Pyrethroid Insecticides: Advances and Challenges in Biomonitoring

Respiratory system: Highly exposed yet under-reported organ in pyrethrin and pyrethroid toxicity

Pyrethrin and pyrethroid are a relatively new class of pesticides with potent insecticidal properties. Pyrethrins are naturally occurring pesticides obtained from the Chrysanthemum cinerariaefolium flower, while pyrethroids are their synthetic derivatives. They are widely used as the insecticides of choice in agriculture, veterinary medicine, public health programs, and household activities. Pyrethrin, being a broad-spectrum insecticide kills a wide range of pests, while pyrethroids last longer in the environment owing to low susceptibility to sunlight, and greater stability and efficacy than parent molecules. Humans can be exposed through inhalation, ingestion, and dermal routes. Indoor usage of an insecticide poses a serious risk to human health, especially to women, children, and stay-at-home people. Although pyrethrin and pyrethroid are generally considered safe, sustained skin or inhalation exposure or direct contact with open wounds results in higher toxicity to mammals. There is a paucity of data on the impact of pyrethrin and pyrethroid on overall pulmonary health. The respiratory system, from the nose, nasal passages, airways, and bronchi to the pulmonary alveoli, is vulnerable to environmental contaminants such as pesticides because of its anatomical location as well as being a highly blood profused organ. Under and over-functioning of the respiratory system triggers diverse pathologies such as serious infections, allergies, asthma, metastatic malignancies, and auto-immune conditions. While the association between workplace-related pesticide exposures and respiratory diseases and symptoms is well documented, it is important to understand the adverse health impact of pyrethrin and pyrethroid on the general population for awareness and also for better regulation and implementation of the law.

An in silico investigation of the toxicological effects and biological activities of 3-phenoxybenzoic acid and its metabolite products

We aimed to elucidate the toxic effects and biological activities of 3-phenoxybenzoic acid (3PBA) and its metabolite products.

Numerous in silico methods were used to identify the toxic effects and biological activities of 3PBA, including PASS online, molecular docking, ADMETlab 2.0, ADMESWISS, MetaTox, and molecular dynamic simulation.

Ten metabolite products were identified via Phase II reactions (O-glucuronidation, O-sulfation, and methylation).

All of the investigated compounds were followed by Lipinski's rule, indicating that they were stimulants or inducers of hazardous processes.

Because of their high gastrointestinal absorption and ability to reach the blood-brain barrier, the studied compounds' physicochemical and pharmacokinetic properties matched existing evidence of harmful effects, including haematemesis, reproductive dysfunction, allergic dermatitis, toxic respiration, and neurotoxicity.

The studied compounds have been linked to the apoptotic pathway, the reproductivity system, neuroendocrine disruptors, phospholipid-translocating ATPase inhibitors, and JAK2 expression.

An O-glucuronidation metabolite product demonstrated higher binding affinity and interaction with CYP2C9, CYP3A4, caspase 3, and caspase 8 than 3PBA and other metabolite products, whereas metabolite products from methylation were predominant and more toxic.

Our in silico findings partly meet the 3Rs principle by minimizing animal testing before more study is needed to identify the detrimental effects of 3PBA on other organs (liver, kidneys).

Future research directions may involve experimental validation of in silico predictions, elucidation of molecular mechanisms, and exploration of therapeutic interventions.

These findings contribute to our understanding of the toxicological profile of 3PBA and its metabolites, which has implications for risk assessment and regulatory decisions.

Silicone wristbands as personal passive sampling devices: Current knowledge, recommendations for use, and future directions

Personal chemical exposure assessment is necessary to determine the frequency and magnitude of individual chemical exposures, especially since chemicals present in everyday environments may lead to adverse health outcomes. In the last decade, silicone wristbands have emerged as a new chemical exposure assessment tool and have since been utilized for assessing personal exposure to a wide range of chemicals in a variety of populations. Silicone wristbands can be powerful tools for quantifying personal exposure to chemical mixtures in a single sample, associating exposure with health outcomes, and potentially overcoming some of the challenges associated with quantifying the chemical exposome. However, as their popularity grows, it is crucial that they are used in the appropriate context and within the limits of the technology. This review serves as a guide for researchers interested in utilizing silicone wristbands as a personal exposure assessment tool. Along with briefly discussing the passive sampling theory behind silicone wristbands, this review performs an in-depth comparison of wristbands to other common exposure assessment tools, including biomarkers of exposure measured in biospecimens, and evaluates their utility in exposure assessments and epidemiological studies. Finally, this review includes recommendations for utilizing silicone wristbands to evaluate personal chemical exposure and provides suggestions on what research is needed to recognize silicone wristbands as a premier chemical exposure assessment tool.

Comparative Assessment of Pesticide Exposures in Domestic Dogs and Their Owners Using Silicone Passive Samplers and Biomonitoring

Pesticides are used extensively in residential settings for lawn maintenance and in homes to control household pests including application directly on pets to deter fleas and ticks. Pesticides are commonly detected in the home environment where people and pets can be subject to chronic exposure. Due to increased interest in using companion animals as sentinels for human environmental health studies, we conducted a comparative pesticide exposure assessment in 30 people and their pet dogs to determine how well silicone wristbands and silicone dog tags can predict urinary pesticide biomarkers of exposure. Using targeted gas chromatography-mass spectrometry analyses, we quantified eight pesticides in silicone samplers and used a suspect screening approach for additional pesticides. Urine samples were analyzed for 15 pesticide metabolite biomarkers. Several pesticides were detected in >70% of silicone samplers including permethrin, N,N-diethyl-meta-toluamide (DEET), and chlorpyrifos. Significant and positive correlations were observed between silicone sampler levels of permethrin and DEET with their corresponding urinary metabolites (r_s = 0.50-0.96, p < 0.05) in both species. Significantly higher levels of fipronil were observed in silicone samplers from participants who reported using flea and tick products containing fipronil on their dog. This study suggests that people and their dogs have similar pesticide exposures in a home environment.

