Evaluation of acute sensory--motor effects and test sensitivity using termiticide workers exposed to chlorpyrifos

Sensory and motor testing was performed on a group of termiticide workers primarily using chlorpyrifos-containing products to evaluate both the acute effects from current exposure and sensitivity of the measures to detect effects. The study group comprised 106 applicators and 52 nonexposed participants. Current exposure was measured by urinary concentrations of 3,5,6-trichloro-2-pyridinol (TCP) collected the morning of testing. The mean TCP value for the 106 applicators was 200 microg/g creatinine. Participants received 4--5 h of testing and were evaluated using a sensory--motor test battery recommended by a National Institute for Occupational Safety and Health (NIOSH)-sponsored advisory panel to be appropriate for testing effects from pesticide exposures. Measurements testing olfactory dysfunction, visual acuity, contrast sensitivity, color vision, vibrotactile sensitivity, tremor, manual dexterity, eye--hand coordination, and postural stability were analyzed. Study results indicated limited acute effects from exposure to chlorpyrifos using urinary TCP as a measure of current exposure. The effects occurred primarily on measures of postural sway in the eyes closed and soft-surface conditions, which suggests a possible subclinical effect involving the proprioceptive and vestibular systems. Several other tests of motor and sensory functions did not show any evidence of acute exposure effects, although statistically significant effects of urinary TCP on the Lanthony color vision test scores and one contrast sensitivity test score were found. The visual measures, however, were not significant when a step-down Bonferroni correction was applied. Information also is presented on the sensitivity of the measures to detect effects in an occupationally exposed population using standard error of the parameter estimates.

Intermediate syndrome secondary to ingestion of chlorpiriphos

A rural-area resident male patient deliberately ingested chlorpiriphos, an organophosphate insecticide. Although presented with cholinergic symptoms initially, he suffered general condition deterioration after 4 d characterized by muscular weakness, hypotonia, arreflexia and recumbent dyspnea requiring ventilatory support. These clinical manifestations occur from liposoluble organophosphates or metabolites with long-lasting half time, causeing delayed inhibition of acetylcholinesterase and subsequent burn out of the neuromuscular junction from acetylcholine overstimulation.

Protective effects of zinc in chlorpyrifos induced hepatotoxicity: a biochemical and trace elemental study

The toxicological literature is replete with studies attempting to explain the mechanism of action of organophosphorus (OP) insecticides to their anticholinesterase activities, but not much is known about the metabolism and detoxification of these compounds. The goal of this study was to ascertain the toxic effects of chlorpyrifos, one of the most widely used OPs, on the liver of male rats and also to evaluate the protective potential of zinc in mediating its toxic effects. It was observed that chlorpyrifos (13.5 mg/kg body weight) treatment resulted in significant inhibition (p < 0.001) of serum and hepatic acetylcholinesterase (AChE) activities after 8 wk. However, zinc-treated (227 mg/L drinking water) animals resulted in significant normalization of the inhibited AChE activities. Similarly, a significant increase in the levels of various serum and liver marker enzymes (viz. alkaline phosphatase, aspartate aminotransferase [AST], and alanine aminotransferase [ALT]) was observed following treatment with chlorpyrifos. However, coadministration of zinc to these animals restored these enzymes to within normal limits, even though some increase in the activity of serum ALT and hepatic alkaline phosphatase still persisted at the end of the study. Chlorpyrifos treatment diminished serum and hepatic zinc levels significantly (p < 0.01 to p < 0.001) compared to normal control animals. Serum iron concentrations also plummeted significantly following chlorpyrifos treatment. On the contrary, serum copper levels were significantly increased (p < 0.01) in chlorpyrifos-treated animals, but they were normalized following zinc supplementation to the rats in this group. Interestingly, chlorpyrifos treatment resulted in elevated hepatic levels of copper, iron, and selenium, but zinc treatment could only partially restore the raised elemental concentrations. These data clearly demonstrate the potential role of zinc in mediating the toxic effects of chlorpyrifos, presumably because of their antioxidant properties and also their possible interaction with other trace elements in maintaining the cellular harmony.

