Biphasic Dissipation Kinetics for Dislodgeable Foliar Residues in Estimating Postapplication Occupational Exposures to Endosulfan

Gajbhiye

Bull Environ Contam Toxicol

2008

120

Persistence and leaching of thiamethoxam in soil were studied under laboratory conditions. The persistence studies carried out at two fortification levels and under three moisture regimes revealed that thiamethoxam persisted beyond 90 days in all the treatments with half-life varying from 46.3 to 301.0 days. Under dry conditions, the dissipation was faster at 10 mg kg(-1) level as compared to 1 mg kg(-1), whereas the reverse trend was observed under field capacity moisture and submerged conditions. The effect of moisture was prominent and longer persistence was observed under dry conditions (t1/2 200.7-301.0 days) followed by field capacity moisture (t1/2 91.2-94.1 days) and submerged condition (t1/2 46.3-75.3 days). The leaching experiment carried out under laboratory conditions showed that on leaching the soil column with water equivalent to 65 cm rainfall, 66-79% of the applied thiamethoxam was recovered from leachate and no residues were detected in soil. Results showed that thiamethoxam has a potential to leach down under heavy rainfall conditions.

Section: Resultsmentioning

confidence: 96%

Soil Dissipation and Leaching Behavior of a Neonicotinoid Insecticide Thiamethoxam

Gajbhiye

Bull Environ Contam Toxicol

2008

120

“…For example, dissipation rates can be used to determine when workers can safely reenter fields and glasshouses following a pesticide application [1], and may also be used to estimate the potential exposure of individuals who may come in contact with, for example, sprayed sports turf or golf greens [2,3]. Dissipation rates also have application in consumer safety.…”

Section: Discussionmentioning

confidence: 99%

Development of a Data Set of Pesticide Dissipation Rates in/on Various Plant Matrices for the Pesticide Properties Database (PPDB)

Lewis¹,

Tzilivakis²

2017

Preprint

Data relating to the rate at which pesticide active substances dissipate on or within various plant matrices are important for a range of different risk assessments; however, despite the importance of this data, dissipation rates are not included in the most common online data resources. Databases have been collated in the past, but these tend not to be maintained or regularly updated. The purpose of the exercise described herein was to collate a new database in a format compatible with the main online pesticide database resource (the Pesticide Properties Database, PPDB), to validate this database in line with the Pesticide Properties Database protocols and thus ensure that the data is maintained and updated in future. Data was collated using a systematic review approach using several scientific databases. Collated literature was subjected to a quality assessment, and then data was extracted into an MS Excel spreadsheet. The outcome of the study is a database based on data collated from 1390 published articles covering over 400 pesticides and over 200 crops across a wide variety of different matrices (leaves, fruits, seeds etc.) for pesticide residues on the crop surface, as well as residues absorbed within the plant material. This data is now fully incorporated into the PPDB.Data Set: available as a supplementary file: "Plant dissipation data August 2017.xlxs". Data Set License:This data set was made available under a CC-BY license.Keywords: pesticide dissipation; risk assessment; environmental fate SummaryData relating to the rate at which pesticide active substances dissipate or decay on or within various plant matrices (e.g., leaves, stems, seeds, fruits) are important for a range of different risk assessments. For example, dissipation rates can be used to determine when workers can safely reenter fields and glasshouses following a pesticide application [1], and may also be used to estimate the potential exposure of individuals who may come in contact with, for example, sprayed sports turf or golf greens [2,3]. Dissipation rates also have application in consumer safety. For example, these values are used in calculations for predicting residue concentrations in harvested produce and for determining the time interval needed between crop spraying and harvesting or potential processing/consumption in order to minimise residue concentrations [4,5]. Dissipation rates also have value when considering the potential risk to non-target and beneficial organisms (e.g., pollinators) that may forage or otherwise come in contact with a pesticide treated plant, as well as informing on how long the chemical is likely to offer satisfactory pest control before it decays [6][7][8]. As a consequence, plant matrix half-lives are often an important input parameter into various risk assessment models [9][10][11][12].In this context, dissipation rate is defined as the rate at which the pesticide active substance disappears from the part of the plant measured due to the combined effects of different processes Preprints (www...

J Expo Sci Environ Epidemiol

“…This is important because dioxin sprayed on foliage is often bound to substrates like leaf waxes, and, thus, while it may persist, its bioavailability rapidly decreases (Karch et al, 2004). Decline in DFR is typically a first-order exponential process, although it may be biphasic for some chemicals (Whitmyre et al, 2003). TCDD dissipation from a surface (primarily due to photolysis) has a half-life 1-3 days (Karch et al, 2004).…”

Section: Pesticide Exposure Assessment Practicementioning

confidence: 99%

Assessing exposure to allied ground troops in the Vietnam War: A comparison of AgDRIFT and Exposure Opportunity Index models

Ginevan¹,

Ross

Watkins³

2008

The AgDRIFT aerial dispersion model is well validated and closely related to the AGDISP model developed by the USDA Forest Service to determine on-and off-target deposition and penetration of aerially applied pesticide through foliage of trees. The Exposure Opportunity Index (EOI) model was developed to estimate relative exposure of ground troops in Vietnam to aerially applied herbicides. We compared the output of the two models to determine whether their predictions were in substantial agreement, but found a total lack of concordance. While the AgDRIFT model estimated that ground-level deposition through foliage was reduced more than 20 orders of magnitude at less than 1 km from the flight line, the EOI model predicted deposition declines less than one order of magnitude 4 km from the flight line. Interestingly the EOI model predicts a four-fold variability in EOI on the flight line, where exposure should be essentially invariant because the spray apparatus is designed to apply herbicide at a constant rate. We believe that the EOI model cannot be used to provide individual exposure estimates for the purpose of conducting epidemiologic studies. Moreover, evaluation of the position data for both herbicide spray swaths and troop locations, together with the actual patterns of spray deposition predicted by the AgDRIFT model, suggests that precise individual-level exposure assessments for ground troops in Vietnam are impossible. However, we suggest that well-validated tools like AgDRIFT can be used to estimate exposure to groups of individuals.