Impact of organophosphate pesticides on anurans: a mini review

Organophosphate pesticides exposure in pregnant women and maternal and cord blood thyroid hormone concentrations

Hypothyroidism in pregnancy: Prevalence, associated factors and biochemical monitoring

OBJECTIVES/SPECIFIC AIMS: Little is known about potentially obesogenic endocrine-disruptors’ effects on excessive gestational weight gain (GWG) and postpartum weight retention (PPWR), which increase risk of adverse pregnancy and postnatal outcomes. We explored associations between prenatal organophosphate (OP) pesticide exposure and increased weight both during and after pregnancy. METHODS/STUDY POPULATION: Three dimethyl (DM) and three diethyl (DE) OP metabolites were measured in spot urine samples collected at <18, 18-25, and >25 gestational weeks among 688 participants in the Generation R Study. Metabolite levels were expressed as molar concentration/gram creatinine and log10-transformed. GWG and PPWR were calculated as the difference between weight at each prenatal/postnatal visit or maximum gestational weight and pre-pregnancy weight. In covariate-adjusted regression models we assessed associations of metabolite concentrations at each prenatal visit and, where appropriate, averaged across pregnancy with early-to-mid pregnancy, mid-to-late pregnancy, late pregnancy-to-maximum, and total GWG; insufficient and excessive GWG according to Institute of Medicine guidelines; and long-term PPWR at 6 and 10 years postpartum. Based on OP pesticides’ lipophilicity and association with hypomethylation, we investigated interactions with pre-pregnancy body mass index, periconceptional folic acid supplementation, and breastfeeding duration. RESULTS/ANTICIPATED RESULTS: A 10-fold increase in late pregnancy DE metabolite concentration was associated with 1.34 kg [95% confidence interval: 0.55, 2.12] higher late pregnancy-to-maximum GWG. A 10-fold increase in mean DE metabolite concentration across pregnancy was associated with 2.41 kg [0.62, 4.20] lower PPWR at 6 years. Stratified analysis suggested that the prenatal finding was driven by women with pre-pregnancy BMI ≥25 kg/m2, while the postnatal finding was driven by women with pre-pregnancy BMI <25 kg/m2 and with inadequate folic acid supplementation. We found no associations between OP pesticide metabolites and insufficient or excessive weight gain and no interaction with breastfeeding. DISCUSSION/SIGNIFICANCE OF IMPACT: In this longitudinal analysis, we observed a positive association of OP pesticide metabolites with GWG in late pregnancy among overweight/obese women, potentially reflecting inhibition of OP pesticide detoxification by oxidative stress. Postnatally, under/normal weight women with higher OP pesticide metabolites had lower PPWR, possibly due to better metabolic function and a more healthful diet. These results suggest that there may be a critical period during the late phase of pregnancy when OP pesticide exposure may increase GWG, and this association may be amplified in overweight/obese women. Areas for future research include examination of how the interaction between OP pesticides and polymorphisms of the paraoxonase (PON1) gene, which detoxifies OP pesticides, affect GWG/PPWR; exploration of the interplay among maternal pre-pregnancy BMI, oxidative stress, and PON1 levels; and characterization of the variability of OP pesticides exposure across pregnancy using more frequent repeated urine samples.

