Permanent Paralysis at Sites of Dermal Exposure to Chlorpyrifos

Outcome of patients with chlorpyrifos intoxication

INTRODUCTION

There is a paucity of literature analyzing outcome of chlorpyrifos intoxication.

METHODS

A total of 40 patients with chlorpyrifos intoxication were seen at Chang Gung Memorial Hospital between 2008 and 2017. Patients were stratified into two subgroups according to their prognosis, as good (n = 12) or poor (n = 28). Good prognosis group were defined as patients who survived without serious complications, and poor prognosis group included patients who died and survived after development of severe complications. Demographic, clinical, laboratory, and mortality data were obtained for analysis.

RESULTS

Patients aged 53.8 ± 16.3 years and most were male (80.0%). All patients (100.0%) developed acute cholinergic crisis such as emesis (45.0%), respiratory failure (42.5%), tachycardia (30.0%), kidney injury (22.5%), and seizure (7.5%). Intermediate syndrome developed in 12.5% of patients, but none had delayed neuropathy (0%). The poor prognosis group suffered higher incidences of respiratory failure (p = 0.011), kidney injury (p = 0.026), and prolonged corrected QT interval (p = 0.000), and they had higher blood urea nitrogen level (p = 0.041), lower Glasgow coma scale score (p = 0.011), and lower monocyte count (p = 0.023) than good prognosis group. All patients were treated with atropine and pralidoxime therapy, but six patients (15.0%) still died of intoxication. In a multivariate logistic regression model, blood urea nitrogen was a significant risk factor for poor prognosis (odds ratio: 1.375, 95% confidence interval: 1.001-1.889, p = 0.049). Nevertheless, no mortality risk factor could be identified.

CONCLUSION

The mortality rate of patients with chlorpyrifos intoxication was 15.0%. Furthermore, acute cholinergic crisis, intermediate syndrome, and delayed neuropathy developed in 100.0%, 12.5%, and 0% of patients, respectively.

Organophosphate neurotoxicity to the voluntary motor system on the trail of environment-caused amyotrophic lateral sclerosis: the known, the misknown, and the unknown

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset paralytic disorder. It is characterized by progressive degeneration of the motor neurons controlling voluntary movement. The underlying mechanisms remain elusive, a fact that has precluded development of effective treatments. ALS presents as a sporadic condition 90-95% of the time, i.e., without familial history or obvious genetic mutation. This suggests that ALS has a strong environmental component. Organophosphates (OPs) are prime candidate neurotoxicants in the etiology of ALS, as exposure to OPs was linked to higher ALS incidence among farmers, soccer players, and Gulf War veterans. In addition, polymorphisms in paraoxonase 1, an enzyme that detoxifies OPs, may increase individual vulnerability both to OP poisoning and to the risk of developing ALS. Furthermore, exposure to high doses of OPs can give rise to OP-induced delayed neuropathy (OPIDN), a debilitating condition akin to ALS characterized by similar motor impairment and paralysis. The question we pose in this review is: "what can we learn from acute exposure to high doses of neurotoxicants (OPIDN) that could help our understanding of chronic diseases resulting from potentially decades of silent exposure (ALS)?" The resemblances between OPIDN and ALS are striking at the clinical, etiological, neuropathological, cellular, and potentially molecular levels. Here, we critically present available evidence, discuss current limitations, and posit future research. In the search for the environmental origin of ALS, OPIDN offers an exciting trail to follow, which can hopefully lead to the development of novel strategies to prevent and cure these dreadful disorders.

Factors that contribute to insecticide poisoning among immigrant agricultural workers in Thailand

BACKGROUND

There has been a strong increase in the international movement of workers during the last few decades. As Thailand's economy has rapidly developed during the past 20 years, it has attracted growing numbers of laborers from the bordering countries of Myanmar, Lao PDR, and Cambodia. Numbers of migrant workers in Thai agriculture have risen to the extent that the sector's continued growth has become increasingly dependent on migrant workers.

OBJECTIVE

The purpose of this study was to explore the factors that contribute to the development of symptoms of insecticide poisoning among immigrant agricultural workers in the eastern region of Thailand.

METHODS

Data were collected via interviews (N = 891), and the levels of cholinesterase activity in the workers' blood were tested using reactive test strips.

RESULTS

Only 4.4% of the workers had normal levels of cholinesterase activity and 75.1% had levels that were abnormal. Regarding factors that affect gastrointestinal symptoms of poisoning, being aged 45 to 50 increased the risk of developing gastrointestinal symptoms (odds ratio (OR): 2.51; 95% CI: 1.41-4.46), as did using a backpack spraying technique (OR: 3.74; 95% CI: 2.16-6.49) and having only moderate levels of self-protection behavior while spraying the insecticides (OR: 2.23; 95% CI: 1.16-4.29). Having an at risk level of cholinesterase activity increased the risk of gastrointestinal symptoms (OR: 3.25; 95% CI: 1.05-10.04) and the risk of respiratory symptoms (OR: 2.75; 95% CI: 1.17-6.44).

