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by absorption of light or photons. It is defined as the interaction of one or more photons wi ...
. The main biodegradative pathway for PCP is reductive dehalogenation. In this process, the compound PCP is broken down to tetrachlorophenols,
trichlorophenols, and
dichlorophenols. Another pathway is methylation to pentachloroanisole (a more lipid-soluble compound). These two methods eventually lead to ring cleavage and complete degradation.
In shallow waters, PCP is also quickly removed by photolysis. In deep or turbid water processes, sorption and biodegradation take place.
In reductive soil and sediments, PCP can be degraded within 14 days to 5 years, depending on the anaerobic soil bacteria that are present. However, adsorption of PCP in soils is pH dependent because it increases under acidic conditions and decreases in neutral and basic conditions.
Synthesis
PCP can be produced by the
chlorination of
phenol
Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire.
The molecule consists of a phenyl group () ...
in the presence of
catalyst
Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
(anhydrous
aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
or
ferric chloride
Iron(III) chloride describes the inorganic compounds with the formula (H2O)x. Also called ferric chloride, these compounds are some of the most important and commonplace compounds of iron. They are available both in anhydrous and in hydrated f ...
) and a temperature up to about 191 °C. This process does not result in complete chlorination and commercial PCP is only 84–90% pure. The main contaminants include other polychlorinated phenols,
polychlorinated dibenzo-p-dioxins, and
polychlorinated dibenzofurans. Some of these species are even more toxic than the PCP itself.
Pentachlorophenol by country
Pentachlorophenol is classified as a
persistent organic pollutant (POP). In May 2015, countries which have signed the
Stockholm Convention voted 90–2 to ban pentachlorophenol use. The United States is not a signatory and has not banned the chemical.
New Zealand
PCP was used in New Zealand as a timber preservative and antisapstain treatment, but since 1988 is no longer used.
It was also sold as a moss killer to the general public (by Shell, at least) in the form of a 115g/L aqueous solution and labelled as a poison.
United States
Since the early 1980s, the purchase and use of PCP in the U.S. has not been available to the general public. Nowadays, most of the PCP used in the U.S. is restricted to the treatment of
utility pole
A utility pole, commonly referred to as a transmission pole, telephone pole, telecommunication pole, power pole, hydro pole, telegraph pole, or telegraph post, is a column or post used to support overhead power lines and various other public util ...
s and
railroad ties. In the United States, any drinking-water supply with a PCP concentration exceeding the
MCL, 1
ppb, must be notified by the water supplier to the public.
Disposal of PCP and PCP-contaminated substances are regulated under
RCRA as F-listed (F021) or D-listed (D037) hazardous wastes. Bridges and similar structures such as piers can still be treated with pentachlorophenol.
Chile
PCP was widely used in Chile until the early 1990s as a fungicide to combat the so-called "blue stain" in pine timber under the name of Basilit.
See also
*
Chlorophenol
*
Collision between MV Testbank and MV Seadaniel
*
Creosote
Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood, or fossil fuel. They are typically used as preservatives or antiseptics.
Some creosote types w ...
*
Dichlorophenol
*
Havertown Superfund
*
Monochlorophenol
*
Trichlorophenol
References
Cited sources
*
External links
*
Non-CCA Wood Preservatives: Guide to Selected Resources - National Pesticide Information Centeratsdr.cdc.gov on pentachlorophenolEPA study that used the fungus Phanerochaete chrysosporium to aid in bioremediation of pentachlorophenol in soilEPA ReRegistration – www.regulations.gov -Search docket ID EPA-HQ-OPP-2014-0653.
{{Authority control
Fungicides
Endocrine disruptors
Chlorobenzene derivatives
Phenols
Persistent organic pollutants under the Stockholm Convention
Steroid sulfotransferase inhibitors
Uncouplers
IARC Group 1 carcinogens
Disinfectants