Organophosphate pesticides (OP) are a class of acetylcholinesterase (AChE) inhibitors, which have effects on the central and peripheral nervous systems. OP's inhibit AChE through phosphorylation of the active site serine, which leads to a toxic and potentially lethal buildup of the neurotransmitter acetylcholine (ACh) causing excess stimulation of cholinergic neurons. OP's are widely used to suppress the activity and growth of insect pest populations in both agriculture and household settings. The objective of this study was to examine both organismal and cellular morphological changes caused by OP exposure. Specifically, zebrafish (Danio Rerio) embryos were exposed to sub‐lethal concentrations of Chlorpyrifos (CPF) and its bioactive form Chlorpyrifos‐oxon (CPO), and compared to vehicle controls (MeOH). Gross morphological changes were observed at 72 hours via light microscopy and morphological changes to cholinergic neurons were observed via confocal microscopy of wholemount immuno‐labeled embryos using anti‐ChAT. Light microscopy observations of the embryos showed varying degrees of cardiac edema in both CPF and CPO exposed embryos. Additionally, mild kyphosis was observed in CPF and strong kyphosis in CPO exposed embryos. Confocal observations of the trunk spinal region showed embryos exposed to CPF lost dorsal neural tube cell staining and dark pockets, possibly indicating cell death, were observed along the ventral neural tube. For CPO exposed embryos, cells bodies in the neural tube were disorganized. Additionally, axon projections across the neural tube showed differences in branching and spacing in both CPF and CPO exposed embryos. Together our results showed that OP exposure causes changes in neuronal cytoarchitecture and embryo morphology. Understanding the developmental effects of these pesticides is particularly important since developmental changes have significant effects on adult systems and children represent a vulnerable population.Support or Funding InformationDepartment of Defense, ARO 66377‐RT‐REP; Keck Foundation Undergraduate Fellowship to T.H.W.; James Irvine Foundation Chair in Biological Sciences to E.A.F.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Background. Consumption of organically grown food has been shown to result in significant reductions in organophosphate (OP) pesticide exposure in non-occupationally exposed populations, and 40% of Americans consume organic food at least occasionally. Aims. The purpose of this study was to assess dietary exposure to OP pesticides based on data from food frequency questionnaires (FFQ) and information on organic food consumption habits, and to empirically compare those exposure assessments with measurements of urinary OP pesticide biomarkers. Methods. Dietary exposure to OP pesticides was assessed in 800 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) in two ways:1)by measurement of urinary dialkylphosphate (DAP) concentrations, and 2)by multiplying average dietary intake of each of 20 food items by average residue levels of each of 10 OP pesticides in those items, and summing across foods and pesticides. Dietary intake was based on individual FFQ responses, and residue levels were obtained from the USDA’s Pesticide Data Program. Participants were categorized as “often or always”, “sometimes” or “seldom or never” consumers of organic food, based on self-report. Results. In preliminary analysis, we observe a significant linear relationship between predicted dietary exposure and DAP levels in participants who reported seldom or never consuming organic foods (R2=0.71). No relationship was observed between FFQ-based exposure predictions and DAP measurements for participants who reported that they sometimes, often or always consumed organic food. DAP levels in participants who reported at least occasional consumption of organic food were significantly lower than those who do not, after adjustment for food intake. Conclusions. This work suggests that OP pesticide exposure can be predicted using FFQ and residue data for people who do not consume organic diets. These data also support previous research demonstrating that consumption of organic food is associated with lower urinary DAP concentrations.

Acetylcholinesterase (AChE) is one of the important enzymes located in the central and peripheral nervous system of organisms. The primary physiological function of AChE is to regulate the concentration of the neurotransmitter acetylcholine (ACh) by a process of hydrolyzing ACh into acetyl and choline. This natural AChE receptor ACh regulatory mechanism can be disrupted by an array of several other compounds that have different chemical and structural characteristics. Our main focus is on inhibition of AChE by organophosphate (OP) compounds. We have disclosed several different potential mechanisms of OP and AChE in a previous study (Rathnayake and Northrup, 2016). In this extended study, we have performed protein and ligand docking, and molecular dynamic (MD) calculations to validate the reaction mechanisms in our previous study and to find the important parameters and behavioral activities of OPs in their targeted biological system AChE. To achieve these goals, we have conducted docking and MD simulations on ten OP compounds with AChE. Our results show that, depending on the size of the OPs, they tend to interact in two distinct locations in the active site of AChE. Acute OP poisoning may be happening in the reaction site that is in the deepest part of the active site by relatively smaller OP compounds, while less potent OP poisoning can be predicted by relatively larger OP compounds in the other reaction site. Further analysis is still underway to characterize additional activities of OPs on AChE.