Administration of succinylcholine for electroconvulsive therapy after organophosphate poisoning: a case study

A 53-year-old man was admitted to the hospital psychiatric unit for evaluation and treatment following a recent suicide attempt, which involved ingestion of an unknown amount of Dursban (DowElanco, Indianapolis, Ind) and a self-inflicted knife wound to the abdomen. Dursban is a commercially prepared organophosphate insecticide in which the active ingredient is chlorpyrifos in a petroleum distillate solvent. The patient received 7 electroconvulsive therapy treatments during a 2-week hospital stay. The anesthetic regimen included methohexital for induction and succinylcholine for neuromuscular relaxation. Cholinesterase levels were low on admission at 5,780 IU (reference range, 11,000-15,000), yet succinylcholine was used successfully at low doses.

Pitfalls when determining tissue distributions of organophosphorus chemicals: sodium fluoride accelerates chemical degradation

This paper describes the tissue distributions of dichlorvos, an organophosphate, and chlorpyrifos-methyl, an organophosphorothioate, in a male individual who died after ingesting an insecticidal preparation containing these chemicals and the results of an in vitro stability study on dichlorvos and chlorpyrifos-methyl in blood and buffers. Tiny amounts of dichlorvos, 0.067 and 0.027 mg/L, were detected in the vitreous humor and cerebrospinal fluid, respectively. Although dichlorvos (0.082-8.99 mg/L or mg/kg) was detected in the thoracic aortic blood, thoracic inferior vena caval blood, pericardial fluid, bile, and spleen, it was strongly suggested that it had diffused postmortem from the stomach, which contained 879 mg, because no dichlorvos was detected in the other blood samples and tissues tested. Substantial amounts (0.615-4.15 mg/L) of chlorpyrifos-methyl were detected in all blood samples, and the order of its concentrations was as follows: pulmonary vessel blood > thoracic inferior vena caval blood > blood in the right cardiac chambers > blood in the left cardiac chambers approximately thoracic aortic blood > right femoral venous blood. The total amount of chlorpyrifos-methyl in the stomach was 612 mg. However, it was strongly suggested that virtually no chlorpyrifos-methyl diffused from the stomach into surrounding fluids and tissues postmortem because no chlorpyrifos-methyl was detected in the bile and little was found in the pericardial fluids. Neither compound was detected in the urine. In vitro experiments showed that dichlorvos (10 mg/L) almost disappeared from fresh (pH 7.4) and acidified (pH 6.2) blood samples within 24 and 72 h, respectively. However, 53 and 77% of the original amount of dichlorvos in 0.05M phosphate buffers at pH 7.4 and 6.2 were detected 72 h later. Chlorpyrifos-methyl (1 mg/L) was very stable in blood samples, regardless of the pH, during the 72-h study period, but in the pH 7.4 and 6.2 phosphate buffers, approximately 80% of the original amount had degraded after 72 h. These results indicate that organophosphates are degraded more rapidly by esterase activities than by chemical mechanisms and that organophosphorothioates are hydrolyzed chemically in aqueous solutions but are very stable in biological specimens and not metabolized by esterases. When sodium fluoride was added to blood samples, dichlorvos degraded completely within 15 min, and chlorpyrifos-methyl became very unstable. Thus, when analyzing samples to detect organophosphorus chemicals, this common preservative should not be added to fluid specimens.

