Pesticide exposures to migrant farmworkers in Eastern NC: detection of metabolites in farmworker urine associated with housing violations and camp characteristics.

BACKGROUND: The purpose of this paper is to present and evaluate descriptively bivariate associations between urinary metabolites of pesticides and herbicides and migrant camp conditions, violations, and personal worker behaviors at home for farmworkers who do not apply pesticides. METHODS: We studied 183 migrant farmworker camps in eastern North Carolina in 2010. Data and urine samples were collected from 371 men. Predictor measures included violations in six domains of housing regulations and nonviolation characteristics and personal behaviors that might impact urinary metabolites. RESULTS: Cockroaches and bathroom violations were predictive of increased exposure to pyrethroids and cyfluthrin/chlorpyrifos, respectively. Changing and storing clothing and shoes in sleeping rooms increased the number of detects for the diazinon metabolite. CONCLUSIONS: Farmworkers had exposures to multiple chemicals. No single housing domain was identified as critical to mitigating housing-related exposure; specific attention should be paid to changing and storing soiled clothing in sleeping rooms, and insect infestations.

A physiologically based pharmacokinetic model for trichloroethylene in the male long-evans rat.

A physiologically based pharmacokinetic (PBPK) model for trichloroethylene (TCE) in the male Long-Evans (LE) rat was needed to aid in evaluation of neurotoxicity data collected in this rodent stock. The purpose of this study was to develop such a model with the greatest possible specificity for the LE rat. The PBPK model consisted of 5 compartments: brain, fat, slowly perfused tissue, rapidly perfused viscera, and liver. Partition coefficients (blood, fat, muscle, brain, liver) were determined for LE rats. The volumes of the brain, liver, and fat compartments were estimated for each rat, with tissue-specific regression equations developed from measurements made in LE rats. Vapor uptake data from LE rats were used for estimation of Vmaxc. As blood flow values for LE rats were not available, values from Sprague-Dawley (SD) and Fischer-344 (F344) rats were used in separate simulations. The resulting values of Vmaxc were used to simulate tissue (blood, liver, brain, fat) TCE concentrations, which were measured during (5, 20, 60 min) and after (60 min of TCE followed by 60 min of air) flow-through inhalation exposures of LE rats to 200, 2000, or 4000 ppm TCE. Simulation of the experimental data was improved by use of F-344 blood-flow values and the corresponding Vmaxc (8.68 mg/h/kg) compared to use of SD flows and the associated Vmaxc (7.34 mg/h/kg). Sensitivity analysis was used to determine those input parameters with the greatest influence on TCE tissue concentrations. Alveolar ventilation consistently (across exposure concentration, exposure duration, and target tissue) had the greatest impact on TCE tissue concentration. The PBPK model described here is being used to explore the relationship between measures of internal dose of TCE and neurotoxic outcome.

Collecting urine samples from young children using cotton gauze for pesticide studies.

To estimate pesticide exposure, urine samples are often needed to analyze pesticide metabolites. However, this is difficult for children wearing diapers because simple and feasible techniques suitable for field collection are not available. The objectives of this study were to test the validity of using cotton gauze pad as a medium for collecting urine samples from young children and to examine the stability of the recoveries for creatinine and pesticide metabolites over 24 h. Urine spiked with a pesticide and four metabolites, 2,4-dichlorophenoxyacetic acid (which is mainly eliminated from urine unchanged), 3-phenoxybenzoic acid (metabolite for synthetic pyrethroids), atrazine mercapturate (metabolite for atrazine), malathion dicarboxylic acid (metabolite for malathion), and 2-isopropyl-4-methyl-6-hydroxypyrimidine (metabolite for diazinon) was added to the gauze pads and kept in jars at 37 degrees C in a water bath. Urine was expressed from the gauze pads immediately and after 1, 2, 4, 8, and 24 h, then analyzed. The recoveries, calculated as the percentage of concentration in expressed urine divided by that of the control urine sample, were within a range of 70-130%. The metabolite and creatinine concentrations did not change with time in either expressed urine samples or controls. The results suggest that cotton gauze pad is a promising candidate for collecting urine samples from young children wearing diapers for studies in which these five urinary pesticide metabolites are to be analyzed.