Studies have shown that organophosphate pesticides (OPs) exposure may disrupt thyroid endocrine functions in animal models, agricultural population, occupational workers, and work-related population. However, the relationships between OPs exposure and thyroid hormone levels in the general population are unclear. This study aimed to explore the relationships of OPs exposure with thyroid hormone and antibody levels in the general population. We analyzed a sample of 1089 US adults from the National Health and Nutrition Examination Survey (NHANES) 2001-2002. OPs exposure was estimated using measures of six non-specific dialkyl phosphate metabolites (DAPs), e.g., dimethylphosphate (DMP). Multiple linear regression models were used to examine the associations of OPs exposure with thyroid hormone and antibody levels. The medians of urinary ∑DAPs detected in males and females were 32.98nmol/g creatinine and 40.77nmol/g creatinine, with statistical significance (p = 0.001). After controlling for sociodemographic factors, we found that concentrations of urinary OPs metabolites were positively associated with the serum thyroid stimulating hormone (TSH) in the general US population, particularly in males; OPs metabolites were associated with the serum TgAb, tT3, fT3, and TSH. These findings showed that thyroid hormone and antibody disruption are probably associated with OPs exposure in the general population; more studies are needed to confirm our findings.

Pesticides are used extensively throughout the world in agriculture and in pest control as well as for community health purposes. Organophosphate (OP) pesticide self-poisoning is an important clinical problem in rural regions of the developing world that kills an estimated 200,000 people every year. Unintentional poisoning kills far fewer people but is an apparent problem in places where highly toxic OP pesticides are available. Neurologic dysfunction is the best documented health effect of pesticide exposure. High-level exposure has both acute and long-term neurologic signs and symptoms, and adverse effects have been reported in most type of pesticides, including organophosphate (OP), carbamate, organochlorine, and pyrethroid insecticides, herbicides, fungicides, and fumigants. Acute OP pesticide exposure can involve in wide range of both central and peripheral neurologic symptoms. Increased neurologic symptom prevalence may provide early evidence of neurologic dysfunctions, before clinically measurable signs are evident.In this study, we analyzed the cross-sectional data on neurologic signs and symptoms from 225 rural children, both males (n = 132) and females (n = 93) who were occupationally and paraoccupationally exposed to methyl OPs (dichlorvos, fenthion, malathion, methyl parathion) and ethyl OPs (chlorpyrifos, diazinon, ethyl parathion) as they belonged to agricultural families handling, mixing, and spraying the OP pesticides. The children completed a specially designed questionnaire (Q16) on neurologic symptoms associated with pesticide exposure with their parental help. A suitable reference group consisting of rural children (n = 50) never involved in pesticide handling (neither outdoor nor indoor) belonging to similar socioeconomic strata included in the study to compare the prevalence of various neurologic symptoms between the two groups.Among all the neurologic self-reported symptoms, headache, watering in eyes, and burning sensation in eye/face were the most important clinical manifestations attributed to OP pesticide exposure. These symptoms could probably be the consequence of chronic effects of most pesticides on the central nervous system. The muscarinic symptoms reported the maximum prevalence of salivation (18.22%), whereas lacrimation was observed in 17.33% cases, followed by diarrhea in 9.33% cases. The nicotinic clinical manifestations of acute OP poisoning revealed excessive sweating in 13.78% cases and tremors in 9.3% cases followed by mydriasis in 8.4% exposed children. The characteristic cholinergic symptoms, such as insomnia, headache, muscle cramps, weakness, and anorexia were also reported by both male and female exposed children. The high frequency of neurologic symptoms observed in the study may be due to parasympathetic hyperactivity due to the accumulated ACh resulting from AChE inhibition.

Prenatal and postnatal exposure to organophosphate pesticides and childhood neurodevelopment in Shandong, China

Organophosphate pesticides: Another silent liver hazard?

