Long-term psychological and neurological complications of lindane poisoning

Association between pesticide exposure and colorectal cancer risk and incidence: A systematic review

BACKGROUND

Studies investigating the association between pesticide exposure and colorectal cancer (CRC) risk have been inconclusive.

OBJECTIVES

Investigate the association between pesticide exposure and CRC risk through a systematic literature review.

METHODS

CRC has the fourth-highest rate of cancer-caused death in the US after lung cancer, breast cancer in women, and prostate cancer in men. Here we have conducted a systematic literature search on studies examining the association between any pesticide exposure and CRC risk using PubMed, MEDLINE via EBSCO host, and Embase according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist.

RESULTS

Following the review, 139 articles were included for qualitative evaluation. Study participants were farmers, pesticide applicators, pesticide manufacturers, spouses of pesticide applicators, farm residents, Korean veterans of the Vietnam War, rural communities, and those who consumed food with pesticide residues. The studies' results were split between those with significant positive (39 significant results) and inverse (41 significant results) associations when comparing pesticide exposure and CRC risk.

DISCUSSION

From our literature review, we have identified a similar number of significant positive and inverse associations of pesticide exposure with CRC risk and therefore cannot conclude whether pesticide exposure has a positive or inverse association with CRC risk overall. However, certain pesticides such as terbufos, dicamba, trifluralin, S-ethyl dipropylthiocarbamate (EPTC), imazethapyr, chlorpyrifos, carbaryl, pendimethalin, and acetochlor are of great concern not only for their associated elevated risk of CRC, but also for the current legal usage in the United States (US). Aldicarb and dieldrin are of moderate concern for the positive associations with CRC risk, and also for the illegal usage or the detection on imported food products even though they have been banned in the US. Pesticides can linger in the soil, water, and air for weeks to years and, therefore, can lead to exposure to farmers, manufacturing workers, and those living in rural communities near these farms and factories. Approximately 60 million people in the US live in rural areas and all of the CRC mortality hotspots are within the rural communities. The CRC mortality rate is still increasing in the rural regions despite the overall decreasing of incidence and mortality of CRC elsewhere. Therefore, the results from this study on the relationship between pesticide exposure and CRC risk will help us to understand CRC health disparities.

Human health risk assessments of organochlorine pesticides in some food crops from Esa-Oke farm settlement, Osun State, Nigeria

Seasonal levels of organochlorine pesticides (OCPs) in yam, cassava, sweet potato and cocoyam samples collected from Esa-Oke Farm Settlement, Osun State, Nigeria were evaluated. Sampling regiment for three sites lasted four months each during the dry and wet seasons. The dried samples were extracted using Soxhlet extractor with dichloromethane (DCM) as the extraction solvent, while the identification and estimation of OCPs in the crop filtrates, after clean-up, were carried out with Gas Chromatography equipped with Time-of-Flight Mass Spectroscopy Detector (GC-TOFMS). Ten OCPs determined in the crops had the overall seasonal mean levels that ranged from 158 ng/g (dieldrin) to 544 ng/g (heptachlor) and the seasonal mean burden per OCP occurred in the order: heptachlor epoxide (518) > heptachlor (447) > p,p'-DDE (431) > dieldrin (349) > chlordane (327) > aldrin (321) > p,p'-DDD (313) > methoxychlor (303) > endosulfan I (287) > p,p'-DDT (284) for wet season while this order was not the same for dry season of the same crop with heptachlor epoxide (415) > p,p'-DDE (373) > aldrin (305) > heptachlor (307) > methoxychlor (288) > chlordane (274) > p,p'-DDT (263) > p,p'-DDD (263) > endosulfan I (260) > dieldrin (246). For all of the OCPs, the estimated daily intake (EDI) and health risk indices (HRI) were significantly higher than the recommended values. Thus, a regular large-scale consumption of crop products from the farm settlement could result in grave public health concern in the course of time.

