Increased risk of attention-deficit/hyperactivity disorder associated with exposure to organophosphate pesticide in Taiwanese children

The contribution of environmental pollutants to the risk of autism and other neurodevelopmental disorders: A systematic review of case-control studies

Exposure to environmental pollutants, such as metals, pesticides, and air pollutants during early life, is a risk factor for neurodevelopmental disorders (NDDs), including Autism Spectrum Disorder (ASD). Our systematic review aimed to select and summarize more recent case-control studies that examined the association between prenatal and early postnatal exposure to environmental pollutants and NDDs. We searched five databases (Web of Science, PubMed, Embase, Scopus, Ovid), screened 2261 records, and included 24 eligible case-control studies. Meta-analyses were conducted on subgroups of at least three studies that shared both the outcome and the exposure. A noteworthy discovery from this literature review is the existence of non-linear or non-monotonic dose-response relationships between the exposure to certain metals and the risk of ASD. The meta-analysis revealed a significant association between exposure to particular matter (PM)10 during the first year of life and the risk of ASD. Overall, studies included in our systematic review indicate that exposure to several pollutants within the first three years of life was significantly associated with the risk of NDDs.

Systematic Review and Meta-analysis of the Relationship Between Exposure to Parental Substance Use and Attention-Deficit/Hyperactivity Disorder in Children

Attention-deficit/hyperactivity disorder (ADHD) is characterized by persistent patterns of inattention, hyperactivity, and impulsiveness. Among US children and adolescents aged 3-17 years, 9.4% have a diagnosis of ADHD. Previous research suggests possible links between parental substance use and ADHD among children. We conducted a systematic review and meta-analysis of 86 longitudinal or retrospective studies of prenatal or postnatal alcohol, tobacco, or other parental substance use and substance use disorders and childhood ADHD and its related behavioral dimensions of inattention and hyperactivity-impulsivity. Meta-analyses were grouped by drug class and pre- and postnatal periods with combined sample sizes ranging from 789 to 135,732. Prenatal exposure to alcohol or tobacco and parent substance use disorders were consistently and significantly associated with ADHD among children. Other parental drug use exposures resulted in inconsistent or non-significant findings. Prevention and treatment of parental substance use may have potential for impacts on childhood ADHD.

The research landscape concerning environmental factors in neurodevelopmental disorders: Endocrine disrupters and pesticides-A review

In recent years, environmental epidemiology and toxicology have seen a growing interest in the environmental factors that contribute to the increased prevalence of neurodevelopmental disorders, with the purpose of establishing appropriate prevention strategies. A literature review was performed, and 192 articles covering the topic of endocrine disruptors and neurodevelopmental disorders were found, focusing on polychlorinated biphenyls, polybrominated diphenyl ethers, bisphenol A, and pesticides. This study contributes to analyzing their effect on the molecular mechanism in maternal and infant thyroid function, essential for infant neurodevelopment, and whose alteration has been associated with various neurodevelopmental disorders. The results provide scientific evidence of the association that exists between the environmental neurotoxins and various neurodevelopmental disorders. In addition, other possible molecular mechanisms by which pesticides and endocrine disruptors may be associated with neurodevelopmental disorders are being discussed.

Early childhood exposure to environmental phenols and parabens, phthalates, organophosphate pesticides, and trace elements in association with attention deficit hyperactivity disorder (ADHD) symptoms in the CHARGE study

BACKGROUND

A growing body of literature investigated childhood exposure to environmental chemicals in association with attention-deficit/hyperactivity disorder (ADHD) symptoms, but limited studies considered urinary mixtures of multiple chemical classes. This study examined associations of concurrent exposure to non-persistent chemicals with ADHD symptoms in children diagnosed with autism spectrum disorder (ASD), developmental delay (DD), and typical development (TD).

METHODS

A total of 549 children aged 2-5 years from the Childhood Autism Risks from Genetics and Environment (CHARGE) case-control study were administered the Aberrant Behavior Checklist (ABC). This study focused on the ADHD/noncompliance subscale and its two subdomains (hyperactivity/impulsivity, inattention). Sixty-two chemicals from four classes (phenols/parabens, phthalates, organophosphate pesticides, trace elements) were quantified in child urine samples, and 43 chemicals detected in > 70% samples were used to investigate their associations with ADHD symptoms. Negative binomial regression was used for single-chemical analysis, and weighted quantile sum regression with repeated holdout validation was applied for mixture analysis for each chemical class and all chemicals. The mixture analyses were further stratified by diagnostic group.

RESULTS

A phthalate metabolite mixture was associated with higher ADHD/noncompliance scores (median count ratio [CR] = 1.10; 2.5th, 97.5th percentile: 1.00, 1.21), especially hyperactivity/impulsivity (median CR = 1.09; 2.5th, 97.5th percentile: 1.00, 1.25). The possible contributors to these mixture effects were di-2-ethylhexyl phthalate (DEHP) metabolites and mono-2-heptyl phthalate (MHPP). These associations were likely driven by children with ASD as these were observed among children with ASD, but not among TD or those with DD. Additionally, among children with ASD, a mixture of all chemicals was associated with ADHD/noncompliance and hyperactivity/impulsivity, and possible contributors were 3,4-dihydroxy benzoic acid, DEHP metabolites, MHPP, mono-n-butyl phthalate, and cadmium.

CONCLUSIONS

Early childhood exposure to a phthalate mixture was associated with ADHD symptoms, particularly among children with ASD. While the diverse diagnostic profiles limited generalizability, our findings suggest a potential link between phthalate exposure and the comorbidity of ASD and ADHD.

The susceptibility of humans to neurodegenerative and neurodevelopmental toxicities caused by organophosphorus pesticides

The toxicology field is concerned with the impact of organophosphorus (OP) compounds on human health. These compounds have been linked to an increased risk of neurological disorders, including neurodegenerative and neurodevelopmental diseases. This article aims to review studies on the role of OP compounds in developing these neurological disorders and explore how genetic variations can affect susceptibility to the neurotoxicity of these pesticides. Studies have shown that exposure to OP compounds can lead to the development of various neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), attention deficit hyperactivity disorder (ADHD), autism, intellectual disability, and other developmental neurotoxicities. Apart from inhibiting the cholinesterase enzyme, OP compounds are believed to cause other pathological mechanisms at both the extracellular level (cholinergic, serotonergic, dopaminergic, glutamatergic, and GABAergic synapses) and the intracellular level (oxidative stress, mitochondrial dysfunction, inflammation, autophagy, and apoptosis) that contribute to these disorders. Specific genetic polymorphisms, including PON1, ABCB1, NOS, DRD4, GST, CYP, and APOE, have increased the risk of developing OP-related neurological disorders.

Frequency of urinary pesticides in children: a scoping review

Pesticides are any mix of ingredients and substances used to eliminate or control unwanted vegetable or animal species recognized as plagues. Its use has been discussed in research due to the scarcity of strong scientific evidence about its health effects. International literature is still insufficient to establish a global recommendation through public policy. This study aims to explore international evidence of the presence of pesticides in urine samples from children and their effects on health through a scoping review based on the methodology described by Arksey and O'Malley. The number of articles resulting from the keyword combination was 454, and a total of 93 manuscripts were included in the results and 22 were complementary. Keywords included in the search were: urinary, pesticide, children, and childhood. Children are exposed to pesticide residues through a fruit and vegetable intake environment and household insecticide use. Behavioral effects of neural damage, diabetes, obesity, and pulmonary function are health outcomes for children that are commonly studied. Gas and liquid chromatography-tandem mass spectrometry methods are used predominantly for metabolite-pesticide detection in urine samples. Dialkylphosphates (DAP) are common in organophosphate (OP) metabolite studies. First-morning spot samples are recommended to most accurately characterize OP dose in children. International evidence in PubMed supports that organic diets in children are successful interventions that decrease the urinary levels of pesticides. Several urinary pesticide studies were found throughout the world's population. However, there is a knowledge gap that is important to address (public policy), due to farming activities that are predominant in these territories.

