Bibliography Tag: analytical methods

Blair and Zahm, 1993

Blair, A., & Zahm, S. H.; “Patterns of pesticide use among farmers: implications for epidemiologic research;” Epidemiology, 1993, 4(1), 55-62; DOI: 10.1097/00001648-199301000-00011.

ABSTRACT:

Epidemiologic studies of farmers have linked pesticides with certain cancers. Information on exposures from many of these studies was obtained by interview of farmers or their next-of-kin. The reliability and validity of data on pesticide use obtained by recall, often years after the event, have been questioned. Pesticide use, however, is an integral component in most agricultural operations, and the farmers’ knowledge and recall of chemicals used may be better than for many other occupations. Contrary to general belief, many farmers typically use only a few pesticides during their lifetimes and make only a few applications per year. Data from U.S. Department of Agriculture surveys indicate that herbicides are applied to wheat, corn, soybeans, and cotton and that application of insecticides to corn averages two or fewer times per year. In epidemiologic studies at the National Cancer Institute, the proportion of farmers ever reporting lifetime use of five or more different chemicals was 7% for insecticides and 20% for herbicides. Surrogate respondents have often been used in epidemiologic studies of cancer; they are able to recall pesticide use with less detail than the farmers themselves. The pesticides reported by surrogates were the same as reported by subjects themselves, but with less frequency. Comparison of reporting by cases and controls provided no evidence of case-response (differential) bias; thus, inaccurate recall of pesticide use by subjects or surrogates would tend to diminish risk estimates and dilute exposure-response gradients. FULL TEXT


Potera, 2015

Potera, C.; “Tracking organophosphates: new method for assessing long-term dietary exposures;” Environmental Health Perspectives, 2015, 123(5), A135; DOI: 10.1289/ehp.123-A135.

ABSTRACT:

Not Available

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Oseland et al., 2020

Oseland, E., Bish, M., Steckel, L., & Bradley, K.; “Identification of environmental factors that influence the likelihood of off-target movement of dicamba;” Pest Management Science, 2020, 76(9), 3282-3291; DOI: 10.1002/ps.5887.

ABSTRACT:

BACKGROUND: Commercialization of dicamba-resistant soybean and cotton and subsequent post-emergence applications of dicamba contributed to at least 1.4 and 0.5 million hectares of dicamba-injured soybean in the United States in 2017 and 2018, respectively. This research was initiated to identify environmental factors that contribute to off-target dicamba movement. A survey was conducted following the 2017 growing season to collect information from dicamba applications that remained on the target field and those where dicamba moved. Weather and environmental data surrounding applications were collected and used to identify factors that reduce the likelihood of off-target movement. Soil pH was one factor identified in the model, and field experiments were conducted in 2018 and 2019 to validate the model. Three commercially-available dicamba formulations and one formulation currently in development were applied to soil at five distinct pH values. Sensitive soybean was used as a bioassay plant to detect dicamba volatilization.

RESULTS: Wind speeds the day of and following application, nearest water source to the field, soybean production acreage in the county, and soil pH were identified as factors that influence the likelihood for off-target movement. In the field study, when dicamba was applied to pH-adjusted soil and placed under low tunnels for 72 h, dicamba volatility increased when soil pH decreased as the model predicted. Dicamba choline, which is not commercially available, had reduced volatility compared to other formulations tested.

CONCLUSION: Results of this study identified specific factors that contribute to successful and unsuccessful dicamba applications and should be considered prior to applications.


Qi et al., 2020

Qi, M., Huo, J., Li, Z., He, C., Li, D., Wang, Y., Vasylieva, N., Zhang, J., & Hammock, B. D.; “On-spot quantitative analysis of dicamba in field waters using a lateral flow immunochromatographic strip with smartphone imaging;” Analytical and Bioanalytical Chemistry, 2020, 412(25), 6995-7006; DOI: 10.1007/s00216-020-02833-z.