The long-term environmental risks from the aging of organochlorine pesticide lindane

Although increased contact time (aging) of pesticides in the soil decreases their bioavailability, this does not mean that the bound residues formed during the aging process pose fewer risk to the soil environment. Here the earthworm Eisenia fetida was exposed to organochlorine pesticide lindane in soil under different durations of lindane aging and exposure. The results of de novo RNA sequencing followed by molecular and biochemical validations demonstrated the aged lindane showed a different tendency to disrupt acetylcholine (ACh) transmission with the effects of fresh lindane to gamma-aminobutyric acid. Using own-developed earthworm activity test, we confirmed aged lindane prompted earthworms to exclusively exhibit a significant hypoactivity in locomotion, which could be explained by the inhibition of Ach system. This study suggested that the toxicity of pesticides would not depend solely on their free state components, and the awareness of long-term environmental risks from the bound states needs to be raised.

Phenotyping Cellular Viability by Functional Analysis of Ion Channels: GlyR-Targeted Screening in NT2-N Cells

Glycine receptor chloride channels (GlyRs) are attractive drug targets for therapeutic intervention and are also more and more recognized in the context of in vitro neurotoxicity and developmental neurotoxicity testing. Assaying the functional properties of GlyR can serve as an indicator of cellular viability and the integrity of the developing and mature central nervous system. Human pluripotent NTERA-2 (NT2) stem cells undergo neuronal differentiation upon stimulation with retinoic acid and express a large variety of neuronal proteins-including GlyR. YFP-I152L, a halide-sensitive variant of yellow fluorescent protein, allows high-throughput fluorescence-based functional analysis of GlyRs in NT2 cells. Here we describe a protocol for phenotyping of cellular viability by functional analysis of GlyR in neuronally differentiated NT2 (NT2-N) cells using YFP-I152L as a reporter of functional integrity of GlyRs. The protocol describes neuronal differentiation of NT2 stem cells, transient transfection of NT2-N cells with YFP-I152L as well as functional imaging and analysis of data from high-content imaging.

Species variation in pesticide-induced blood-brain barrier dysfunction

Neurological disorders following acute or chronic exposure to pesticides have been reported in a number of human cases. However, the mechanism(s) by which pesticides produce central nervous system dysfunction is not clear. The objective of the present study was to examine the functional status of blood-brain barrier (BBB) in rats and mice exposed to selected pesticides of different chemical groups. Adult male albino rats and mice were exposed (1/10 of LD50) daily to dichlorvos (organophosphate), lindane (organochlorine) and carbofuran (carbamate) through oral intubation for 3 days. The status of BBB was evaluated by determining brain sodium fluorescein dye uptake and brain uptake index (BUI) in relation to serum dye level. The brain dye uptake and BUI in pesticide-exposed rats did not differ significantly in comparison to that of controls. However, brain dye uptake and BUI were increased significantly in mice exposed to dichlorvos (85%, 40%), lindane (79%, 26%) and carbofuran (129%, 61%). The results of this study show that mouse BBB system is more sensitive to pesticide-induced breach as compared to that of rat. These variations may have a role in determining the outcome of pesticide neurotoxicity in different species.

A Recombinant Human Pluripotent Stem Cell Line Stably Expressing Halide-Sensitive YFP-I152L for GABAAR and GlyR-Targeted High-Throughput Drug Screening and Toxicity Testing

