Spike-timing-dependent plasticity induction reveals dissociable supplementary- and premotor-motor pathways to automatic imitation.

Humans tend to spontaneously imitate others' behavior, even when detrimental to the task at hand. The action observation network (AON) is consistently recruited during imitative tasks. However, whether automatic imitation is mediated by cortico-cortical projections from AON regions to the primary motor cortex (M1) remains speculative. Similarly, the potentially dissociable role of AON-to-M1 pathways involving the ventral premotor cortex (PMv) or supplementary motor area (SMA) in automatic imitation is unclear. Here, we used cortico-cortical paired associative stimulation (ccPAS) to enhance or hinder effective connectivity in PMv-to-M1 and SMA-to-M1 pathways via Hebbian spike-timing-dependent plasticity (STDP) to test their functional relevance to automatic and voluntary motor imitation. ccPAS affected behavior under competition between task rules and prepotent visuomotor associations underpinning automatic imitation. Critically, we found dissociable effects of manipulating the strength of the two pathways. While strengthening PMv-to-M1 projections enhanced automatic imitation, weakening them hindered it. On the other hand, strengthening SMA-to-M1 projections reduced automatic imitation but also reduced interference from task-irrelevant cues during voluntary imitation. Our study demonstrates that driving Hebbian STDP in AON-to-M1 projections induces opposite effects on automatic imitation that depend on the targeted pathway. Our results provide direct causal evidence of the functional role of PMv-to-M1 projections for automatic imitation, seemingly involved in spontaneously mirroring observed actions and facilitating the tendency to imitate them. Moreover, our findings support the notion that SMA exerts an opposite gating function, controlling M1 to prevent overt motor behavior when inadequate to the context.

Cortico-cortical paired associative stimulation (ccPAS) over premotor-motor areas affects local circuitries in the human motor cortex via Hebbian plasticity.

Transcranial magnetic stimulation (TMS) studies have shown that cortico-cortical paired associative stimulation (ccPAS) can strengthen connectivity between the ventral premotor cortex (PMv) and the primary motor cortex (M1) by modulating convergent input over M1 via Hebbian spike-timing-dependent plasticity (STDP). However, whether ccPAS locally affects M1 activity remains unclear. We tested 60 right-handed young healthy humans in two studies, using a combination of dual coil TMS and ccPAS over the left PMv and M1 to probe and manipulate PMv-to-M1 connectivity, and single- and paired-pulse TMS to assess neural activity within M1. We provide convergent evidence that ccPAS, relying on repeated activations of excitatory PMv-to-M1 connections, acts locally over M1. During ccPAS, motor-evoked potentials (MEPs) induced by paired PMv-M1 stimulation gradually increased. Following ccPAS, the threshold for inducing MEPs of different amplitudes decreased, and the input-output curve (IO) slope increased, highlighting increased M1 corticospinal excitability. Moreover, ccPAS reduced the magnitude of short-interval intracortical inhibition (SICI), reflecting suppression of GABA-ergic interneuronal mechanisms within M1, without affecting intracortical facilitation (ICF). These changes were specific to ccPAS Hebbian strengthening of PMv-to-M1 connectivity, as no modulations were observed when reversing the order of the PMv-M1 stimulation during a control ccPAS protocol. These findings expand prior ccPAS research that focused on the malleability of cortico-cortical connectivity at the network-level, and highlight local changes in the area of convergent activation (i.e., M1) during plasticity induction. These findings provide new mechanistic insights into the physiological basis of ccPAS that are relevant for protocol optimization.

Occupational exposure to pesticides and symptoms of depression in agricultural workers. A systematic review.