Concentrations of urinary biomarkers and predictors of exposure to pyrethroid insecticides in young, Polish, urban-dwelling men

Pyrethroid insecticides are a class of pesticides with multiple agricultural and residential applications. However, widespread use of these chemicals may pose a threat to human health. Biomarkers of pyrethroid exposure are frequently detected in populations around the world, but some groups may be underrepresented. Moreover, there is an ongoing debate on factors contributing to pyrethroid burden in humans. To address these problems, we measured urinary biomarkers of pyrethroid exposure in urine samples from 306 young men living in urban area of Łódź, Poland, and gathered questionnaire data to identify predictors of exposure. Limit of detection (LOD) of gas chromatography-mass spectrometry (GC-MS) method was 0.1 ng/mL for all quantified pyrethroid metabolites, namely cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DCCA), trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (trans-DCCA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), and 3-phenoxybenzoic acid (3-PBA). Detection rate ranged from 32% (cis-DBCA) to 76% (trans-DCCA). Concentrations of urinary biomarkers in studied sample were in lower range of these observed in similar studies, with unadjusted geometric means (GMs) of most prevalent biomarkers, trans-DCCA and 3-PBA, equal to 0.268 and 0.228 ng/mL, respectively. As for questionnaire data, the statistical analysis revealed that non-dietary factors, especially dog ownership and pesticide use on household pets, contribute significantly to urinary trans-DCCA and 3-PBA concentrations (p ≤ 0.009). Moreover, a few dietary sources of exposure were identified, such as seeds and nuts consumption for 3-PBA (p < 0.001) and vegetable juice intake for trans-DCCA (p = 0.015). Multivariate analyses further highlighted the importance of non-dietary factors in pyrethroid exposure. Compared to other works, our results confirm widespread exposure to pyrethroids observed in other studies and stress the role of residential pyrethroid use in pyrethroid burden in humans.

Development of nanobody-based flow-through dot ELISA and lateral-flow immunoassay for rapid detection of 3-phenoxybenzoic acid

As a major metabolite of pyrethroid pesticides, 3-phenoxybenzoic acid (3-PBA) can be an indicator of health risk and human exposure assessment. Based on nanobodies (Nbs), we have developed a rapid flow-through dot enzyme linked immunosorbent assay (dot ELISA) and gold nanoparticle (GNP) lateral-flow immunoassay for detecting 3-PBA. The limit of detection (LOD) values for detecting 3-PBA by flow-through dot ELISA and GNP lateral-flow immunoassay were 0.01 ng mL-1 and 0.1 ng mL-1, respectively. The samples (urine and lake water) with and without 3-PBA were detected by both nanobody-based flow-through dot ELISA and GNP lateral-flow immunoassay, as well as liquid chromatography-mass spectrometry (LC-MS) for validation. There was good consistency between the results of the immunoassays. This demonstrated that the two developed nanobody-based immunoassays are suitable for rapid detection of 3-PBA.

Synthetic pyrethroids common metabolite 3-phenoxybenzoic acid induces caspase-3 and Bcl-2 mediated apoptosis in human hepatocyte cells

Synthetic pyrethroids are a group of insecticides frequently used in public health and agriculture, and 3-PBA is a common metabolite of them. Although the liver is the primary organ responsible for metabolizing many compounds including pesticides, to the authors' knowledge there have been no studies on the direct hepatotoxic effects of 3-PBA. Therefore, this study aimed to investigate the possible hepatotoxic effects of 3-PBA on a Human Hepatoma Cell Line (HepG2) and the underlying apoptotic mechanisms. Firstly, an LC₅₀ of 1041.242 µM was calculated for 3-PBA by using the WST-1 test with concentrations ranging between 1 µM and 10 mM. Following that, the HepG2 cells in the experimental group were exposed to 3 different concentrations of 3-PBA (1/5 LC₅₀, 1/10 LC₅₀ and 1/20 LC₅₀) for 24 hours. The apoptotic mechanism was evaluated by using flow cytometry, and immunofluorescence assays for Caspase 3 and Bcl-2. In the flow cytometry assay, the total number of apoptotic cells increased in a dose dependent manner (p < 0.05). In the immunofluorescence assay, the Caspase 3 protein showed strong immunoreactivity in the experimental groups, while the reaction to the Bcl-2 protein was minimal. These results demonstrated that 3-PBA has a significant hepatotoxic effect on HepG2 cells and induces apoptosis via the regulation of Caspase-3 and Bcl-2. Furthermore, our results could further the understanding of the fundamental molecular mechanisms of 3-PBA hepatotoxicity. More studies are needed to determine the effects of long-term exposure to 3-PBA and also the molecular mechanisms underlying hepatotoxicity.

Influence of bifentrin, a pyrethriod pesticide, on human colorectal HCT-116 cells attributed to alterations in oxidative stress involving mitochondrial apoptotic processes

The widespread use of pesticides is beneficial for food production; however, there are numerous adverse consequences reported in the ecosystem and humans associated with exposure to these contaminants. The pyrethriod bifenthrin (BIF) is utilized for (1) maintenance, growth, and storage of agricultural products; (2) control of internal and external parasites of farm animals; and (3) eradication of insects threatening public health. Numerous data are available regarding environmental and ecological impact of pyrethriods on the central and peripheral nervous systems; however few studies focused on non-target tissues especially in humans. Therefore, the aim of this investigation was to determine the potential cytotoxic effects of BIF on a non-target tissue using human colorectal HCT-116 cells as a model. Data demonstrated that BIF reduced cell viability and disrupted mitochondrial functions which were accompanied by increased reactive oxygen species (ROS) levels indicating the presence of oxidative stress. BIF produced a significant elevation in levels of malondialdehyde (MDA) supporting the role of oxidative stress in pesticide-mediated toxicity. Concomitantly, a fall of mitochondrial transmembrane potential (Δψ), consequently producing perturbation of fluidity as well as excitability of cellular membranes was noted. Our results also indicated that BIF induced a rise in DNA damage as evidenced by the comet assay. An increase in mitogen-activated protein kinases (MAPKs), JNK (N-terminal Kinase), p38, and ERK (extracellular-signal-regulated kinase) suggested an apoptotic effect. Data thus indicated that BIF-induced cytotoxicity in human colorectal HCT-116 cells was associated with oxidative stress, mitochondrial dysfunction, and apoptosis.

