Acetylcholinesterase and neuropathy target esterase activities in 11 cases of symptomatic flight crew members after fume events

Comparison of acetylcholinesterase among employees based on job positions and personal protective equipment in fuel station

The purpose of this study was to compare the levels of acetylcholinesterase (AChE) among employees based on job positions and the wearing of personal protective equipment (PPE) in fuel station areas. The sample group consisted of 200 people sorted into various groups, including (i) Inside fuel dispenser area (I-FDA) group consisting of 100 employees for refueling, cashier, and loading fuel into storage tanks, and (ii) Outside fuel dispenser area (O-FDA) group, consisting of 100 employees working in convenience stores, food stores, coffee shops, and offices, as well as general staff and car washers. Data were collected using interview questionnaires and blood samples were analyzed for AChE activity. The results showed that the I-FDA group had a significantly lower mean of serum AChE (7.38±1.73 U/ml) than the O-FDA group (7.85±1.49 U/ml) (p<0.05). The I-FDA group had a 2.43 times higher risk of abnormal serum AChE than the O-FDA group (OR=2.43, 95%CI=1.05-5.60). When considering the risk factors for job positions, it was found that refueling and cashier positions had lower AChE activity levels than those who did not (p<0.05). In the part, employees for food sales in a closed building and those wearing PPE masks had significantly higher AChE activity levels than those who did not or who wore them (p<0.05). Based on the aforementioned, employers at fuel stations should strictly determine the appropriate measures for wearing a PPE mask. Further, employees should be provided accommodation away from oil supply or enclosed buildings during breaks to reduce the effects on the neurotransmitter.

Health consequences of exposure to aircraft contaminated air and fume events: a narrative review and medical protocol for the investigation of exposed aircrew and passengers

Thermally degraded engine oil and hydraulic fluid fumes contaminating aircraft cabin air conditioning systems have been well documented since the 1950s. Whilst organophosphates have been the main subject of interest, oil and hydraulic fumes in the air supply also contain ultrafine particles, numerous volatile organic hydrocarbons and thermally degraded products. We review the literature on the effects of fume events on aircrew health. Inhalation of these potentially toxic fumes is increasingly recognised to cause acute and long-term neurological, respiratory, cardiological and other symptoms. Cumulative exposure to regular small doses of toxic fumes is potentially damaging to health and may be exacerbated by a single higher-level exposure. Assessment is complex because of the limitations of considering the toxicity of individual substances in complex heated mixtures.There is a need for a systematic and consistent approach to diagnosis and treatment of persons who have been exposed to toxic fumes in aircraft cabins. The medical protocol presented in this paper has been written by internationally recognised experts and presents a consensus approach to the recognition, investigation and management of persons suffering from the toxic effects of inhaling thermally degraded engine oil and other fluids contaminating the air conditioning systems in aircraft, and includes actions and investigations for in-flight, immediately post-flight and late subsequent follow up.

Three patients with probable aerotoxic syndrome

Introduction: "Aerotoxic syndrome" is a debated entity. Regulatory authorities consider long-term health effects to be an unlikely consequence of exposure to contaminated air because several air quality monitoring studies report low concentrations of toxic chemicals in cabin air. We describe two pilots and one flight attendant, who developed ill health during their flying career which improved after cessation of flying.Case details: The most frequently reported symptoms were headache, balance problems, fatigue, gastro-intestinal complaints and cognitive impairment. One of these patients had reduced levels of butyrylcholinesterase after a flight suggesting exposure to organophosphate compounds had occurred. All three were found to have elevated neuronal and glial auto-antibodies, biomarkers of central nervous system injury, and all three had genetic polymorphisms of paraoxonase (PON-1) and two of cytochrome P450, leading to a reduced ability to metabolize organophosphate compound (OPs).Discussion: A similar constellation of symptoms has been described in other studies of aircrew, although objective evidence of exposure is lacking in most of these studies. Reduced levels of butyrylcholinesterases in one of our cases is suggestive of causation and elevated neuronal and glial autoantibodies provide objective evidence of damage to the central nervous system. We consider further research is warranted.

Neurotoxicity in acute and repeated organophosphate exposure

The term organophosphate (OP) refers to a diverse group of chemicals that are found in hundreds of products worldwide. As pesticides, their most common use, OPs are clearly beneficial for agricultural productivity and the control of deadly vector-borne illnesses. However, as a consequence of their widespread use, OPs are now among the most common synthetic chemicals detected in the environment as well as in animal and human tissues. This is an increasing environmental concern because many OPs are highly toxic and both accidental and intentional exposures to OPs resulting in deleterious health effects have been documented for decades. Some of these deleterious health effects include a variety of long-term neurological and psychiatric disturbances including impairments in attention, memory, and other domains of cognition. Moreover, some chronic illnesses that manifest these symptoms such as Gulf War Illness and Aerotoxic Syndrome have (at least in part) been attributed to OP exposure. In addition to acute acetylcholinesterase inhibition, OPs may affect a number of additional targets that lead to oxidative stress, axonal transport deficits, neuroinflammation, and autoimmunity. Some of these targets could be exploited for therapeutic purposes. The purpose of this review is thus to: 1) describe the important uses of organophosphate (OP)-based compounds worldwide, 2) provide an overview of the various risks and toxicology associated with OP exposure, particularly long-term neurologic and psychiatric symptoms, 3) discuss mechanisms of OP toxicity beyond cholinesterase inhibition, 4) review potential therapeutic strategies to reverse the acute toxicity and long term deleterious effects of OPs.