BACKGROUND: The use of pesticides can result in harm to both the environment and human health. There is a growing concern in the field of occupational health about the impact on the mental health of agricultural workers. OBJECTIVES: The objective of this review was to systematize scientific evidence from the last ten years on the impact of occupational exposure to pesticides on the development of depression symptoms in agricultural workers. METHODS: We conducted a comprehensive search in the PubMed and Scopus databases from 2011 to September 2022. Our search included studies in English, Spanish, and Portuguese that examined the association between occupational exposure to pesticides and symptoms of depression in agricultural workers, following the guidelines recommended by the PRISMA statement and the PECO strategy (Population, Exposure, Comparison, and Outcomes). RESULTS: Among the 27 articles reviewed, 78% of them indicated a link between exposure to pesticides and the incidence of depression symptoms. The pesticides most frequently reported in the studies were organophosphates (17 studies), herbicides (12 studies), and pyrethroids (11 studies). The majority of the studies were rated as having intermediate to intermediate-high quality, with the use of standardized measures to assess both exposure and effect. CONCLUSION: The updated evidence presented in our review indicates a clear association between pesticide exposure and the development of depressive symptoms. However, more high-quality longitudinal studies are necessary to control for sociocultural variables and utilize pesticide-specific biomarkers and biomarkers of depression. Given the increased use of these chemicals and the health risks associated with depression, it is crucial to implement more stringent measures to monitor the mental health of agricultural workers regularly exposed to pesticides and to enhance surveillance of companies that apply these chemicals.

An educational intervention on the risk perception of pesticides exposure and organophosphate metabolites urinary concentrations in rural school children in Maule Region, Chile.

BACKGROUND: Organophosphate (OP) pesticides can be hazardous to human health if not applied with appropriate precautions. There is evidence in the Maule region of Chile that rural schoolchildren are exposed to OP pesticides. OBJECTIVE: To evaluate the effectiveness of an educational intervention on OP exposure and understanding of pesticides and their hazards (risk perception) in two school communities in the Maule Region of Chile during 2016. METHOD: We conducted a quasi-experimental study about the effects on OP pesticide exposure of a community outreach and education program (COEP) administered in four 2-h sessions that's included hands-on activities among 48 schoolchildren from two rural schools. The intervention was directed to groups of parents and school-children separately, and aimed to educate them about the risks of exposure to pesticides and their effects on health. We measured 3,5,6-trichloro-2-pyridinol (TCPy), 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMPY), malathion dicarboxylic acid (MDA), p-nitrophenol (PNP), specific urinary metabolites of the OP pesticides chlorpyrifos, diazinon, malathion and parathion, respectively, as well as the non-specific diethylakylphosphates (DEAPs) and dimethylalkylphosphates (DMAPs) in 192 urine samples of schoolchildren collected before and after the intervention. The risk perception of school children and their parents was also assessed through a questionnaire before and after the intervention. Generalized Estimated Equations were used to account for each child's repeated measures during four sessions, two in September 2016 (pre-intervention) and two in November 2016 (post-intervention). RESULTS: The intervention level had significant effect on the risk perception of adults and children, which increased after the intervention. However, the intervention was not associated with reduced of urinary metabolites levels, with no significant differences between the pre and post measures. The detection frequencies were 1.1% (MDA), 71.4% (TCPy), 43.3% (IMPY), 98.96% (PNP), and 100% (DEAPs and DMAPs). Higher DEAPs urine concentrations were associated with eating more fruit at school (p = 0.03), a younger age (p = 0.03), and being male (p = 0.01). DMAPs showed no associations with potential predictor variables (e.g. OPs applied at home, fruit consumption at school, among others). Higher TCPy was associated with attending a school closer to farms (p = 0.04) and living in a home closer to farm fields (p = 0.01); higher PNP was marginally associated with children younger age (p = 0.035). CONCLUSION: Environmental exposure to OP pesticides was unchanged even after behavior changes. It is possible that a longer time period is needed to observe changes in both behavior and urinary metabolites. The levels of DEP and DMP metabolites found here are above the reference population of the US, and our findings indicate exposure to a wide variety of OP pesticides. Given that individual-level interventions were not associated with lower exposures, efforts to reduce exposure must occur upstream and require stricter regulation and control of pesticide use by government agencies.

Reliability and factorial validity of a questionnaire to assess organophosphate pesticide exposure to agricultural workers in Maule, Chile.

The aim was to evaluate the reliability and validity of a questionnaire to assess organophosphate pesticide (OP) exposure in agricultural workers. We then enrolled a random sample of 114 agricultural workers from the region of Maule, Chile (mean age = 50 years [SD = 12]). An internal consistency analysis (Cronbach's alpha> 0.70) and a Varimax rotational factorial analysis were applied. The instrument had a high reliability to predict likely occupational pesticide exposures: Cronbach's alpha = 0.95, the Kaiser-Meyer-Olkin (KMO) measure was 0.90 and the Bartell sphericity test = p < 0.001. Four factors explaining 68% of the variance were extracted. The factors identified were as follows: (1) labor conditions during application of OPs; (2) use of personal protective equipment; (3) workplace conditions related to OP exposure and (4) home conditions related to OP exposure. The questionnaire has adequate metric properties to characterize likely OP exposure of agricultural workers and to explore associated working and home conditions.