Worldwide use of organophosphate pesticides as agricultural chemicals aims to maintain a stable food supply, while their toxicity remains a major public health concern. A common mechanism of acute neurotoxicity following organophosphate pesticide exposure is the inhibition of acetylcholinesterase (AChE). To support Next Generation Risk Assessment for public health upon acute neurotoxicity induced by organophosphate pesticides, physiologically based kinetic (PBK) modeling-facilitated quantitative in vitro to in vivo extrapolation (QIVIVE) approach was employed in this study, with fenitrothion (FNT) as an exemplary organophosphate pesticide. Rat and human PBK models were parametrized with data derived from in silico predictions and in vitro incubations. Then, PBK model-based QIVIVE was performed to convert species-specific concentration-dependent AChE inhibition obtained from in vitro blood assays to corresponding in vivo dose-response curves, from which points of departure (PODs) were derived. The obtained values for rats and humans were comparable with reported no-observed-adverse-effect levels (NOAELs). Humans were found to be more susceptible than rats toward erythrocyte AChE inhibition induced by acute FNT exposure due to interspecies differences in toxicokinetics and toxicodynamics. The described approach adequately predicts toxicokinetics and acute toxicity of FNT, providing a proof-of-principle for applying this approach in a 3R-based chemical risk assessment paradigm.

Background:Because of the widespread use of organophosphate (OP) pesticides in agriculture, they are major environmental contaminants in developing countries. OP pesticides decrease sperm concentration and affect its quality,viability, and motility. Studies have demonstrated the association between abnormal semen analysis and OP pesticidesexposure among the high-risk population. As there is limited data on the percentage of OP pesticides exposure, thestudy aimed to determine the OP pesticides exposure in Southern Indian men with idiopathic abnormal semen analysisand find the possible source of their OP pesticides exposure.Materials and Methods:In this cross-sectional pilot study, fifty men with idiopathic abnormal semen analysisas cases and fifty men with normal semen analysis as controls were recruited. Detailed history was taken andgeneral and systemic examinations were carried out. OP pesticides exposure was determined by assessment ofpseudocholinesterase and acetylcholinesterase levels and urinary OP pesticides metabolites dialkyl phosphate(DAP) consisting of dimethyl phosphate (DMP), diethyl thiophosphate (DETP), and diethyl dithiophosphate(DEDTP).Results:Cases had statistically significantly lower levels of pseudocholinesterase (5792.07 ± 1969.89 vs. 10267.01± 3258.58 IU/L) (P=0.006) and acetylcholinesterase [102.90 (45.88-262.74) vs. 570.31 (200.24-975.30) IU/L](P=0.001) as compared to controls. Cases had a statistically significantly higher percentage of urinary DAP positivityas compared to controls (80 vs. 38%, P<0.0001). Hence, cases had a significantly higher percentage of OP pesticidesexposure as compared to controls (20 vs. 4%, P=0.015). OP-exposed cases had significantly higher urinary DETPand DEDTP levels as compared to OP non-exposed cases. Also, urinary DETP and DEDTP levels were significantlynegatively associated with sperm concentration, motility, and normal morphology among OP-exposed cases.Conclusion: Southern Indian men with idiopathic abnormal semen analysis had a significantly higher percentage ofOP pesticides exposure as compared to men with a normal semen analysis.

Organophosphate pesticide exposure during pregnancy and childhood and onset of juvenile delinquency by age 16 years: The CHAMACOS cohort