Assessment of Preschool Children's Exposure Levels to Organophosphate and Pyrethroid Pesticide: A Human Biomonitoring Study in Two Turkish Provinces

Pesticides are products developed to prevent, destroy, repel or control certain forms of plant or animal life that are considered to be pests. However, now they are one of the critical risk factors threatening the environment, and they create a significant threat to the health of children. Organophosphate (OP) and pyrethroid (PYR) pesticides are widely used in Turkey as well as all over the world. The main focus of this presented study was to analyze the OP and PYR exposure levels in urine samples obtained from 3- to 6-year-old Turkish preschool children who live in the Ankara (n:132) and Mersin (n:54) provinces. In order to measure the concentrations of three nonspecific metabolites of PYR insecticides and four nonspecific and one specific metabolite of OPs, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses were performed. The nonspecific PYR metabolite 3-phenoxybenzoic acid (3-PBA) found in 87.1% of samples (n = 162) and the specific OP metabolite 3,5,6-trichloro-2-pyridinol (TCPY) found in 60.2% of samples (n = 112) were the most frequently detected metabolites in all urine samples. The mean concentrations of 3-PBA and TCPY were 0.38 ± 0.8 and 0.11 ± 0.43 ng/g creatinine, respectively. Although due to the large individual variation no statistically significant differences were found between 3-PBA (p = 0.9969) and TCPY (p = 0.6558) urine levels in the two provinces, significant exposure differences were determined both between provinces and within the province in terms of gender. Risk assessment strategies performed in light of our findings do not disclose any proof of a possible health problems related to analyzed pesticide exposure in Turkish children.

Behavioral and neuroinflammatory changes caused by glyphosate: Base herbicide in mice offspring

BACKGROUND

Glyphosate is a pesticide considered of low toxicity, but scientific evidences show it can be harmful to health. This study aimed to evaluate the toxicity in mice offspring exposed to glyphosate-based herbicide (GBH) during the intrauterine period.

METHODS

Female matrices received glyphosate 0.3 mg/kg daily per oral throughout the gestational period, which was variable between 18 and 22 days. From the 25th until the 28th days post-birth, mice offspring were subjected to behavioral tests, and the prefrontal cortex was processed for immunohistochemical analysis.

RESULTS

Two significant behavioral changes were observed: anxiety in the GLIF0.3 group, increase in the behavior burying marbles in the marble-burying test and hyperactivity, expressed by the significant increase of the crossing number in the open field test. The increased microglia, TNF-alpha, and astrocyte expression were also observed in the prefrontal cortex of offspring treated with GLIF0.3.

CONCLUSION

Exposure to GBH during mice intrauterine development induces hyperactive and anxious behavior, evidencing neuroinflammation.

Neurobehavioral Effects of Low-Dose Chronic Exposure to Insecticides: A Review

The modes of action of insecticides frequently involve a neurotoxic effect; therefore, the study of neurotoxic effects caused by long-term and low-dose insecticide exposure is of particular interest. This study looks at whether or not new studies conducted after 2009 and up to 2021 have provided new evidence for a better understanding of the actual neurobehavioral risk associated with long-term insecticide exposure. We selected and reviewed studies carried out on the neurobehavioral effects of neurotoxic insecticides (organophosphates and/or carbamates, pyrethroids, multiple or undefined insecticides, and organochlorines) considering occupational and non-occupational exposures. The articles were also scored and ranked based on seven parameters. Eighty-six studies were chosen for a final review process from among the 950 scientific papers identified. Twenty-six addressed occupational exposure and six environmental exposure. Among the latter group of studies, 17 focused on rural residents, to be assumed exposed because of living in rural areas, and 43 on the general population. Pending doubts have not been resolved in the last ten years due to the presence of contradictory and hardly comparable results and the fact that in most of the studies showing an evident neurobehavioral impairment the frequent presence of a previous episode of poisoning and hospitalization, with severe brain hypoxia, impaired the possibility of confirming the presence of a causal association with insecticide exposure. Interestingly, the most severely exposed groups, such as applicators who did not wear personal protective equipment, performed worse on neurobehavioral tests. As for residential exposure, there is sufficient evidence to suggest that prenatal OP exposure may increase the risk of ADHD in children.

Early childhood exposure to environmental phenols and parabens, phthalates, organophosphate pesticides, and trace elements in association with attention deficit hyperactivity disorder (ADHD) symptoms in the CHARGE study

Background

Agrowing body of literature investigated childhood exposure to environmental chemicals in association with attention deficit hyperactivity disorder (ADHD) symptoms, but limited studies considered urinary mixtures of multiple chemical classes. This study examined associations of concurrent exposure to non-persistent chemicals with ADHD symptoms in children diagnosed with autism spectrum disorder (ASD), developmental delay, and typical development.

Methods

A total of 574 children aged 2-5 years from the Childhood Autism Risks from Genetics and Environment (CHARGE) case-control study was administered the Aberrant Behavior Checklist (ABC). This study focused on the Hyperactivity subscale and its two subdomains (hyperactivity/impulsivity, inattention). Sixty-two chemicals from four classes (phenols/parabens, phthalates, organophosphate pesticides, trace elements) were quantified in child urine samples, and 43 chemicals detected in >70% samples were used in statistical analyses. Weighted quantile sum regression for negative binomial outcomes with repeated holdout validation was performed to investigate covariate-adjusted associations between mixtures and ABC scores in 574 children. The mixture analyses were further restricted to 232 children with ASD.

Results

Phthalate metabolite mixtures, weighted for mono-n-butylphthalate (MNBP), mono-2-heptyl phthalate, and mono-carboxy isononyl phthalate, were associated with the Hyperactivity subscale (mean incidence rate ratio [mIRR] = 1.11; 2.5th, 97.5th percentile: 1.00, 1.23), especially the hyperactivity/impulsivity subdomain (mIRR = 1.14; 2.5th, 97.5th percentile: 1.06, 1.26). These associations remained similar after restricting to children with ASD. The inattention subdomain was associated with a phenols/parabens mixture, weighted for several parabens and bisphenols (mIRR = 1.13; 2.5th, 97.5th percentile: 1.00, 1.28) and a total mixture, weighted for 3,4-dihydroxy benzoic acid, MNBR and mono-(2-ethyl-5-carboxypentyl) phthalate (mIRR = 1.11; 2.5th, 97.5th percentile: 1.01,1.25) only among children with ASD.

Conclusions

Concurrent exposure to phthalate mixtures was associated with hyperactivity in early childhood. Though causal inference cannot be made based on our cross-sectional findings, this study warrants further research on mixtures of larger number of chemicals from multiple classes in association with ADHD-related behaviors in young children.

Multiple neurological effects associated with exposure to organophosphorus pesticides in man

This article reviews available data regarding the possible association of organophosphorus (OP) pesticides with neurological disorders such as dementia, attention deficit hyperactivity disorder, neurodevelopment, autism, cognitive development, Parkinson's disease and chronic organophosphate-induced neuropsychiatric disorder. These effects mainly develop after repeated (chronic) human exposure to low doses of OP. In addition, three well defined neurotoxic effects in humans caused by single doses of OP compounds are discussed. Those effects are the cholinergic syndrome, the intermediate syndrome and organophosphate-induced delayed polyneuropathy. Usually, the poisoning can be avoided by an improved administrative control, limited access to OP pesticides, efficient measures of personal protection and education of OP pesticide applicators and medical staff.