Laboratory of the Neuropsychology and Cognitive Neurosciences Research Center of Universidad Católica del Maule, Chile.

The Laboratory of the Neuropsychology and Cognitive Neurosciences Research Center (CINPSI Neurocog), located in the "Technological Park" building of the Catholic University of Maule (Universidad Católica del Maule, UCM) campus in Talca, Chile, has been established as "Psychology Lab" recently in July, 2016. Our lines of work include basic and applied research. Among the basic research, we study executive functions, decision-making, and spatial cognition. In the applied field, we have studied neuropsychological and neurobehavioral effects of pesticides exposure, among other interests. One of our aims is to develop collaboration both national and internationally. It is important to mention that to date there are only few psychology laboratories and research centers in Chile involved with the fields of neuropsychology and neurosciences. Thus, this scientific effort could be a groundbreaking initiative to develop specific knowledge in this area locally and interculturally through its international collaborations.

Exposure to organophosphate (OP) pesticides and health conditions in agricultural and non-agricultural workers from Maule, Chile.

The objective was to evaluate the characteristics of exposure to OP pesticides and health status in Chilean farm workers from the Maule Region. An occupational health questionnaire was administered in 207 agricultural and non-agricultural workers. For the group of agricultural workers, we asked about specific occupational exposure history and symptoms of OP pesticide poisoning. The main health problem of the exposed group was previous OP pesticide poisoning (p < 0.001). Fifty-six percent of agricultural workers reported symptoms consistent with acute OP pesticide poisoning. The use of respiratory personal protective equipment and younger age were protective against these symptoms, and number of years of OP pesticide exposure was positively associated with reporting symptoms of poisoning. Of the pesticide applicators 47 % reported using chlorpyrifos. The regulations regarding use and application of pesticides should be strengthened, as should training and intervention with workers to improve the use of personal protective equipment.

Slow-wave brain connectivity predicts executive functioning and group belonging in socially vulnerable individuals.

Important efforts have been made to describe the neural and cognitive features of healthy and clinical populations. However, the neural and cognitive features of socially vulnerable individuals remain largely unexplored, despite their proneness to developing neurocognitive disorders. Socially vulnerable individuals can be characterised as socially deprived, having a low socioeconomic status, suffering from chronic social stress, and exhibiting poor social adaptation. While it is known that such individuals are likely to perform worse than their peers on executive function tasks, studies on healthy but socially vulnerable groups are lacking. In the current study, we explore whether neural power and connectivity signatures can characterise executive function performance in healthy but socially vulnerable individuals, shedding light on the impairing effects that chronic stress and social disadvantages have on cognition. We measured resting-state electroencephalography and executive functioning in 38 socially vulnerable participants and 38 matched control participants. Our findings indicate that while neural power was uninformative, lower delta and theta phase synchrony are associated with worse executive function performance in all participants, whereas delta phase synchrony is higher in the socially vulnerable group compared to the control group. Finally, we found that delta phase synchrony and years of schooling are the best predictors for belonging to the socially vulnerable group. Overall, these findings suggest that exposure to chronic stress due to socioeconomic factors and a lack of education are associated with changes in slow-wave neural connectivity and executive functioning.

Effects of combat sports on cognitive function in older people: a systematic review.

INTRODUCTION: This systematic review aimed to analyze the available body of published peer-reviewed studies on the effects of combat sports compared with active/passive control on cognitive function and electrophysiological markers of brain activity in older people. EVIDENCE ACQUISITION: The studies were searched in Scopus, Web of Science, PubMed, MEDLINE, and PsycINFO databases from deadline to June 2023. The PRISMA, TESTEX, RoB, and GRADE scales assessed the evidence's methodological quality and certainty of evidence. The protocol was registered in PROSPERO (code: CRD42022361695). EVIDENCE SYNTHESIS: After reviewing 3768 studies, seven combat sports interventions (score ≥60% in methodological quality) were selected, composed of 381 older people (63% female), with a mean age of 66 years. In the selected studies, interventions based on judo, karate, and taekwondo were carried out, where it was not possible to verify the benefits of combat sports in cognitive function and electrophysiological markers of brain activity regarding active/passive control groups, although the individual results of the analyzed studies indicate that the practice of combat sports favor selective attention, divided attention, executive function, visual perception, and cognitive processing speed in older people. CONCLUSIONS: The available evidence does not allow a definite recommendation regarding combat sports as an effective cognitive function intervention in older people.