Researchers often use urinary biomonitoring as the basis for estimating exposures to organophosphate pesticides (OPs), including dietary exposures. In this issue of EHP investigators report a new method to estimate long-term exposure to OPs via produce.1 This method appears to be an improvement over estimates based on urine biomarkers, which reflect exposure only in the previous few days. The researchers analyzed dietary data for nearly 4,500 men and women enrolled in the Multi-Ethnic Study of Atherosclerosis (MESA), a long-term study of cardiovascular disease risk factors in older people. Every two years participants completed a food frequency questionnaire about their typical consumption of an extensive list of foods, including 20 specific fruits and vegetables. They also were asked whether they ate organically grown produce “seldom or never,” “sometimes,” or “often or always.” Consumers who want to avoid organophosphates but can’t afford to go completely organic can take a targeted approach, choosing organic only for fruits and vegetables that tend to have the highest pesticide residues. The authors estimated individuals’ OP exposures by combining this dietary intake information with pesticide residue data reported by the U.S. Department of Agriculture (USDA). For a subset of participants, they then compared estimated individual exposure levels against concentrations of OP metabolites known as dialkylphosphates (DAPs) measured in urine samples. Participants in this subset who reported often or always eating organic produce had the lowest urinary concentrations of DAP (median 106 nmol/g creatinine), while those who rarely or never ate organic produce had the highest DAP concentrations (median 163 nmol/g creatinine); those who sometimes ate organic produce fell in between (median 121 nmol/g creatinine). Importantly, these comparisons were among people who reported eating comparable amounts of fruits and vegetables. This avoided potential confounding by overall produce intake (in the larger cohort, the authors found that people who reported eating more organic produce also tended to eat more produce overall).1 “The health benefits of eating fruits and vegetables—whether organic or conventional—are well established. Our research strengthens claims2 that selecting organic produce reduces exposure to OPs,” says study leader Cynthia Curl, now an assistant professor at Boise State University. Most OPs break down to DAPs, yet specific OPs can vary widely in terms of toxicity.3 The USDA’s Pesticide Data Program measures residues of more than 450 pesticides in foods on an “as eaten” basis—for instance, bananas are peeled before they are tested.4 By combining food consumption information and USDA residue data for specific pesticides on specific foods, researchers may be able to estimate exposures more accurately in future studies on pesticides and health. Curl’s paper “breaks important methodological ground by describing a relatively low-cost, noninvasive method for the characterization of long-term dietary exposures,” says Charles Benbrook, program leader of the Measure to Manage program at the Washington State University Center for Sustaining Agriculture and Natural Resources. “Many claims are made today about food quality, and they need intense scrutiny.” Benbrook was not involved in the study. Curl plans to use the novel technique to examine how pesticide intake affects neurocognitive end points in the MESA population. Exposures to OPs (and other pesticides) have been associated in some studies with increased risk for dementia in adults5 and impaired intellectual development in children.6 Surveys suggest that about 40% of Americans buy some organic food.7 However, the higher cost of organic produce can put an organic diet out of reach for some consumers. “If you want to reduce your OP exposure, but can’t afford to eat exclusively organic, a targeted approach to buy organically may reduce your exposure,” says Curl. She suggests using the Environmental Working Group’s Dirty Dozen™ and Clean Fifteen™ lists as a guide to deciding when to choose organic produce. The Dirty Dozen list includes fruits and vegetables that tend to have the highest levels of pesticide residues—for 2015 the list includes apples, peaches, and nectarines. The Clean Fifteen, on the other—which includes avocados, pineapples, and corn—are the items that tend to have the lowest pesticide residues.8 A new review in Consumer Reports gives similar advice.9

The impact of organophosphate pesticide (OPP) exposure on osteoporosis in adult population remains unclear. Thus, it is necessary to explore the association between the exposure to a mixture of OPPs and the prevalence of osteoporosis as well as to identify the major contributor of OPPs in this association. Participants were selected from the 2005-2008 cycle of the NHANES cross-sectional study. OPP exposure was estimated using six different metabolites found in urine. Dual-energy X-ray absorptiometry (DXA) was used to measure bone mineral density (BMD). Survey-weighted generalized linear regression models (SWGLMs) were used to estimate the association between individual OPP exposure and osteoporosis/BMD. Weighted quantile sum (WQS) regression and quantile g-computation (Qgcomp) models were used to assess the mixture of OPPs and identify the key pollutants. SWGLMs indicated that higher concentrations of dimethyl dithiophosphate (DMDTP) and diethyl dithiophosphate (DEDTP) were associated with increased osteoporosis risk in the upper quartiles. WQS models revealed a significant combined effect of six OPP metabolites on osteoporosis (OR = 1.35, 95% CI: 1.06-1.73, P = 0.015), femoral neck BMD (β = -0.012, 95% CI: -0.020, -0.004, P = 0.003) and lumbar spine BMD (β = -0.015, 95% CI: -0.025, -0.006, P = 0.001), with DMDTP and DEDTP identified as key pollutants. Results from the Qgcomp models showed no substantial changes. This study indicated that exposure to both individual OPPs and their mixtures were associated with decreased BMD and increased osteoporosis risk, with DMDTP and DEDTP identified as major contributors to these associations. This underscores the need to prioritize control of these two pollutants to limit their exposure for osteoporosis prevention.