Analysis of six pyrethroid insecticide metabolites in cord serum using a novel gas chromatography-ion trap mass spectrometry method

A Novel Biomonitoring Method to Detect Pyrethroid Metabolites in Saliva of Occupationally Exposed Workers as a Tool for Risk Assessment

Saliva is valuable in exposure assessment having been successfully used for drug and environmental pollutant detection, providing a surrogate measure of plasma concentrations. Pyrethroid biomarkers have not previously been assessed in saliva, although are prime candidates for saliva detection. This study's objectives were to 1) develop a liquid-liquid extraction (LLE) method to quantify six pyrethroid metabolites using gas chromatography/ion trap mass spectrometry and 2) assess its application for an occupationally exposed population. Several solvents and mixing protocols were optimized for metabolite recovery. The optimized method was applied to a population of pest control operators (PCOs) and compared against a urine sample before and after a full workday using pesticides. A questionnaire collected demographic information, occupational history, and occupational and non-occupational exposure data. LLE recoveries ranged from 85% - 104% and 72% - 88% for toluene and dichloromethane using slow mixing, and 49% - 103% for methyl tert-butyl ether by fast mixing. Urinary 3-Phenoxybenzoic acid (3PBA) was detected in 100% of pre- and post-work urine samples. Three PCOs had increased urinary pyrethroid metabolite levels post-work. Salivary 3PBA was present below detection limit in two of the three PCO's post-work saliva samples, demonstrating that salivary 3PBA could be measured in PCOs after the workday. This study presents preliminary findings of a potential, low-risk biomonitoring technique that may be utilized in future occupational pyrethroid exposure and risk assessment research.

Gestational Exposure to Cyfluthrin through Endoplasmic Reticulum (ER) Stress-Mediated PERK Signaling Pathway Impairs Placental Development

Cyfluthrin, a typical type II pyrethroid pesticide, is widely used in house hygiene and agricultural pest control. Several epidemiological investigations have found that maternal pyrethroid exposure is connected to adverse pregnancy outcomes. However, the underlying mechanisms remain to be elucidated. Thus, we evaluated the effect of cyfluthrin exposure during pregnancy on placenta development in vivo. In the current study, Pregnant SD rats were randomly divided into four groups and administered 6.25, 12.5, and 25 mg/kg body weight cyfluthrin or an equivalent volume of corn oil by gavage from GD0 to GD19. The results have shown that gestational exposure to cyfluthrin exerted no effect on the fetal birth defect, survival to PND4, or fetal resorption and death. However, live fetuses and implantation sites significantly decreased in the high-dose cyfluthrin-treated group. Moreover, a significant reduction in placenta weight and diameter was observed in rats. Correspondingly, the fetal weight and crown-rump length from dams exposed to cyfluthrin were reduced. Cyfluthrin-treat groups, the total area of the placenta, spongiotrophoblast area, and labyrinth area had abnormal changes. Meanwhile, the area of blood sinusoid and CD34-positive blood vessel numbers in the placenta were considerably reduced, as well as abnormal expression of placental pro-angiogenic and anti-angiogenic factors in dams exposed to cyfluthrin. Further observation by transmission electron microscopy revealed significant changes in the ultrastructure of the medium-dose and high-dose groups. Additional experiments showed gestational exposure to cyfluthrin inhibited proliferation and induced apoptosis of placentas, as decreased PCNA-positive cells and increased TUNEL-positive cells. Furthermore, western blot and qPCR analysis revealed that gestational exposure to medium-dose and high-dose cyfluthrin increased the expression of GRP78, and three downstream mRNA and proteins (p-eIF2α, ATF4, and CHOP) of the PERK signaling, indicating that endoplasmic reticulum (ER) stress-mediated PERK/eIF2α/ATF4/CHOP signaling pathway in rat placentas was activated. Our study demonstrated that gestational exposure to cyfluthrin leads to placental developmental disorder, which might be associated with ER stress-mediated PERK signaling pathway.

Maternal and fetal tissue distribution of α-cypermethrin and permethrin in pregnant CD-1 mice

Pyrethroid insecticides are widely used throughout agriculture and household products. Recent studies suggest that prenatal exposure to these insecticides may adversely affect fetal development; however, little is known about the distribution of these chemicals in pregnant animals. The present study aimed to address this gap in knowledge by investigating the distribution of two commonly used pyrethroid insecticides, permethrin and α-cypermethrin, in maternal and fetal tissues of pregnant CD-1 mice. Dams were dosed from gestational days 6 to 16 via oral gavage with permethrin (1.5, 15, and 50 mg/kg), α-cypermethrin (0.3, 3, and 10 mg/kg), or corn oil vehicle. Pyrethroid levels were determined in gestational day 16 tissues collected 90 min after the final dose was administered. Across maternal tissues, levels of both pyrethroids were the highest in maternal ovaries, followed by liver and brain, respectively. In addition, levels of both pyrethroids in maternal tissues and placenta were significantly higher than those in the fetal body and amniotic fluid, suggesting that these compounds may exhibit low transfer across the mouse placenta. While additional toxicokinetic studies are needed to verify the time course of pyrethroids in the fetal compartment, these findings support investigation into indirect modes of action relevant to the effects of pyrethroids on mammalian fetal development.

A narrative review of converging evidence addressing developmental toxicity of pyrethroid insecticides

Pyrethroid insecticides are broadly used in agriculture and household products throughout the world. Exposure to this class of insecticides is widespread, and while generally believed to be safe for use, there is increasing concern regarding their effects on neurodevelopment. Due to the critical roles that molecular targets of pyrethroids play in the regulation of neurodevelopment, particular focus has been placed on evaluating the effects of in utero and childhood pyrethroid exposure on child cognition and behavior. As such, this narrative review synthesizes an assessment of converging study types; we review reports of neonatal pyrethroid levels together with current epidemiological literature that convergently address the risk for developmental toxicity linked to exposure to pyrethroid insecticides. We first address studies that assess the degree of direct fetal exposure to pyrethroids in utero through measurements in cord blood, meconium, and amniotic fluid. We then focus on the links between prenatal exposure to these insecticides and child neurodevelopment, fetal growth, and other adverse birth outcomes. Furthermore, we assess the effects of postnatal exposure on child neurodevelopment through a review of the data on pediatric exposures and child cognitive and behavioral outcomes. Study quality was evaluated individually, and the weight of evidence was assessed broadly to characterize these effects. Overall, while definitive conclusions cannot be reached from the currently available literature, the available data suggest that the potential links between pyrethroid exposure and child neurodevelopmental effects deserve further investigation.