Merging models and biomonitoring data to characterize sources and pathways of human exposure to organophosphorus pesticides in the Salinas Valley of California

Association between organophosphorus pesticides and obesity among American adults

OBJECTIVE

To investigate any connections between urinary organophosphorus pesticide (OPP) metabolites and adiposity measures.

METHODS

In this study, data from the National Health and Nutrition Examination Survey (NHANES) projects from 2003 to 2008, 2011 to 2012, and 2015 to 2018 were analysed. Obesity was defined as a body mass index (BMI) of 30 kg/m² or higher. Abdominal obesity was defined as a waist circumference (WC) over 102 cm for men and 88 cm for women. Four urinary OPP metabolites (dimethyl phosphate [DMP], diethyl phosphate [DEP], dimethyl phosphorothioate [DMTP], and diethyl phosphorothioate [DETP]) and adiposity measures were examined using multiple linear regression and logistic regression analyses. The correlations between a variety of urinary OPP metabolites and the prevalence of obesity were investigated using weighted quantile sum regression and quantile g-computation regression.

RESULTS

In this analysis, a total of 9,505 adults were taken into account. There were 49.81% of male participants, and the average age was 46.00 years old. The median BMI and WC of the subjects were 27.70 kg/m2 and 97.10 cm, respectively. Moreover, 35.60% of the participants were obese, and 54.42% had abdominal obesity. DMP, DMTP, and DETP were discovered to have a negative correlation with WC and BMI in the adjusted models. DMP (OR = 0.93 [95% CI: 0.89-0.98]), DEP (OR = 0.94 [95% CI: 0.90-0.99]), DMTP (OR = 0.91 [95% CI: 0.86-0.95]), and DETP (OR = 0.85 [95% CI: 0.80-0.90]) exhibited negative associations with obesity prevalence. Similar correlations between the prevalence of abdominal obesity and the urine OPP metabolites were discovered. Moreover, the mixture of urinary OPP metabolites showed negative associations with adiposity measures, with DMTP and DETP showing the most significant effects.

CONCLUSION

Together, higher levels of urinary OPP metabolites in the urine were linked to a decline in the prevalence of obesity.

Association of urinary organophosphate metabolites with adult asthma patients: a cross-sectional population-based study

Human health is adversely affected by exposure to organophosphate (OP) pesticides. This study aims to investigate the correlation between urinary OP metabolites and the prevalence of asthma. In cross-sectional studies, data from the National Health and Nutrition Examination Survey (NHANES) projects conducted between 2003-2008, 2011-2012, and 2015-2018 were analyzed. Multiple logistic regressions and restricted cubic spline (RCS) regressions were utilized to examine the relationship between four urinary OP metabolites, namely dimethyl phosphate (DMP), diethyl phosphate (DEP), dimethyl phosphorothioate (DMTP), and diethyl phosphorothioate (DETP), and the prevalence of asthma. Additionally, quantile g-computation (QG-C) regression was employed to evaluate the association between urinary OP metabolites (both individual and combined exposures) and asthma prevalence. The results showed that a total of 9316 adults, including 1298 participants with asthma, were included in the analysis. The median age of the participants was 47.37 years, and 50.27% were female. In the comprehensive model, the third tertile of DMP and DEP exhibited a positive association with asthma prevalence compared to the first tertile (odds ratio [95% confidence interval]: 1.26 [1.01-1.57], Ptrend = 0.036; and 1.25 [1.07-1.51], Ptrend = 0.008, respectively). Moreover, a linear relationship was observed between DMP, DEP, and asthma prevalence (P for nonlinearity = 0.320 and 0.553, respectively). The QG-C regression revealed a positive association between the mixture of urinary OP metabolites and asthma prevalence (OR = 1.04 [1.01-1.07], P = 0.025), with DEP contributing the most substantial effect (weight = 0.564). Our findings suggest that exposure to OP pesticides is associated with an increased prevalence of asthma, with DEP demonstrating the strongest impact.

Cannabis sativa: A look at protozoa, helminths, insect vectors, and pests

Active principles extracted from plants, such as essential oils, have been commonly described in the literature as therapeutic targets for numerous pathological conditions. Cannabis sativa, which has an ancient and peculiar history, has been used for various purposes, from recreational to compounds of pharmacotherapeutic and industrial importance, such as pesticides based on this plant. It is a plant that contains approximately 500 described cannabinoid compounds and is the target of in vitro and in vivo studies at different locations. This review clarifies the role of cannabinoid compounds in parasitic infections caused by helminths and protozoa. In addition, this study briefly presented the use of C. sativa constituents in the formulation of pesticides for vector control, as the latter topic is justified by the economic burden faced by several regions where vector-borne diseases are a troubling reality. Studies involving cannabis compounds with pesticidal potential should be encouraged, especially those that evaluate their effectiveness against the different life cycles of insects, seeking to interrupt vector proliferation after egg laying. Actions aimed at the management and cultivation of plant species with ecologically correct pharmacotherapeutic and pesticide potentials are becoming urgent.

Fosthiazate exposure induces oxidative stress, nerve damage, and reproductive disorders in nontarget nematodes

As a forceful nematicide, fosthiazate has been largely applied in the management of root-knot nematodes and other herbivorous nematodes. However, the toxicity of fosthiazate to nontarget nematodes is unclear. To explore the toxicity and the mechanisms of fosthiazate in nontarget nematodes, Caenorhabditis elegans was exposed to 0.01-10 mg/L fosthiazate. The results implied that treatment with fosthiazate at doses above 0.01 mg/L could cause injury to the growth, locomotion behavior, and reproduction of the nematodes. Moreover, L1 larvae were more vulnerable to fosthiazate exposure than L4 larvae. Reactive oxygen species (ROS) production and lipofuscin accumulation were fairly increased in 1 mg/L fosthiazate-exposed nematodes. Treatment with 0.1 mg/L fosthiazate significantly inhibited the activity of acetylcholinesterase (p < 0.01). Furthermore, subacute exposure to 10 mg/L fosthiazate strongly influenced the expression of genes related to oxidative stress, reproduction, and nerve function (e.g., gst-1, sod-1, puf-8, wee-1.3, and ace-1 genes). These findings suggested that oxidative stress, reproduction and nerve disorders could serve as key endpoints of toxicity induced by fosthiazate. The cyp-35a family gene was the main metabolic fosthiazate in C. elegans, and the cyp-35a5 subtype was the most sensitive, with a change in expression level of 2.11-fold compared with the control. These results indicate that oxidative stress and neurological and reproductive disorders played fundamental roles in the toxicity of fosthiazate in C. elegans and may affect the abundance and function of soil nematodes.

Determinants of organophosphorus pesticide urinary metabolite levels in pregnant women from the CHAMACOS cohort

Organophosphosphorus pesticides (OPs) are widely used as insecticides in agriculture. Human exposure to OPs has been linked to adverse effects including poorer child neurodevelopment, reduced birth weight, altered serum hormone levels, and reduced semen quality. We measured six OP dialkyl phosphate (DAP) metabolites [three dimethyl alkylphosphates (DMs) and three diethyl alkylphosphates (DEs)] in urine samples collected two times during pregnancy (~13 and ~26 weeks gestation) from 594 women participating in the CHAMACOS birth cohort study and resided in an agricultural community in the United States (U.S.) between 1999 and 2000. Previous studies have shown these women have higher OP exposures compared with the general U.S. population. We examined bivariate associations between prenatal DAP metabolite levels and exposure determinants such as age, season, years living in the US, housing characteristics, fruit and vegetable consumption, occupation and residential proximity to agricultural fields. Final multivariable models indicated that season of urine collection was significantly associated (p < 0.01) with specific gravity-adjusted DM, DE and total DAP metabolites; samples collected in fall and winter had higher concentrations than those collected in spring-summer. Specific gravity-adjusted levels of DM and total DAP metabolites were significantly higher in women who had resided in the U.S. for 5 years or less (p < 0.05). Levels of DM metabolites also increased with daily fruit and vegetable servings (p < 0.01), and levels of DE metabolites were higher in residences with poorer housekeeping quality (p < 0.01) and in mothers that worked in agriculture (p < 0.05). These findings suggest that there are multiple determinants of OP exposure in pregnant women.