ABSTRACT:

Dicamba herbicide is increasingly used in the world, in particular’ with the widespread cultivation of genetically modified dicamba-resistant crops. However, the drift problem in the field has caused phytotoxicity against naive, sensitive crops, raising legal concerns. Thus, it is particularly timely to develop a method that can be used for on-the-spot rapid detection of dicamba in the field. In this paper, a lateral flow immunochromatographic strip (LFIC) was developed. The quantitative detection can be conducted by an app on a smartphone, named “Color Snap.” The tool reported here provides results in 10 min and can detect dicamba in water with a LOD (detection limit) value of 0.1 mg/L. The developed LFIC shows excellent stability and sensitivity appropriate for field analysis. Our sensor is portable and excellent tool for on-site detection with smartphone imaging for better accuracy and precision of the results.


Riter et al., 2020


Riter, L. S., Sall, E. D., Pai, N., Beachum, C. E., & Orr, T. B.; “Quantifying Dicamba Volatility under Field Conditions: Part I, Methodology;” Journal of Agricultural and Food Chemistry, 2020, 68(8), 2277-2285; DOI: 10.1021/acs.jafc.9b06451.

ABSTRACT:

Quantitative assessment of the volatility of field applied herbicides requires orchestrated sampling logistics, robust analytical methods, and sophisticated modeling techniques. This manuscript describes a comprehensive system developed to measure dicamba volatility in an agricultural setting. Details about study design, sample collection, analytical chemistry, and flux modeling are described. A key component of the system is the interlaboratory validation of an analytical method for trace level detection (limit of quantitation of 1.0 ng/PUF) of dicamba in polyurethane foam (PUF) air samplers. Validation of field sampling and flux methodologies was conducted in a field trial that demonstrated agreement between predicted and directly measured dicamba air concentrations at a series of off-target locations. This validated system was applied to a field case study on two plots to demonstrate the utility of these methods under typical agricultural conditions. This case study resulted in a time-varying volatile flux profile, which showed that less than 0.2 +/- 0.05% of the applied dicamba was volatilized over the 3-day sampling period. FULL TEXT


Moore et al., 2014

Moore, C. A., Wilkinson, S. C., Blain, P. G., Dunn, M., Aust, G. A., & Williams, F. M.; “Percutaneous absorption and distribution of organophosphates (chlorpyrifos and dichlorvos) following dermal exposure and decontamination scenarios using in vitro human skin model;” Toxicology Letters, 2014, 229(1), 66-72; DOI: 10.1016/j.toxlet.2014.06.008.

ABSTRACT:

To date, there has been little research investigating low-level human exposure to chemicals, and so the aim of this study was to examine the percutaneous penetration of organophosphates (dichlorvos and chlorpyrifos) using low-level exposure scenarios in vitro. Dermal absorption of chlorpyrifos applied in different vehicles was measured at 0, 4, 8 and 24 h, after dose application for 4 and 24 h exposure (finite dose, 500 ng/cm(2)) in isopropanol (IPA), isopropyl myristate (IPM) and propylene glycol (PG). Dichlorvos was applied to the skin for 24 h (infinite dose, 1 mg/cm(2) and 10 mg/cm(2); finite dose, 5 mug/cm(2)) using the same vehicles. Human skin was mounted in flow through diffusion cells with minimum essential medium eagle pH 7.4 (supplemented with 2% BSA) as receptor fluid. Following exposure, the skin surface dose was removed by tissue swabbing, the stratum corneum removed by sequential tape stripping, and the skin digested prior to scintillation counting (chlorpyrifos), or GC/MS analysis (dichlorvos). The dermal absorption of chlorpyrifos was the greatest following application in PG (19.5% of dose), when compared with absorption from the IPA and IPM vehicles (10.3% and 1.9% absorbed respectively). However, dichlorvos showed greater dermal absorption than chlorpyrifos from all vehicles used, with greatest absorption from the IPA vehicle (38.6% absorbed). Although dichlorvos exhibited a short lag time (0.6 h from IPA and IP vehicles, and 0.4 h from PG), chlorpyrifos displayed greater propensity to accumulate in the stratum corneum and epidermis/dermis. These results demonstrate that prompt skin surface decontamination would be required for both dichlorvos and chlorpyrifos (and chemicals with similar properties) in the event of skin contact. The magnitude of the skin reservoir formed with chlorpyrifos was time dependent, therefore, prompt decontamination of this and similar chemicals would be required to reduce delayed systemic absorption.