Effectiveness of Adapted Taekwondo, Multi-Component Training and Walking Exercise on Health Status in Independent Older Women: Study Protocol for a Randomized Controlled Trial (TKD & Aging Project).

This study protocol aims to analyze and compare the effects of an adapted taekwondo program with respect to multi-component training and walking exercise on health status in independent older women. Secondarily, we analyze the variability of the inter-individual response and compare it according to the designated training system. The sample will consist of 64 women between 60 and 65 years, randomly assigned to experimental group 1 (n = 16; adapted taekwondo), experimental group 2 (n = 16; multi-component training), experimental group 3 (n = 16, walking exercise) or control group (n = 16; no intervention). The experimental groups will perform the designated training for three sessions (60 min per session) per week over 16-weeks, while the control group will not receive any treatment. The main outcome will provide information about (i) blood pressure, (ii) lipid profile, (iii) frequency of food consumption, (iv) body composition, (v) cognitive status, (vi) brain activity, (vii) health-related quality of life (HRQoL) and (viii) physical-functional fitness. Our hypothesis indicates that adapted taekwondo produces more significant effects and greater inter-individual responses in cognitive status, brain activity, HRQoL, and postural balance than the others training methods. If this intervention proves effective, it could be an alternative for older women.

Affective modulation of cognitive control: A systematic review of EEG studies.

In recent years, a growing corpus of research has been conducted utilizing a variety of behavioral and neurophysiological methodologies to investigate the relationship of emotion and cognition, yielding unique insights into fundamental concerns about the human mind and mental disease. Electroencephalography (EEG) has been utilized to investigate how emotional states alter neural markers of cognitive control. The current study is a systematic analysis of EEG research that looks at affective modulation (mood, emotion) of cognitive control and its many sub-processes (e.g., cognitive flexibility, inhibitory control, and working memory). The PRISMA standards were followed in this review, which looked at experimental designs and tasks, as well as methodological elements of EEG recording and analysis across research. A total of 35 articles were chosen for qualitative synthesis as a consequence of the search. The examination of event-related potentials (ERPs), which showed affective modulation of 19 different components, was the most common electrophysiological approach used across research. The majority of the investigations focused on N2 and P3, indicating that affective induction has a strong influence on attentional processes and response inhibition. Future research should look into different methodologies such as source location and connection metrics to better understand the brain's areas and dynamic response during affective induction activities. It is also suggested that the technical components of the report be more explicit in order to promote study comparability and replication.

Health Effects of Pesticide Exposure in Latin American and the Caribbean Populations: A Scoping Review.

BACKGROUND: Multiple epidemiological studies have shown that exposure to pesticides is associated with adverse health outcomes. However, the literature on pesticide-related health effects in the Latin American and the Caribbean (LAC) region, an area of intensive agricultural and residential pesticide use, is sparse. We conducted a scoping review to describe the current state of research on the health effects of pesticide exposure in LAC populations with the goal of identifying knowledge gaps and research capacity building needs. METHODS: We searched PubMed and SciELO for epidemiological studies on pesticide exposure and human health in LAC populations published between January 2007 and December 2021. We identified 233 publications from 16 countries that met our inclusion criteria and grouped them by health outcome (genotoxicity, neurobehavioral outcomes, placental outcomes and teratogenicity, cancer, thyroid function, reproductive outcomes, birth outcomes and child growth, and others). RESULTS: Most published studies were conducted in Brazil (37%, n=88) and Mexico (20%, n=46), were cross-sectional in design (72%, n=167), and focused on farmworkers (45%, n=105) or children (21%, n=48). The most frequently studied health effects included genotoxicity (24%, n=62) and neurobehavioral outcomes (21%, n=54), and organophosphate (OP) pesticides were the most frequently examined (26%, n=81). Forty-seven percent (n=112) of the studies relied only on indirect pesticide exposure assessment methods. Exposure to OP pesticides, carbamates, or to multiple pesticide classes was consistently associated with markers of genotoxicity and adverse neurobehavioral outcomes, particularly among children and farmworkers. DISCUSSION: Our scoping review provides some evidence that exposure to pesticides may adversely impact the health of LAC populations, but methodological limitations and inconsistencies undermine the strength of the conclusions. It is critical to increase capacity building, integrate research initiatives, and conduct more rigorous epidemiological studies in the region to address these limitations, better inform public health surveillance systems, and maximize the impact of research on public policies. https://doi.org/10.1289/EHP9934.