Exposure forecasting - ExpoCast - for data-poor chemicals in commerce and the environment

Estimates of exposure are critical to prioritize and assess chemicals based on risk posed to public health and the environment. The U.S. Environmental Protection Agency (EPA) is responsible for regulating thousands of chemicals in commerce and the environment for which exposure data are limited. Since 2009 the EPA's ExpoCast ("Exposure Forecasting") project has sought to develop the data, tools, and evaluation approaches required to generate rapid and scientifically defensible exposure predictions for the full universe of existing and proposed commercial chemicals. This review article aims to summarize issues in exposure science that have been addressed through initiatives affiliated with ExpoCast. ExpoCast research has generally focused on chemical exposure as a statistical systems problem intended to inform thousands of chemicals. The project exists as a companion to EPA's ToxCast ("Toxicity Forecasting") project which has used in vitro high-throughput screening technologies to characterize potential hazard posed by thousands of chemicals for which there are limited toxicity data. Rapid prediction of chemical exposures and in vitro-in vivo extrapolation (IVIVE) of ToxCast data allow for prioritization based upon risk of adverse outcomes due to environmental chemical exposure. ExpoCast has developed (1) integrated modeling approaches to reliably predict exposure and IVIVE dose, (2) highly efficient screening tools for chemical prioritization, (3) efficient and affordable tools for generating new exposure and dose data, and (4) easily accessible exposure databases. The development of new exposure models and databases along with the application of technologies like non-targeted analysis and machine learning have transformed exposure science for data-poor chemicals. By developing high-throughput tools for chemical exposure analytics and translating those tools into public health decisions ExpoCast research has served as a crucible for identifying and addressing exposure science knowledge gaps.

Occupational and residential exposures to organophosphate and pyrethroid pesticides in a rural setting

Organophosphate (OP) and pyrethroid pesticides (PYR) are extensively used in agriculture, resulting in higher exposures among farmworkers. The present study reports the occurrence of 8 urinary OP and PYR metabolites in a sample of farmworkers and residents from Sucs (n = 87), a rural township in North West Catalonia (Spain). The aim of the present study was to examine differences in urinary pesticide metabolite concentrations between occupationally-exposed (farmworkers; n = 45) and environmentally-exposed subjects (n = 42) and to assess the relationship between pesticide's exposures and occupational activities in a real-case scenario. Six OP and two PYR metabolites have been investigated, urine samples were extracted using SPE extraction and analyzed by UPLC-MS/MS. Three OP metabolites were commonly detectable in urine, namely TCPY (metabolite of chlorpyrifos), PNP (parathion) and DEAMPY (pirimiphos). Regarding pyrethroids, the two analyzed metabolites, 3-PBA and 4F-3-PBA, were detected in a high proportion of urine samples. Differences in concentrations between both groups were statistically significant for TCPY and 4F-3-PBA (Mann-Whitney U Test for independent groups, p < 0.05). In the case of TCPY, the concentrations were higher among the farmworkers, which is consistent with their occupational activity. The small differences found in DEAMPY, PNP, 3-PBA or even the significant higher concentrations of 4F-3-PBA among rural population suggest a general exposure to these compounds, even in those who do not carry an occupational activity. Specific personal protective equipment (PPE) among farmworkers, such as the use of gloves and mask during mixing, showed a decrease in the exposure levels, although the differences were not statistically significant. However, a positive association was found between the use of a cap during mixing (for PNP and 3-PBA) and during application (only for 3-PBA). However, this piece of cloth is mainly used for sun protection, and when not cleaned after the handling of pesticides, it might represent a continuous source of exposure through dermal contact. Farmworkers using tractors with cabin had statistically significant lower concentrations of DEAMPY than those using a tractor without cabin. The previous results suggest that occupational protections should be encouraged among farmworkers and other potential workers handling with pesticides.

Carbon nanomaterials for the detection of pesticide residues in food: A review

In agricultural fields, pesticides are widely used, but their residual presence in the environment poses a threat to humans, animals, insects, and ecosystems. The overuse of pesticides for pest control, enhancement of crop yield, etc. leaves behind a significant residual amount in the environment. Various robust, reliable, and reusable methods using a wide class of composites have been developed for the monitoring and controlling of pesticides. Researchers have discovered that carbon nanomaterials have a wide range of characteristics such as high porosity, conductivity and easy electron transfer that can be successfully used to detect pesticide residues from food. This review emphasizes the role of carbon nanomaterials in the field of pesticide residue analysis in different food matrices. The carbon nanomaterials including carbon nanotubes, carbon dots, carbon nanofibers, graphene/graphene oxides, and activated carbon fibres are discussed in the review. In addition, the review examines future prospects in this research area to help improve detection techniques for pesticides analysis.

Pyrimethanil and chlorpyrifos air concentrations and pregnant women's urinary metabolites in the Infants' Environmental Health Study (ISA), Costa Rica

BACKGROUND

Only few studies have compared environmental pesticide air concentrations with specific urinary metabolites to evaluate pathways of exposure. Therefore, we compared pyrimethanil and chlorpyrifos concentrations in air with urinary 4-hydroxypyrimethanil (OHP, metabolite of pyrimethanil) and 3,5,6-trichloro-2-pyridinol (TCPy, metabolite of chlorpyrifos) among pregnant women from the Infant's Environmental Health Study (ISA) in Matina County, Costa Rica.

METHODS

During pregnancy, we obtained repeat urinary samples from 448 women enrolled in the ISA study. We extrapolated pyrimethanil and chlorpyrifos concentrations measured with passive air samplers (PAS) (n = 48, from 12 schools), across space and time using a Bayesian spatiotemporal model. We subsequently compared these concentrationswith urinary OHP and TCPy in 915 samples from 448 women, usingseparatemixed models andconsidering several covariables.

RESULTS

A 10% increase in air pyrimethanil (ng/m3) was associated with a 5.7% (95% confidence interval (CI 4.6, 6.8) increase in OHP (μg/L). Women living further from banana plantations had lower OHP: -0.7% (95% CI -1.2, -0.3) for each 10% increase in distance (meters) as well as women who ate rice and beans ≥15 times a week -23% (95% CI -38, -4). In addition, each 1 ng/m3 increase in chlorpyrifos in air was associated with a 1.5% (95% CI 0.2, 2.8) increase in TCPy (μg/L), and women working in agriculture tended to have increased TCPy (21%, 95% CI -2, 49).

CONCLUSION

The Bayesian spatiotemporal models were useful to estimate pyrimethanil and chlorpyrifos air concentrations across space and time. Our results suggest inhalation of pyrimethanil and chlorpyrifos is a pathway of environmental exposure. PAS seems a useful technique to monitor environmental current-use pesticide exposures. For future studies, we recommend increasing the number of locations of environmental air measurements, obtaining all air and urine measurements during the same month, and, ideally, including dermal exposure estimates as well.

In-silico Studies Calculated a New Chitin Oligomer Binding Site Inside Vicilin: A Potent Antifungal and Insecticidal Agent

Vicilins are major seed storage proteins and show differential binding affinities toward sugar moieties of fungal cell wall and insect gut epithelium. Hence, purpose of study is the thorough in-silico characterization of interactions between vicilin and chitin oligomer followed by fungal and insecticidal bioassays. This work covers the molecular simulation studies explaining the interactions between Pisum sativum vicilin (PsV) and chitin oligomer followed by protein bioassay against different pathogens. LC-MS/MS of purified PsV (∼50 kDa) generated residual data along high pea vicilin homology (UniProtKB ID; P13918). Predicted model (PsV) indicated the characteristic homotrimer joined through head-to-tail association and each monomer is containing a bicupin domain. PsV site map analysis showed a new site (Site 4) into which molecular docking confirmed the strong binding of chitin oligomer (GlcNAc)₄. Molecular dynamics simulation data (50 ns) indicated that chitin-binding site was comprised of 8 residues (DKEDRNEN). However, aspartate and glutamate significantly contributed in the stability of ligand binding. Computational findings were further verified via significant growth inhibition of Aspergillus flavus, A. niger, and Fusarium oxysporum against PsV. Additionally, the substantial adult population of Brevicoryne brassicae was reduced and different life stages of Tribolium castaneum also showed significant mortality.