Chlorpyrifos: a ten-year US poison center exposure experience

We performed a retrospective review of data based on poison center exposure inquiries related to chlorpyrifos (CP) and the corresponding poison center-determined medical outcomes reported to the Toxic Exposure Surveillance System (TESS) of the American Association of Poison Control Centers. Ten y (1985-1994) of TESS data were obtained. Medical outcomes representing all inquiries, accidental/unintentional inquiries, and intentional/suicidal inquiries were tabulated. Published TESS data was also tabulated to allow comparison of CP exposure inquiries to all non-pharmaceutical and insecticides/pesticides exposure inquiries for like time periods. Frequency of antidote use, product sales data, CP-related fatality reports, and pertinent issues related to telephone derived surveillance data were also reviewed; 36, 183 CP exposure inquiries were identified. Of all CP exposure inquiries, 27, 473 (75.9%) were assessed as having no significant health consequences; 4,511 (12.5%) outcomes were judged unrelated and 2,980 (8.2%) were unable to be followed. Reported significant medical outcomes for the remaining exposure inquiries were moderate 1,092 (3.0%), major 119 (0.3%) and death 8 (0.02%). Considering only calls with outcomes judged causally related to CP, where a given level of effect could reasonably be determined, 95.8% (27,473/28,692) of these calls resulted in no significant health effects. Use of antidotes specific to organophosphates were infrequent [atropine, 1.0% (385) and 2-PAM, 0.5% (177) of all cases respectively]. Despite the number of reported CP exposure inquiries, relatively few resulted in outcomes of consequence. TESS data suggested that the majority of patients undergoing medical evaluation and/or treatment after a suspected CP exposure do not require specific antidotes. TESS data serves as a useful first step in evaluating product safety. Assessment of product toxicity requires additional investigation of reported adverse effects and circumstances related to the incident.

Pralidoxime continuous infusion in the treatment of organophosphate poisoning

OBJECTIVE

To report a case of organophosphate poisoning treated with a continuous infusion of pralidoxime chloride.

CASE SUMMARY

A 27-year-old white man presented with extreme agitation, muscle weakness and fasciculations, and respiratory failure after ingesting an organophosphate pesticide (Dursban, active ingredients chlorpyrifos and xylene) as a suicide attempt. Atropine sulfate and pralidoxime chloride were administered intermittently, but the patient continued to be extremely agitated and have muscle fasciculations. Subsequently, a continuous intravenous infusion of pralidoxime (8 mg/mL concentration) at 500 mg/h was initiated to help control breakthrough nicotinic symptoms. Therapy with atropine and pralidoxime was continued for approximately 72 hours. Therapy was discontinued due to the predominance of anticholinergic symptoms and the patient's increased awareness.

DISCUSSION

Severe organophosphate poisoning with nicotinic and/or central manifestations should be treated with pralidoxime in addition to atropine. The rationale supporting the use of pralidoxime as a continuous infusion in this case includes: (1) slow absorption of organophosphate compounds following exposure to large quantities, (2) unknown quantity ingested, (3) delayed nicotinic effects from redistribution of lipid-soluble organophosphate and metabolic activation of phosphorothioates such as chlorpyrifos, and (4) intensive care monitoring. There is limited documentation in the literature of continuous infusions of pralidoxime used to treat organophosphate poisoning and the stability of the admixture is unknown.

CONCLUSIONS

A continuous pralidoxime infusion successfully managed the prolonged nicotinic symptoms seen after ingestion of an organophosphate. A continuous infusion of pralidoxime may be particularly useful in cases of organophosphate poisoning when the extent of chemical exposure or quantity of chemical ingested is unknown but potentially toxic and the therapy must be symptomatically managed.

Life-threatening organophosphate-induced delayed polyneuropathy in a child after accidental chlorpyrifos ingestion

Life-threatening organophosphate-induced delayed polyneuropathy with transient bilateral vocal cord paralysis occurred in a 3-year-old child. Recovery was slow after prolonged ventilatory support. Patients who recover from serious organophosphate intoxications should be closely monitored for the development of organophosphate-induced delayed polyneuropathy.