Neurotoxicity of pesticides in the context of CNS chronic diseases

Following the introduction and application of pesticides in human life, they have always been along with health concerns both in acute poisoning and chronic toxicities. Neurotoxicity of pesticides in chronic exposures has been known as one of the most important human health problems, as most of these chemicals act through interacting with some elements of nervous system. Pesticide-induced neurotoxicity can be defined in different categories of neurological disorders including neurodegenerative (Alzheimer, Parkinson, amyotrophic lateral sclerosis, multiple sclerosis), neurodevelopmental (attention deficit hyperactivity disorder, autism spectrum disorders, developmental delay, and intellectual disability), neurobehavioral and neuropsychiatric (depression/suicide attempt, anxiety/insomnia, and cognitive impairment) disorders some of which are among the most debilitating human health problems. In this review, neurotoxicity of pesticides in the mentioned categories and sub-categories of neurological diseases have been systematically presented in relation to different route of exposures including general, occupational, environmental, prenatal, postnatal, and paternal.

Exposure to organophosphorus compounds of Japanese children and the indoor air quality in their residences

Several organophosphorus compounds such as organophosphate pesticides (OPPs) and trialkylphosphates (TAPs) are suspected to inhibit cholinesterase activities, to affect endocrine systems or to possibly be carcinogenic. To evaluate their adverse effects on health with chronic exposure in the general population, especially in children, we measured the household exposure to OPPs and TAPs by Japanese children via all exposure pathways and the contribution of indoor air quality. First-morning void urine was collected from subjects aged 6 to 15 years (n = 132), and airborne organophosphorus compounds were sampled in the subject's bedroom for 24 h. Airborne levels of nine OPPs and three TAPs and their urinary metabolites were determined. No significant correlations were detected for any compounds between their airborne concentrations and the urinary excretion amounts of their corresponding metabolites. The estimated daily intakes were as follows (median, μg/kg b.w./d): chlorpyrifos, 0.042; diazinon, 0.067; tri-n-butylphosphate, 0.094. The 95th percentiles of the intakes for fenthion, fenitrothion and the above three compounds did not exceed their reference limit values, although one subject had a daily intake of tri-n-butylphosphate that was about twice its reference limit value. The concentration levels of the urinary metabolite of tri-n-butylphosphate in our subjects tended to be higher than those for children in many other countries. The fractions of the amounts absorbed by inhalation to the amounts absorbed via all of the exposure pathways was only 2.3 % (median) for tri-n-butylphosphate. Inhalation did not seem to contribute very much as an absorption pathway of the organophosphorus compounds in these Japanese children while they were at home. The exposure amounts of OPPs were not suggested to be high enough to adversely affect the health of these children at present on the basis of their daily intakes compared to their reference limit values.

Exposure to non-persistent pesticides in the Spanish population using biomonitoring: A review

Although Spain does not have a regular national human biomonitoring program yet, different research groups are active in evaluating the exposure of children and adults to chemicals. In the last seven years, several studies in Spain have evaluated the internal exposure of the population to currently used pesticides. The present review analyzes the scope of these studies, the employed analytical methods and the main results of the exposure and risk, mainly for children and mothers. The frequency of exposure to biomarkers of exposure to organophosphate pesticides is high. Some non-specific dialkyl phosphate metabolites (DAPs), such as the diethyl phosphate (DEP), present Detection Frequencies (DFs) in the range of 65-92% in various studies. Also, the specific biomarker of the chlorpyrifos (3,5,6-trichloro-2-pyridinol, TCPy), achieves Detection Frequencies between 74% and 100% in many studies. For pyrethroids, the metabolite 3-phenoxybenzoic acid (PBA) is present, in general, in more than the 65% of the studied samples. Highly polar herbicides were only assessed in one study and both glyphosate and its metabolite aminomethylphosphonic acid showed Detection Frequencies around 60%. However, putting the biomonitoring data in a risk assessment context, the mean Hazard Quotient (HQ), used as a metric for the individual risk, ranges from 0.0006 (glyphosate) to 0.93 in farm workers (parathion), which means that is unlike that the exposure poses a health concern (HQ < 1).

Degradation of pesticides diazinon and diazoxon by phosphotriesterase: insight into divergent mechanisms from QM/MM and MD simulations

Enzymatic hydrolysis by phosphotriesterase (PTE) is one of the most effective ways of degrading organophosphorus pesticides, but the catalytic efficiency depends on the structural features of substrates. Here the enzymatic degradation of diazinon (DIN) and diazoxon (DON), characterized by PS and PO, respectively, have been investigated by QM/MM calculations and MM MD simulations. Our calculations demonstrate that the hydrolysis of DON (with PO) is inevitably initiated by the nucleophilic attack of the bridging-OH^- on the phosphorus center, while for DIN (with PS), we proposed a new degradation mechanism, initiated by the nucleophilic attack of the Zn_α-bound water molecule, for its low-energy pathway. For both DIN and DON, the hydrolytic reaction is predicted to be the rate-limiting step, with energy barriers of 18.5 and 17.7 kcal mol^-1, respectively. The transportation of substrates to the active site, the release of the leaving group and the degraded product are generally verified to be favorable by MD simulations via umbrella sampling, both thermodynamically and dynamically. The side-chain residues Phe132, Leu271 and Tyr309 play the gate-switching role to manipulate substrate delivery and product release. In comparison with the DON-enzyme system, the degraded product of DIN is more easily released from the active site. These new findings will contribute to the comprehensive understanding of the enzymatic degradation of toxic organophosphorus compounds by PTE.

Role of endocrine disrupting chemicals in children's neurodevelopment

Environmental stressors, like endocrine disrupting chemicals (EDC), are considered important contributors to the increased rates of neurodevelopmental dysfunctions. Considering the cumulative research on adverse neurodevelopmental effects associated with prenatal exposure to EDC, the purpose of this study was to review the available limited literature about the effects of postnatal exposure to EDC on child neurodevelopment and behaviour. Despite widespread children's exposure to EDC, there are a limited number of epidemiological studies on the association of this exposure with neurodevelopmental disorders, in particular in the postnatal period. The available research suggests that postnatal EDC exposure is related to adverse neurobehavioral outcomes in children; however the underlying mechanisms of action remain unclear. Timing of exposure is a key factor determining potential neurodevelopmental consequences, hence studying the impact of multiple EDC co-exposure in different vulnerable life periods could guide the identification of sensitive subpopulations. Most of the reviewed studies did not take into account sex differences in the EDC effects on children neurodevelopment. We believe that the inclusion of sex in the study design should be considered as the role of EDC on children neurodevelopment are likely sex-specific and should be taken into consideration when determining susceptibility and potential mechanisms of action.

Chlorpyrifos residue level and ADHD among children aged 1-6 years in rural China: A cross-sectional study

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders in childhood and is caused by both genetic and environmental factors. As genetic factors are nonmodifiable, environmental factors have attracted increasing attention.

OBJECTIVE

To investigate the relationships between urinary chlorpyrifos (CPF) levels, blood micronutrient levels, and ADHD prevalence in children living in rural areas of China.

METHODS

This cross-sectional study collected data on CPF exposure (according to urinary levels), blood micronutrient levels, and ADHD prevalence in children aged 1-6 years in rural China. The CPF levels were determined by mass spectrometry. Blood levels of micronutrients, including zinc, iron, calcium, copper, magnesium, and vitamin D, were measured by professional detection kits. ADHD was diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition. Descriptive statistics and univariate analysis were conducted using SPSS 21.0, and path analysis was conducted using Mplus 8.0.

RESULTS

Of the 738 children who met the eligibility criteria, 673 children (673/738, 91.2%) were included in the final analysis. Baseline questionnaires and urine samples were collected from all 673 subjects. A total of 672 children provided blood samples for micronutrient testing, and 651 completed the ADHD assessment. Approximately one-fifth of children (144/673, 21.4%) had detectable levels of CPF in their urine, and 6.9% (45/651) were diagnosed with ADHD. Path analysis showed that the total effect of CPF exposure on ADHD risk was 0.166 (P < 0.05), with a direct effect of 0.197 (P < 0.05) and an indirect effect of -0.031 (P < 0.05) via vitamin D. The mediating effect of urinary CPF levels on ADHD risk via vitamin D was 18.67%.