Incorporating human exposure information in a weight of evidence approach to inform design of repeated dose animal studies

Human health risks from chronic exposures to environmental chemicals are typically estimated from potential human exposure estimates and dose-response data obtained from repeated-dose animal toxicity studies. Various criteria are available for selecting the top (highest) dose used in these animal studies. For example, toxicokinetic (TK) and toxicological data provided by shorter-term or dose range finding studies can be evaluated in a weight of evidence approach to provide insight into the dose range that would provide dose-response data that are relevant to human exposures. However, there are concerns that a top dose resulting from the consideration of TK data may be too low compared to other criteria, such as the limit dose or the maximum tolerated dose. In this paper, we address several concerns related to human exposures by discussing 1) the resources and methods available to predict human exposure levels and the associated uncertainty and variability, and 2) the margin between predicted human exposure levels and the dose levels used in repeated-dose animal studies. A series of case studies, ranging from data-rich to data-poor chemicals, are presented to demonstrate that expected human exposures to environmental chemicals are typically orders of magnitude lower than no-observed-adverse-effect levels/lowest-observed-adverse-effect levels (NOAELs/LOAELs) when available (used as conservative surrogates for top doses). The results of these case studies support that a top dose based, in part, on TK data is typically orders of magnitude higher than expected human exposure levels.

Assessing Human Exposure to SVOCs in Materials, Products, and Articles: A Modular Mechanistic Framework

A critical review of the current state of knowledge of chemical emissions from indoor sources, partitioning among indoor compartments, and the ensuing indoor exposure leads to a proposal for a modular mechanistic framework for predicting human exposure to semivolatile organic compounds (SVOCs). Mechanistically consistent source emission categories include solid, soft, frequent contact, applied, sprayed, and high temperature sources. Environmental compartments are the gas phase, airborne particles, settled dust, indoor surfaces, and clothing. Identified research needs are the development of dynamic emission models for several of the source emission categories and of estimation strategies for critical model parameters. The modular structure of the framework facilitates subsequent inclusion of new knowledge, other chemical classes of indoor pollutants, and additional mechanistic processes relevant to human exposure indoors. The framework may serve as the foundation for developing an open-source community model to better support collaborative research and improve access for application by stakeholders. Combining exposure estimates derived using this framework with toxicity data for different end points and toxicokinetic mechanisms will accelerate chemical risk prioritization, advance effective chemical management decisions, and protect public health.

Organophosphate metabolite concentrations in maternal urine during pregnancy

The burden of organophosphate (OP) pesticides in pregnant women from Tarragona (n = 157), a Mediterranean area of intense agricultural activity, has been assessed from the study of hydroxylated organic metabolites in urine samples in the three trimesters of pregnancy. 2-Diethylamino-6-methylpyrimidin-4-ol (DEAMPY), a metabolite of pirimiphos, was the compound found in higher concentration, medians 0.66-2.8 μg/g creatinine. 4-Nitrophenol (PNP), a metabolite of parathion, medians 0.24-0.41 μg/g creatinine, was the second most abundant compound. 2-Isopropyl-6-methyl-4-pyrimidol (IMPY), a metabolite of diazinon, was also present but in lower concentrations. Except for DEAMPY, the concentrations found in this cohort were lower than those reported in studies from other countries. Intraclass correlation coefficients (ICCs) were calculated for the compounds found in more than the 35% of the samples, the reliability between trimesters was poor (<0.40) to fair (0.40-0.60). Statistically significant differences were observed for the creatinine adjusted concentrations of the most abundant OP metabolites in these trimesters when examined with the Wilcoxon signed rank test for paired data. In general, no association was found between urinary OP metabolites and most demographic and lifestyle predictors. However, a positive significant association was observed for women with vegetarian diet and for women of higher economic status and eventual consumption of organic food which showed higher PNP concentrations. These results suggest that higher fruit and vegetable consumption may involve higher OP pesticide ingestion but the overall association was weak.

Insecticidal activity and biochemical composition of Citrullus colocynthis, Cannabis indica and Artemisia argyi extracts against cabbage aphid (Brevicoryne brassicae L.)

Plant extracts contain many active compounds, which are tremendously fruitful for plant defence against several insect pests. The prime objectives of the present study were to calculate the extraction yield and to evaluate the leaf extracts of Citrullus colocynthis (L.), Cannabis indica (L.) and Artemisia argyi (L.) against Brevicoryne brassicae and to conduct biochemical analysis by gas chromatography-mass spectrometry (GC-MS). The results suggested that when using ethanol, C. colocynthis produced a high dry yield (12.45%), followed by that of C. indica and A. argyi, which were 12.37% and 10.95%, respectively. The toxicity results showed that A. argyi was toxic to B. brassicae with an LC₅₀ of 3.91 mg mL⁻¹, followed by the toxicity of C. colocynthis and C. indica, exhibiting LC₅₀ values of 6.26 and 10.04 mg mL⁻¹, respectively, which were obtained via a residual assay; with a contact assay, the LC₅₀ values of C. colocynthis, C. indica and A. argyi were 0.22 mg mL⁻¹, 1.96 and 2.87 mg mL⁻¹, respectively. The interaction of plant extracts, concentration and time revealed that the maximum mortality based on a concentration of 20 mg L⁻¹ was 55.50%, the time-based mortality was 55% at 72 h of exposure, and the treatment-based mortality was 44.13% for A. argyi via the residual assay. On the other hand, the maximum concentration-based mortality was 74.44% at 20 mg mL⁻¹, the time-based mortality was 66.38% after 72 h of exposure, and 57.30% treatment-based mortality was afforded by A. argyi via the contact assay. The biochemical analysis presented ten constituents in both the A. argyi and C. colocynthis extracts and twenty in that of C. indica, corresponding to 99.80%, 99.99% and 97% of the total extracts, respectively. Moreover, the detected caryophylleneonides (sesquiterpenes), α-bisabolol and dronabinol (Δ⁹-THC) from C. indica and erucylamide and octasiloxane hexamethyl from C. colocynthis exhibited insecticidal properties, which might be responsible for aphid mortality. However, A. argyi was evaluated for the first time against B. brassicae. It was concluded that all the plant extracts possessed significant insecticidal properties and could be introduced as botanical insecticides after field evaluations.

Mother/child organophosphate and pyrethroid distributions

The present study reports one of the few cases in which organophosphate (OP) and pyrethroid (PYR) pesticide human exposure is evaluated in family contexts by the analysis of mother/child pair samples. Urinary concentrations of 6 organic metabolites of organophosphates and 2 pyrethroids were measured in mothers and their 7-to 8-year-old children (n = 168) in a general population from the central area of Slovenia. The results were adjusted for specific gravity and creatinine. The most abundant OP metabolite in children was 4-nitrophenol (PNP) (median 0.7 ng/ml) and in mothers (0.45 ng/ml), representing parathion exposure. 3-Phenoxibenzoic acid (3-PBA) (0.26 ng/ml), the general metabolite of pyrethroids, and 3,5,6-trichloro-2-pyridinol (TCPY) (0.16 ng/ml; chlorpyriphos) were the second most abundant compounds in children and mothers, respectively. The geometric mean specific gravity adjusted concentrations of OPs and PYRs were statistically significantly higher in children than in their mothers (between 3% and 24% higher), with the exception of TCPY (26% lower). All OP and PYR metabolites found in higher concentration in children showed significant positive correlations with the metabolite concentrations found in the mothers (p < 0.05 and 0.01), involving the fact that higher maternal concentrations were associated with higher children levels. These differential mother-children distributions and significant correlations were observed for the 2 types of pesticides studied, OPs and PYRs, which have different chemical properties. This agreement is consistent with the incorporation of the pesticides because of the general activities developed in the family context, instead of pesticide-dependent specific inputs. Comparison of the estimated daily intakes with the acceptable daily intakes of all detected metabolites revealed no significant risk of adverse health effects from exposure to these pesticides.