Column extraction of chlorpyrifos from contaminated fish

A method for measuring chlorpyrifos in fish, which combines extraction, filtration, and cleanup in one step, is described. Minced fish samples were mixed with potassium dihydrogen phosphate and disodium hydrogen phosphate, ground with anhydrous sodium sulfate, and eluted from a prepacked chromatographic column containing silica gel. The endogenous coextractives were retained by the column while chlorpyrifos was quantitatively eluted with 40 mL of 5% ether in hexane. Recoveries averaged 86.8% for unexposed fish fortified with 2-12 ppm of chlorpyrifos. The method was applied to the analysis of fish from a lagoon contaminated with chlorpyrifos by a spray treatment of a wooden bridge for termites.

Chlorpyrifos toxicosis in two cats

Organophosphate compounds are widely employed for control of external parasites in cats and for control of insects in homes and yards. Chlorpyrifos is a long-acting organophosphate (OP) available for use as a systemically and topically acting parasiticide and insecticide in cattle. Its use on cats is not recommended, and no previous clinical cases of toxicosis have been described. Two cases of chronic chlorpyrifos toxicosis in cats are presented and pathophysiology as well as treatment are discussed. The cats had been showing signs of chronic organophosphate toxicosis before diazepam administration. Signs of acute organophosphate toxicosis were precipitated after diazepam was given. Treatment with pralidoxime chloride (2-PAM) and atropine was attempted. Response to treatment was dramatic and complete recovery was achieved with six injections of pralidoxime and atropine administration.

Conditioning of physical symptoms after neurotoxic exposure

Psychologic reactions to a neurotoxic exposure can produce prolonged physical symptoms which are as debilitating as the direct effects of the neurotoxic substance. A group of patients exist who experience reoccurrence of exposure-related symptoms when exposed to a variety of common environmental substances, such as perfume, gasoline, and cigarette smoke. We propose a classical conditioning model to explain the development of this phenomenon. Identification and treatment of these individuals are also discussed.

Toxicologic evaluation of chlorpyrifos in cats

Twenty-four male domestic shorthair cats were used to evaluate the acute and chronic effects of a single, toxic but sublethal, orally administered dose of chlorpyrifos. A dosage of 10 mg/kg of body weight did not induce clinical signs of toxicosis, but a dosage of 40 mg/kg induced clinical signs of toxicosis, and 1 of 12 cats died. Chlorpyrifos given at a dosage of 0.1 mg/kg to 2 cats reduced whole blood and plasma cholinesterase (Che) activities to values obtained after cats were given doses that induced clinical signs of toxicosis. Regeneration time for whole blood and plasma Che activities ranged from 7 to 28 days. Brain Che activity was considerably decreased in 1 cat that died 4.5 hours after dosing, but was normal in all others at 28 days after dosing. Other than decreased Che activity, significant changes were not seen in hematologic or serum biochemical values. Toxin-related lesions were not seen during macroscopic or microscopic examination.

Chlorpyrifos poisoning treated with ipratropium and dantrolene: a case report

A patient suffering from chlorpyrifos poisoning and manifesting copious endotracheal secretions was successfully treated by inhalation of ipratropium.

Toxicosis in newborn pigs associated with cutaneous application of an aerosol spray containing chlorpyrifos

Weakness, lethargy, ataxia, lateral recumbency, limb paddling, tremors, salivation, and diarrhea were observed in newborn pigs on a commercial swine farm. Many pigs became moribund and died. All had been treated with an aerosol wound spray containing 2.5% chlorpyrifos. A controlled study was undertaken to determine whether the aerosol spray was the cause of these clinical signs. Pigs exposed to aerosol spray containing 2.5% chlorpyrifos at 3 hours (n = 4) and 6 hours (n = 3) after birth developed clinical signs similar to those on the farm; none survived. Pigs exposed at 24 hours (n = 5) after birth developed clinical signs consistent with those that had developed in pigs on the farm; 3 died and 2 survived. Of 3 pigs exposed to the same spray at 36 hours after birth, 1 developed tremors 7.5 hours later and diarrhea 9 hours later, then returned to normal.