Relationship between Organophosphate and Pyrethroid Insecticides in Blood and Their Metabolites in Urine: A Pilot Study

We conducted a pilot study to examine the relationship between organophosphate (OP) and pyrethroid (PYR) insecticides in blood and their metabolites in urine. A total of 30 pregnant women were enrolled in the study, and blood and urine was sampled from each subject during a regular clinic visit. Two OP and nine PYR insecticides were selected for blood sample analysis, while six OP and five PYR metabolites were analyzed for urine specimens. Both types of samples were processed and analyzed on gas chromatography-mass spectrometry. For OPs in blood, chlorpyrifos had a higher mean concentration (73.33 µg/L) than terbufos. For PYRs in blood, cypermethrin and imiprothrin were the most frequently detected species with the highest mean concentrations (151.25 and 141.25 µg/L). The concentrations of PYRs appeared to be higher than that of OPs, and the most frequently detected PYRs were commonly used in domestic products, suggesting that the exposure could mostly originate from use of domestic insecticides. The correlation between insecticides in blood and their metabolites in urine was significantly high (r = 0.795 for OPs and 0.882 for PYRs, p < 0.001), indicating routine exposure at a steady state. Residents should be cautious with domestic use of insecticide products to lower their exposure.

Pesticide interactions and risks of sperm chromosomal abnormalities

Disentangling the separate and synergistic effects of chemicals poses methodological challenges for accurate exposure assessment and for investigating epidemiologically how chemicals affect reproduction. We investigated combined exposures to ubiquitous contemporary use pesticides, specifically organophosphates (OP) and pyrethroids (PYR), and their association with germ cell abnormalities among adult men. Fluorescence in situ hybridization was used to determine disomy in sperm nuclei and urine was analyzed for concentrations of PYR metabolites (3-phenoxybenzoic acid; 3PBA) and OP dialkyl phosphate (DAP) metabolites. Incidence rate ratios using Poisson models were estimated for each disomy type by exposure quartile of DAP metabolites and 3PBA, controlling for confounders. The shape of the associations between PYRs, OPs and disomy were frequently nonmonotonic. There were consistent interactions between OP and PYR metabolite concentrations and the risk for sperm abnormalities. Taking both chemicals into account simultaneously resulted in quantitatively different associations than what was reported previously for OPs and PYRs separately, demonstrating the importance of modeling multiple concentrations simultaneously. Methods investigating interactions using Poisson models are needed to better quantify chemical interactions and their effects on count-based health outcomes, the importance of which was shown here for germ cell abnormalities.

Pesticide exposures and respiratory health in general populations

Human exposures to pesticides can occur in the workplace, in the household and through the ambient environment. While several articles have reviewed the impact of pesticide exposures on human respiratory health in occupational settings, to the best of our knowledge, this article is the first one to review published studies on the association between pesticide exposures and human respiratory health in the general populations. In this article, we critically reviewed evidences up to date studying the associations between non-occupational pesticide exposures and respiratory health in general populations. This article also highlighted questions arising from these studies, including our recent analyses using the data from the Canadian Health Measures Survey (CHMS), for future research. We found few studies have addressed the impact of environmental pesticide exposures on respiratory health, especially on lung function, in general populations. In the studies using the data from CHMS Cycle 1, exposures to OP insecticides, pyrethroid insecticides, and the organochlorine pesticide DDT were associated with impaired lung function in the Canadian general population, but no significant associations were observed for the herbicide 2,4-D. Future research should focus on the potential age-specific and pesticide-specific effect on respiratory health in the general population, and repeated longitudinal study design is critical for assessing the temporal variations in pesticide exposures. Research findings from current studies of non-occupational pesticide exposures and their health impact in general population will help to improve the role of regulatory policies in mitigating pesticide-related public health problems, and thereafter providing greater benefit to the general population.

Urinary concentrations of pyrethroid metabolites and its association with lung function in a Canadian general population

OBJECTIVES

While there is increasing concern about the health impact of pyrethroid insecticides, little is known about their effect on lung function. In this cross-sectional study, urinary concentrations of pyrethroid (PYR) metabolites and their associations with lung function were examined among a Canadian general population using data from the Canadian Health Measures Survey (CHMS).

METHODS

Urinary concentrations of 5 pyrethroid metabolites (3-PBA, 4-F-3-PBA, cis-DCCA, trans-DCCA and cis-DBCA) were available for 5436 CHMS participants aged 6-79 years. Lung function parameters considered were forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio and forced expiratory flow between 25% and 75% of FVC. Multiple linear regression analyses were used to examine associations between PYR concentrations and lung function in children (6-11 years), adolescents (12-19 years) and adults (20-79 years), respectively.

RESULTS

Almost all CHMS participants (99.8%) had PYR metabolites detectable in urine. In multiple linear regression analyses, 1 unit increase in log transformed urinary concentration (nmol/g creatinine) of total pyrethorid metabolites (ΣPYR) was associated with a 17.4 mL reduction in FEV1 (p=0.045) in children, a 37.1 mL reduction in FVC (p=0.05) in adolescents and a 0.3% (p=0.01) increase in FEV1/FVC ratio in adults.

CONCLUSIONS

These results show evidence of widespread exposures to pyrethroid insecticides among the Canadian general population. Pyrethroid exposures were associated with lower FEV1 in children, lower FVC in adolescents and relatively higher FEV1/FVC ratio in adults. Further research is necessary to confirm the potential effect of pyrethroid insecticides on lung function reported in this study.

d-Phenothrin-induced oxidative DNA damage in rat liver and kidney determined by HPLC-ECD/DAD