GABA_ARs and GlyRs are considered attractive drug targets for therapeutic intervention and are also increasingly recognized in the context of in vitro neurotoxicity (NT) and developmental neurotoxicity (DNT) testing. However, systematic human-specific GABA_AR and GlyR-targeted drug screening and toxicity testing is hampered due to lack of appropriate in vitro models that express native GABA_ARs and GlyRs. We have established a human pluripotent stem cell line (NT2) stably expressing YFP-I152L, a halide-sensitive variant of yellow fluorescent protein (YFP), allowing for fluorescence-based functional analysis of chloride channels. Upon stimulation with retinoic acid, NT2 cells undergo neuronal differentiation and allow pharmacological and toxicological evaluation of native GABA_ARs and GlyRs at different stages of brain maturation. We applied the cell line in concentration-response experiments with the neurotransmitters GABA and glycine as well as with the drugs strychnine, picrotoxin, fipronil, lindane, bicuculline, and zinc and demonstrate that the established in vitro model is applicable to GABA_AR and GlyR-targeted pharmacological and toxicological profiling. We quantified the proportion of GABA_AR and GlyR-sensitive cells, respectively, and identified percentages of approximately 20% each within the overall populations, rendering the cells a suitable model for systematic in vitro GABA_AR and GlyR-targeted screening in the context of drug development and NT/DNT testing.

Relevance study of bare and coated zero valent iron nanoparticles for lindane degradation from its by-product monitorization

Zero-valent iron nanoparticles (NZVI) as well as polymer-stabilized nanoparticles were synthesized and used for lindane (γ-hexachlorocyclohexane) degradation in aqueous solution. To study the effectiveness of the different coated nanoparticles, simple and rapid analytical methods have been developed to measure and to detect lindane and its by-products. For the monitorization of lindane degradation solid-phase extraction (SPE) was used, while volatile by-products formation measurement was carried out by headspace-solid phase microextraction (HS-SPME) followed by GC/MS. The SPE-GC/MS method provides low detection limits (0.2 μg L(-1)), high recovery (above 95%) and it is a valuable tool for kinetic studies of the degradation process for each polymer used, while HS-SPME-GC/MS has proved to be an effective tool for the extraction and evaluation of volatile degradation by-products.

The relationships between pesticide metabolites and neurobehavioral test performance in the third National Health and Nutrition Examination Survey

Regression analysis was used to estimate and test for relationships between urinary pesticide metabolites and neurobehavioral test performance in adults, 20 to 59 years old, participating in the third National Health and Nutrition Examination Survey. The 12 pesticide metabolites included 2 naphthols, 8 phenols, a phenoxyacetic acid, and a pyridinol. The 3 neurobehavioral tests included in the survey were simple reaction time, symbol-digit substitution, and serial digit learning. As the 2,4-dichlorophenol, 2,5-dichlorophenol, and the pentachlorophenol concentrations increased, performance on the serial digit learning test improved. As the 2,5-dichlorophenol concentration increased, performance on the symbol-digit substitution test improved. At low concentrations, the parent compounds of these metabolites may act at acetylcholine and γ-aminobutyric acid synapses in the central nervous system to improve neurobehavioral test performance.

Mechanism of action of the insecticides, lindane and fipronil, on glycine receptor chloride channels

BACKGROUND AND PURPOSE

Docking studies predict that the insecticides, lindane and fipronil, block GABA(A) receptors by binding to 6' pore-lining residues. However, this has never been tested at any Cys-loop receptor. The neurotoxic effects of these insecticides are also thought to be mediated by GABA(A) receptors, although a recent morphological study suggested glycine receptors mediated fipronil toxicity in zebrafish. Here we investigated whether human α1, α1β, α2 and α3 glycine receptors were sufficiently sensitive to block by either compound as to represent possible neurotoxicity targets. We also investigated the mechanisms by which lindane and fipronil inhibit α1 glycine receptors.

EXPERIMENTAL APPROACH

Glycine receptors were recombinantly expressed in HEK293 cells and insecticide effects were studied using patch-clamp electrophysiology.

KEY RESULTS

Both compounds completely inhibited all tested glycine receptor subtypes with IC(50) values ranging from 0.2-2 µM, similar to their potencies at vertebrate GABA(A) receptors. Consistent with molecular docking predictions, both lindane and fipronil interacted with 6' threonine residues via hydrophobic interactions and hydrogen bonds. In contrast with predictions, we found no evidence for lindane interacting at the 2' level. We present evidence for fipronil binding in a non-blocking mode in the anaesthetic binding pocket, and for lindane as an excellent pharmacological tool for identifying the presence of β subunits in αβ heteromeric glycine receptors.