CONCLUSION

Higher levels of CPF exposure are associated with higher risk of ADHD. Additionally, increasing vitamin D levels may have a beneficial effect on the relationship between CPF exposure and ADHD risk. Our findings highlight the importance of modifying environmental factors to reduce ADHD risk and provide insight into future ADHD interventions.

Association Between Exposure to Pesticides and ADHD or Autism Spectrum Disorder: A Systematic Review of the Literature

OBJECTIVE

To conduct a systematic review of studies assessing the relationship between exposure to pesticides and ADHD or Autism Spectrum Disorder (ASD).

METHODS

Based on a pre-registered protocol in PROPSERO (CRD42018107847), we searched PubMed, Ovid databases, and ISI Web of Knowledge with no date/language/document type restrictions, up to May 2019. The Newcastle Ottawa Scale was used to assess study quality.

RESULTS

Among the 29 retained studies, 13 focused on ADHD, 14 on ASD, and two on both disorders. Ten studies reported a significant association between exposure to pesticides and ADHD/ADHD symptoms and 12 studies found a significant association with ASD/ASD traits. The strengths of the association and the possible confounders controlled for varied substantially across studies.

CONCLUSION

Whilst there is some evidence suggesting a possible link between pesticides and ADHD/ASD, heterogeneity across studies prevents firm conclusions. We provide methodological indications for future studies.

Exposome of attention deficit hyperactivity disorder in Taiwanese children: exploring risks of endocrine-disrupting chemicals

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is diagnosed in ~7% of school-aged children. The role of endocrine-disrupting chemicals (EDC) and oxidative stress in ADHD etiology are not clear.

OBJECTIVE

Assessment of the associations between simultaneous exposure to multiple compounds and ADHD in children.

METHODS

The case-control study included 76 clinically diagnosed ADHD cases and 98 controls, aged 4-15 years old. Concentrations quartiles of urinary metabolites of acrylamide, acrolein, nonylphenol, phthalates, and organophosphate pesticides and biomarkers of oxidative stress were used to fit logistic regressions for each compound and weighted quantiles sum (WQS) regression for the mixture.

RESULTS

Positive dose-response relationships with ADHD were observed for 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA) (odds ratio(OR)_Q4 = 3.73, 95%CI [1.32, 11.04], p_trend = 0.003), dimethyl phosphate (DMP) (OR_Q4 = 4.04, 95%CI [1.34, 12.94], p_trend = 0.014) and diethyl phosphate (OR_Q4 = 2.61, 95%CI = [0.93, 7.66], p_trend = 0.030), and for the mixture of compounds (OR_WQS = 3.82, 95%CI = [1.78, 8.19]) with the main contributions from HNE-MA (28.9%) and DMP (18.4%).

CONCLUSIONS

The dose-response relationship suggests enhanced susceptibility to EDC burden in children even at lower levels, whereas the main risk is likely from organophosphate pesticides. HNE-MA is recommended as a sensitive biomarker of lipid peroxidation in the further elucidation of the oxidative stress role in ADHD etiology.

Neurological Sequela of Acute Pesticide Poisoning Among Adults in Central Taiwan

Background and Purpose: Cases of acute pesticide poisoning account for significant morbidity and mortality in developing countries; however, its burden in Taiwan remains unknown. The study examined acute pesticide poisoning (APP) involving adults in the central region of Taiwan, which is a mainly agricultural sub-urban area.

Methods: The retrospective study evaluated the outcome and neurological sequelae of patients with APP in a Taiwanese cohort between April 2002 and February 2019. The pesticides were classified according to the Insecticide Resistance Action Committee Mode of Action (MoA) classification. The clinical characteristics, duration of hospitalization (days), follow-up duration (years), in-hospital mortality, neurological sequela, and imaging findings were recorded. Furthermore, multivariate logistic regression analyses were performed.

Results: We identified 299 patients with APP comprising 206 (68.9%) adult men with a mean exposure age of 56.4 ± 16.8 years. Paraquat, organophosphates, pyrethroids, carmabates, and phosphinic acid were the most commonly known reported poisoning agents. The mortality rate was highest in users with paraquat (77.1%), followed by phosphinic acid (22.2%), carbamates (16.7%), and organophosphates (15.8%). After a mean follows up of 3.69 ± 2.26 years, the most common neurological sequela was a cognitive decline (56 among 225 survivors, 24.89%), peripheral neuropathy (11 among 225 survivors, 4.89%), tremor (10 among 225 survivors, 4.44%), ataxia (3/225, 1.33%), and parkinsonism feature (2/225, 0.89%). Brain imaging studies revealed basal ganglion lesions on CT or hyperintensity on T2-weighted MRI images in 26 among 46 patients (56.5%). The basal ganglion lesions on brain imaging had a positive correlation with neurological sequelae.

Conclusion: Acute pesticide poisoning (APP)-related mortality is high especially paraquat intoxication, and cognitive decline, as well as peripheral neuropathy, were the most common neurological sequelae among survivors, which is highly correlated with basal ganglia lesions on brain imaging.

Chlorpyrifos and other pesticide exposure and suspected developmental delay in children aged under 5 years: a case-control study in Phitsanulok, Thailand

Background: Developmental delay among children under 5 years of age is a serious global public health problem and much research has been carried out to find potential causes. Pesticides - especially organophosphates - are suspected to be one of the main causes of the problem.  This study aimed to investigate the association between pesticide use by the mother during pregnancy and preschool children development using a case-control study.

Methods: Data on prenatal and postnatal pesticide exposure of 442 children with suspected developmental delay, and 413 controls with normal development were included for analysis. The children were matched for gender, age, and residency. Data on pesticide exposure were collected via interview with the mother, and data on pregnancy outcomes abstracted from hospital records.  

Results: Chlorpyrifos exposure significantly increased the risk of developmental delay with an odds ratio (OR) of 3.71 (95% CI 1.03-13.36) for ever use of the pesticide, and an OR of 5.92 (95% CI 1.01-34.68) for postnatal exposure (p <0.05). Some other pesticides also had a positive association with developmental delay but none were statistically significant (p <0.05). Those pesticides were insecticide, fungicide, herbicide, and molluscicide. Individual pesticides with a positive association were glyphosate, paraquat, butachlor, methyl parathion (pholidon), savin, methomyl, endosulfan, carbosulfan, methamidophos, monochrotofos, mancozeb, and bordeaumixture.

Conclusions: This case-control study found that chlorpyrifos and some other pesticides exposure during pregnancy were positively associated with developmental delay in children aged under 5 years. Further research should be conducted to better understand this potential effects of pesticides on child neurodevelopment, and the public - especially those who plan to have families - should be informed.

Monitoring and risk assessment of pesticide residues in selected herbal medicinal products in Ghana

The high patronage of herbal medicinal products in Ghana for the treatment of diverse disease conditions raises concerns about patient safety, given that much of the raw materials for production are obtained from the wild or farmlands potentially exposed to varied agrochemical residues. Therefore, the work sought to investigate the contamination of herbal medicinal products with pesticide residues and assess the potential risk posed to patients. As a result, validated gas chromatography with mass spectrometry as a detector was used to determine forty-two pesticides in thirty herbal medicinal products. The performance parameters of the method such as linearity, accuracy, and precision were found as acceptable. Pesticide residues such as chlorpyrifos and/or bifenthrin were found in 4/30 herbal medicinal products. Specifically, 3/30 herbal medicinal products contained only one pesticide, while 1/30 was contaminated with both pesticide residues. The levels of pesticide residue contamination ranged between 2.5 and 5.0 µg/kg. The acute hazard quotient and chronic hazard quotient for the two pesticide residues were evaluated and ranged between 0.21 and 0.92% and between 8.21 × 10^-4 and 5.88 × 10^-3%. The detected pesticide residue levels are below the maximum residue limit values, which may not cause acute and chronic health risks due to intake of the selected herbal medicinal product. Nevertheless, patient safety and potential public health risk can be reduced by regular monitoring, and regulation of pesticide residue levels in herbal medicinal products.