The objective of this study was to assess the risk of genotoxicity of d-phenothrin by measuring the oxidative stress it causes in rat liver and kidney. The level of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG)/10(6) 2'-deoxyguanosine (dG) was measured by using high performance liquid chromatography (HPLC) with a diode array (DAD) and an electrochemical detector (ECD). Sixty male Wistar albino rats were randomly divided into five experimental groups and one control group of 10 rats/group. d-phenothrin was administered intraperitoneally (IP) to the five experimental groups at 25 mg/kg (Group I), 50 mg/kg (Group II), 66.7 mg/kg (Group III), 100 mg/kg (Group IV), and 200 mg/kg (Group V) for 14 consecutive days, and the control group received only the vehicle, dimethyl sulfoxide (DMSO). DNA from samples frozen in liquid nitrogen was isolated with a DNA isolation kit. Following digestion with nuclease P1 and alkaline phosphatase (ALP), hydrolyzed DNA was subjected to HPLC. The dG and 8-oxodG levels were analyzed with a DAD and ECD, respectively. In the experimental groups, the mean 8-oxodG/10(6) dG levels were 48.15 ± 7.43, 68.92 ± 20.66, 82.07 ± 14.15, 85.08 ± 28.50, and 89.14 ± 21.73 in livers and 39.06 ± 7.63, 59.69 ± 14.22, 61.13 ± 17.46, 65.13 ± 23.40, and 72.66 ± 19.04 in kidneys of Groups I, II, III, IV, and V, respectively. The mean 8-oxodG/10(6) dG levels in the control groups were 44.96 ± 12.66 for the liver and 39.07 ± 4.80 for the kidney. A statistically significant (p < 0.05), dose-dependent increase in oxidative DNA damage was observed in both organs of animals exposed to d-phenothrin when compared to controls. Furthermore, the liver showed a significantly higher level of oxidative DNA damage than the kidney (p < 0.01). In conclusion, d-phenothrin administered to rats intraperitoneally for 14 consecutive days generated free radical species in a dose-dependent manner and caused oxidative DNA damage in the liver and kidney.

A permethrin/allethrin mixture induces genotoxicity and cytotoxicity in human peripheral blood lymphocytes

Two pyrethroids, permethrin and allethrin, are often combined for large-scale use in public health programs to control vector-borne diseases. In this study, the genotoxic potential of a commercial formulation of permethrin and allethrin was examined using cultured human peripheral blood lymphocytes (PBL). Genotoxicity was evaluated using the cytokinesis-block micronucleus cytome (CBMN cyt) assay by measuring the frequency of micronuclei (MN), nuclear division index (NDI), formation of nucleoplasmic bridges (NPB) and nuclear buds (NBUD), as well as apoptotic and necrotic cells. Human PBL were treated with different concentrations of a permethrin/allethrin mixture (1/0.01, 5/0.07, and 10/0.14 μg/ml) for 24 or 36 h. The highest concentration (10/0.14 μg/ml) of permethrin/allethrin mixture significantly increased MN frequency and percent apoptotic cells after incubations for 24 or 36 h. The NDI was markedly decreased in response to treatment with 5/0.07 or 10/0.14 μg/ml permethrin/allethrin for both 24 and 36 h. Exposure to the permethrin/allethrin mixture did not significantly alter formation of NBUD, NPB, or percent necrotic cells. The MN frequency was significantly correlated with the number of apoptotic and necrotic cells but inversely correlated with NDI. Data demonstrated that a mixture of permethrin and allethrin induced concentration- and time-dependent cytotoxic and genotoxic damage to human PBL in vitro.

Within- and between-child variation in repeated urinary pesticide metabolite measurements over a 1-year period

BACKGROUND

Children are exposed to pesticides from many sources and routes, including dietary and incidental ingestion, dermal absorption, and inhalation. Linking health outcomes to these exposures using urinary metabolites requires understanding temporal variability within subjects to avoid exposure misclassification.

OBJECTIVES

We characterized the within- and between-child variability of urinary organophosphorus and pyrethroid metabolites in 23 participants of the Children's Pesticide Exposure Study-Washington over 1 year and examined the ability of one to four spot urine samples to categorize mean exposures.

METHODS

Each child provided urine samples twice daily over 7- to 16-day sessions in four seasons in 2003 and 2004. Samples were analyzed for five pyrethroid and five organophosphorus (OP) metabolites. After adjusting for specific gravity, we used a customized maximum likelihood estimation linear mixed-effects model that accounted for values below the limit of detection to calculate intraclass correlation coefficients (ICC) and conducted surrogate category analyses.

RESULTS

Within-child variability was 2-11 times greater than between-child variability. When restricted to samples collected during a single season, ICCs were higher in the fall, winter, and spring than in summer for OPs, and higher in summer and winter for pyrethroids, indicating an increase in between-person variability relative to within-person variability during these seasons. Surrogate category analyses demonstrated that a single spot urine sample did not categorize metabolite concentrations well, and that four or more samples would be needed to categorize children into quartiles consistently.

CONCLUSIONS

Urinary biomarkers of these short half-life pesticides exhibited substantial within-person variability in children observed over four seasons. Researchers investigating pesticides and health outcomes in children may need repeated biomarker measurements to derive accurate estimates of exposure and relative risks.

Evaluation of changes in monoamine levels and apoptosis induced by cyfluthrin in rats

The aim of this study was to evaluate monoamine and mitochondrial cytochrome c levels and lipid peroxidation in adult male rats treated with cyfluthrin (14 mg kg⁻¹dose; approximately 1/10 of the LD₅₀value) for 14 days. This study also examined cyfluthrin induced-apoptosisviathe signaling proteins Bcl-2, caspase-9 and caspase-3, and possible anti-apoptotic effects of Alfa-basic crystallin.

Human biological monitoring of suspected endocrine-disrupting compounds

Endocrine-disrupting compounds are exogenous agents that interfere with the natural hormones of the body. Human biological monitoring is a powerful method for monitoring exposure to endocrine disrupting compounds. In this review, we describe human biological monitoring systems for different groups of endocrine disrupting compounds, polychlorinated biphenyls, brominated flame retardants, phthalates, alkylphenols, pesticides, metals, perfluronated compounds, parabens, ultraviolet filters, and organic solvents. The aspects discussed are origin to exposure, metabolism, matrices to analyse, analytical determination methods, determinants, and time trends.

Environmental exposure to pyrethroids and sperm sex chromosome disomy: a cross-sectional study

BACKGROUND

The role of environmental pesticide exposures, such as pyrethroids, and their relationship to sperm abnormalities are not well understood. This study investigated whether environmental exposure to pyrethroids was associated with altered frequency of sperm sex chromosome disomy in adult men.

METHODS

A sample of 75 subjects recruited through a Massachusetts infertility clinic provided urine and semen samples. Individual exposures were measured as urinary concentrations of three pyrethroid metabolites ((3-phenoxybenzoic acid (3PBA), cis- and trans- 3-(2,2-Dichlorovinyl)-1-methylcyclopropane-1,2-dicarboxylic acid (CDCCA and TDCCA)). Multiprobe fluorescence in situ hybridization for chromosomes X, Y, and 18 was used to determine XX, YY, XY, 1818, and total sex chromosome disomy in sperm nuclei. Poisson regression analysis was used to examine the association between aneuploidy rates and pyrethroid metabolites while adjusting for covariates.