Neurobehavioral, Neuromotor, and Neurocognitive Effects in Agricultural Workers and Their Children Exposed to Pyrethroid Pesticides: A Review.

In recent years, pyrethroids have emerged as a less toxic alternative to eliminate insect pests. However, some animal studies and studies with children show that these pesticides are toxic and lead to neurobehavioral effects similar to other pesticides, such as organophosphates. The purpose of this review was to systematize the epidemiological scientific evidence about the neurobehavioral, neuromotor, and neurocognitive effects in agricultural workers and their children exposed to pyrethroid pesticides. We conducted two searches (with different terms) in PubMed and Scopus databases, including articles in Spanish and English language on the effects of occupational exposure to pyrethroid pesticides associated with neurobehavioral, neuromotor, and neurocognitive functioning of agricultural workers and their children. There were no filters by year, and the search included studies till march 2021. To develop the search, we followed the recommendations contained in the PRISMA guidelines and the PICO strategy. The results show that in 66.6% of the studies reviewed (8 of 12 studies), agricultural workers or their children occupationally exposed to pyrethroid pesticides have a higher risk of presenting difficulties in their neurocognitive, neuromotor, or neurobehavioral performance, mainly associated with attention, processing speed (linked to hand-eye coordination), and motor coordination. There are still few studies that address this issue. However, the quality of most of the research conducted (83% intermediate or high quality) confirms the risk for neurobehavioral health in agricultural workers due to occupational exposure to pyrethroids. More research is required evaluating the exposure to pyrethroids, including biomarkers and validated neurobehavioral and neuromotor tests, in addition to evaluating the effect of simultaneous exposure to other hazardous pesticides. Assuming that the use of pyrethroids is increasing considerably and faster than the scientific evidence, it is suggested as a precautionary principle to regulate, more strictly, the sale of pyrethroids and other pesticides.

Environmental Health Risk Perception: Adaptation of a Population-Based Questionnaire from Latin America.

BACKGROUND: Environmental risk assessments and interventions to mitigate environmental risks are essential to protect public health. While the objective measurement of environmental hazards is important, it is also critical to address the subjective perception of health risks. A population's perception of environmental health hazards is a powerful driving force for action and engagement in safety and health behaviors and can also inform the development of effective and more sustainable environmental health policies. To date, no instruments are available to assess risk perception of environmental health hazards in South America even though there are many concerning issues in the region, including mining. OBJECTIVE: We aimed to adapt and validate an environmental health risk perception questionnaire in a Chilean population affected by mining activity among other risks frequently reported in Latin American countries and included the collection of information on trust on public information sources. METHODS: We adapted an Australian risk perception questionnaire for validation in an adult population from a Chilean mining community. This adaptation included two blinded translations (direct, inverse), a pre-test study (n = 20) and a review by environmental health experts. Principal Component Analyses (PCA) was used to identify factors within major domains of interest. The Bartlett test of sphericity, Kaiser-Meyer-Olkin (KMO) measure and the Cronbach α test were used to assess the instrument's validity and reliability. The instrument was pilot tested in 205 adults from a mining community in Chañaral. RESULTS: The final adapted questionnaire proved to be a good instrument to measure risk perception in a community chronically exposed to mining waste. For community risks, four factors explained 59.4% of the variance. "Global Issues" (30.2%) included air pollution, contamination of mining, ozone layer depletion and vector diseases. For personal risks, the first two components explained 59.5% of the variance, the main factor (36.7%) was "unhealthy behaviors within the household". For trust in information, the first factor (36.2%) included as main sources "Media and authorities". The Cronbach α ranged between 0.68 and 0.75; and the KMO test between 0.7 to 0.79 for community and personal risks and trust. CONCLUSIONS: The final questionnaire is a simple, reliable and useful instrument that can assist in evaluating environmental health risk perceptions in Latin American countries.