Organophosphorus Compounds at 80: Some Old and New Issues

One of the major classes of pesticides is that of the organophosphates (OPs). Initial developments date back almost 2 centuries but it was only in the mid-1940s that OPs reached a prominent status as insecticides, a status that, albeit declining, is still ongoing. OPs are highly toxic to nontarget species including humans, the primary effects being an acute cholinergic toxicity (responsible for thousands of poisoning each year) and a delayed polyneuropathy. Several issues of current debate and investigation on the toxicology of OPs are discussed in this brief review. These include (1) possible additional targets of OPs, (2) OPs as developmental neurotoxicants, (3) OPs and neurodegenerative diseases, (4) OPs and the "aerotoxic syndrome," (5) OPs and the microbiome, and (6) OPs and cancer. Some of these issues have been debated and studied for some time, while others are newer, suggesting that the study of the toxicology of OPs will remain an important scientific and public health issue for years to come.

Renal damage induced by the pesticide methyl parathion in male Wistar rats

Little information is apparently available regarding the nephrotoxic effects induced by pesticides. The aim of this study was to examine the influence of low doses of methyl parathion (MP) on the structure and function of the kidney of male Wistar rats. A corn oil (vehicle) was administered to control rats, whereas treated rats received MP at 0.56 mg/kg orally (1/25 of LD₅₀), every third day, for 8 weeks. At the end of each week following MP exposure, creatinine and glucose levels were measured in plasma, while glucose, inorganic phosphate, total proteins, albumin, and activity of γ-glutamyltranspeptidase (GGT) were determined in urine. Kidney histological study was also performed. Compared with control rats, MP significantly increased plasma glucose and creatinine levels accompanied by decreased urinary flow rate and elevated urinary excretion rates of glucose, phosphate, and albumin. Further, the activity of GGT in urine was increased significantly. The proximal cells exhibited cytoplasmic vacuolization, positive periodic acid Schiff inclusions, and brush border edge loss after 2 or 4 weeks following MP treatment. Finally, renal cortex samples were obtained at 2, 4, 6, and 8 weeks of MP treatment, and the concentrations of reduced glutathione (GSH) and glutathione peroxidase (GPx) activity were measured. The mRNA expression levels of BAX and tumor necrosis factor-α (TNF-α) were also determined (RT-PCR). MP significantly decreased renal GSH levels, increased GPx activity, as well as downregulated the mRNA expression of TNF-α and BAX. Densitometry analysis showed a significant reduction in TNF-α and BAX mRNA expression levels at 2 and 4 weeks following MP treatment. Low doses of MP produced structural and functional damage to the proximal tubules of male rat kidney.

L- and T-type calcium channel blockers protect against the inhibitory effects of mipafox on neurite outgrowth and plasticity-related proteins in SH-SY5Y cells

Some organophosphorus compounds (OP), including the pesticide mipafox, produce late onset distal axonal degeneration, known as organophosphorus-induced delayed neuropathy (OPIDN). The underlying mechanism involves irreversible inhibition of neuropathy target esterase (NTE) activity, elevated intracellular calcium levels, increased activity of calcium-activated proteases and impaired neuritogenesis. Voltage-gated calcium channels (VGCC) appear to play a role in several neurologic disorders, including OPIDN. Therefore, this study aimed to examine and compare the neuroprotective effects of T-type (amiloride) and L-type (nimodipine) VGCC blockers induced by the inhibitory actions of mipafox on neurite outgrowth and axonal proteins of retinoic-acid-stimulated SH-SY5Y human neuroblastoma cells, a neuronal model widely employed to determine the neurotoxicity attributed to OP. Both nimodipine and amiloride significantly blocked augmentation of intracellular calcium levels and activity of calpains, as well as decreased neurite length, number of differentiated cells, and lowered concentrations of growth-associated protein 43 (GAP-43) and synapsin induced by mipafox. Only nimodipine inhibited reduction of synaptophysin levels produced by mipafox. These findings demonstrate a role for calcium and VGCC in the impairment of neuronal plasticity mediated by mipafox. Data also demonstrated the neuroprotective potential of T-type and L-type VGCC blockers to inhibit OP-mediated actions, which may be beneficial to counteract cases of pesticide poisoning.

The impact of repeated organophosphorus pesticide exposure on biomarkers and neurobehavioral outcomes among adolescent pesticide applicators

Egyptian adolescents are hired as seasonal workers to apply pesticides to the cotton crop and may perform this occupation for several years. However, few studies examined the effects of repeated pesticide exposure on health outcomes The goal of this study was to determine the impact of repeated pesticide exposure on neurobehavioral (NB) performance and biomarkers of exposure (urinary metabolite) and effect (cholinesterase activity). Eighty-four adolescents from two field stations in Menoufia, Egypt, were examined four times: before and during pesticide application season in 2010 and again before and during application season in 2011. At each of the four time points, participants completed a questionnaire, performed an NB test battery, and were assessed for urinary levels of the chlorpyrifos metabolite TCPy (3,5,6-trichloro-2-pyridinol) and blood cholinesterase activity. Following the study cohort over two consecutive pesticide application seasons revealed that TCPy levels significantly increased following exposure, and returned to baseline levels following the end of the application season. Blood butyryl cholinesterase activity exhibited a similar pattern. Although NB outcomes displayed learning and practice effects over time, deficits in performance were significantly associated with increased TCPy levels with reduction in the number of NB measures showing improvement over time. Biomarkers of exposure and effect demonstrated changes associated with pesticide application and recovery after application ended. Deficits in NB performance were correlated with elevated pesticide exposure. Data demonstrated that repeated pesticide exposure may exert a long-term adverse impact on human health.