RESULTS

Between 25-56% of the sample were above the limit of detection (LOD) for the pyrethroid metabolites. All sex chromosome disomies were increased by 7-30% when comparing men with CDCCA and TDCCA levels above the LOD to those below the LOD. For 3PBA, compared to those below the LOD, those above the LOD had YY18 disomy rates 1.28 times higher (95% CI: 1.15, 1.42) whereas a reduced rate was seen for XY18 and total disomy (IRR = 0.82; 95% CI: 0.77, 0.87; IRR = 0.93; 95% CI: 0.87-0.97), and no association was seen for XX18 and 1818.

CONCLUSIONS

Our findings suggest that urinary concentrations of CDCCA and TDCCA above the LOD were associated with increased rates of aneuploidy. However the findings for 3BPA were not consistent. This is the first study to examine these relationships, and replication of our findings is needed before the association between pyrethroid metabolites and aneuploidy can be fully defined.

Environmental and occupational pesticide exposure and human sperm parameters: a systematic review

Of continuing concern are the associations between environmental or occupational exposures to pesticides and semen quality parameters. Prior research has indicated that there may be associations between exposure to pesticides of a variety of classes and decreased sperm health. The intent of this review was to summarize the most recent evidence related to pesticide exposures and commonly used semen quality parameters, including concentration, motility and morphology. The recent literature was searched for studies published between January 2007 and August 2012 that focused on environmental or occupational pesticide exposures. Included in the review are 17 studies, 15 of which reported significant associations between exposure to pesticides and semen quality indicators. Two studies also investigated the roles genetic polymorphisms may play in the strength or directions of these associations. Specific pesticides targeted for study included dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexane (HCH), and abamectin. Pyrethroids and organophosphates were analyzed as classes of pesticides rather than as individual compounds, primarily due to the limitations of exposure assessment techniques. Overall, a majority of the studies reported significant associations between pesticide exposure and sperm parameters. A decrease in sperm concentration was the most commonly reported finding among all of the pesticide classes investigated. Decreased motility was also associated with exposures to each of the pesticide classes, although these findings were less frequent across studies. An association between pesticide exposure and sperm morphology was less clear, with only two studies reporting an association. The evidence presented in this review continues to support the hypothesis that exposures to pesticides at environmentally or occupationally relevant levels may be associated with decreased sperm health. Future work in this area should focus on associations between specific pesticides or metabolic products and sperm quality parameters. Analysis of effects of varying genetic characteristics, especially in genes related to pesticide metabolism, also needs further attention.

Critical consideration of the multiplicity of experimental and organismic determinants of pyrethroid neurotoxicity: a proof of concept

Pyrethroids (PYR) are pesticides with high insecticidal activity that may disrupt neuronal excitability in target and nontarget species. The accumulated evidence consistently showed that this neurophysiologic action is followed by alterations in motor, sensorimotor, neuromuscular, and thermoregulatory responses. Nevertheless, there are some equivocal results regarding the potency of PYR in lab animals. The estimation of potency is an important step in pesticide chemical risk assessment. In order to identify the variables influencing neurobehavioral findings across PYR studies, evidence on experimental and organismic determinants of acute PYR-induced neurotoxicity was reviewed in rodents. A comprehensive analysis of these studies was conducted focusing on test material and dosing conditions, testing conditions, animal models, and other determinants such as testing room temperature. Variations in the severity of the neurotoxicity, under lab-controlled conditions, was explained based upon factors including influence of animal species and age, test material features such as chemical structure and stereochemistry, and dosing conditions such as vehicle, route of exposure, and dose volume. If not controlled, the interplay of these factors may lead to large variance in potency estimation. This review examined the scope of acute toxicological data required to determine the safety of pesticide products, and factors and covariates that need to be controlled in order to ensure that predictivity and precaution are balanced in a risk assessment process within a reasonable time-frame, using acute PYR-induced neurotoxicity in rodents as an exemplar.

Surface functionalization of silver nanoparticles: novel applications for insect vector control

Every day, people and animals contract debilitating and life threatening diseases due to bites from infected flies, ticks, and mosquitoes. The current methods utilized to fight against these diseases are only partially effective or safe for humans and animals. When it comes to insect vector control, a conceptual paradigm shift is urgently needed. This work proposes a novel synthetic scheme to produce a nanoparticle-pesticide core-shell conjugate to be used as an active agent against arthropod vectors, such as mosquitoes. As a proof of concept, we conjugated nanosilver to the pyrethroid pesticide deltamethrin. First, electron microscopy and Fourier transform infrared spectroscopy verified the presence of a 15 nm nanosilver core surrounded by deltamethrin. Second, when the conjugate was exposed to mosquitoes for a 24 h bioassay, mortality was observed at 9 × 10(-4) M. Silver was detected in the hemolymph of mosquitoes exposed to the conjugate. We concluded that the newly developed nanoconjugate did not inactivate the primary function of the pesticide and was effective in killing mosquitoes at low concentrations. These results demonstrate the potential to use nanoparticle surfaces to kill insects, specifically vectors of human pathogens.

Ecotoxicology of organofluorous compounds

Organofluorous compounds have been developed for myriad purposes in a variety of fields, including manufacturing, industry, agriculture, and medicine. The widespread use and application of these compounds has led to increasing concern about their potential ecological toxicity, particularly because of the stability of the C-F bond, which can result in chemical persistence in the environment. This chapter reviews the chemical properties and ecotoxicology of four groups of organofluorous compounds: fluorinated refrigerants and propellants, per- and polyfluorinated compounds (PFCs), fluorinated pesticides, and fluoroquinolone antibiotics. These groups vary in their environmental fate and partitioning, but each raises concern in terms of ecological risk on both the regional and global scale, particularly those compounds with long environmental half-lives. Further research on the occurrence and toxicities of many of these compounds is needed for a more comprehensive understanding of their ecological effects.