CONCLUSIONS AND IMPLICATIONS

This study implicates glycine receptors as novel vertebrate toxicity targets for fipronil and lindane. Furthermore, lindane interacted with pore-lining 6' threonine residues, whereas fipronil may have both pore and non-pore binding sites.

Lindane toxicity: a comprehensive review of the medical literature

Lindane is an organochloride pesticide, first introduced as a scabicide for human use in the 1950s. Because of its low cost and efficacy, it quickly became a first-line treatment for scabies and head lice, but not long after its use became widespread, its safety was called into question, primarily regarding its neurotoxic effects. We intend to show through review of the literature and databases that lindane has been associated with numerous severe and fatal adverse reactions. This review will summarize 67 cases of adverse reactions and deaths associated with the medical use of lindane. Many of the most serious events and fatalities occurred in pediatric and geriatric populations. We concede that toxicity frequently arises from misuse, but labeled usage of lindane caused 43% of the serious adverse reactions of this review. Moreover, the numerous instances of lindane misuse elucidate the importance of clear labeling and instructions, especially with a product with a narrow therapeutic index. Therefore, this report attempts to elucidate the dangers of lindane as a medical treatment for scabies and head lice by providing a comprehensive review of all documented adverse drug reactions since its introduction.

Reductive dechlorination of gamma-hexachlorocyclohexane using Fe-Pd bimetallic nanoparticles

Nanoscale Fe-Pd bimetallic particles were synthesized and used for degradation of lindane (gamma-hexachlorocyclohexane) in aqueous solution. Batch studies showed that 5mg/L of lindane was completely dechlorinated within 5 min at a catalyst loading of 0.5 g/L and the degradation process followed first-order kinetics. GC-MS analysis in corroboration with GC-ECD results showed the presence of cyclohexane as the final degradation product. The proposed mechanism for the reductive dechlorination of lindane involves Fe corrosion-induced hydrogen atom transfer from the Pd surface. The enhanced degradation efficiency of Fe-Pd nanoparticles is attributed to: (1) high specific surface area of the nanoscale metal particles (60 m(2)/g), manyfold greater that of commercial grade micro- or milli-scale iron particles (approximately 1.6m(2)/g); and, (2) increased catalytic reactivity due to the presence of Pd on the surface. Recycling and column studies showed that these nanoparticles exhibit efficient and sustained catalytic activity.

Neurobehavioural effects of pesticides with special focus on organophosphorus compounds: which is the real size of the problem?

The risk of neurobehavioural impairment as a consequence of a prolonged, low dose exposure to neurotoxic pesticides is not clearly demonstrated despite numerous publications addressing the topic. We reviewed the 24 papers published on human neurobehavioural effects of organophosphorus and/or carbamates pesticides up to May 1st 2008. Variables evaluated were compound/s addressed, number of subjects, approach to measure or estimate exposure, characteristics of control groups and presence of confounders, methodological approach, and type of alteration, taking into account cognitive, sensory-motor, psychological, and psychomotor measures. A total of 6 papers considered the whole spectrum of functions, the studies yielding positive or uncertain results were 13 (68%) for cognitive function, 11 (69%) for psychomotor function, 11 (65%) for sensory-motor function, and 11 (65%) for psychological function impairment. In 46% of the positive studies a previous severe acute poisoning was reported. Exposure levels were measured only in 5 studies, and very often there were problems in the selection of controls, and firm conclusions on the risk of neurobehavioural effects cannot be reached yet. The main limits of the available data are: limited number of studies and compounds addressed, significant differences in the approach among studies, poor concordance of the results of different studies, and difficulties in controlling confounding factors. Nevertheless, there are sufficient data to conclude that neurobehavioural impairment might be the consequence of an acute poisoning, and possibly the consequence of relatively high and prolonged exposures.