Analytical methods for water disinfection byproducts in foods and beverages.

The determination of exposure to drinking water disinfection byproducts (DBPs) requires an understanding of how drinking water comes into contact with human through multiple pathways. In order to facilitate the investigation of human exposure to DBPs via foods and beverages, analytical method development efforts were initiated for haloacetonitriles, haloketones, chloropicrin, and the haloacetic acids (HAAs) in these matrices. The recoveries of the target analytes were investigated from composite foods and beverages. Individual foods and beverages used to investigate the general applicability of the developed methods were selected for testing based on their watercontent and frequency of consumption. The haloacetonitriles, the haloketones, and chloral hydrate were generally well recovered (70-130%), except for bromochloroacetonitrile (64%) and dibromoacetonitrile (55%), from foods spiked after homogenization and following extraction with methyl-t-butyl ether (MTBE); the addition of acetone was found to be necessary to improve recoveries from beverages. The process of homogenization resulted in decreased recoveries for the more volatile analytes despite the presence of dry ice. The HAAs were generally well recovered (70-130%), except for trichloroacetic acid (58%) and tribromoacetic acid (132%), from foods but low recoveries and emulsion formation were experienced with some beverages. With both groups of analytes, certain matrices were more problematic (as measured by volatility losses, emulsion formation) than others with regard to processing and analyte recovery.

Determination of platinum in rat dorsal root ganglion using ICP-MS.

This study evaluated the performance of inductively coupled plasma mass spectrometry for the determination of platinum (Pt) in rat dorsal root ganglion. The method detection limit was found to be 0.008 ng/mL of Pt, which corresponds to 4 pg of Pt per milligram of ganglia. The standard deviations in the tissue matrix were 5.7% or better and minimum matrix effect was observed. Compared to indium, the use of iridium or a combination of iridium and bismuth as internal standard(s) provided more accurate measurement. The Pt in the tissue digestate was stable for a minimum of 46 d at levels above 0.05 ng/mL. Flow injection analysis using undiluted digestates resulted in approximately 20% signal enhancement. Internal standard correction was necessary to obtain accurate results. The method was used in initial studies in which rats were dosed with cisplatin and has shown that Pt accumulates and persists in dorsal rat ganglion following treatment.

Selective inhibition of cytochrome P450 2E1 in vivo and in vitro with trans-1,2-dichloroethylene.

The effect of trans-1,2-dichloroethylene (DCE), an inhibitor of cytochrome P450 (P450) 2E1, on the catalytic activities and total content of hepatic P450 was determined in vivo and in vitro. Hepatic microsomes were prepared from groups of rats prior to dosing and at 2, 5, 12, and 24 h postdosing, and total P450 content and the activities of P450 1A2, P450 2A1, P450 2B, P450 2C6, P450 2C11, P450 2D1, P450 2E1, and P450 3A were determined. The lowest dose of DCE that yielded maximal inactivation of P450 2E1 was found to be 100 mg/kg. Significant decreases in total content of P450 or the activities of P450 1A2, P450 2A1, P450 2B, P450 2C6, P450 2C11, P450 2D1, and P450 3A were not observed during the 24 h following administration of DCE (100 mg/kg ip), but P450 2E1 activity was diminished about 65% at 2 and 5 h after DCE treatment and returned to control levels at 24 h. Additionally, there was little or no significant effect on the activities of hepatic cytosolic alcohol dehydrogenase or mitochondrial or microsomal aldehyde dehydrogenases 5 h postdosing. DCE showed the same selectivity for P450 inactivation in vitro, and P450 2E1 activity was inhibited by >80% without affecting the other isozymes. However, DCE (5 mM) also proved to be a good competitive inhibitor of the probe activities of P450 1A2 and P450 2C6. The in vivo inhibition of P450 2E1 was accompanied by decreases in the levels of the immunoreactive protein, and an additional immunoreactive band appeared at ca. 30 kDa in the Western blot of microsomes from DCE-treated rats, possibly arising from proteolytic degradation of P450 2E1 protein after covalent modification by the inhibitor. DCE is an effective, relatively nontoxic inhibitor of P450 2E1 in vivo and in vitro that has greater selectivity than other agents currently used.