CONCLUSION

It is recommended that insecticide self-protection measures should be promoted and health monitoring should be implemented for migrant workers affected by high-risk insecticide use.

Clinical features of organophosphate poisoning: A review of different classification systems and approaches

PURPOSE

The typical toxidrome in organophosphate (OP) poisoning comprises of the Salivation, Lacrimation, Urination, Defecation, Gastric cramps, Emesis (SLUDGE) symptoms. However, several other manifestations are described. We review the spectrum of symptoms and signs in OP poisoning as well as the different approaches to clinical features in these patients.

MATERIALS AND METHODS

Articles were obtained by electronic search of PubMed(®) between 1966 and April 2014 using the search terms organophosphorus compounds or phosphoric acid esters AND poison or poisoning AND manifestations.

RESULTS

Of the 5026 articles on OP poisoning, 2584 articles pertained to human poisoning; 452 articles focusing on clinical manifestations in human OP poisoning were retrieved for detailed evaluation. In addition to the traditional approach of symptoms and signs of OP poisoning as peripheral (muscarinic, nicotinic) and central nervous system receptor stimulation, symptoms were alternatively approached using a time-based classification. In this, symptom onset was categorized as acute (within 24-h), delayed (24-h to 2-week) or late (beyond 2-week). Although most symptoms occur with minutes or hours following acute exposure, delayed onset symptoms occurring after a period of minimal or mild symptoms, may impact treatment and timing of the discharge following acute exposure. Symptoms and signs were also viewed as an organ specific as cardiovascular, respiratory or neurological manifestations. An organ specific approach enables focused management of individual organ dysfunction that may vary with different OP compounds.

CONCLUSIONS

Different approaches to the symptoms and signs in OP poisoning may better our understanding of the underlying mechanism that in turn may assist with the management of acutely poisoned patients.

[Evaluation of the impact of exposure to pesticides on the health of the rural population: Vale do Taquari, State of Rio Grande do Sul (Brazil)]

The scope of this cross-sectional study was to assess a possible link between contact with pesticides and the prevalence of chronic disease in the rural population in the south of Brazil. Three municipalities were randomly chosen. The sample selected was recruited over three months (2005) and was composed of 298 subjects of both sexes, between 18 and 65 years of age, who frequented public or private pharmacies for the purchase of medication. Data obtained by means of structured interviews revealed that 68.4% of those interviewed worked in rural activities, and 74.8% of these were members of families working in agriculture with contact with pesticides. The average age was 51+16.5 years of age for the interviewees with contact with pesticides and 50+17.9 years for those without contact. The sample was composed of 36.2% of men, and 57.7% of the individuals had more than four years of education. Direct or indirect contact with pesticides was associated with the report of several diseases, with neurological and oral diseases being the most prevalent. There was a link with painful conditions and individuals with contact with pesticides reported twice as many diseases. The data corroborate the literature and draw attention to the need for promoting measures to protect the health of the rural population.

Topical absorption and systemic toxicity

Dermal absorption of some chemicals and drugs can cause systemic toxicity. We evaluated several case reports from the past decade, which discuss the dermal absorption of a specific chemical and potential local and systemic effects. We focused on herbicide and pesticide exposure along with exposure to cutaneous medication, occupational contact, and cosmeceutical exposure. Although causality cannot be established in most cases, it is critical to be aware of the possible effects of topical absorption that may not be immediately apparent. We recommended further studies on specific chemicals to ascertain causality and determine the highest exposure level with no observed adverse affect level (NOAEL) and the reference dose (RfD). Post-marketing epidemiology data in most geographical areas are markedly limited. A weak link in public health resides in the inadequate reporting and workup of alleged chemically related adverse effects. This arena mandates a re-thinking of how to increase this reporting, and workup, as a backup to our preclinical and clinical studies. Public awareness and funding will be rewarded by increased evidence to backup pre-approval pre-marketing studies.

