Toxicokinetics of captan and folpet biomarkers in dermally exposed volunteers

Revealing the mechanistic interactions of profenofos and captan pesticides with serum protein via biophysical and computational investigations

Profenofos (PF) and captan (CT) are among the most utilized organophosphorus insecticides and phthalimide fungicides, respectively. To elucidate the physicochemical and influential toxicokinetic factors, the mechanistic interactions of serum albumin and either PF or CT were carried out in the current study using a series of spectroscopy and computational analyses. Both PF and CT could bind to bovine serum albumin (BSA), a representative serum protein, with moderate binding constants in a range of 103-104 M-1. The bindings of PF and CT did not induce noticeable BSA's structural changes. Both pesticides bound preferentially to the site I pocket of BSA, where the hydrophobic interaction was the main binding mode of PF, and the electrostatic interaction drove the binding of CT. As a result, PF and CT may not only induce direct toxicity by themselves, but also compete with therapeutic drugs and essential substances to sit in the Sudlow site I of serum albumin, which may interfere with the pharmacokinetics and equilibrium of drugs and other substances causing consequent adverse effects.

Determinants of Pesticide Exposure in Occupational Studies: A Meta-Analysis

Few epidemiological studies use exposure determinants specifically tailored to assess pesticide or plant protection product (PPP) exposures when assessing presumed association between occupational exposure and health outcomes among agricultural workers. This lack of exposure specificity could lead to results that fail to detect an association. It could be related to the lack of consensus on exposure assessment methods and the choice of exposure determinants. We conducted a meta-analysis following the PRISMA checklist to identify PPP exposure determinants used in occupational studies and identified exposure determinants that best characterized agricultural exposures to PPPs. Out of 1436 studies identified, 71 were included. The exposure determinants identified were active ingredients, chemical classes, types of PPP, crops, tasks, frequencies, duration, lifetime exposure days, and intensity-weighted exposure days. Only six over 17 associations between exposure determinants and health outcomes were found with moderate quality of evidence. Overall, epidemiological studies had difficulty defining relevant determinants to characterize PPP exposures for agricultural workers. We recommend that a standardized list of determinants for PPP exposures in occupational exposure studies should include information on formulations, intensity, duration, and frequency of PPP exposure. Harmonized data collection on exposure and health outcomes are required as well as standard units for each exposure determinant.

Identification of pesticides exposure biomarkers for residents living close to vineyards in France

Biomonitoring can be relevant for assessing pesticides exposure of residents living close to vineyards (LCTV). However, because xenobiotics are generally present at low levels in human biological matrices and the sources of pesticide exposure are multiple, several challenges need to be overcome to reliably assess exposure in residents LCTV. This includes particularly identifying the most appropriate exposure biomarkers, the biological matrices in which they should be measured, and analytical methods that are sufficiently sensitive and specific to quantify them. The aim of the present study was to develop a tiered approach to identify relevant biomarkers and matrices for assessing pesticide exposure in residents LCTV. We used samples from a biobank for 121 adults and children included in a national prevalence study conducted between 2014 and 2016 who lived near or far from vineyards. We analyzed five priority pesticides (folpet, mancozeb, tebuconazole, glyphosate, and copper) and their metabolites in urine and hair samples. We identified relevant biomarkers according to three criteria related to: i) the detection frequency of those pesticides and metabolites in urine and hair, ii) the difference in concentrations depending on residence proximity to vineyards and, iii) the influence of other environmental and occupational exposure sources on pesticide levels. This tiered approach helped us to identify three relevant metabolites (two metabolites of folpet and one of tebuconazole) that were quantified in urine, tended to be higher in residents LCTV than in controls, and were not significantly influenced by occupational, dietary, or household sources of pesticide exposure. Our approach also helped us to identify the most appropriate measurement strategies (biological matrices, analytical methods) to assess pesticide exposure in residents LCTV. The approach developed here was a prerequisite step for guiding a large-scale epidemiological study aimed at comprehensively measuring pesticides exposures in French residents LCTV with a view to developing appropriate prevention strategies.