Do endogenous volatile organic chemicals measured in breath reflect and maintain CYP2E1 levels in vivo?

The effect of trans-1,2-dichloroethylene (DCE), an inhibitor of cytochrome P450 (P450) 2E1 (CYP2E1), on the composition and quantity of volatile organic chemicals (VOCs) expired in the breath of male F-344 rats was determined in parallel with hepatic P450 activity and content. Hepatic microsomes were prepared from groups of rats prior to dosing and at 2, 5, 12, and 24 hr postdosing with DCE (100 mg/kg ip), and total P450 content and the activity of CYP2E1 was determined. Breath was collected from parallel groups of rats predose and at several intervals that encompassed the time points for rats euthanized for microsome preparation. Over 100 breath components were identified by GC/MS and quantitated by GC/FID. The overall change in the profile of breath VOCs resulting from administration of DCE was striking. An increase of approximately 1000% was measured in the mass of non-DCE-derived VOCs exhaled 4-6 hr after dosing, but there was no increase in hepatic lipid peroxidation. In addition to hexane, short-chain methyl ketones were particularly affected, and percentage increases in response to inhibition were inversely related to chain length, with acetone and 2-butanone > 2-pentanone >> 2-hexanone > 2-heptanone. There were no statistically significant decreases in total content of P450, but the activity of CYP2E1 was diminished about 65% at 2 and 5 hr after DCE treatment. However, 24 hr after inhibitor administration the total mass of VOCs expired was only marginally elevated above baseline and CYP2E1 activity was not significantly different from that of untreated rats. The compounds most markedly increased upon inhibition of CYP2E1 are also excellent inducers of that isozyme, and this finding is consistent with the hypothesis that these chemicals are important to the normal homeostasis of CYP2E1. The increase in breath components observed following inhibition of CYP2E1 suggests that VOCs in breath can reflect the activity of that isozyme in vivo.

Uptake and decay of volatile organic compounds at environmental concentrations: application of a four-compartment model to a chamber study of five human subjects.

Five subjects were exposed to nine volatile organic compounds (VOCs) at concentrations that can be encountered in everyday life. Breath samples were collected during a 10-h uptake phase and a 24-h decay phase. It was possible to determine four distinct slopes in the decay curve for each chemical. The distribution in the body and residence times in different tissues were calculated using a linear four-compartment mass-balance model. The model was used to predict breath concentrations for two subjects in a second chamber experiment including the same nine VOCs, representing three chemical classes (aromatic, aliphatic, and chlorinated compounds). Predicted values were generally within 25% of those observed, suggesting that the model parameters calculated here could be useful in estimating exposure and body burden to other VOCs in these three classes. Median residence times for the nine VOCs ranged from 3-12 min for compartment 1 (metabolizing); 0.3-2 h for compartment 2; 2-5 h for compartment 3; and 1-4 d for compartment 4. The fraction of the parent compound exhaled at equilibrium was estimated to range from 0.06-0.16 for four aromatic compounds and decane; 0.22-0.23 for trichloroethylene and dichloromethane; 0.35 for hexane; and 0.88 for 1,1,1-trichloroethane. Limited blood measurements were obtained for six of the nine VOCs in two subjects simultaneously with the breath samples over four-hour decay periods. Blood/breath ratios agreed well between the two subjects, but were higher than human blood/air partition coefficients reported in subjects exposed to high concentrations. This observation is consistent with results from other studies at relatively low concentrations.

The impact of dose rate on the neurotoxicity of acrylamide: the interaction of administered dose, target tissue concentrations, tissue damage, and functional effects.

