Overview
of Pentachlorophenol Poisoning (Penta
poisoning)
Pentachlorophenol (PCP), commonly known as penta, has
been used as a fungicide, molluscicide, insecticide, and wood preservative. Its
use is now permitted only for industrial purposes; agricultural and domestic
uses are prohibited, because it is classified as a highly hazardous pesticide.
The oral LD50 of
penta in rats is 150–210 mg/kg body wt. Common signs of poisoning include
nervousness, rapid pulse and respiratory rate, weakness, fever, muscle tremors,
convulsions, loss in righting reflexes, and asphyxial spasms followed by death.
Corneal injury may result from splashes or vapor overexposure. Chronic
poisoning results in emaciation, fatty liver, nephrosis, and weight loss.
The persistence of penta in soil and water and
apparent widespread use has resulted in significant exposure to animals. Young
swine have died after dermal exposure to freshly penta-treated wood used in
farrowing crates or farrowing houses. In vivo studies in swine demonstrated
that exposure to penta-contaminated soil can result in significant dermal
absorption of the pesticide. Penta can be absorbed through intact skin and
lungs and is an intense irritant to the skin and mucous membranes. Penta
absorption in skin was greater in water or water-based mixtures than in 100%
ethanol. Because animals typically have access to water at all times, this
hydrophilic characteristic of penta suggests enhanced dermal absorption.
When absorbed, penta increases metabolism by
uncoupling cellular phosphorylation. Animals fed in troughs made of lumber
treated with PCP may salivate and have irritated oral mucosa. Both penta
and its major metabolite, tetrachlorohydroquinone (TCHQ), can induce epidermal
hyperplasia in mice.
Poultry have been exposed to sawdust and shavings
from penta-treated wood. Associated adverse effects include reduced growth
rates, kidney hypertrophy, and decreased humoral immune response. Penta
exposure can also result in an off-taste to eggs and meat as a result of
degradation of chlorophenols to chloroanisols. Vaporization or leaching of
penta in pens, enclosures, homes, and barns has caused illness and death.
Cattle and pigs exposed to wood treated with
commercial grade penta had increased mortality, possibly decreased fertility in
boars, and reduced productivity (milk, meat, etc). The lethal dose in cattle
and sheep is ~120–140 mg/kg body wt.
Commercial lots of technical-grade penta contain
small but biologically significant amounts of highly toxic impurities such as
chlorinated dioxins and dibenzofurans, tetrachlorophenols, and
hydroxychlorodiphenyl ethers; these compounds can exert their own effects such
as early fetotoxicity. Commercial-grade penta causes hepatic porphyria,
increased microsomal monooxygenase activity, and increased liver weight. Pure
penta was not teratogenic in rats.
Penta can cause residues in animal tissues. Also, a
significant amount of hexachlorobenzene is metabolized in animal tissues to
penta. Pentachlorophenol is considered to be a carcinogen and a tumor promoter,
although studies have shown that the pure material does not increase the
incidence of tumors in rats and mice. The technical-grade material has also
been shown to be immunotoxic in laboratory studies. Penta must be handled very
carefully and kept away from animal contact.
Whole blood analysis for penta may aid in the
diagnosis of poisoning; diagnosis is usually made on the basis of the signs and
the proximity of treated lumber in the animal’s environment.
There is no known antidote. Termination of exposure,
bathing dermally exposed animals, oral administration of activated charcoal,
and supportive therapy may be indicated. Bathing should be done gently with
cold water and detergent so as not to cause vasodilation and increased
absorption. Antipyretics, eg, aspirin and acetaminophen, should not be used. Treatment
involves cooling the animal and administering fluids, electrolytes, and
anticonvulsants. Read more --------
Overview of Pentachlorophenol
Poisoning - Merck Veterinary Manual
www.merckvetmanual.com › Toxicology › Pentachlorophenol
Poisoning
By P. K. Gupta, PhD, Post Doc (USA), PGDCA,
MSc VM & AH BVSc, FNA VSc, ... FAEB, FACVT (USA), Gold
Medalist, Editor-in-Chief, Toxicology International.
No comments:
Post a Comment