Assessment of children's exposure to currently used pesticides in wallonia, Belgium

In spring 2016, a study was carried out to characterize currently used pesticide (CUP) exposure among children living in Wallonia (Belgium). Pesticides were measured in both first morning urine voids of 258 children aged from 9 to 12 years and in ambient air collected close to the children's schools. Out of the 46 pesticides measured in the air, 19 were detected with frequencies varying between 11 % and 100 %, and mean levels ranging from <0.04 to 2.37 ng/m³. Only 3 parent pesticides were found in 1-10% of the urine samples, while all the metabolites analyzed were positively detected at least once. The captan metabolite (THPI) was quantified in 23.5 % of the samples, while 3,5,6-trichloro-2-pyridinol (chlopryrifos metabolite) was detected in all urines with levels ranging from 0.36-38.96 μg/l. 3-phenoxybenzoic acid (3-PBA), trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (t-DCCA) and diethylphosphate were the most abundant pyrethroid metabolites and dialkylphosphate measured. The air inhalation was demonstrated to be a minor route of exposure for the selected CUPs. Statistical regressions highlighted predictors of exposure for some pesticides such like consumption of grey bread, presence of carpets at home or indoor use of pesticides, although no clear source was identified for most of them.

Wastewater-based epidemiology approach to assess population exposure to pesticides: a review of a pesticide pharmacokinetic dataset

Wastewater-based epidemiology is an innovative approach to estimate a population's intentional and unintentional consumption of chemicals based on biomarker assays found in wastewater. This method can provide real-time objective information on the xenobiotics to which a population is directly or indirectly exposed. This approach has already been used to assess the population exposure to four classes of pesticides: organochlorines (chlordecone), triazines, organophosphates, and pyrethroids. This review aims to obtain the data (excretion rates) and characteristics (pesticide and metabolites stability, including in-sewer one) for other pesticides to broaden the scope of this new method. Excretion rates and stability descriptions for 14 pesticides, namely 2,4-D, aldrin, carbaryl, chlorobenzilate, dieldrin, diquat, ethion, glufosinate, glyphosate, folpet, malathion, parathion, penconazole, and tebuconazole, will be discussed in a practical framework.

Biomarkers of Exposure to Pyrimethanil After Controlled Human Experiments

Pyrimethanil (PYM) is a fungicide used pre- and post-harvest on many crops. It has a low acute toxicity but is of toxicological concern because of its antiandrogenic properties. The aim of the current work was to investigate some metabolism and estimate elimination kinetics of PYM in humans after experimental oral and dermal exposure. A liquid chromatography triple quadrupole mass spectrometry (LC–MS-MS) method was developed and validated for the analysis of PYM and its metabolite 4-hydroxypyrimethanil (OH–PYM) in human urine. The method was applied to analyze urine obtained from two volunteers experimentally exposed to PYM. The elimination of OH–PYM seemed to follow first-order kinetics and a two-phase excretion. After the oral exposure, the elimination half-life of OH–PYM in the rapid phase was 5 and 3 h for the female and male volunteer, respectively. In the slower phase, it was 15 h in both volunteers. After the dermal exposure, the half-life in the rapid phase was 8 h in both volunteers. In the slower phase, it was 30 and 20 h, respectively. About 80% of the oral dose was recovered as urinary OH–PYM in both volunteers. The dermal dose recovered as urinary OH–PYM was 9.4% and 19%, in the female and male volunteer, respectively. OH–PYM was mainly found as a conjugate of sulfonate and glucuronic acid. No free PYM was found. The analytical method showed good within-run, between-run and between-batch precision with a coefficient of variation between 6% and 12%. A limit of detection of 0.1 ng/mL and a limit of quantification of 0.4 ng/mL were achieved for both the analytes. The method was applied to biomonitor PYM exposure in populations in Sweden. OH–PYM was detected in nearly 50% and 96% of samples from the environmentally and occupationally exposed populations, respectively.

Kinetic time courses of lambda-cyhalothrin metabolites after dermal application of Matador EC 120 in volunteers