[Pesticide exposure in Chile and population health: urgency for decision making]. / Exposición a plaguicidas en Chile y salud poblacional: urgencia para la toma de decisiones.

In the last 25 years, Chile has had an expanding role as an agro-export country in the global economy, with efficient rates of productivity in the region, based on the technological development of agriculture, with of large monocultures whose productivity depends on the intensive application of agrochemicals. This form of agriculture has also lacked efficient regulations and surveillance, so it is difficult to estimate the real magnitude of the exposed population and its effects on health in the short or long term. This systematic review compiles the epidemiological evidence generated from studies conducted in several regions of Chile regarding pesticide exposure and health effects. Of the total number of articles, 50% included agricultural workers, 25% children, and 25% women of childbearing age, with the greatest effects being the neurotoxic (54%), genotoxic (31%) and reproductive (15%). The evidence collected shows that in Chile the levels of exposure to pesticides in the general and occupational population are higher than international studies levels. It is urgent to protect the health of both the occupational and general population and especially children through a stricter control of the sale and use of pesticides, with comprehensive surveillance systems in environmental health and educational actions in the social and cultural context of rural communities. It is a priority to strengthen research with national relevance on health effects, and strictly restrict the use of pesticides already prohibited in developed countries due to their high level of risk to human and environmental health.

Psychometric Validation of a Questionnaire to Assess Perception and Knowledge About Exposure to Pesticides in Rural Schoolchildren of Maule, Chile.

Exposure to pesticides during infancy is associated with numerous adverse health outcomes. The assessment of knowledge and perception of pesticides exposure and risk among children has not been thoroughly studied. The aim of the study was to evaluate the reliability and validity of a questionnaire that measures the knowledge and perception of exposure to organophosphate pesticides among rural schoolchildren. The questionnaire was administered to 151 schoolchildren between 9 and 13years from four Chilean rural schools. An internal consistency analysis of the ordinal alpha coefficient and a polychoric factor analysis for categorical data were used. The results show that the ordinal alpha was 0.95. Polychoric matrices of rotated components show the 17 questions summarized pesticide knowledge in five factors extracted after promax rotation. This factorial model explains 56.3% of the variance. The questions were grouped as follows: knowledge about pesticides (Factor 1); knowledge of health effects related to pesticides exposure (Factor 2); pesticide exposure through the growing of fruits and vegetables (Factor 3); perception and action against pesticides exposure at school (Factor 4); and perception and action against pesticides exposure at home (Factor 5). The questionnaire provides a useful tool for examining pesticide exposure in agricultural regions, allowing younger community members to participate.

Levels of Polychlorinated Dibenzo-p-Dioxins/Furans (PCDD/Fs) and Dioxin-Like Polychlorinated Biphenyls (DL-PCBs) in Human Breast Milk in Chile: A Pilot Study.

Persistent organic pollutants (POPs) are organic compounds that resist biochemical degradation, moving long distances across the atmosphere before deposition occurs. Our goal was to provide up-to-date data on the levels of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in breast milk from Chilean women and to estimate the exposure of infants due to breast milk consumption. In Chile, we conducted a cross-sectional study based on methodologies proposed by the WHO, with a sample of 30 women recruited from three defined areas: 10 from the Arica Region (urban; Arica and Parinacota Region), 10 from Coltauco (rural; O'Higgins Region), and 10 from Molina (40% rural; Maule Region). High-resolution gas chromatography coupled with high-resolution mass spectrometry (HRGC/HRMS) was performed on pooled samples from each area. We calculated equivalent toxic concentrations (WHO-TEQ) based on the current WHO Toxic Equivalency Factors (TEF). The minimum and maximum values of ∑ PCDDs/Fs + DL-PCBs-TEQ were 4.317 pg TEQ/g fat in Coltauco and 6.31 pg TEQ/g fat in Arica. Molina had a total TEQ of 5.50 pg TEQ/g fat. The contribution of PCDD/Fs was approximately five-fold higher than that of DL-PCBs. The Estimated Daily Intake (EDI) of ∑ PCDDs/Fs + DL-PCBs based on the three pooled samples ranged between 6.71 and 26.28 pg TEQ/kg body weight (bw)/day, with a mean intake of 16.11 (±6.71) pg TEQ/kg bw/day in breastfed children from 0 to 24 months old. These levels were lower than those reported in international studies. Despite the fact that the observed levels were low compared to those in most industrialized countries, the detection of a variety of POPs in breast milk from Chilean women indicates the need for follow-up studies to determine whether such exposures during childhood could represent a health risk in adulthood.