Prenatal exposure to organophosphate pesticides and functional neuroimaging in adolescents living in proximity to pesticide application

We have reported consistent associations of prenatal organophosphate pesticide (OP) exposure with poorer cognitive function and behavior problems in our Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a birth cohort of Mexican American youth in California's agricultural Salinas Valley. However, there is little evidence on how OPs affect neural dynamics underlying associations. We used functional near-infrared spectroscopy (fNIRS) to measure cortical activation during tasks of executive function, attention, social cognition, and language comprehension in 95 adolescent CHAMACOS participants. We estimated associations of residential proximity to OP use during pregnancy with cortical activation in frontal, temporal, and parietal regions using multiple regression models, adjusting for sociodemographic characteristics. OP exposure was associated with altered brain activation during tasks of executive function. For example, with a 10-fold increase in total OP pesticide use within 1 km of maternal residence during pregnancy, there was a bilateral decrease in brain activation in the prefrontal cortex during a cognitive flexibility task (β = -4.74; 95% CI: -8.18, -1.31 and β = -4.40; 95% CI: -7.96, -0.84 for the left and right hemispheres, respectively). We also found that prenatal OP exposure was associated with sex differences in brain activation during a language comprehension task. This first functional neuroimaging study of prenatal OP exposure suggests that pesticides may impact cortical brain activation, which could underlie previously reported OP-related associations with cognitive and behavioral function. Use of fNIRS in environmental epidemiology offers a practical alternative to neuroimaging technologies and enhances our efforts to assess the impact of chemical exposures on neurodevelopment.

Urinary metabolites of organophosphate and pyrethroid pesticides in children from an Italian cohort (PHIME, Trieste)

Urinary metabolites of organophosphate (OP) and pyrethroid (PYR) pesticides from seven years old children of a birth cohort study (n=199; PHIME cohort of Trieste, Italy) have been measured. Six OP and two PYR metabolites have been investigated, 2-diethylamino-6-methylpyrimidin-4-ol (DEAMPY, pirimiphos metabolite) was the one found at higher concentrations, median 3.4 ng/mL specific gravity adjusted (SG adjusted), followed by 4-nitrophenol (PNP, median 1.4 ng/mL SG adjusted) and 3,5,6-trichloro-2-pyridinol (TCPY, median 0.36 ng/mL SG adjusted), parathion and chlorpyriphos metabolites, respectively. TCPY concentrations were low in comparison to other distributions of OP metabolites in children from other studies. Accordingly, the PHIME cohort showed a distinct OP metabolite distribution with high concentrations of pirimiphos and parathion. Another specific characteristic of this cohort was the high concentration of 3-phenoxybenzoic acid (3-BPA, median 0.36 ng/mL SG adjusted), a general metabolite of PYR pesticides. Evaluation of anthropometric and socio-demographic characteristics of children and families only showed a positive association between family educational level and urinary concentrations of DEAMPY metabolite (p<0.05), which could reflect distinct dietary habits depending on the educational level. Estimated daily intakes were evaluated, all studied metabolites were found within safe levels.

Stereoselective environmental behavior and biological effect of the chiral organophosphorus insecticide isofenphos‑methyl

The enantiomeric environmental behaviors, bioactivities and toxicities of isofenphos‑methyl enantiomers were characterized systematically in this study. (R)‑Isofenphos‑methyl was degraded preferentially in Yangtze River water and different types of vegetables with an enantiomeric fraction (EF) of 0.6 to 0.96. However, (R)‑isofenphos‑methyl was amplified in both Nanjing (EF = 0.32) and Nanchang (EF = 0.27) soil. Our investigations found that there no bidirectional chiral inversion occurred in either Yangtze River water or soils. The bioactivity of (S)‑isofenphos‑methyl was higher than that of its (R)‑enantiomer against different insect targets, such as Meloidogyne incognita, Nilaparvata lugens, Plutella xylostella and Macrosiphum pisi (3.7 to 149 times). (S)‑Isofenphos‑methyl showed higher toxicity for the nontarget organism (1.1 to 32 times). However, (R)‑isofenphos‑methyl possesses 4.0 times more potency than the (S)-form for the nontarget soil organism Eisenia foetida. This study generally could provide more scientific guidance for the corresponding risk assessments of pesticides in addition to providing a new theoretical basis for scientifically and rationally using isofenphos‑methyl.

Determinants of Exposure to Pyrethroid Insecticides in the VHEMBE Cohort, South Africa

Exposure to pyrethroid insecticides has been linked to adverse health effects, and can originate from several sources, including indoor residual spraying (IRS) for malaria control, home pest control, food contamination, and occupational exposure. We aimed to explore the determinants of urinary pyrethroid metabolite concentrations in a rural population with high pesticide use. The Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) is a birth cohort of 752 mother-child pairs in Limpopo, South Africa. We measured pyrethroid metabolites in maternal urine and collected information on several factors possibly related to pesticide exposure, including IRS, home pesticide use, and maternal factors (e.g., dietary habits and body composition). We performed statistical analysis using both conventional bivariate regressions and Bayesian variable selection methods. Urinary pyrethroid metabolites are consistently associated with pesticide factors around homes, including pesticide application in yards and food stocks, and IRS in the home during pregnancy, while more distant factors such as village spraying are not. High fat intake is associated with higher metabolite concentrations, and women from homes drawing water from wells or springs had marginally higher levels. Home pesticide use is the most consistent correlate of pyrethroid metabolite concentrations, but IRS, dietary habits, and household water source may also be important exposure determinants.

Maternal residential pesticide use and risk of childhood leukemia in Costa Rica

Evidence suggests that early-life exposure to pesticides inside the home may be associated with childhood leukemia, however data from Latin American countries are limited. We examined whether self-reported maternal residential pesticide use and nearby pesticide applications-before and after child's birth-were associated with acute lymphoblastic leukemia (ALL) in the Costa Rican Childhood Leukemia Study (CRCLS), a population-based case-control study (2001-2003). Cases (n = 251 ALL) were diagnosed between 1995 and 2000 (age <15 years at diagnosis) and were identified through the Costa Rican Cancer Registry and National Children's Hospital. Population controls (n = 577) were drawn from the National Birth Registry. We fitted unconditional logistic regression models adjusted for child sex, birth year, and socioeconomic status to estimate the exposure-outcome associations and also stratified by child sex. We observed that self-reported maternal insecticide use inside the home in the year before pregnancy, during pregnancy, and while breastfeeding was associated with increased odds of ALL among boys [adjusted Odds Ratio (aOR) = 1.63 (95% confidence interval [95% CI]: 1.05-2.53), 1.75 (1.13-2.73), and 1.75 (1.12-2.73), respectively. We also found evidence of exposure-response relationships between more frequent maternal insecticide use inside the home and increased odds of ALL among boys and girls combined. Maternal report of pesticide applications on farms or companies near the home during pregnancy and at any time period were also associated with ALL. Our study in Costa Rica highlights the need for education to minimize pesticide exposures inside and around the home, particularly during pregnancy and breastfeeding.

Prenatal Organophosphate Pesticide Exposure and Traits Related to Autism Spectrum Disorders in a Population Living in Proximity to Agriculture

BACKGROUND

Prenatal exposure to organophosphate (OP) pesticides has been linked with poorer neurodevelopment and behaviors related to autism spectrum disorders (ASD) in previous studies, including in the Center for Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, a birth cohort living in the agricultural Salinas Valley in California.

OBJECTIVES

To investigate the association of prenatal exposure to OP pesticides with traits related to ASD, in childhood and adolescents in CHAMACOS.

METHODS

We assessed OP exposure during pregnancy with measurements of dialkyl phosphates (DAP) metabolites in urine, and residential proximity to OP use during pregnancy using California's Pesticide Use Reporting (PUR) data and estimated associations with ASD-related traits using linear regression models. We measured traits reported by parents and teachers as well as the child's performance on tests that evaluate the ability to use facial expressions to recognize the mental state of others at 7, 10¹/₂, and 14 years of age.