Lindane neurotoxicity in childhood

Lindane (gamma-benzene-hexachloride) has been widely used as an antiscabetic and a pediculicidal agent for the past 50 years with reasonably good efficacy. After its initial use as a first-line therapy, there have been several reports of its neurotoxicity, especially among infants and young children. Literature review reveals that the risk of its neurotoxicity is minimal if used properly and strictly according to the prescribed recommendations. However, following availability of other safer and equally efficacious alternatives, it is now being regarded as a second-line therapy for scabies and pediculosis.

Neurochemical targets and behavioral effects of organohalogen compounds: an update

Organohalogen compounds (OHCs) have been used and still are used extensively as pesticides, flame retardants, hydraulic fluids, and in other industrial applications. These compounds are stable, most often lipophilic, and may therefore easily biomagnify. Today these compounds are found distributed both in human tissue, including breast milk, and in wildlife animals. In the late 1960s and early 1970s, high levels of the polychlorinated biphenyls (PCBs) and the pesticide dichlorodiphenyl trichloroethane (DDT) were detected in the environment. In the 1970s it was discovered that PCBs and some chlorinated pesticides, such as lindane, have neurotoxic potentials after both acute and chronic exposure. Although the use of PCBs, DDT, and other halogenated pesticides has been reduced, and environmental levels of these compounds are slowly diminishing, other halogenated compounds with potential of toxic effects are being found in the environment. These include the brominated flame retardants, chlorinated paraffins (PCAs), and perfluorinated compounds, whose levels are increasing. It is now established that several OHCs have neurobehavioral effects, indicating adverse effects on the central nervous system (CNS). For instance, several reports have shown that OHCs alter neurotransmitter functions in CNS and Ca2+ homeostatic processes, induce protein kinase C (PKC) and phospholipase A2 (PLA2) mobilization, and induce oxidative stress. In this review we summarize the findings of the neurobehavioral and neurochemical effects of some of the major OHCs with our main focus on the PCBs. Further, we try to elucidate, on the basis of available literature, the possible implications of these findings on human health.

Lindane stimulates neutrophils by selectively activating phospholipase C and phosphoinositide-kinase activity

The organochlorine insecticide lindane is a known activator of neutrophil responses. In this work we delineated the biochemical pathways by which lindane stimulates neutrophil oxidant production. Plasma membrane GTPase activity was not stimulated by lindane, ruling out a role for lindane-induced activation of G-proteins or G-protein coupled receptors, whereas inhibition of phospholipase C inhibited lindane-induced oxidant production. Together these data pointed to phospholipase C as the direct target of lindane activation. Type I phosphoinositide 3-kinase was not significantly activated by lindane and an inhibitor of phosphoinositide 3-kinases inhibited oxidant production by only 40%. Thus, Type I phosphoinositide 3-kinase played a minor role, if any, in lindane-induced oxidant production. Lindane stimulated an increase in phosphatidylinositol phosphate suggesting a Type II or III phosphotidylinositol 3-kinase or phosphatidylinositol 4-kinase activity was also stimulated.

Efficacy of a reduced application time of Ovide lotion (0.5% malathion) compared to Nix creme rinse (1% permethrin) for the treatment of head lice