Kezic and Nielsen, 2009

Kezic, S., & Nielsen, J. B.; “Absorption of chemicals through compromised skin;” International Archives of Occupational and Environmental Health, 2009, 82(6), 677-688; DOI: 10.1007/s00420-009-0405-x.

ABSTRACT:

Skin is an important route of entry for many chemicals in the work place. To assess systemic uptake of a chemical in contact with the skin, quantitative information on dermal absorption rates of chemicals is needed. Absorption rates are mainly obtained from studies performed with intact, healthy skin. At the work place, however, a compromised skin barrier, although not necessarily visible is common, e.g. due to physical and chemical damage. As reviewed in this article, there are several lines of evidence that reduced integrity of the skin barrier may increase dermal absorption of chemicals in the occupational setting. An impaired skin barrier might lead not only to enhanced absorption of a specific chemical, but also to entrance of larger molecules such as proteins and nanoparticles which normally are not able to penetrate intact skin. In addition to environmental influences, there is increasing evidence that some individuals have an intrinsically affected skin barrier which will facilitate entrance of chemicals into and through the skin making these persons more susceptible for local as well for systemic toxicity. This review addresses mechanisms of barrier alteration caused by the most common skin-damaging factors in the occupational settings and the consequences for dermal absorption of chemicals. Furthermore, this review emphasizes the importance of maintained barrier properties of the skin. FULL TEXT


Mahler et al., 2021

Mahler, B. J., Nowell, L. H., Sandstrom, M. W., Bradley, P. M., Romanok, K. M., Konrad, C. P., & Van Metre, P. C.; “Inclusion of Pesticide Transformation Products Is Key to Estimating Pesticide Exposures and Effects in Small U.S. Streams;” Environmental Science & Technology, 2021; DOI: 10.1021/acs.est.0c06625.

ABSTRACT:

Improved analytical methods can quantify hundreds of pesticide transformation products (TPs), but understanding of TP occurrence and potential toxicity in aquatic ecosystems remains limited. We quantified 108 parent pesticides and 116 TPs in more than 3700 samples from 442 small streams in mostly urban basins across five major regions of the United States. TPs were detected nearly as frequently as parents (90 and 95% of streams, respectively); 102 TPs were detected at least once and 28 were detected in >20% samples in at least one region-TPs of 9 herbicides, 2 fungicides (chlorothalonil and thiophanate-methyl), and 1 insecticide (fipronil) were the most frequently detected. TPs occurred commonly during baseflow conditions, indicating chronic environmental TP exposures to aquatic organisms and the likely importance of groundwater as a TP source. Hazard quotients based on acute aquatic-life benchmarks for invertebrates and nonvascular plants and vertebrate-centric molecular endpoints (sublethal effects) quantify the range of the potential contribution of TPs to environmental risk and highlight several TP exposure-response data gaps. A precautionary approach using equimolar substitution of parent benchmarks or endpoints for missing TP benchmarks indicates that potential aquatic effects of pesticide TPs could be underestimated by an order of magnitude or more. FULL TEXT


Geer et al., 2004

Geer, L. A., Cardello, N., Dellarco, M. J., Leighton, T. J., Zendzian, R. P., Roberts, J. D., & Buckley, T. J.; “Comparative analysis of passive dosimetry and biomonitoring for assessing chlorpyrifos exposure in pesticide workers;” Annals of Occupational Hygeine, 2004, 48(8), 683-695; DOI: 10.1093/annhyg/meh056.

ABSTRACT:

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the US Environmental Protection Agency (EPA) has the authority to regulate the use of pesticides to prevent unreasonable adverse human health effects associated with pesticide exposure. Accordingly, the EPA requires pesticide registrants to perform studies evaluating the potential for pesticide handler exposure. Data from five such studies that included exposure measurements based on both external measurements and biological monitoring were used to examine methods of assessment, routes and determinants of exposure and dose to the pesticide chlorpyrifos. Eighty workers across four job classes were included: mixer/loaders (M/L, n = 24), mixer/loader/applicators (M/L/A, n = 37), applicators (A, n = 9) and re-entry scouts (RS, n = 10). Results showed that doses were highly variable and differed by job class (P < 0.05) with median total (inhalation and dermal combined) exposure-derived absorbed doses (EDADtot) of 129, 88, 85 and 45 microg/application for A, M/L/A, M/L and RS, respectively. Doses derived from the measurement of 3,5,6-trichloro- 2-pyridinol (3,5,6-TCP) in urine were similar in magnitude but differed in rank with median values of 275, 189, 122 and 97 microg/application for A, M/L, RS, and M/L/A, respectively. The relative contribution of dermal to inhalation exposure was examined by their ratio. The median ratios of exposure-derived absorbed dermal dose (EDADderm) (assuming 3% absorption) to exposure-derived absorbed inhalation dose (EDADinh) (assuming 100% absorption) across job classes were 1.7, 1.5, 0.44 and 0.18 for RS, M/L, A and M/L/A, respectively, with an overall median of 0.6. For 34 of 77 workers (44%), this ratio exceeded 1.0, indicating the significance of the dermal exposure pathway. Different dermal absorption factor (DAF) assumptions were examined by comparing EDADtot to the biomarker-derived absorbed dose (BDAD) as a ratio where EDADtot was calculated assuming a DAF of 1, 3 and 10%. Median ratios of 0.45, 0.71 and 1.28, respectively, were determined suggesting the DAF is within the range of 3-10%. A simple linear regression of urinary 3,5,6-TCP against EDADtot indicates a positive association explaining 29% of the variability in the 3,5,6-TCP derived estimate of dose. A multiple linear regression model including the variables EDADderm, EDADinh and application type explained 46% of the variability (R2 = 0.46) in the urinary dose estimate. EDADderm was marginally significant (P = 0.066) while EDADinh was not (P = 0.57). The EDADderm regression coefficient (0.0007) exceeded the coefficient for EDADinh (0.00002) by a factor of 35. This study demonstrates the value of the pesticide registrant database for the purpose of evaluating pesticide worker exposure. It highlights the significance of the dermal exposure pathway, and identifies the need for methods and research to close the gap between external and internal exposure measures. FULL TEXT


Meuling et al., 2005

Meuling, W. J., Ravensberg, L. C., Roza, L., & van Hemmen, J. J.; “Dermal absorption of chlorpyrifos in human volunteers;” International Archives of Occupational and Environmental Health, 2005, 78(1), 44-50; DOI: 10.1007/s00420-004-0558-6.

ABSTRACT:

OBJECTIVE: The methods and results are described of a study on the dermal absorption of chlorpyrifos (CPF) in humans established via urinary excretion of the metabolite 3,5,6-trichloro-2-pyridinol (TCP).

METHODS: Two dermal, single, doses of CPF were applied in two study groups (A and B) each comprising three apparently healthy male volunteers who gave their written informed consent. The clinical part of the study was conducted in compliance with the ICH Guideline and the EC principles of good clinical practice (GCP). An approximately 0.5 ml dilution of CPF in ethanol was applied to an area of approximately 100 cm(2) of the volar aspect of the forearm, resulting in doses of either 5 mg (A) or 15 mg (B) of CPF per study subject. Duration of dermal exposure was 4 h, after which the non-absorbed fraction was washed off. The following samples were collected at pre-determined intervals for the determination of either CPF or its metabolite TCP: dosing solutions, wash-off fractions and urine samples collected up to 120 h after dosing.

RESULTS: A relatively large fraction of CPF (42%-67% of the applied dose) was washed off from the exposed skin area. Application of either 5 mg (A) or 15 mg CPF (B) resulted in the total urinary excretion of 131.8 microg (A) or 115.6 microg (B) of TCP 120 h after dosing. This indicated that 4.3% of the applied dose has been absorbed (A), while in group (B) no significant increase in urinary TCP (115.6 microg) was established. The latter indicates that an increase in the dermal dose at a fixed area does not increase absorption, which suggests that the percutaneous penetration rate was constant. Further, it was observed that the clearance of CPF by the body was not completed within 120 h, suggesting that CPF or TCP was retained by the skin and/or accumulated in the body. A mean elimination half-life of 41 h was established.

CONCLUSION: The results show that daily occupational exposure to CPF may result in accumulation of CPF and/or its metabolites, possibly resulting in adverse effects. FULL TEXT