Health agencies are often required to predict the effects of long term low level exposure in humans based on annual data involving short-term high-level exposures. Uncertainties in extrapolation can be, in part, based on potentially different mechanism associated with different exposure scenarios. This study evaluated the adequacy of short-term exposures to acrylamide for predicting neurotoxicity produced by long-term exposures. The neurotoxic effects of acrylamide (ip) were assessed in rats after acute (0-150 mg/kg), 10-day (0-30 mg/kg), 30-day (0-20 mg/kg), and 90-day (0-10 mg/kg) exposures. Behavioral endpoints included motor activity, grip strength, and the acoustic startle response. Histological examination of sciatic nerve and spinal cord was also performed. Internal and target tissue doses were estimated by measurement of the concentration of acrylamide in serum and sciatic nerve. Functional and pathological results demonstrated that the effects of acrylamide depended on the dose rate and that the neurotoxicity of acrylamide was less than that predicted by a strict dose x time relationship. Behavioral endpoints showed both qualitative and quantitative changes as a function of dose rate. Recovery of behavioral function in these studies was independent of the duration of dosing. Because duration of dosing had no impact on the kinetics of acrylamide, these data indicate that the toxicity of acrylamide is not due to an accumulation of acrylamide in the target tissue. The less than strict cumulative toxicity of acrylamide may result from an interaction between administered dose, tissue damage, and repair processes.

The influence of cytochrome P450 enzyme activity on the composition and quantity of volatile organics in expired breath.

Abstract We have previously described a method to capture, identify and quantify volatile components in expired breath. The purpose of this research is to provide a non-invasive means to measure biomarkers of metabolism in vivo. In the present studies, the effect of 1-aminobenzotriazole (ABT), an inhibitor of diverse cytochrome P450 (P450) enzymes, on the composition of volatile organic chemicals (VOCs) expired in the breath of male F-344 rats was determined in parallel with the catalytic activities and total content of hepatic P450. lntraperitoneal administration of ABT (100 mg kg-(1)) to rats resulted in markedly diminished hepatic microsomal P450 content and activities. The extent of inhibition was near maximal at 4 h, at which time approximately 50% of the total P450 content, about 65% of the CYPlA2 activity, 55% of the CYP2E1 activity, and about 80% of CYP2B activity were lost. Inhibition was maintained to 48 h post-dosing, but P450 content and activities had largely been restored by day 7. Concomitant with the inhibition of P450 were corresponding increases (up to several hundred-fold) in the molar amount of volatiles appearing in the breath of ABT-treated animals, and the rebound of P450 levels was attended by corresponding decreases in the appearance of breath volatiles. These studies indicate that P450 plays a major role in the metabolism of VOCs appearing in breath, and that these chemicals can serve as markers on P450 activity in vivo.

The identification of polar organic compounds found in consumer products and their toxicological properties.

Exposure to volatile organic compounds (VOCs) in the indoor environment has received substantial research attention in the past several years, with the goal of better understanding the impact of such exposures on human health and well-being. Many VOCs can arise from consumer products used within the indoor environment. The VOCs emitted from five representative consumer products were collected onto Tenax-GC and subjected to thermal desorption and analysis by gas chromatography, in combination with low-resolution mass spectrometry (MS), high-resolution MS, and matrix-isolation Fourier transform infrared spectroscopy for structural characterization. An emphasis was placed on the polar organic compounds often used to provide fragrance in these products. The structures of a number of these compounds were confirmed, and an electronic literature search was carried out on them to determine any known toxic properties. The search revealed that many of the VOCs possess toxic properties when studied at acute, relatively high-level exposures. In addition, toxic effects were reported for a few of the chemicals, such as benzaldehyde, alpha-terpineol, benzyl acetate, and ethanol, at relatively low dose levels of 9-14 mg/kg. In general, the data were unclear as to the effect of chronic, low-level exposures. The widespread use of such chemicals suggests that the health effects of chronic exposures need to be determined. Validated analytical methods for the quantitative characterization of polar organic compounds at low concentrations will be required to make such work possible.