Longitudinal exposure to pyrethroids (3-PBA and trans-DCCA) and 2,4-D herbicide in rural schoolchildren of Maule region, Chile.

BACKGROUND: Several studies showed that early exposure to pesticides affects the development and health of children. In Maule, there is previous evidence of the high exposure to organophosphate pesticides (OP) of schoolchildren. However, to date, there are no studies assessing exposure to pyrethroids and the herbicide 2,4-D. Objetive. To evaluate children's exposure to pyrethroids insecticides 3-phenoxybenzoic acid (3-PBA), trans 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (trans-DCCA) and 2,4 dichlorophenoxyacetic acid (2,4-D) herbicides. METHOD: Longitudinal study with 48 schoolchildren from two rural schools in the Maule region, Chile. Urinary metabolites of pyrethroids 3-PBA, Trans-DCCA and 2,4-D herbicides were evaluated in 2016 and 2017. Mann-Whitney U for repeated measurements and Spearman's rho correlation tests were used for data analysis. Also, we used a system of impulsive differential equations for mathematical modeling. RESULTS: All the schoolchildren assessed had more than two pesticide urinary metabolites in both years, with the 3-PBA metabolite being the most frequent. There was an increase in concentrations of urinary 3-PBA in November 2017, compared to 2016 (from 0.69 µg/L to 1.90 µg/L). In 2016, the specific metabolites of 3-PBA were correlated with Trans-DCCA, 2,4-D, chlorpyrifos, diazinon, and para-nitrophenol. In 2017, 3-PBA was correlated with 2,4-D, and Trans-DCCA. The concentrations of 3-PBA of Chilean children were higher than studies conducted in the USA that found an association of prenatal exposure to these metabolites with cognitive difficulties. CONCLUSIONS: We found high concentrations of pyrethroid metabolites among all the schoolchildren assessed, which may impact on their health and development. These insecticides had received no attention from the scientific community in Chile, and neither from the government agencies, despite the increased use of these chemicals in recent years. This is the first study in South America that confirms the exposure to pyrethroids and herbicides through biomarkers in human population living near farm fields.

Validity and Reliability of an Assessment Tool for the Screening of Neurotoxic Effects in Agricultural Workers in Chile.

There is a substantial use of pesticides within the agricultural industry of Chile, with neurotoxic effects through mechanisms of acetylcholinesterase inhibition. These pesticides result in deterioration in health, increasing the risk of diseases such as Parkinson's and Alzheimer's in highly exposed occupational population. To date, there are no brief assessment tools to monitor cognitive impairment in agricultural workers chronically exposed to these pesticides. Method. 234 agricultural workers and 305 nonagricultural workers were assessed two times (test-retest) through a brief tool which comprised three tests (clock-drawing test (CDT); frontal assessment battery (FAB); trail making tests (TMT) A and B). The full scale of WAIS-IV was administered as a gold standard to 18% of the sample of agricultural workers. Factor analysis was used to evaluate the factor structure, and validity and test-retest reliability were assessed concurrently. Results. Cronbach's alpha values were satisfactory or above (>0.60). Test-retest correlations were all significantly correlated (p < 0.001). All the tests had a significant correlation with the full scale IQ score of WAIS-IV (p < 0.05). The Kaiser-Meyer-Olkin (KMO) measure was 0.74, and the Bartell sphericity test = p < 0.001. Three factors explaining 61.62% of the variance were extracted. Two items of the FAB test were dropped of the final factor solution. Normative data transformed into percentile scores and stratified by age and educational level were obtained for Chilean agricultural workers. Conclusion. The brief assessment tool has adequate metric properties as a screening instrument. This allows for a simple administration test (10 to 15 minutes) that can potentially be used for the rapid monitoring of cognitive deterioration in the face of occupational exposure to pesticides in agricultural workers.