Design, evaluation and structure-activity relationship studies of the AChE reactivators against organophosphorus pesticides

Organophosphate pesticides (OPPs; e.g. chlorpyrifos, diazinon, paraoxon) are a wide and heterogeneous group of organophosphorus compounds. Their biological activity of inhibiting acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) ranks them as life endangering agents. The necessary treatment after OPP exposure involves the use of parasympatolytics (e.g. atropine), oxime reactivators (e.g. obidoxime), and anticonvulsive drugs (e.g. diazepam). Therefore, the reactivators of AChE are essential compounds in the treatment of OPP intoxications. Commercial AChE reactivators (e.g. pralidoxime, HI-6, obidoxime, trimedoxime, methoxime) were originally developed for other members of the organophosphate family, such as nerve agents (e.g. sarin, soman, tabun, VX). Pralidoxime, HI-6, and methoxime were found to be weak reactivators of OPP-inhibited AChE. Obidoxime and trimedoxime showed satisfactory reactivation against various OPPs with minor toxicity issues. During the last two decades, the treatment of OPP exposure has become more widely discussed because of growing agricultural production, industrialization, and harmful social issues (e.g. suicides). In this review is the summarized design, evaluation, and structure-activity relationship studies of recently produced AChE reactivators. Since pralidoxime, over 300 oximes have been produced or tested against OPP poisoning, and several novel compounds show very promising abilities as comparable (or higher) to commercial oximes. Some of these are highlighted for their further testing of OPP exposure and, additionally, the main structure-activity relationship of AChE reactivators against OPP is discussed.

Spectrophotometric determination of plasma and red blood cell cholinesterase activity of 53 fruit farm workers pre- and post-exposed chlorpyrifos for one fruit crop

We sought to investigate the early biological effects of chlorpyrifos among 53 Thai fruit farm workers by measuring the plasma cholinesterase (PChE) and red blood cell cholinesterase (AChE) activities, a biomarker of organophosphate (OPs) pesticide during one fruit crop. The ChE activity (V(m)/K(m)) was spectrophotometrically analyzed before and after exposing to chlorpyrifos. The V(m)/K(m) values of both non-spraying and spraying seasons are found as normal distribution pattern. The median PChE and AChE activities among farm workers in the non-spraying season were 2.3 x 10(-3) s(-1) and 7.26 x 10(-5) s(-1), respectively. The median PChE and AChE activities of the farm workers in the spraying season were 2.02 x 10(-3) s(-1) and 5.95 x 10(-5) s(-1), respectively. The mean V(m)/K(m) values of PChE shifted left (t-test, p=0.013), indicating a decrease in PChE activity in the farm workers exposed to chlorpyrifos. However, the V(m)/K(m) values of AChE in nonspraying season and in the spraying season were not different (t-test, p=0.246). We propose that PChE activity can be used as a biomarker for monitoring early toxicity induced by chlorpyrifos insecticide.

Organophosphate-Induced Delayed Polyneuropathy

Organophosphate-induced delayed polyneuropathy (OPIDP) is a rare toxicity resulting from exposure to certain organophosphorus (OP) esters. It is characterised by distal degeneration of some axons of both the peripheral and central nervous systems occurring 1-4 weeks after single or short-term exposures. Cramping muscle pain in the lower limbs, distal numbness and paraesthesiae occur, followed by progressive weakness, depression of deep tendon reflexes in the lower limbs and, in severe cases, in the upper limbs. Signs include high-stepping gait associated with bilateral foot drop and, in severe cases, quadriplegia with foot and wrist drop as well as pyramidal signs. In time, there might be significant recovery of the peripheral nerve function but, depending on the degree of pyramidal involvement, spastic ataxia may be a permanent outcome of severe OPIDP. Human and experimental data indicate that recovery is usually complete in the young. At onset, the electrophysiological changes include reduced amplitude of the compound muscle potential, increased distal latencies and normal or slightly reduced nerve conduction velocities. The progression of the disease, usually over a few days, may lead to non-excitability of the nerve with electromyographical signs of denervation. Nerve biopsies have been performed in a few cases and showed axonal degeneration with secondary demyelination. Neuropathy target esterase (NTE) is thought to be the target of OPIDP initiation. The ratio of inhibitory powers for acetylcholinesterase and NTE represents the crucial guideline for the aetiological attribution of OP-induced peripheral neuropathy. In fact, pre-marketing toxicity testing in animals selects OP insecticides with cholinergic toxicity potential much higher than that to result in OPIDP. Therefore, OPIDP may develop only after very large exposures to insecticides, causing severe cholinergic toxicity. However, this was not the case with certain triaryl phosphates that were not used as insecticides but as hydraulic fluids, lubricants and plasticisers and do not result in cholinergic toxicity. Several thousand cases of OPIDP as a result of exposure to tri-ortho-cresyl phosphate have been reported, whereas the number of cases of OPIDP as a result of OP insecticide poisoning is much lower. In this article, we mainly discuss OP pesticide poisoning, particularly when caused by chlorpyrifos, dichlorvos, isofenphos, methamidophos, mipafox, trichlorfon, trichlornat, phosphamidon/mevinphos and by certain carbamates. We also discuss case reports where neuropathies were not convincingly attributed to fenthion, malathion, omethoate/dimethoate, parathion and merphos. Finally, several observational studies on long-term, low-level exposures to OPs that sometimes reported mild, inconsistent and unexplained changes of unclear significance in peripheral nerves are briefly discussed.