Long term exposure to cypermethrin induces nigrostriatal dopaminergic neurodegeneration in adult rats: postnatal exposure enhances the susceptibility during adulthood

The study aimed to investigate the effects of cypermethrin on biochemical, histopathological, and motor behavioral indices of the nigrostriatal dopaminergic system in adult rats treated with or without cypermethrin (1/10 adult dose) during postnatal days 5-19. Spontaneous locomotor activity (SLA) and rotarod tests were performed to assess motor behavior. Levels of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum, and tyrosine hydroxylase (TH) immunoreactivity and 4',6-diamidino-2-phenylindole (DAPI)/Fluoro-Jade B staining in the substantia nigra were measured to assess dopaminergic neurodegeneration. Postnatal treated animals did not exhibit significant changes in any measured parameters. The significant reduction in the time of stay on rotarod, spontaneous locomotor activity, dopamine, 3,4-dihydroxyphenylacetic acid, and tyrosine hydroxylase immunoreactivity while an increase in homovanillic acid level and Fluoro-Jade B-positive cells were observed in cypermethrin treated adult rats. These changes were more pronounced in the animals treated with cypermethrin during postnatal days followed by adulthood compared with adulthood alone. The results obtained thus demonstrate that exposure to cypermethrin during adulthood induces dopaminergic neurodegeneration in rats and postnatal exposure enhances the susceptibility of animals to dopaminergic neurodegeneration if rechallenged during adulthood.

Measurement of pyrethroid, organophosphorus, and carbamate insecticides in human plasma using isotope dilution gas chromatography-high resolution mass spectrometry

We have developed a gas chromatography-high resolution mass spectrometry method for measuring pyrethroid, organophosphorus, carbamate and fipronil pesticides and the synergist piperonyl butoxide in human plasma. Plasma samples were extracted using solid phase extraction and were then concentrated for injection and analysis using isotope dilution gas chromatography-high resolution mass spectrometry. The limits of detection ranged from 10 to 158 pg/mL with relative recoveries at concentrations near the LODs (e.g., 25 or 250 pg/mL) ranging from 87% to 156% (9 of the 16 compounds were within ±15% of 100%). The extraction recoveries ranged from 20% to 98% and the overall method relative standard deviations were typically less than 20% with some exceptions. Analytical characteristics were determined at 25, 250, and 1000 pg/mL.

Age, dose, and time-dependency of plasma and tissue distribution of deltamethrin in immature rats

The major objective of this project was to characterize the systemic disposition of the pyrethroid, deltamethrin (DLT), in immature rats, with emphasis on the age dependence of target organ (brain) dosimetry. Postnatal day (PND) 10, 21, and 40 male Sprague-Dawley rats received 0.4, 2, or 10 mg DLT/kg by gavage in glycerol formal. Serial plasma, brain, fat, liver, and skeletal muscle samples were collected for up to 510 h and analyzed for DLT and/or 3-phenoxybenzoic acid (PBA) content by high-performance liquid chromatography. Toxicokinetic data from previous experiments of the same design with young adult (PND 90) rats (Kim, K.-B., Anand, S. S., Kim, H. J., White, C. A., and Bruckner, J. V. [2008]. Toxicokinetics and tissue distribution of deltamethrin in adult Sprague-Dawley rats. Toxicol. Sci. 101, 197-205) were used to compare to immature rat data. Plasma and tissue DLT levels were inversely related to age. Preweanlings and weanlings showed markedly elevated brain concentrations and pronounced salivation, tremors, choreoathetosis, and eventual fatalities. Plasma DLT levels did not reliably reflect brain levels over time. Plasma:brain ratios were time and dose dependent, but apparently not age dependent. Brain levels were better correlated with the magnitude of salivation and tremors than plasma levels. Hepatic intrinsic clearance of DLT progressively increased during maturation, as did the hepatic extraction ratio. Thus, limited capacity to metabolically inactivate DLT appeared primarily responsible for the inordinately high target organ doses and acute neurotoxicity in pups and weanling rats. Hepatic blood flow was not rate limiting in any age group. Limited DLT hydrolysis was manifest in vivo in the pups by relatively low plasma PBA levels. Elevated exposure of the immature brain to a pyrethroid may prove to be of consequence for long-term, as well as short-term neurotoxicity.

Pyrethrin and pyrethroid illnesses in the Pacific northwest: a five-year review

OBJECTIVE

Pyrethrin and pyrethroid insecticides are commonly applied in homes and businesses and on some agricultural crops. This research used a two-state regional approach to analyze reports of acute pesticide poisonings due to pyrethrin and pyrethroid insecticides.

METHODS

The Washington State Department of Health and the Oregon Public Health Division collected pesticide poisoning surveillance data from 2001 through 2005. Cases were included if they involved exposure to at least one pyrethrin or pyrethroid insecticide. Descriptive statistics were calculated; differences between categories were assessed using Chi-square analysis.

RESULTS

A total of 407 cases fit our definition. Overall, the rate of poisoning in Oregon was significantly higher than in Washington (incidence rate ratio 1.70, 95% confidence interval 1.40, 2.07), and rates for both states generally increased during the time period. For both states, most exposures resulted in low severity illnesses (92%), and most were classified as possible cases (73%). Only about one-fourth of cases were related to a person's work. The most common category of clinical signs and symptoms of illness was respiratory (52% of cases), followed by neurological (40% of cases). Exposure route was predominantly inhalation; there was no association between route and case severity. There was a significant association between illness severity and losing time from work or regular activities (p<0.0001).

CONCLUSIONS

Although the majority of pyrethrin and pyrethroid poisoning cases were low in severity, adverse reactions have occurred, as transpired in Oregon in 2005. Regional analysis has the potential to improve the surveillance system and provide unique opportunities for targeting preventive interventions.

Comparison of urinary concentrations of 3-phenoxybenzoic acid among general residents in rural and suburban areas and employees of pest control firms

OBJECTIVES

The purpose of this study is to determine the levels of urinary 3-phenoxybenzoic acid (3-PBA) among general populations in rural and suburban areas and employees of pest control firms to evaluate the differences in the level of environmental or occupational pyrethroid (PYR) pesticides to which those populations are exposed.