Our objective was to conduct a randomized, investigator-blinded evaluation of the pediculicidal and ovicidal activity of a reduced application time (20 minutes) of Ovide (0.5% malathion) compared to Nix (1% permethrin) in a south Florida population infested with Pediculus humanus capitis. Either Ovide or Nix was applied according to the label instructions. However, Ovide application time was reduced to 20 minutes. At day 8, subjects with live lice were re-treated with the same product and procedure as on day 1. Ovicidal and pediculicidal efficacy were evaluated at days 8 and 15. A subject free of lice and viable eggs at day 15 was considered to be a treatment success. Percent efficacy was calculated using the number of subjects free of lice and viable eggs per total number of subjects treated. We found that a 20-minute application of Ovide was significantly more pediculicidal and ovicidal (98%) compared to Nix (55%) at day 15 (p < 0.0001). The percentage of Ovide subjects who required treatment at day 8 was half that of the Nix group. The reinfestation rate was 0% with Ovide and 33% with Nix. In conclusion, a 20-minute treatment with Ovide, instead of the approved 8- to 12-hour application, cured 40 of 41 subjects (98%), demonstrating superior efficacy to Nix. The poor efficacy of Nix confirms the resistance of head lice to permethrin in south Florida.

Reversible neurotoxicity after an overdose of topical lindane in an infant

Lindane (gamma benzene hexachloride) is a widely prescribed topical scabicide because of its efficacy and cost-effectiveness. Although toxicity from a single proper application of lindane is generally not observed, the hazards of repeated applications, industrial exposure, and accidental ingestion have been well documented. We herein describe an infant with reversible neurotoxicity following repeated applications of 1% lindane for the treatment of scabies. The role of factors predisposing to increased absorption and the recommendations to minimize potential neurotoxicity are emphasized.

Epidemiology of lindane exposures for pediculosis reported to Poison Centers in Texas, 1998-2002

BACKGROUND

Lindane (gamma-benzene hexachloride), commonly used as a treatment for pediculosis, has been associated with adverse reactions and has recently undergone increased regulation.

OBJECTIVE

We sought to describe the patterns of a large number of lindane exposures reported to poison centers in Texas during 1998-2002.

METHODS

Data on all lindane exposures for pediculosis reported to the Texas Poison Center Network were analyzed.

RESULTS

There were 528 reported human exposures to lindane for pediculosis. The incidence of lindane exposures has decreased by 52% from 1998 to 2002. Misuse or abuse of lindane was reported in at least 87% of the cases. Of those cases with a known patient age, 45% were less than age 6 yrs, 23% age 6-19 yrs, and 32% over age 19 yrs. Female patients accounted for 55% of reported cases. Of those cases with a known medical outcome, 61% reported no effects. The most frequently reported symptoms were vomiting, nausea, and ocular irritation or ocular pain.

CONCLUSION

The number of reported lindane exposures in Texas is decreasing. The majority of reported exposures involve misuse or abuse of the product. The pattern of symptoms reported in Texas was consistent with the literature.

Neurobehavioral effects of pesticides: state of the art

The authors have reviewed the literature on neurobehavioral toxicity of pesticides to assess the status of knowledge on this matter. Some data suggest that exposure to DDT and fumigants may be associated with permanent decline in neurobehavioral functioning and increase in psychiatric symptoms, but, due to the limited number of studies available and the scarce knowledge on exposure levels, no firm conclusion can be drawn. Data on subjects acutely poisoned with organophosphorous compounds suggest that an impairment in neurobehavioral performance and, in some cases, emotional status may be observed as a long-term sequela, but the possibility still remains that these effects were only an aspecific expression of damage and not of direct neurotoxicity. Studies carried out on subjects chronically exposed to organophosphates, but never acutely poisoned, do not provide univocal results but the slight changes consistently observed in sheep dippers suggest the need of focusing on activities characterized by relatively higher exposure levels. In general, the main limits of existing knowledge are the variability of the testing methods used, which makes it difficult to compare the results of single studies, and the scarce knowledge on exposure levels. A promising approach may be the conduction of prospective longitudinal or cohort studies, where exposure and dose assessment can be more easily controlled, or the evaluation of cohorts of workers a priori selected for the availability of environmental and biological monitoring data. The follow up of the populations under study may give an answer at the problem of the prognostic significance of the observed changes. Also the protocols used to assess neurobehavioral functioning need to be standardized.