RESULTS

Prenatal DAPs were associated with poorer parent and teacher reported social behavior [e.g., a 10-fold DAP increase was associated with a 2.7-point increase (95% confidence interval (CI): 0.9, 4.5) in parent-reported Social Responsiveness Scale, Version 2, T-scores at age 14]. We did not find clear evidence of associations between residential proximity to OP use during pregnancy and ASD-related traits.

CONCLUSIONS

These findings contribute mixed evidence linking OP pesticide exposures with traits related to developmental disorders like ASD. Subtle pesticide-related effects on ASD-related traits among a population with ubiquitous exposure could result in a rise in cases of clinically diagnosed disorders like ASD. https://doi.org/10.1289/EHP2580.

Silicone Wristband Passive Samplers Yield Highly Individualized Pesticide Residue Exposure Profiles

Monitoring human exposure to pesticides and pesticide residues (PRs) remains crucial for informing public health policies, despite strict regulation of plant protection product and biocide use. We used 72 low-cost silicone wristbands as noninvasive passive samplers to assess cumulative 5-day exposure of 30 individuals to polar PRs. Ethyl acetate extraction and LC-MS/MS analysis were used for the identification of PRs. Thirty-one PRs were detected of which 15 PRs (48%) were detected only in worn wristbands, not in environmental controls. The PRs included 16 fungicides (52%), 8 insecticides (26%), 2 herbicides (6%), 3 pesticide derivatives (10%), 1 insect repellent (3%), and 1 pesticide synergist (3%). Five detected pesticides were not approved for plant protection use in the EU. Smoking and dietary habits that favor vegetable consumption were associated with higher numbers and higher cumulative concentrations of PRs in wristbands. Wristbands featured unique PR combinations. Our results suggest both environment and diet contributed to PR exposure in our study group. Silicone wristbands could serve as sensitive passive samplers to screen population-wide cumulative dietary and environmental exposure to authorized, unauthorized and banned pesticides.

Prenatal Residential Proximity to Agricultural Pesticide Use and IQ in 7-Year-Old Children

BACKGROUND

Residential proximity to agricultural pesticide use has been associated with neural tube defects and autism, but more subtle outcomes such as cognition have not been studied.

OBJECTIVES

We evaluated the relationship between prenatal residential proximity to agricultural use of potentially neurotoxic pesticides and neurodevelopment in 7-year-old children.

METHODS

Participants included mothers and children (n=283) living in the agricultural Salinas Valley of California enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study. We estimated agricultural pesticide use within 1 km of maternal residences during pregnancy using a geographic information system, residential location, and California’s comprehensive agricultural Pesticide Use Report data. We used regression models to evaluate prenatal residential proximity to agricultural use of five potentially neurotoxic pesticide groups (organophosphates, carbamates, pyrethroids, neonicotinoids, and manganese fungicides) and five individual organophosphates (acephate, chlorpyrifos, diazinon, malathion, and oxydemeton-methyl) and cognition in 7-year-old children. All models included prenatal urinary dialkyl phosphate metabolite concentrations.

RESULTS

We observed a decrease of 2.2 points [95% confidence interval (CI): −3.9, −0.5] in Full-Scale IQ and 2.9 points (95% CI: −4.4, −1.3) in Verbal Comprehension for each standard deviation increase in toxicity-weighted use of organophosphate pesticides. In separate models, we observed similar decrements in Full-Scale IQ with each standard deviation increase of use for two organophosphates (acephate and oxydemeton-methyl) and three neurotoxic pesticide groups (pyrethroids, neonicotinoids, and manganese fungicides).

CONCLUSIONS

This study identified potential relationships between maternal residential proximity to agricultural use of neurotoxic pesticides and poorer neurodevelopment in children. https://doi.org/10.1289/EHP504.

Exposure to multiple chemicals in a cohort of reproductive-aged Danish women

BACKGROUND

Current exposure assessment research does not sufficiently address multi-pollutant exposure and their correlations in human media. Understanding the extent of chemical exposure in reproductive-aged women is of particular concern due to the potential for in utero exposure and fetal susceptibility.

OBJECTIVES

The objectives of this study were to characterize concentrations of chemical biomarkers during preconception and examine correlations between and within chemical classes.

METHODS

We examined concentrations of 135 biomarkers from 16 chemical classes in blood and urine from 73 women aged 18-40 enrolled in Snart Foraeldre/Milieu, a prospective cohort study of pregnancy planners in Denmark (2011-2014). We compared biomarker concentrations with United States similarly-aged, non-pregnant women who participated in the National Health and Nutrition Environmental Survey (NHANES) and with other international biomonitoring studies. We performed principal component analysis to examine biomarker correlations.

RESULTS

The mean number of biomarkers detected in the population was 92 (range: 60-108). The most commonly detected chemical classes were phthalates, metals, phytoestrogens and polycyclic aromatic hydrocarbons. Except blood mercury, urinary barium and enterolactone, geometric means were higher in women from NHANES. Chemical classes measured in urine generally did not load on a single component, suggesting high between-class correlation among urinary biomarkers, while there is high within-class correlation for biomarkers measured in serum and blood.

CONCLUSIONS

We identified ubiquitous exposure to multiple chemical classes in reproductive-aged Danish women, supporting the need for more research on chemical mixtures during preconception and early pregnancy. Inter- and intra-class correlation between measured biomarkers may reflect common exposure sources, specific lifestyle factors or shared metabolism pathways.

The Global Food System as a Transport Pathway for Hazardous Chemicals: The Missing Link between Emissions and Exposure

BACKGROUND

Food is a major pathway for human exposure to hazardous chemicals. The modern food system is becoming increasingly complex and globalized, but models for food-borne exposure typically assume locally derived diets or use concentrations directly measured in foods without accounting for food origin. Such approaches may not reflect actual chemical intakes because concentrations depend on food origin, and representative analysis is seldom available. Processing, packaging, storage, and transportation also impart different chemicals to food and are not yet adequately addressed. Thus, the link between environmental emissions and realistic human exposure is effectively broken.

OBJECTIVES

We discuss the need for a fully integrated treatment of the modern industrialized food system, and we propose strategies for using existing models and relevant supporting data sources to track chemicals during production, processing, packaging, storage, and transport.

DISCUSSION

Fate and bioaccumulation models describe how chemicals distribute in the environment and accumulate through local food webs. Human exposure models can use concentrations in food to determine body burdens based on individual or population characteristics. New models now include the impacts of processing and packaging but are far from comprehensive. We propose to close the gap between emissions and exposure by utilizing a wider variety of models and data sources, including global food trade data, processing, and packaging models.

CONCLUSIONS

A comprehensive approach that takes into account the complexity of the modern global food system is essential to enable better prediction of human exposure to chemicals in food, sound risk assessments, and more focused risk abatement strategies. Citation: Ng CA, von Goetz N. 2017. The global food system as a transport pathway for hazardous chemicals: the missing link between emissions and exposure. Environ Health Perspect 125:1-7; http://dx.doi.org/10.1289/EHP168.