METHODS

Spot urine specimens were collected from male residents in a rural area (n = 143) and male residents in a suburban area (n = 66) in August of 2005 and 2007, respectively. Male employees of pest control firms, who also provided their urine specimens at the time of a health-checkup in August 2007, were classified either as sprayers (n = 14) or as non-sprayers (n = 16) according to the presence of spraying during the pre-checkup week. Urinary concentrations of 3-PBA were determined using gas chromatography-mass spectrometry and corrected for the urinary creatinine concentrations. An analysis of covariance was used to examine the statistical difference in 3-PBA concentrations between these four groups after adjustment for age, body mass index, and current smoking/drinking habits.

RESULTS

Multiple comparisons indicated no differences in adjusted 3-PBA concentrations between the groups of general residents from the rural areas (0.33 microg/g cre in geometric mean) and suburban area (0.51 microg/g cre). The group of sprayers showed a much higher level of 3-PBA concentrations (25.0 microg/g cre) than the other three groups. A statistically significant difference, though to a lesser extent, was also exhibited in 3-PBA concentrations between the group of non-sprayers (5.6 microg/g cre) and that of general residents.

CONCLUSIONS

The results indicated that the levels of background low-dose exposure to PYRs are not likely to differ evidently among general populations according to the area of residence. Moreover, employees of pest control firms, who have been away from PYR spraying operations for a week or more, still retain much higher urinary 3-PBA concentrations than general populations.

Relationship between dietary habits and urinary concentrations of 3-phenoxybonzoic acid in a middle-aged and elderly general population in Japan

OBJECTIVES

The ingestion of pesticides in the daily diet is assumed to be the main modality of pesticide exposure for most people. A widely used class of pesticides in agricultural or residential settings is pyrethroid. We have examined the relationship between the intake frequency of selected items of vegetables and fruits and urinary metabolites of pyrethroid pesticides in a healthy general population.

METHODS

A total of 535 residents (184 men and 351 women) who attended a healthcare checkup program conducted in a rural area of Hokkaido, Japan, in August 2005 provided informed consent for their spot urine samples to be used for the determination of 3-phenoxybenzoic acid (3-PBA) levels. They also completed a self-administered questionnaire regarding the intake frequency of 12 food items. The concentrations of creatinine-corrected 3-PBA were predicted by the intake frequency of each item, using analysis-of-covariance models to adjust for age, sex, body mass index, and drinking and smoking status.

RESULTS

Both a significant association between the 3-PBA concentration and the frequency of tomato consumption and a significant positive linear trend was found in female subjects. In contrast, no such association was found in the male subjects.

CONCLUSIONS

The frequency of tomato consumption was confirmed to strongly predict the urinary pyrethroid metabolite levels in the general population-presumably because tomatoes are most often consumed raw and unpeeled (more so than all other vegetables and fruits analyzed in the current study). However, it should be noted that the 3-PBA levels, even among those subjects with the highest consumption of tomatoes, were far below the levels of toxicological significance, although the health consequences from long-term low-level exposure to pyrethroid requires further exploration.

Biological monitoring of exposure to pyrethrins and pyrethroids in a metropolitan population of the Province of Quebec, Canada

Pyrethroid and pyrethrins are neurotoxic insecticides widely used to control agricultural and domestic insect pests. The general population is potentially chronically exposed through food consumption, but the actual exposure is poorly documented in Canada. This study aimed at obtaining an indication of the absorption of those insecticides in residents of Montreal Island, the largest metropolitan area of the Province of Quebec, Canada. We randomly recruited 120 adults and 120 children aged 18-64 and 6-12 years old, of which 81 adults and 89 children completed the study. The absorption of pyrethroids and pyrethrins was assessed through measurements of six urinary metabolites: chrysanthemum dicarboxylic acid (CDCA), cis- and trans-2,2-(dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acids (cDCCA and tDCCA), cis-2,2-(dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (DBCA), 3-phenoxybenzoic acid (PBA) and 4-fluoro-3-phenoxybenzoic acid (FPBA). Metabolites were determined in 12-h urine collections for children and 2-consecutive 12-h collections for adults, and were analyzed by gas-chromatography/mass spectrometry. In both adults and children, the relative distribution of the various metabolites was as follows: tDCCA>PBA>cDCCA>CDCA>DBCA>FPBA. In adults, median (95th percentiles) cumulative amounts of these metabolites were 12.0 (231.1), 8.2 (177.9), 5.0 (110.1), 0.3 (8.2), 0.1 (4.7) and 0.1 (0.5)pmol/kg bw, respectively, in nighttime 12-h urine collections. Corresponding values in children were 12.6 (207.7), 10.2 (73.2), 5.1 (59.6), 2.1 (14.2), 0.1 (4.9) and 0.1 (0.8)pmol/kg bw. The main metabolites observed are indicative of exposure mainly to permethrin and cypermethrin and amounts absorbed are in the same range in adults and children. The distribution levels of the main metabolites in our sample also appeared similar to those reported in the US population.

Pyrethrin and pyrethroid exposures in the United States: a longitudinal analysis of incidents reported to poison centers

INTRODUCTION

Citing the Food Quality Protection Act, the US Environmental Protection Agency (EPA) decided to phase out and eliminate organophosphate insecticide use in residential environments. The phase out process spanned from 2000 to 2005, and it may have resulted in increased consumer use of insecticides containing other active ingredients. This study utilized data from the national Poison Control Center to assess possible changes in exposure incidents involving pyrethrin and pyrethroid insecticides during the phase out of organophosphates from residential uses.

METHODS

We extracted pyrethrin and pyrethroid insecticide exposure data from the American Association of Poison Control Centers Toxic Exposure Surveillance System (TESS) annual reports from 2000 to 2005. We examined pyrethrin and pyrethroid incidents by total exposures for each year, and we stratified exposures by age range, reason, number of cases treated in a health care facility, and medical outcome. Cases were examined as a proportion of all insecticide exposures. We calculated the annual incidence rates for exposures involving pyrethrin and pyrethroid insecticides of the population served.

RESULTS

Pyrethrin and pyrethroid exposures increased annually in number and as a percentage of all insecticide exposure incidents. The increase in cases was observed for all age categories and exposure reasons. A statistically significant correlation was observed between advancing years (2000-2005) and the number of pyrethrin and pyrethroid incidents (p<.01). While the number of incidents treated in a health care facility increased annually during the study period, the proportion was constant (0.185 +/- 0.012) over the six year period. During the study period, the incidence rate for pyrethrin and pyrethroid exposures increased each year. 44% of all medical outcomes data was recorded, and the majority of outcomes resulted in no symptoms (37%) or minor symptoms (53%).

