Dislodgeable residues of ethion in Florida citrus and relationships to weather variables

Nigg, H. N.; Allen, J. C.; Brooks, R. F.; Edwards, G. J.; Thompson, Neal P.; King, Roy W.; Blagg, A. H.

doi:10.1007/bf02097767

Cited by 21 publications

(18 citation statements)

References 16 publications

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“…For the 15.0 and 0.93 kL/ha applications, time alone explained only 67 and 55% of the residue data variation, respectively. These results are very similar to the previously described Florida citrus foliage ethion residue disappearance model where 94% of the variation was explained by the time-weather model and 57% by time alone (7), and the Florida citrus foliage models for parathion where 90% of the variation was explained by the time-weather model and 30% by time alone, and for carbophenothion, where 93% of the variation was explained by the time-weather model and 47% by time alone (8).…”

Section: Discussionsupporting

confidence: 89%

“…A recent report stresses field monitoring with portable equipment for actual residue levels before worker reentry (6). A third approach utilizes the prediction of pesticide levels on leaf surfaces through the use of weather models of pesticide behavior (7,8).…”

Section: Discussionmentioning

confidence: 99%

“…Time was the most highly correlated individual variable (Tables I and II) with California data, whereas in Florida, rainfall, air tem-Figure 2. Parathion exponential decay models compared with data using (A) exponential of time alone (7) in days and (B) exponential of a linear sum of time (7) in days, heating-degree-days (HDD) in °C-days, and cumulative rainfall (CR) in inches (dilute application) perature, and solar radiation were generally the most highly correlated variables. This supports the supposition of Nigg et al (9) that time would probably be the most important environmental parameter in an empirical weather model under stable weather conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Experimental design, application methodology, sampling, analytical methodology, and the residue data have been previously reported (1). The first-order weather decay model, statistics, heating-degree-day transformation, and computer programs have also been previously reported (7,8).…”

Section: Methodsmentioning

confidence: 99%

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A comparison of time and time-weather models for predicting parathion disappearance under California conditions

Nigg¹,

Allen²

1979

Environ. Sci. Technol.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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A comparison of time and time-weather models for predicting parathion disappearance under California conditions

Nigg¹,

Allen²

1979

Environ. Sci. Technol.

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“…This was based on several other published exposure-assessment studies that measured oxon as well as thioate levels during residue analysis (Ralls et al, 1966;Kansouh & Hopkins, 1968;Wolfe et al, 1975;Spear et al, 1975Spear et al, , 1977aSpear et al, , 1977bNigg et al, 1977;Maddy & Meinders, 1987;Costello et al, 1989;Schneider et al, 1990;Spencer et al, 1991;McCurdy et al, 1994). The derived pesticide levels were also assumed to contain a proportion of OP breakdown products.…”

Section: Derivation Of Dermal Thioateioxon Contamination Valuesmentioning

confidence: 99%

Simulated Dermal Contamination With Capillary Samples and Field Cholinesterase Biomonitoring

Yuknavage¹,

Fenske²,

Kalman³

et al. 1997

Journal of Toxicology and Environmental Health

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The extensive international use of organophosphorus compounds (OP) results in numerous acute intoxications each year. OPs inhibit acetylcholinesterase, the enzyme responsible for breaking down the neurotransmitter acetylcholine. The World Health Organization recognizes cholinesterase (ChE) biomonitoring as a preventive measure against O P overexpo sure. The aim of this study was to determine if dermal OP contamination could interfere with current field ChE biomonitoring assays, which use a fingerstick blood sample. In this study we also sought to determine if high levels of a plasma enzyme, A-esterase, could protect ChE from inhibition by hydrolyzing environmentally generated oxons potentially present in a fingerstick sample. A heparinized venous blood sample was collected from a volunteer. Erythrocyte acetylcholinesterase (AChE) and plasma butyrylcholinesterase (PChE) activities were measured using a field-based colorimetric cholinesterase kit. ChE dose-response curves were constructed by allowing 10-p1 blood samples to contact environmentally realistic levels of OP thioate and oxon for 10 s. An inhibition threshold could not be established for PChE when exposed to oxon within the time necessary to perform a fingerstick analysis. AChE was also inhibited by trace amounts of oxon consistent with previously reported environmental levels. These findings suggest that the reliability of fieldbased biomonitoring results i s limited if OP residues remain on a skin surface at the time of sample collection. A-esterase's role in protecting ChE activity was investigated using capillary and venous blood from 30 unexposed individuals. Baseline ChE activities were measured, as were. individual A-esterase activities using paraoxon, diazoxon, and phenyl-

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Pesticide persistence on foliage

Willis

McDowell

1987

Reviews of Environmental Contamination and Toxicology

114

115

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Background: Foliage residue decline data are used to re ne the risk assessment for herbivorous birds and mammals foraging in elds treated with plant protection products. For evaluation, current EFSA guidance has a clear focus on single-rst order (SFO) kinetic models. However, other kinetic models are well established in other areas of environmental risk evaluations (eg, soil residue assessment), and easyto-use calculation tools have become available now. We provide case studies with 6 fungicides how such evaluations can be conducted with two of these tools (KinGUII and TREC) that have been developed by Bayer. Results: SFO kinetics provided the best ts only for 13 of 36 residue decline studies conducted in a standardized design under eld conditions. Biphasic models (double rst order in parallel, hockey stick) were often superior and sometimes more conservative for risk assessment. The additional effort is manageable when using software such as KinGUII and TREC, and appears justi ed by the more reliable outcome of the evaluations. Conclusions: Further research would be useful to better assess the extent to which non-SFO better ts foliage residue decline, but our study suggests that it may be a signi cant proportion. Therefore we encourage the use of biphasic models in the regulatory risk assessment for herbivorous birds and mammals, in the ongoing revision of the European Food Safety Authority (EFSA) guidance document from 2009.

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Dislodgeable residues of ethion in Florida citrus and relationships to weather variables

Cited by 21 publications

References 16 publications

A comparison of time and time-weather models for predicting parathion disappearance under California conditions

A comparison of time and time-weather models for predicting parathion disappearance under California conditions

Simulated Dermal Contamination With Capillary Samples and Field Cholinesterase Biomonitoring

Pesticide persistence on foliage

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