Urinary concentrations of organophosphate and carbamate pesticides in residents of a vegetarian community

Few population studies have measured urinary levels of pesticides in individuals with vegan, vegetarian, or organic diets. The objectives of this study were to evaluate whether a vegan/vegetarian diet was associated with increased exposure to organophosphate and carbamate pesticides, and to evaluate the impact of organic consumption on pesticide exposure in vegans and vegetarians. In the current pilot study conducted in 2013-2014, we collected spot urine samples and detailed 24h recall dietary data in 42 adult residents of Amirim, a vegetarian community in Northern Israel. We measured urinary levels of non-specific organophosphate pesticide metabolites (dialkylphosphates, (DAPs)) and specific metabolites of the current-use pesticides chlorpyrifos (3,5,6-trichloro-2-pyridinol (TCPy)), propoxur (-isopropoxyphenol (IPPX)), and carbaryl (1-naphthol). Six DAP metabolites were detected in between 67 and 100% of urine samples, with highest geometric mean concentrations for dimethylphosphate (19.2μg/g). Creatinine-adjusted median concentrations of total DAPs and of TCPy were significantly higher in Amirim residents compared to the general Jewish population in Israel (0.29μmol/g compared to 0.16, p<0.05 for DAPs and 4.32μg/g compared to 2.34μg/g, p<0.05 for TCPy). Within Amirim residents, we observed a positive association between vegetable intake and urinary TCPy levels (rho=0.47, p<0.05) and lower median total dimethyl phosphate levels in individuals reporting that >25% of the produce they consume is organic (0.065μmol/L compared to 0.22, p<0.05). Results from this pilot study indicate relatively high levels of urinary organophosphate pesticide metabolite concentrations in residents of a vegetarian community, a positive association between vegetable intake and urinary levels of a chlorpyrifos specific metabolite, and lower levels of total dimethyl phosphate in individuals reporting higher intake of organic produce. Results suggest that consumption of organic produce may offer some protection from increased exposure to organophosphate pesticide residues in vegetarians.

Urinary organophosphate metabolite levels in Palestinian pregnant women: results of the Middle East Regional Cooperation Project

The purpose of the study was to measure urinary organophosphate (OP) metabolites in Palestinian pregnant women, and to compare levels with those in pregnant women in Jerusalem and women from the general population in Israel. We measured six dialkyl phosphates in urine samples collected from 148 pregnant women from the West Bank area. Median total dimethyl phosphate (DM(total)) levels were significantly lower in Palestinian women compared to Jerusalem pregnant women and women in Israel (p = 0.041). In Palestinian women reporting that their place of residence was near an agricultural field, DM(total) levels were significantly higher (p = 0.037). Lower urinary excretion of dimethyl phosphate pesticide metabolites in Palestinian women compared to Israeli women may result from lower consumption of fruits and vegetables in the Palestinian population. Our findings highlight differences in OP pesticide exposure in populations with close geographical proximity but with differences in culture, diet, lifestyle, and regulatory oversight of pesticides.

Applicability of western chemical dietary exposure models to the Chinese population

A range of exposure models, which have been developed in Europe and North America, are playing an increasingly important role in priority setting and the risk assessment of chemicals. However, the applicability of these tools, which are based on Western dietary exposure pathways, to estimate chemical exposure to the Chinese population to support the development of a risk-based environment and exposure assessment, is unclear. Three frequently used modelling tools, EUSES, RAIDAR and ACC-HUMANsteady, have been evaluated in terms of human dietary exposure estimation by application to a range of chemicals with different physicochemical properties under both model default and Chinese dietary scenarios. Hence, the modelling approaches were assessed by considering dietary pattern differences only. The predicted dietary exposure pathways were compared under both scenarios using a range of hypothetical and current emerging contaminants. Although the differences across models are greater than those between dietary scenarios, model predictions indicated that dietary preference can have a significant impact on human exposure, with the relatively high consumption of vegetables and cereals resulting in higher exposure via plants-based foodstuffs under Chinese consumption patterns compared to Western diets. The selected models demonstrated a good ability to identify key dietary exposure pathways which can be used for screening purposes and an evaluative risk assessment. However, some model adaptations will be required to cover a number of important Chinese exposure pathways, such as freshwater farmed-fish, grains and pork.

Performance of the CalTOX fate and exposure model in a case study for a dioxin-contaminated site

Soil with high levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) is found at contaminated sites all over the world. Transfer of PCDD/Fs from contaminated soil to the food chain could lead to elevated human exposure. As a complement to available monitoring data, multimedia fate and exposure modeling can be applied to support risk assessment of sites with PCDD/F contaminated soil. In this study, we evaluated the performance of the CalTOX fate and exposure model for 2,3,7,8-substituted PCDD/Fs against measured concentrations in air, soil, grass, carrots, potatoes, milk, meat, and eggs from a contaminated site in northern Sweden. The calculated total toxic equivalent (TEQ) concentrations agree with measurements within a factor of 10 for all exposure media but one. Results for individual congeners demonstrated that the model did not always perform well at describing key processes that mobilize PCDD/Fs out of soils, such as transfer into root crops and ingestion of soil by chickens. Uncertainty in only a small subset of input parameters affects the model output. Improved information and models describing transfer of soil particles onto leafy vegetation by rain splash and biotransfer factors for PCDD/Fs to milk, meat, and eggs are particular research needs to reduce uncertainties in model-based assessments.

Organophosphate pesticide exposure, PON1, and neurodevelopment in school-age children from the CHAMACOS study

INTRODUCTION

Organophosphate (OP) pesticides remain widely used in agriculture. Previously, we reported that PON1 genotype was directly associated with neurodevelopment at age two, and that PON1 genotype may increase susceptibility to OP exposure.

OBJECTIVES

We examined the relationships of maternal and child PON1 genotype and enzyme activity levels and neurodevelopment at school age and examined their interaction with maternal dialkyl phosphate (DAP) metabolite levels to investigate differential susceptibility to OP-related neurotoxicity.

METHODS

Participants were from the CHAMACOS longitudinal birth cohort of Latino families in an agricultural region of California. We measured DAP metabolites of OP pesticides in maternal and child urine samples, and analyzed PON1192 and PON1-108 genotypes and enzyme activity [arylesterase (ARYase), paraoxonase (POase)] in maternal and child blood. We examined their association with children׳s performance on the Conners׳ Kiddie Continuous Performance Test (K-CPT) at 5 years (n=296) and the Wechsler Intelligence Scale for Children (WISC-IV) at 7 years (n=327).

RESULTS

Maternal and child PON1 genotype was not related to performance on K-CPT or WISC, although WISC scores tended to be lowest in children and children of mothers who carried the PON-108TT genotype. Pregnancy ARYase levels were positively associated with all WISC subscales (e.g., 4.0 point increase in Full Scale IQ per standard deviation increase in ARYase, 95% CI=1.6, 6.4), while pregnancy POase levels were positively associated with WISC Processing Speed only. Maternal PON1-108 weakly modified the relationship of maternal DAPS and K-CPT scores (pinteraction=0.21) and WISC verbal IQ (pinteraction=0.71). The association between DAPs and Full-Scale IQ was strongest for children of mothers with lowest-tertile ARYase levels (pinteraction=0.27). This relationship held for both diethyl and dimethyl DAPs and for all subscales of the WISC.

CONCLUSIONS

We extend our previous findings that PON1 genotype and enzyme levels may be directly related to performance on certain domains of neurodevelopment in school-age children. Lower maternal PON1 enzyme levels during pregnancy may also increase susceptibility of children to neurotoxicity from OP pesticide exposure.

Bayesian Networks as a screening tool for exposure assessment

A tiered approach to contamination exposure assessment is currently adopted in many countries. Increasing the site-specific information in exposure assessments is generally recommended when guideline values for contaminants in soil are exceeded. This work details a Bayesian Network (BN) approach to developing a site-specific environmental exposure assessment that focuses on the simple mapping and assessment of assumptions and the effect of new data on assessment outcomes. The BN approach was applied to a floodplain system in New South Wales, Australia, where site-specific information about elevated antimony (Sb) concentrations and distribution in soils was available. Guidelines for exposure assessment in Australia are used as a template for this site, although the approach is generic. The BN-based assessment used an iterative approach starting with limited soil Sb data (41 samples ranging from 0 to 18 mg kg-(1) Sb) and extending the model with more detailed Sb data (145 samples ranging from 0 to 40 mg kg-(1) Sb). The analyses identified dominant exposure pathways and assessed the sensitivity of these pathways to changes in assumptions and the level of site-specific information available. In particular, there was a 10.8% probability of exceeding the tolerable daily intake of Sb in the case study when the limited soil Sb data was used, which increased to 26.2% with the more detailed sampling regime. There was also a 47% decrease in the probability of overexposure to Sb when the dermal bioavailability of arsenic (a similar metalloid) was used as a surrogate measure instead of a default bioavailability of 100%. We conclude that the BN approach to soil exposure assessment has merit both in the context of Australian and international soil exposure assessments.