Associations between pesticide mixtures applied near home during pregnancy and early childhood with adolescent behavioral and emotional problems in the CHAMACOS study

Supplemental Digital Content is available in the text.

Studies suggest that exposure to pesticides during pregnancy and early childhood is associated with adverse child neurodevelopment. Research to date has focused primarily on exposure to single pesticides or pesticide classes in isolation; there are little data on the effect of exposure to pesticide mixtures on child and adolescent neurodevelopment.

Association of activities related to pesticide exposure on headache severity and neurodevelopment of school-children in the rural agricultural farmlands of the Western Cape of South Africa

OBJECTIVE

Children and adolescents living in agricultural areas are likely to be exposed to mixtures of pesticides during their daily activities, which may impair their neurodevelopment. We investigated various such activities in relation to headache severity and neurodevelopment of school-children living in rural agricultural areas in the Western Cape of South Africa.

METHOD

We used baseline date from 1001 school-children of the Child Health Agricultural Pesticide Cohort Study in South Africa (CapSA) aged 9-16 from seven schools and three agriculture areas in the Western Cape. Questionnaires were administrated to assess activities related to pesticide exposure and health symptoms addressing four types of activities: 1) child farm activities related to pesticide handling, 2) eating crops directly from the field, 3) contact with surface water around the field, and 4) seen and smelt pesticide spraying activities. Neurocognitive performance across three domains of attention, memory and processing speed were assessed by means of an iPad-based cognitive assessment tool, Cambridge Automated NeuroPsychological Battery (CANTAB). Headache severity was enquired using a standard Headache Impact Test (HIT-6) tool. Cross-sectional regression analysis was performed.

RESULTS

About 50% of the cohort report to have ever been engaged in activities related to pesticide exposure including farm activities, eating crops directly from the field and leisure activities. Headache severity score was consistently increased in relation to pesticide-related farm activities (score increase of 1.99; 95% CI: 0.86, 3.12), eating crops (1.52; 0.41, 2.67) and leisure activities of playing, swimming or bathing in nearby water (1.25; 0.18, 2.33). For neurocognitive outcomes, an overall negative trend with pesticide exposure-related activities was observed. Among others, involvement in pesticide-related farm activities was associated with a lower multi-tasking accuracy score (-2.74; -5.19, -0.29), while lower strategy in spatial working memory (-0.29; -0.56; -0.03) and lower paired associated learning (-0.88; -1.60, -0.17) was observed for those who pick crops off the field compared to those who do not pick crops off the field. Eating fruits directly from the vineyard or orchard was associated with a lower motor screening speed (-0.06; -0.11, -0.01) and lower rapid visual processing accuracy score (-0.02; -0.03, 0.00).

CONCLUSIONS

Children who indicate activities related to pesticide exposure may be at higher risk for developing headaches and lower cognitive performance in the domains of attention, memory and processing speed. However, self-reported data and cross-sectional design are a limitation. Future research in CapSA will consider pesticide exposure estimations via urinary biomarkers and longitudinal assessment of cognitive functions.

Chlorpyrifos and other pesticide exposure and suspected developmental delay in children aged under 5 years: a case-control study in Phitsanulok, Thailand

Background: Developmental delay among children under 5 years of age is a serious global public health problem and much research has been carried out to find potential causes. Pesticides - especially organophosphates - are suspected to be one of the main causes of the problem.  This study aimed to investigate the association between pesticide use by the mother during pregnancy and preschool children development using a case-control study. Methods: Data on prenatal and postnatal pesticide exposure of 442 children with suspected developmental delay, and 413 controls with normal development were included for analysis. The children were matched for gender, age, and residency. Data on pesticide exposure were collected via interview with the mother, and data on pregnancy outcomes abstracted from hospital records.   Results: Chlorpyrifos exposure significantly increased the risk of developmental delay with an odds ratio (OR) of 3.71 (95% CI 1.03-13.36) for ever use of the pesticide, and an OR of 5.92 (95% CI 1.01-34.68) for postnatal exposure (p <0.05). Some other pesticides also had a positive association with developmental delay but none were statistically significant (p <0.05). Those pesticides were insecticide, fungicide, herbicide, and molluscicide. Individual pesticides with a positive association were glyphosate, paraquat, butachlor, methyl parathion (pholidon), savin, methomyl, endosulfan, carbosulfan, methamidophos, monochrotofos, mancozeb, and bordeaumixture. Conclusions: This case-control study found that chlorpyrifos and some other pesticides exposure during pregnancy were positively associated with developmental delay in children aged under 5 years. Further research should be conducted to better understand this potential effects of pesticides on child neurodevelopment, and the public - especially those who plan to have families - should be informed.

Exposure and cumulative risk assessment to non-persistent pesticides in Spanish children using biomonitoring

The main objective of the present research is to evaluate the exposure to pesticides in children (n = 568) from the Valencian Region (Spain). Six non-specific and 20 specific metabolites of organophosphate pesticides (OPs), herbicides (Herb), and pyrethroids (Pyr) were analyzed in urine samples. The biomarkers with the highest detection frequencies (>70%) were diethyl phosphate, p-nitrophenol, 3-phenoxybenzoic acid, and 3,5,6-trichloro-2-pyridinol, whose geometric mean concentrations (ng·ml-n1) were 1.53, 1.03, 1.51 and 1.19, respectively. Robust regression models showed that the province of residence and the recent consumption of vegetables, legumes and cereals were some of the most important predictors of pesticide exposure. Pesticide risk assessment is estimated using two different strategies: one based on the pesticides' mode of action (MoA); and the other based on cumulative assessment groups (CAGs), proposed by EFSA. The estimated daily intakes (EDIs) ranged from 0.08 (chlorpyrifos) to 1.62 μg·kg bw-1 (λ-cyhalothrin). The MoA approach resulted in hazard quotients ranging from 0.01 (chlorpyrifos) to 0.65 (λ-cyhalothrin), and a hazard index for OPs lower than 1. Similarly, the risk assessment based on CAGs led to total margins of exposure (MOETs) far from 100. In conclusion, both risk assessment strategies does not reveal any evidence of a potential health risk due to pesticide exposure in Spanish children.

Health status among greenhouse workers exposed to different levels of pesticides: A genetic matching analysis

(1) Objective: Greenhouse workers are considered a special occupational group who are exposed to more toxic and harmful substances than ordinary farmers. The health problem of this group is a public health problem that warrants attention. Taking greenhouse workers in Ningxia, China, as the research sample, this study analyzed the health risk to practitioners posed by the greenhouse working environment. (2) Method: To analyze the relationship between pesticide exposure and the health of greenhouse workers, the genetic matching method was used to exclude the influence of covariates on the results. (3) Results: The results showed a statistical significance regarding the prevalence of cardiovascular diseases (CVD), skeletal muscle system diseases (SMSD) and digestive diseases between the different exposure groups. Researching the disease symptoms found that different levels of exposure to pesticides in greenhouses could cause multisystem and multisymptom discomfort. In addition to some irritant symptoms such as eye itching, itching, and sneezing, there were also differences in terms of the frequency of discomfort such as back pain, a decline in sleep quality, memory loss, joint pain, swelling and weakness, upper abdominal pain and flatulence, in the different exposure groups. (4) Conclusion: Different levels of exposure to pesticides in greenhouses may be one of the risk factors for practitioners to suffer from various systemic diseases, affecting their health and work efficiency. This hazard is manifested not only in some acute irritant symptoms but also in chronic diseases due to long-term exposure.