A breath sampling device for measuring human exposure to volatile organic compounds in microgravity.

A compact device for the collection of alveolar air (breath) from humans aboard spacecraft was developed. The system uses silicone one-way valves that operate independent of gravity, and provide minimal backpressure. Small charcoal filters clean ambient air used for inhalation. The device provided good recoveries of organic compounds at the 20 ng/L level, with generally low carryover of these compounds to a blank sample following a sample at exposure to 100 ng/L. When water accumulated in the system, this carryover increased for highly water soluble compounds. The new device was used in parallel with a larger, previously developed alveolar air sampler that requires gravity for proper operation; comparable results were obtained with the two units. The device measures 47 x 34 x 11.4 cm and weighs approximately 3.2 kg. Sufficient space is available within the case to accommodate a number of sample collection options.

Determination of acrylamide in rat serum and sciatic nerve by gas chromatography-electron-capture detection.

A modified method for the derivatization and determination of acrylamide as 2-bromopropenamide by gas chromatography-electron-capture detection was developed and applied to serum and sciatic nerve from rats. The method was accurate and precise over the calibration range 2.24-7.47 micrograms/ml in serum diluted 1:125 and 4-122 micrograms/g in sciatic nerve homogenate (5 mg/ml). limits of detection were estimated to be 1200 ng/ml in undiluted serum and 3 micrograms/g in intact sciatic nerve. The use of less dilute samples to allow for lower limits of detection appears feasible. The time-course of acrylamide in serum and sciatic nerve was studied after acute dosing and indicated elimination half-lives of 1.8 and 2.0 h for serum and sciatic nerve, respectively. A dose-effect relationship was established for each matrix after acute dosing and the measured acrylamide concentrations in serum (microgram/ml) were approximately the same as in sciatic nerve (microgram/g).

Elimination of volatile organic compounds in breath after exposure to occupational and environmental microenvironments.

Breath measurements offer the potential for a direct and noninvasive evaluation of human exposure to volatile organic compounds (VOCs) in the environments in which people live and work. This research study was conducted to further evaluate and develop the potential of this exposure assessment methodology. Several people were exposed to the atmosphere in six microenvironments for several hours. Air concentrations of VOCs were measured during these exposures and breath samples were collected and analyzed at multiple time points after the exposure to evaluate elimination kinetics for 21 VOCs. A new alveolar breath collection technique was applied. Elimination half-lives were estimated using a mono- and bi-exponential model. The alveolar breath collection and analysis methodology proved to be very useful for collecting many samples in short time intervals and this capability was very important for more accurately describing the initial phase of the decay curves. Breath decay curves were generated from samples collected over a four hour period after exposure for 21 of 24 target VOCs. A biexponential function generally provided a better fit for the decay data than did the monoexponential function, supporting a multi-compartment uptake and elimination model for the human body.

A device for sampling of human alveolar breath for the measurement of expired volatile organic compounds.

This report describes the development of a portable spirometer capable of collecting primarily alveolar breath into 1.8-L canisters for subsequent gas chromatographic/mass spectrometric (GC/MS) analysis. Based on CO2 measurements, greater than 97% of the breath collected is alveolar in origin. Sample collection takes place in approximately two minutes. Clean air for inhalation is provided by two organic vapor respirator cartridges. Studies of the breakthrough volume of test compounds at both the 5- and 50-micrograms/m3 levels indicate that each cartridge filter can be used to sample over 300 L of air and that this volume is not altered by intermittent use and storage of the filter for up to five days. In experiments designed to mimic human breathing, recoveries of test compounds through the device at the 5-mu/m3 level ranged from 87 to 112%. Essentially no volatile organic compound (VOC) memory (i.e., adsorption carryover by the device) was measured at the 50-micrograms/m3 level. The data suggest that the device can be used successfully for organic compounds with volatilities greater than that of p-dichlorobenzene.