Pesticide exposure and neurodevelopmental outcomes: review of the epidemiologic and animal studies

Assessment of whether pesticide exposure is associated with neurodevelopmental outcomes in children can best be addressed with a systematic review of both the human and animal peer-reviewed literature. This review analyzed epidemiologic studies testing the hypothesis that exposure to pesticides during pregnancy and/or early childhood is associated with neurodevelopmental outcomes in children. Studies that directly queried pesticide exposure (e.g., via questionnaire or interview) or measured pesticide or metabolite levels in biological specimens from study participants (e.g., blood, urine, etc.) or their immediate environment (e.g., personal air monitoring, home dust samples, etc.) were eligible for inclusion. Consistency, strength of association, and dose response were key elements of the framework utilized for evaluating epidemiologic studies. As a whole, the epidemiologic studies did not strongly implicate any particular pesticide as being causally related to adverse neurodevelopmental outcomes in infants and children. A few associations were unique for a health outcome and specific pesticide, and alternative hypotheses could not be ruled out. Our survey of the in vivo peer-reviewed published mammalian literature focused on effects of the specific active ingredient of pesticides on functional neurodevelopmental endpoints (i.e., behavior, neuropharmacology and neuropathology). In most cases, effects were noted at dose levels within the same order of magnitude or higher compared to the point of departure used for chronic risk assessments in the United States. Thus, although the published animal studies may have characterized potential neurodevelopmental outcomes using endpoints not required by guideline studies, the effects were generally observed at or above effect levels measured in repeated-dose toxicology studies submitted to the U.S. Environmental Protection Agency (EPA). Suggestions for improved exposure assessment in epidemiology studies and more effective and tiered approaches in animal testing are discussed.

SVOC exposure indoors: fresh look at dermal pathways

This paper critically examines indoor exposure to semivolatile organic compounds (SVOCs) via dermal pathways. First, it demonstrates that--in central tendency--an SVOC's abundance on indoor surfaces and in handwipes can be predicted reasonably well from gas-phase concentrations, assuming that thermodynamic equilibrium prevails. Then, equations are developed, based upon idealized mass-transport considerations, to estimate transdermal penetration of an SVOC either from its concentration in skin-surface lipids or its concentration in air. Kinetic constraints limit air-to-skin transport in the case of SVOCs that strongly sorb to skin-surface lipids. Air-to-skin transdermal uptake is estimated to be comparable to or larger than inhalation intake for many SVOCs of current or potential interest indoors, including butylated hydroxytoluene, chlordane, chlorpyrifos, diethyl phthalate, Galaxolide, geranyl acetone, nicotine (in free-base form), PCB28, PCB52, Phantolide, Texanol and Tonalide. Although air-to-skin transdermal uptake is anticipated to be slow for bisphenol A, we find that transdermal permeation may nevertheless be substantial following its transfer to skin via contact with contaminated surfaces. The paper concludes with explorations of the influence of particles and dust on dermal exposure, the role of clothing and bedding as transport vectors, and the potential significance of hair follicles as transport shunts through the epidermis.

PRACTICAL IMPLICATIONS

Human exposure to indoor pollutants can occur through dietary and nondietary ingestion, inhalation, and dermal absorption. Many factors influence the relative importance of these pathways, including physical and chemical properties of the pollutants. This paper argues that exposure to indoor semivolatile organic compounds (SVOCs) through the dermal pathway has often been underestimated. Transdermal permeation of SVOCs can be substantially greater than is commonly assumed. Transport of SVOCs from the air to and through the skin is typically not taken into account in exposure assessments. Yet, for certain SVOCs, intake through skin is estimated to be substantially larger than intake through inhalation. Exposure scientists, risk assessors, and public health officials should be mindful of the dermal pathway when estimating exposures to indoor SVOCs. Also, they should recognize that health consequences vary with exposure pathway. For example, an SVOC that enters the blood through the skin does not encounter the same detoxifying enzymes that an ingested SVOC would experience in the stomach, intestines, and liver before it enters the blood.

Intake fraction for the indoor environment: a tool for prioritizing indoor chemical sources

Reliable exposure-based chemical characterization tools are needed to evaluate and prioritize in a rapid and efficient manner the more than tens of thousands of chemicals in current use. This study applies intake fraction (iF), the integrated incremental intake of a chemical per unit of emission, for a suite of indoor released compounds. A fugacity-based indoor mass-balance model was used to simulate the fate and transport of chemicals for three release scenarios: direct emissions to room air and surface applications to carpet and vinyl. Exposure through inhalation, dermal uptake, and nondietary ingestion was estimated. To compute iF, cumulative intake was summed from all exposure pathways for 20 years based on a scenario with two adults and a 1-year-old child who ages through the simulation. Overall iFs vary by application modes: air release (3.1 × 10(-3) to 6.3 × 10(-3)), carpet application (3.8 × 10(-5) to 6.2 × 10(-3)), and vinyl application (9.0 × 10(-5) to 1.8 × 10(-2)). These iF values serve as initial estimates that offer important insights on variations among chemicals and the potential relative contribution of each pathway over a suite of compounds. The approach from this study is intended for exposure-based prioritization of chemicals released inside homes.

Potential effects of chlorpyrifos on fetal growth outcomes: implications for risk assessment

Chlorpyrifos (CPF) is one of the most widely used organophosphate insecticides in the United States. By December 2000, nearly all residential uses were voluntarily canceled, so that today, CPF is only used to control insect pests on a variety of crops. Periodic review of the potential effects of CPF on all developmental outcomes is necessary in the United States because the Food Quality Protection Act mandates special consideration of risk assessments for infants and children. This article reviews epidemiologic studies examining the association of potential CPF exposure with growth indices, including birth weight, birth length, and head circumference, and animal studies focusing on related somatic developmental endpoints. It differs from earlier reviews by including an additional cohort study and providing in-depth systematic evaluation of the patterns of association across different studies with respect to specificity of biomarkers for CPF, consistency, dose response, strength of association, temporality, and biological plausibility (Hill 1965), as well as consideration of the potential role of effect modification and bias. The review did not identify any strong associations exhibiting consistent exposure-response patterns that were observed in more than one of the four cohort studies evaluated. In addition, the animal data indicate that developmental effects occur at doses that produce substantial maternal toxicity and red blood cell (RBC) acetylcholinesterase (AChE) inhibition. Based on consideration of both the epidemiologic and animal data, maternal RBC AChE inhibition is a more sensitive endpoint for risk assessment than somatic developmental effects reviewed in this article.

Prenatal exposure to organophosphate pesticides and IQ in 7-year-old children

CONTEXT

Organophosphate (OP) pesticides are neurotoxic at high doses. Few studies have examined whether chronic exposure at lower levels could adversely affect children's cognitive development.

OBJECTIVE

We examined associations between prenatal and postnatal exposure to OP pesticides and cognitive abilities in school-age children.

METHODS

We conducted a birth cohort study (Center for the Health Assessment of Mothers and Children of Salinas study) among predominantly Latino farmworker families from an agricultural community in California. We assessed exposure to OP pesticides by measuring dialkyl phosphate (DAP) metabolites in urine collected during pregnancy and from children at 6 months and 1, 2, 3.5, and 5 years of age. We administered the Wechsler Intelligence Scale for Children, 4th edition, to 329 children 7 years of age. Analyses were adjusted for maternal education and intelligence, Home Observation for Measurement of the Environment score, and language of cognitive assessment.

RESULTS

Urinary DAP concentrations measured during the first and second half of pregnancy had similar relations to cognitive scores, so we used the average of concentrations measured during pregnancy in further analyses. Averaged maternal DAP concentrations were associated with poorer scores for Working Memory, Processing Speed, Verbal Comprehension, Perceptual Reasoning, and Full-Scale intelligence quotient (IQ). Children in the highest quintile of maternal DAP concentrations had an average deficit of 7.0 IQ points compared with those in the lowest quintile. However, children's urinary DAP concentrations were not consistently associated with cognitive scores.