Organophosphate Agent Induces ADHD-Like Behaviors via Inhibition of Brain Endocannabinoid-Hydrolyzing Enzyme(s) in Adolescent Male Rats

Anticholinergic organophosphate (OP) agents act on the diverse serine hydrolases, thereby revealing unexpected biological effects. Epidemiological studies indicate a relationship between the OP exposure and development of attention-deficit/hyperactivity disorder (ADHD)-like symptoms, whereas no plausible mechanism for the OP-induced ADHD has been established. The present investigation employs ethyl octylphosphonofluoridate (EOPF) as an OP-probe, which is an extremely potent inhibitor of endocannabinoid (EC, anandamide and 2-arachidonoylglycerol)-hydrolyzing enzymes: that is, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). An ex vivo experiment shows that EOPF treatment decreases FAAH and MAGL activities and conversely increases EC levels in the rat brain. Subsequently, EOPF (treated intraperitoneally once at 0, 1, 2, or 3 mg/kg) clearly induces ADHD-like behaviors (in elevated plus-maze test) in both Wistar and spontaneously hypertensive rats. The EOPF-induced behaviors are reduced by a concomitant administration of cannabinoid receptor inverse agonist SLV-319. Accordingly, the EC system is a feasible target for OP-caused ADHD-like behaviors in adolescent rats.

DRD4 48 bp multiallelic variants as age-population-specific biomarkers in attention-deficit/hyperactivity disorder

The identification of biomarkers to support the diagnosis and prediction of treatment response for attention-deficit/hyperactivity disorder (ADHD) is still a challenge. Our previous works highlighted the DRD4 (dopamine receptor D4) as the best potential genetic marker for childhood diagnosis and methylphenidate (MPH) response. Here, we aimed to provide additional evidence on biomarkers for ADHD diagnosis and treatment response, by using more specific approaches such as meta-analytic and bioinformatics tools. Via meta-analytic approaches including over 3000 cases and 16,000 controls, we demonstrated that, among the different variants studied in DRD4 gene, the 48-base pair, Variable Tandem Repeat Polymorphism, VNTR in exon 3 showed an age/population-specificity and an allelic heterogeneity. In particular, the 7R/"long" allele was identified as an ADHD risk factor in European-Caucasian populations (d = 1.31, 95%CI: 1.17-1.47, Z = 4.70/d = 1.36, 95%CI: 1.20-1.55, Z = 4.78, respectively), also, from the results of last meta-analysis, linked to the poor MPH efficacy. The 4R/"short" allele was a protective factor in European-Caucasian and South American populations (d = 0.83, 95%CI: 0.75-0.92, Z = 3.58), and was also associated to positive MPH response. These results refer to children with ADHD. No evidence of such associations was detected for adults with persistent ADHD (data from the last meta-analysis). Moreover, we found evidence that the 4R allele leads to higher receptor expression and increased sensitivity to dopamine, as compared with the 7R allele (d = 1.20, 95%CI: 0.71-1.69, Z = 4.81), and this is consistent with the ADHD protection/susceptibility effects of the respective alleles. Using bioinformatics tools, based on the latest genome-wide association (GWAS) meta-analysis of the Psychiatry Genomic Consortium (PGC), we demonstrated that the 48 bp VNTR is not in Linkage Disequilibrium with the DRD4 SNPs (Single Nucleotide Polymorphisms), which were not found to be associated with ADHD. Moreover, a DRD4 expression downregulation was found in ADHD specific brain regions (Putamen, Z score = -3.02, P = 0.00252). Overall, our results suggest that DRD4 48 bp VNTR variants should be considered as biomarkers to support the diagnosis of ADHD and to predict MPH response, although the accuracy of such a biomarker remains to be further elucidated.

Seasonal exposure to PM2.5-bound polycyclic aromatic hydrocarbons and estimated lifetime risk of cancer: A pilot study

Limited researches are available on seasonal variation of inhalation exposure of polycyclic aromatic hydrocarbons (PAHs) and its cancer risk assessment in China. We recruited 20 fresh postgraduates and measured outdoor and indoor (dormitories, offices and laboratories) daily PM_2.5 concentrations in four seasons (seven consecutive days in every season) during 2014 -2015, calculated daily potential doses of personal exposure to total Benzo[a]pyrene equivalent concentration (BaPeq) in the microenvironments based on the total BaPeq and the time-activity patterns, and estimated incremental lifetime cancer risk (ILCR) using Monte Carlo method. Daily average concentrations of PM_2.5-bound ∑PAHs on the campus ranked from high to low were winter, autumn, spring, summer in the dormitories and offices. Daily average concentration of PM_2.5-bound ∑PAHs were higher in indoor environments than outdoor in the same season, except for that of PM_2.5-bound ∑PAHs in laboratories in the winter. Median values of ILCR in both sexes from high to low were winter (men vs. women: 5.35e^-9 vs. 4.96e^-9), spring (3.71e^-9 vs. 4.00e^-9), autumn (2.92e^-9 vs. 3.02e^-9), summer (1.71e^-9 vs. 1.87e^-9). Indoor and outdoor PM_2.5-bound PAHs concentrations showed seasonal and spatial variations. The ILCR value for PM_2.5-bound PAHs was higher in women than in men.

A systematic review and meta-analysis examining the interrelationships between chemical and non-chemical stressors and inherent characteristics in children with ADHD

Children may be more vulnerable to the combined interactions of chemical and non-chemical stressors from their built, natural, and social environments when compared to adults. Attention deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed childhood neurodevelopmental disorder and is considered a major public health issue, as 75% of childhood cases persist into adulthood. ADHD is characterized by developmentally inappropriate levels of hyperactivity, impulsivity, and inattention, with the neurotransmitter serotonin regulating these symptoms. Monoamine oxidase A (MAOA) aids in serotonin uptake and is often implicated in behavioral and emotional disorders, including ADHD. When children are exposed to cigarette smoke, bisphenol A (BPA), or organophosphate pesticides, MAOA activity is inhibited. Non-chemical stressors, such as traumatic childhood experiences, and lifestyle factors, complicate the relationship between genotype and exposures to chemical stressors. But the co-occurrence among outcomes between exposures to chemical stressors, non-chemical stressors, and the low activity MAOA genotype suggest that mental illness in children may be influenced by multiple interacting factors. In this systematic review, we examine the existing literature that combines exposures to chemical and non-chemical stressors (specifically childhood trauma), MAOA characteristics, and ADHD diagnosis to investigate the interrelationships present. We observe that chemical (lead [Pb], phthalates/plasticizers, persistent organic pollutants, and cigarette smoke) exposure is significantly related to ADHD in children. We also observed that existing literature examining the interaction between MAOA, exposures to chemical stressors, and traumatic experiences and their effect on ADHD outcomes is sparse. We recommend that future studies investigating childhood ADHD include chemical and non-chemical stressors and inherent characteristics to gain a holistic understanding of childhood mental health outcomes.

In-Silico Identification of Drug Lead Molecule Against Pesticide Exposed-neurodevelopmental Disorders Through Network-Based Computational Model Approach

Background:

Neurodevelopmental Disorders (NDDs) are impairment of the growth and development of the brain or central nervous system, which occurs at the developmental stage. This can include developmental brain dysfunction, which can manifest as neuropsychiatric problems or impaired motor function, learning, language or non-verbal communication. These include the array of disorder, including: Autism Spectrum Disorders (ASD), Attention Deficit Hyperactivity Disorders (ADHD) etc. There is no particular diagnosis and cure for NDDs. These disorders seem to be result from a combination of genetic, biological, psychosocial and environmental risk factors. Diverse scientific literature reveals the adverse effect of environmental factors specifically, exposure of pesticides, which leads to growing number of human pathological conditions; among these, neurodevelopmental disorder is an emerging issue nowadays.

Objective:

The current study focused on in silico identification of potential drug targets for pesticides induced neurodevelopmental disorder including Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) and to design potential drug molecule for the target through drug discovery approaches.