A controlled kinetic study was conducted in volunteers dermally exposed to the widely used lambda-cyhalothrin pyrethroid pesticide to document the time courses of relevant biomarkers of exposure, in order to better assess biomonitoring data in workers. Matador^® EC120 formulation (120 g/l) was applied on 40 cm² of the forearm at a 0.25 mg/kg dose of lambda-cyhalothrin and left without occlusion or washing for 6 h. The application site was then washed thoroughly with soap and water. The kinetic time courses of cis-3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethylcyclopropane carboxylic acid (CFMP) and 3-phenoxybenzoic acid (3-PBA) metabolites were determined in plasma and urine up to 84 h post-application. Results show that the fraction of lambda-cyhalothrin absorbed in the body was rapidly cleared following dermal contact. According to CFMP and 3-PBA plasma profiles, calculated mean apparent absorption half-lives (t_1/2) were 3 and 7.3 h, respectively, and corresponding mean apparent elimination t_1/2 were 11.2 and 7.6 h. These differences suggest some metabolism at the site-of-entry and storage of metabolites by the dermal route. Toxicokinetic parameters calculated from urinary profiles confirm the values of absorption and elimination rates. Metabolites were almost completely excreted over the 84-h period post-application and, on average, 0.12 and 0.08% of the applied lambda-cyhalothrin dose was recovered in the urine as CFMP and 3-PBA, respectively, indicating a low dermal absorption fraction of this pyrethroid. This study showed the potential use of CFMP and 3-PBA biomarkers for the assessment of dermal exposure to lambda-cyhalothrin pyrethroid.

High-throughput method for the analysis of ethylenethiourea with direct injection of hydrolysed urine using online on-column extraction liquid chromatography and triple quadrupole mass spectrometry

Ethylenethiourea (ETU) is of major toxicological concern, since in experimental animal studies, ETU has shown a large spectrum of adverse effects. High occupational exposure can be found among agricultural workers or during manufacturing of ethylenbisdithiocarbamates (EBDC). For the general public, sources of environmental exposure may be residues of ETU in commercial products, food and beverages. For the determination of ETU in human urine we present a high-throughput online on-column extraction liquid chromatography triple quadrupole mass spectrometry method using direct injection of hydrolysed urine samples. This method is simple, user- and environmentally friendly and all sample preparation is performed in 96-well plates. A labelled ETU internal standard was used for quantification. The method showed a good sensitivity with a limit of quantification (LOQ) of 0.5ng ETU/mL urine and the calibration curve was linear in the range 0.25-200ng ETU/mL urine. The within-run, between-run and between-batch precision was between 6% and 13%. Alkaline hydrolysis considerably increased the levels of ETU indicating a potential conjugate. The method was applied in an experimental dermal exposure study in humans, with sample concentrations ranging from 0.4 to 5.0ng ETU/mL urine. The excretion in urine was 10% of the applied dose. The elimination profile seemed to differ between the two individuals. The results show an estimated half-life of ETU between 34 and 72h. Although the experiment is limited to two individuals, the data provide valuable and new information regarding the toxicokinetics of ETU after dermal exposure.

Preformed biomarkers including dialkylphosphates (DAPs) in produce may confound biomonitoring in pesticide exposure and risk assessment

Low levels of pesticides and their metabolites/degradates occur in produce when pesticides are used in conventional or organic crop protection. Human dietary and nonoccupational urine biomonitoring studies may be confounded by preformed pesticide biomarkers in the diet. The extent of formation of putative urine biomarkers, including malathion specific (MMA, MDA; malathion mono- and diacids), organophosphorus generic (DMP, DMTP, DMDTP; dimethyl-, dimethylthio-, and dimethydithiophosphate), pyrethroid generic (3-PBA; 3-phenoxybenzoic acid), and captan-specific metabolites (THPI; tetrahydrophthalimide), was measured in produce samples containing the parent pesticide. Every produce sample of 19 types of fruits and vegetables contained biomarkers of potential human exposure. A total of 134 of 157 (85%) samples contained more molar equivalent biomarkers than parent pesticide. Malathion and fenpropathrin were sprayed (1 lb/A), and the time-dependent formation of pesticide biomarkers in strawberries was investigated under field conditions typical of commercial production in California. Malathion and fenpropathrin residues were always below established residue tolerances. Malathion, MMA, and MDA dissipated, while DMP, DMTP, and DMDTP increased, during a 20 day study period following the preharvest interval. The mole ratios of biomarkers/(malathion + malaoxon) were always greater than 1 and increased from day 4 to day 23 postapplication. Fenpropathrin and 3-PBA also dissipated in strawberries during each monitoring period. The mole ratios of 3-PBA/fenpropathrin were always less than 1 and decreased from day 4 to day 14. The absorption of pesticide biomarkers in produce and excretion in urine would falsely indicate consumer pesticide exposure if used to reconstruct dose for risk characterization.