CONCLUSIONS

Prenatal but not postnatal urinary DAP concentrations were associated with poorer intellectual development in 7-year-old children. Maternal urinary DAP concentrations in the present study were higher but nonetheless within the range of levels measured in the general U.S. population.

Determinants of organophosphorus pesticide urinary metabolite levels in young children living in an agricultural community

Organophosphorus (OP) pesticides are used in agriculture and several are registered for home use. As young children age they may experience different pesticide exposures due to varying diet, behavior, and other factors. We measured six OP dialkylphosphate (DAP) metabolites (three dimethyl alkylphosphates (DMAP) and three diethyl alkylphosphates (DEAP)) in urine samples collected from ∼400 children living in an agricultural community when they were 6, 12, and 24 months old. We examined bivariate associations between DAP metabolite levels and determinants such as age, diet, season, and parent occupation. To evaluate independent impacts, we then used generalized linear mixed multivariable models including interaction terms with age. The final models indicated that DMAP metabolite levels increased with age. DMAP levels were also positively associated with daily servings of produce at 6- and 24-months. Among the 6-month olds, DMAP metabolite levels were higher when samples were collected during the summer/spring versus the winter/fall months. Among the 12-month olds, DMAP and DEAP metabolites were higher when children lived ≤60 meters from an agricultural field. Among the 24-month-olds, DEAP metabolite levels were higher during the summer/spring months. Our findings suggest that there are multiple determinants of OP pesticide exposures, notably dietary intake and temporal and spatial proximity to agricultural use. The impact of these determinants varied by age and class of DAP metabolite.

Occurrence and relationship of organophosphorus insecticides and their degradation products in the atmosphere in Western Canada agricultural regions

This paper presents the atmospheric occurrence and seasonal variations of the most frequently detected organophosphorus insecticides (OPs) and their OP oxon degradation products at Bratt's Lake, Saskatchewan in the Canadian Prairies (April 2003 to March 2004, January-December, 2005) and at Abbotsford in the Lower Frazer Valley (LFV) of British Columbia from May 2004 to December, 2005. During 2005 there were 10 OPs, 8 OP oxons, and 6 other OP degradation products measured. The most frequently detected OPs were chlorpyrifos, malathion, and diazinon. At Bratt's Lake the highest atmospheric concentrations were observed for chlorpyrifos, with maximum concentrations observed during July and August in 2003 showing much higher concentrations than those from 2005. This was related to its usage for grasshopper control in the province. At Abbotsford, diazinon and malathion were observed in much higher atmospheric concentrations than chlorpyrifos. Concentrations reached maximum in spring for diazinon and summer for malathion. This study is the first reported study of seasonal variations of OP oxons with their parent OP. Chlorpyrifos oxon concentrations during July were generally low, indicating strong local source contributions. The chlorpyrifos oxon/chlorpyrifos ratio and diazinon oxon/diazinon ratio showed a strong seasonal variation with increasing ratio from spring to summer which was attributed to increasing sunlight hours. Malathion oxon/mathion at both sites was similar and relatively constant throughout the year. The oxon/thion ratio represents a good indicator of age of source or contributions from local versus regional atmospheric sources.

Enantioselectivity in environmental risk assessment of modern chiral pesticides

Chiral pesticides comprise a new and important class of environmental pollutants nowadays. With the development of industry, more and more chiral pesticides will be introduced into the market. But their enantioselective ecotoxicology is not clear. Currently used synthetic pyrethroids, organophosphates, acylanilides, phenoxypropanoic acids and imidazolinones often behave enantioselectively in agriculture use and they always pose unpredictable enantioselective ecological risks on non-target organisms or human. It is necessary to explore the enantioselective toxicology and ecological fate of these chiral pesticides in environmental risk assessment. The enantioselective toxicology and the fate of these currently widely used pesticides have been discussed in this review article.

Comparison of current-use pesticide and other toxicant urinary metabolite levels among pregnant women in the CHAMACOS cohort and NHANES

BACKGROUND

We measured 34 metabolites of current-use pesticides and other precursor compounds in urine samples collected twice during pregnancy from 538 women living in the Salinas Valley of California, a highly agricultural area (1999-2001). Precursors of these metabolites included fungicides, carbamate, organochlorine, organophosphorus (OP), and pyrethroid insecticides, and triazine and chloroacetanilide herbicides. We also measured ethylenethiourea, a metabolite of the ethylene-bisdithiocarbamate fungicides. Repeat measurements of the compounds presented here have not been reported in pregnant women previously. To understand the impact of the women's regional environment on these findings, we compared metabolite concentrations from the CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas) cohort with U.S. national reference data for 342 pregnant women sampled by the National Health and Nutrition Examination Survey (1999-2002).

RESULTS

The eight metabolites detected in > 50% of samples [2,4-dichlorophenol (2,4-DCP); 2,5-dichlorophenol (2,5-DCP); 1- and 2-naphthol; ortho-phenylphenol (ORTH); para-nitrophenol (PNP); 2,4,6-trichlorophenol (2,4,6-TCP); and 3,4,6-trichloro-2-pyridinol (TCPy)] may be related to home or agricultural pesticide use in the Salinas Valley, household products, and other sources of chlorinated phenols. More than 78% of women in this study had detectable levels of at least one of the OP pesticide-specific metabolites that we measured, and > 30% had two or more. The 95th percentile values of six of the most commonly detected (> 50%) compounds were significantly higher among the CHAMACOS women after controlling for age, race, socioeconomic status, and smoking [(2,4-DCP; 2,5-DCP; ORTH; PNP; 2,4,6-TCP; and TCPy); quantile regression p < 0.05].

CONCLUSIONS

Findings suggest that the CHAMACOS cohort has an additional burden of precursor pesticide exposure compared with the national sample, possibly from living and/or working in an agricultural area.

Multimedia modeling of human exposure to chemical substances: the roles of food web biomagnification and biotransformation

The Risk Assessment IDentification And Ranking (RAIDAR) model is refined to calculate relative human exposures as expressed by total intake, intake fraction (iF), and total body burden (TBB) metrics. The RAIDAR model is applied to three persistent organic pollutants (POPs) and six petrochemicals using four mode-of-entry emission scenarios to evaluate the effect of metabolic biotransformation estimates on human exposure calculations. When biotransformation rates are assumed to be negligible, daily intake and iFs for the nine substances ranged over six orders of magnitude and TBBs ranged over 10 orders of magnitude. Including biotransformation estimates for fish, birds, and mammals reduced substance-specific daily intake and iF by up to 4.5 orders of magnitude and TBB by more than eight orders of magnitude. The RAIDAR iF calculations are compared to the European Union System for the Evaluation of Substances (EUSES) model iF calculations and differences are discussed, especially the treatment of food web bioaccumulation. Model selection and application assumptions result in different rankings of human exposure potential. These results suggest a need to critically consider model selection and to include reliable biotransformation rate estimates when assessing relative human exposure and ranking substances for priority setting. Recommendations for further model evaluations and revisions are discussed.

Pesticides in dust from homes in an agricultural area

We collected indoor dust samples from homes in the Salinas Valley of California. Of 22 pesticides measured in 504 samples, permethrins and the organophosphate chlorpyrifos were present in highest amounts. In multivariate Tobit regression models among samples from 197 separate residences, reported agricultural uses of chlorpyrifos, a herbicide (2,3,5,6-tetrachloroterephthalate (DCPA)), and a fungicide (iprodione) on agricultural fields were significantly (p < 0.01) associated, with 83%, 19%, and 49% increases, respectively, in dust concentrations for each kg applied per day, near participant homes, in the month or season prior to sample collection. However, agricultural use of diazinon, which was 2.2 times that of chlorpyrifos, and of permethrin were not significantly associated with dust levels. Other variables independently associated with dust levels included temperature and rainfall, farmworkers storing work shoes in the home, storing a diazinon product in the home, housing density, having a home less clean, and having an air conditioner. Permethrins, chlorpyrifos, DCPA, and iprodione have either a log octanol-water partition coefficient (K(ow)) greater than 4.0, a very low vapor pressure, or both. Health risk assessments for pesticides that have these properties may need to include evaluation of exposures to house dust.