Methods:

We identified 139 candidate genes for ADHD and 206 candidate genes for ASD from the NCBI database for detailed study. Protein-protein interaction network analysis was performed to identify key genes/proteins in the network by using STRING 10.0 database and Cytoscape 3.3.0 software. The 3D structure of target protein was built and validated. Molecular docking was performed against twenty seven possible phytochemicals i.e. beta amyrin, ajmaline, serpentine, urosolic, huperzine A etc. having neuroprotective activity. The best-docked compound was identified by the lowest Binding Energy (BE). Further, the prediction of drug-likeness and bioactivity analysis of leads were performed by using molinspiration cheminformatics software.

Result & Conclusion:

Based on betweenness centrality and node degree as a network topological parameter, solute carrier family 6 member 4 (SLC6A4) was identified as a common key protein in both the networks. 3-D structure of SLC6A4 protein was designed and validated respectively. Based on the lowest binding energy, beta amyrin (B.E = -8.54 kcal/mol) was selected as a potential drug candidate against SLC6A4 protein. Prediction of drug-likeness and bioactivity analysis of leads showed drug candidate as a potential inhibitor. Beta amyrin (CID: 73145) was obtained as the most potential therapeutic inhibitor for ASD & ADHD in human.

Occupational pesticide exposure and symptoms of attention deficit hyperactivity disorder in adolescent pesticide applicators in Egypt

BACKGROUND

Exposure to environmental chemicals, including organophosphorus pesticides, is associated with behavioral disorders such as attention deficit hyperactivity disorder (ADHD). However, the impact of occupational pesticide exposure on ADHD development in adolescents has not been examined.

OBJECTIVE

We examined the association between exposure to chlorpyrifos and ADHD symptoms among adolescents in Egypt.

METHODS

Adolescent pesticide applicators and non-applicators, 12-21 years old, participated in a 10-month longitudinal study examining health effects from pesticide exposure. Repeated urine and blood samples were collected at various time points during the 10-months to assess biomarkers of chlorpyrifos exposure (urinary trichloro-2-pyridinol or TCPy) and effect (blood acetyl cholinesterase activity and butyryl cholinesterase activity). Parents from a subset of the cohort (N = 64) completed the Short Form of Conners' Parent Rating Scale - Revised. Poisson regressions were used to examine the associations between the number of ADHD symptoms and occupation and biomarkers.

RESULTS

Pesticide applicators had significantly more symptoms of ADHD than participants in the non-applicator group. Urinary TCPy levels were associated with increased symptoms, demonstrating a dose-response effect. Applicators with ADHD reported applying pesticides for more hours during the application season and had greater cumulative TCPy levels than participants without ADHD. One fourth of all applicators met the criteria for an ADHD diagnosis (having 6 or more reported symptoms).

CONCLUSIONS

This study provides preliminary evidence of an association between occupational exposure to chlorpyrifos and ADHD symptoms among adolescent pesticide applicators in spite of its limited small sample size. There is a critical need to investigate the susceptibility of children and adolescents to repeated occupational and environmental exposures to pesticides because the developing brain may be uniquely sensitive to the neurotoxic effects of these agents.

Cohort profile: Beyond birth cohort study - The Korean CHildren's ENvironmental health Study (Ko-CHENS)

The Korean CHildren's ENvironmental health Study (Ko-CHENS) is a nationwide prospective birth cohort showing the correlation between the environmental exposures and the health effects to prevent the environmental diseases in children, and it provides the guidelines for the environmental hazardous factors, applying the life-course approach to the environmental-health management system. The Ko-CHENS consists of 5000 Core and 65,000 Main Cohorts. The children in the Core Cohort are followed up at 6 months, every year before their admission into the elementary school, and every 3 years from the first year after this admission. The children in the Cohort will be followed up through the data links (Statistics Korea, National Health Insurance Service [NHIS], and Ministry of Education). The individual biospecimens will be analyzed for 19 substances. The long-term-storage biological samples will be used for the further substance analysis. The Ko-CHENS will investigate whether the environmental variables including the perinatal outdoor and indoor factors and the greenness contribute causally to the health outcomes in the children and adolescents. In addition to the individual surveys, the assessments of the outdoor exposures and health outcomes will use the national air-quality monitoring data and claim data of the NHIS, respectively. The two big-data forms of the Ko-CHENS are as follows: The Ko-CHENS data that can be linked with the nationally registered NHIS health-related database, including the medical utilization and the periodic health screening, and the birth/mortality database in the Statistics; the other is the Big-CHENS dataset that is based on the NHIS mother delivery code, for which the follow-up of almost 97% of the total birth population is expected. The Ko-CHENS is a very cost-effective study that fully exploits the existing national big-data systems with the data linkage.

Simultaneous Determination of Pyrethroid, Organophosphate and Carbamate Metabolites in Human Urine by Gas Chromatography–Mass Spectrometry (GCMS)

We have developed a rapid, sensitive, and reliable method for simultaneous determination of the urinary metabolites of common insecticides in a single analytical run using gas chromatography–mass spectrometry (GCMS). Thirteen metabolites, one originating from carbamate, six from organophosphates, and seven from pyrethroids, were selected for method validation. Samples at different concentrations (0.5–15 µg/L) were prepared by mixing working solutions containing the analytes with blank urine. After acid hydrolysis for 45 min at 90 °C, samples were processed with liquid–liquid extraction and derivatization by N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) before analysis on GCMS. The limits of detection for all thirteen analytes were below 0.1 µg/L. The recovery rates, evaluated at two concentrations (1, 10 µg/L), were found to be 90.48%, on average. The precision of multiple analyses at three different concentrations (0.5, 5, 15 µg/L) within one day or between 10 days was evaluated, and the resultant relative standard deviations were 8.1% or under. We also applied this method to analyze genuine urine samples collected from 30 human subjects, and successfully detected all the metabolites, with detection frequencies more than 50% for pyrethroid metabolites. In summary, this method is not only as good as others in performance, but is advantageous in terms of cost effectiveness and multiplicity of analytes.

Children's low-level pesticide exposure and associations with autism and ADHD: a review

Pesticides are chemicals that are designed specifically for the purpose of killing or suppressing another living organism. Human toxicity is possible with any pesticide, and a growing body of literature has investigated possible associations with neurodevelopmental disorders. Attention deficit disorder with or without hyperactivity (ADHD) and autism spectrum disorder (ASD) are two of these specific disorders that have garnered particular interest. Exposure to toxic chemicals during critical windows of brain development is a biologically plausible mechanism. This review describes the basic laboratory science including controlled pesticide dosing experiments in animals that supports a mechanistic relationship in the development of ADHD and/or ASD. Epidemiological relationships are also described for low-level pesticide exposure and ADHD and/or ASD. The available evidence supports the hypothesis that pesticide exposure at levels that do not cause acute toxicity may be among the multifactorial causes of ADHD and ASD, though further study is needed, especially for some of the newer pesticides.

The association between exposure to environmental factors and the occurrence of attention-deficit/hyperactivity disorder (ADHD). A population-based retrospective cohort study

BACKGROUND

A number of factors contribute to attention deficit hyperactivity disorder (ADHD) and although they are not fully known, the occurrence of ADHD seems to be a consequence of an interaction between multiple genetic and environmental factors. However, apart from pesticides, the evidence is inadequate and inconsistent as it differs not only in the population and time period analysed, but also in the type of study, the control of the confounding variables and the statistical methods used. In the latter case, the studies also differ in the adjustment of spatial and temporal variability. Our objective here, is to provide evidence on an association between environmental factors and ADHD.