CONCLUSION

TESS data showed a clear increase in cases involving pyrethrins and pyrethroids. The increase was temporally associated with the phase out of organophosphates from residential uses. In the future, medical toxicologists and poison control center personnel should be prepared to respond to an increasing number of pyrethrin and pyrethroid insecticide exposures.

Toxicokinetics and tissue distribution of deltamethrin in adult Sprague-Dawley rats

The objectives of this study were twofold: (1) to characterize the toxicokinetics and dose-dependent systemic/tissue distribution of deltamethrin (DLM) over a range of doses in adult Sprague-Dawley (S-D) rats; (2) to provide comprehensive time course blood and tissue data for development of a physiologically based toxicokinetic (PBTK) model for DLM. DLM is one of the more neurotoxic members of a relatively new and commonly used class of insecticides, the pyrethroids. Despite widespread exposure of the general population to pyrethroids, there is little basic toxicokinetic (TK) data to use in health risk assessments or in development of PBTK models. Male S-D rats were dosed orally with 0.4, 2, or 10 mg DLM/kg dissolved in glycerol formal (GF). Another group received 2 mg/kg iv. Serial blood and tissue samples were taken at sacrifice and analyzed by high-performance liquid chromatography for their DLM content, in order to obtain comprehensive time course data sets for estimation of classical TK, as well as PBTK parameters (e.g., tissues:blood partition coefficients). Gastrointestinal (GI) absorption of DLM was rapid but incomplete. Bioavailability was just 18%. Some 83% of DLM in blood was present in the plasma. Just 0.1-0.3% of systemically absorbed doses reached the brain, the target organ of the bioactive parent compound. Fat, skin and surprisingly, skeletal muscle, accumulated large amounts of the highly lipophilic chemical and served as slow-release depots. Tissue distribution was dose dependent, though generally not proportional to dose. Clearance was dose independent in this dosage range. The time-profiles were used by A. Mirfazaelian et al. (2006, Toxicol. Sci. 93, 432-442) to construct and adjust a PBTK model. Much remains to be learned about physiological/biochemical processes and barriers that govern the GI absorption, transport, brain deposition, and elimination of DLM and other pyrethroids in laboratory animals and humans.

An observational study of 127 preschool children at their homes and daycare centers in Ohio: environmental pathways to cis- and trans-permethrin exposure

The potential exposures of 127 preschool children to the pyrethroid insecticides, cis- and trans-permethrin, in their everyday environments were examined. Participants were recruited randomly from 127 homes and 16 daycare centers in six Ohio (OH) counties. Monitoring was performed over a 48-h period at the children's homes and/or daycare centers. Samples collected included soil, carpet dust, indoor air, outdoor air, diet, hand wipes, surface wipes, transferable residues, and urine. The environmental samples were analyzed for the cis and trans isomers of permethrin, and the urine samples were analyzed for the pyrethroid urinary metabolite, 3-phenoxybenzoic acid (3-PBA), by gas chromatography/mass spectrometry. The isomers were detected most often in the dust (100%) and hand wipe (>78%) samples collected at both homes and daycare centers. The median levels of cis-permethrin (470 and 1010 ng/g) were higher than the median levels of trans-permethrin (344 and 544 ng/g) in the dust samples at both the children's homes and daycare centers, respectively. In the children's hand wipe samples, the median levels of cis- and trans-permethrin were similar, ranging from 0.03 to 0.04 ng/cm(2), at both locations. The urinary metabolite 3-PBA was detected in 67% of the children's urine samples. The median urinary 3-PBA concentration for the children was 0.3 ng/mL, and the maximum value for one child was 33.8 ng/mL. The primary route of the children's exposure to the combined isomers was through dietary ingestion, followed by indirect ingestion. In addition, our calculated aggregate absorbed doses of permethrin accounted for about 60% of the excreted amounts of 3-PBA found in the children's urine. In conclusion, these children were potentially exposed to low levels of permethrin from several sources, and through several pathways and routes.

Formulation-dependent toxicokinetics explains differences in the GI absorption, bioavailability and acute neurotoxicity of deltamethrin in rats

The acute neurotoxicity of pyrethroid insecticides varies markedly with the dosage vehicle employed. The objective of the present study was to assess the influence of two common vehicles on the bioavailability and toxicokinetics (TK) of a representative pyrethroid insecticide, deltamethrin (DLM), to determine whether the vehicles influence toxic potency by modifying the chemical's TK. Adult, male Sprague-Dawley rats were administered DLM iv or po, either by dissolving it in glycerol formal (GF) or by suspending it in Alkamuls (AL). Groups of rats received 10mg DLM/kg by gavage in each vehicle, as well as 2 mg/kg in GF or 10mg/kg in AL by iv injection. Serial blood samples were collected over 96 h and analyzed for their DLM content by HPLC. In a second experiment, plasma, brain, fat, liver and lung DLM concentrations were measured 2h after giving 10mg DLM/kg orally in GF or AL. In a third experiment rats received 2 or 10mg DLM/kg iv in AL or 2mg DLM/kg iv in GF. Lung DLM content was determined 15 min post injection. DLM particle size in both formulations was measured under a phase contrast microscope. DLM appeared to be completely dissolved in GF, while particle size ranged from <5 to >50 microm in AL. The bioavailability of DLM in the aqueous AL suspension was approximately 9-fold lower than in GF (1.7% versus 15%). Blood C(max) (0.95+/-0.27 versus 0.09+/-0.01 microg/ml) and AUC(0)(48h) (5.49+/-0.22 versus 0.61+/-0.14 microg.h/ml) were markedly higher in the GF gavage group. Tissue DLM levels were also significantly higher in the GF animals at 2h. The 10mg/kg po and 2mg/kg iv doses of DLM in GF produced moderate salivation and slight tremors. Rats receiving the insecticide in AL were asymptomatic. IV injection of the AL suspension resulted in trapping of much of the dose in the pulmonary capillaries. As anticipated, the injected suspension had a longer half-life and slower clearance than did the GF formulation. In summary, limited dissolution of the highly lipophilic DLM particles in the AL suspension severely limited DLM's GI absorption, bioavailability, target organ deposition and acute neurotoxic potency.