METHODS

In our study, we used a population-based retrospective cohort in which we matched cases and controls (children free of the disease) by sex and year of birth (n = 5193, 78.9% boys). The cases were children born between 1998 and 2012 and diagnosed with ADHD (n = 116). To evaluate whether there was a geographical pattern in the incidence of ADHD, we first represented the smoothed standardized incidence rates on a map of the region being studied. We then estimated the probability of being a case by using a generalized liner mixed model with a binomial link. As explanatory variables of interest, we included the following environmental variables: distance to agricultural areas, distance to roads (stratified into three categories according to traffic density and intensity), distance to petrol stations, distance to industrial estates, and land use. We control for both observed (individual and family specific variables and deprivation index) and unobserved confounders (in particular, individual and familial heterogeneity). In addition, we adjusted for spatial extra variability.

RESULTS

We found a north-south pattern containing two clusters (one in the centre of the study region and another in the south) in relation to the risk of developing ADHD. The results from the multivariate model suggest that these clusters could be related to some of the environmental variables. Specifically, living within 100 m from an agricultural area or a residential street and/or living fewer than 300 m from a motorway, dual carriageway or one of the industrial estates analysed was associated (statistically significant) with an increased risk of ADHD.

CONCLUSION

Our results indicate that some environmental factors could be associated with ADHD occurring, particularly those associated with exposure to pesticides, organochlorine compounds and air pollutants because of traffic.

Pesticides in indoor and outdoor residential dust: a pilot study in a rural county of Taiwan

We conducted a pilot study to examine pesticides in dust of homes in a rural county of Taiwan. A total of 56 homes of pregnant women were included in the study. Indoor and outdoor dust was collected by a vacuum sampler and a dustpan/brush set, respectively. Nine pesticides were selected for analysis on gas chromatography-mass spectrometry with the detection limits being 0.088 ng/g or lower. The most detected pesticides were cypermethrin and chlorpyrifos, which appeared in 82.7 and 78.8% of indoor samples and 48.2 and 39.3% of outdoor samples, respectively. The detection of pesticides from indoor and outdoor dust, however, was not consistent, indicating different sources of pesticides. In addition to those two most detected, permethrin, prallethrin, and tetramethrin, which were common ingredients of insecticide products for indoor use, were also frequently found in indoor dust, suggesting that indoor use of such pesticide products may have been a major source. Fewer pesticides were found in outdoor dust, but the outdoor detection of chlorpyrifos was significantly associated with farms present inside the circles with radii of 50 and 100 m surrounding the homes (P = 0.021, 0.016). It is suggested that pesticide drift from agricultural areas to residential environments may have occurred. No seasonal effect on distribution of pesticides in dust was found, indicating that pesticides could be routinely used in Taiwan regardless of season. Compared with other international studies, this study shows relatively high levels of chlorpyrifos but low levels of pyrethroids (i.e., cypermethrin), reflecting a different pattern of pesticide use in Taiwan. Further studies need to be warranted for a better understanding of exposure to pesticides and the associated health effects.

The link of organophosphorus pesticides with neurodegenerative and neurodevelopmental diseases based on evidence and mechanisms

Organophosphorus (OP) compounds have been known as the most widely used pesticides during the past half century and there have been a huge body of literature regarding their association with human chronic diseases. Neurodegenerative and neurodevelopmental disorders including Alzheimer, Parkinson, amyotrophic lateral sclerosis (ALS), attention deficit hyperactivity disorder (ADHD), and autism are among the afflicting neurological diseases which overshadow human life and their higher risk in relation to OP exposures have been uncovered by epidemiological studies. In addition, experimental studies exploring the underlying mechanisms have provided some evidence for involvement of cholinergic deficit, oxidative stress, neuro-inflammation, and epigenetic modifications as the processes which are common in the toxicity of the OP and pathophysiology of the mentioned diseases. In addition, genetic mutations and polymorphisms of different variants of some genes like paraoxonase have been shown to be implicated in both susceptibility to OPs toxicity and neurological diseases. In this article, we reviewed the epidemiological as well as experimental studies evidencing the association of exposure to OPs and incidence of neurodegenerative and neurodevelopmental diseases.

Daily Intake Estimation for Young Children's Ingestion of Residential Dust and Soils Contaminated with Chlorpyrifos and Cypermethrin in Taiwan

We estimated the daily intakes of chlorpyrifos and cypermethrin via ingestion of indoor dust and outdoor soils using the Stochastic Human Exposure and Dose Simulation Model on a probabilistic approach for Taiwanese young children. Variables for the estimation, such as concentration, ingestion rate, and body weight, were adopted from previous studies. Monte Carlo simulation was performed with 1,000,000 iterations to simulate a single daily intake, which was shown in terms of percentage of the Acceptable Daily Intake (ADI) of either insecticide. The daily intakes are minimal with a 99% probability, but go up steeply at the 99.9th percentile (13.1% and 20.0% of the ADIs of chlorpyrifos and cypermethrin, respectively). The sensitivity analysis indicates that concentration is the most determinant variable for daily intake estimation, suggesting that high intakes may occur when insecticide concentrations are elevated. Compared to the data of daily intakes via dietary ingestion of vegetables derived from a previous study, the estimated non-dietary intakes are negligible until reaching the highest percentile. Consequently, the non-dietary ingestion exposure to either insecticide is commonly low for young children in Taiwan’s homes, unless high contamination (e.g., indoor insecticide application) occurs in the environment. Care has to be taken to avoid high contamination indoors.

The neurotoxin diethyl dithiophosphate impairs glutamate transport in cultured Bergmann glia cells

Glutamate, the main excitatory neurotransmitter in the vertebrate Central Nervous System, is involved in almost every aspect of brain physiology, and its signaling properties are severely affected in most neurodegenerative diseases. This neurotransmitter has to be efficiently removed from the synaptic cleft in order to prevent an over-stimulation of glutamate receptors that leads to neuronal death. Specific sodium-dependent membrane transporters, highly enriched in glial cells, elicit the clearance of glutamate. Once internalized, it is metabolized to glutamine by the glia-enriched enzyme Glutamine synthetase. Accumulated glutamine is released into the extracellular space for its uptake into pre-synaptic neurons and its conversion to glutamate that is packed into synaptic vesicles completing the glutamate/glutamine cycle. Diverse chemical compounds, like organophosphates, directly affect brain chemistry by altering levels of neurotransmitters in the synaptic cleft. Organophosphate compounds are widely used as pesticides, and all living organisms are continuously exposed to these substances, either in a direct or indirect manner. Its metabolites, like the diethyl dithiophosphate, are capable of causing brain damage through diverse mechanisms including perturbation of neuronal-glial cell interactions and have been associated with attention-deficit disorders and other mental illness. In order to characterize the neurotoxic mechanisms of diethyl dithiophosphate, we took advantage of the well characterized model of chick cerebellar Bergmann glia cultures. A significant impairment of [³H] d-Aspartate transport was found upon exposure to the metabolite. These results indicate that glia cells are targets of neurotoxic substances such as pesticides and that these cells might be critically involved in the associated neuronal death.

Pesticide exposure and health conditions among orange growers in Southern Brazil

This study aimed to evaluate the exposure to pesticides through the biomarkers analysis, as well as life habits and use of Personal Protective Equipment (PPE) in a group of farmers who grow citrus in the Vale do Caí region, in Rio Grande do Sul, southern Brazil. The study population consisted of 73 volunteer farmers, 45 males and 28 females, aged between 13 and 69 years old. The control group consisted of 30 individuals who were not exposed to pesticides. Measures of urea, creatinine, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT), plasma cholinesterase (BChE) activity, and hematological parameters were analyzed. The study population also answered a structured questionnaire on life habits and health. The results showed that BChE activity was significantly lower in the exposed group than in the control group. AST, ALT, and creatinine were increased in the group of women exposed to pesticides when compared to the control group. GGT, urea, and hematological parameters did not show statistical differences for both male and female group. The most prevalent symptom reported by farmers after exposure to pesticides was headache. Furthermore, it was verified that the use of complete PPE is only made by 38% of the studied population.