Residue dislodgeable

Data collected in drift studies may later be interpreted in risk assessments in conjunction with toxicity data for specific sensitive areas. Eor example, a risk assessment for determination of appropriate mitigation (if necessary) may include field study data on exposure risk from drift, along with information on other routes of exposure (e.g., dislodgable residues, runoff, etc.) and toxicity data from laboratory and/or field study models. The results of such an assessment may be used to estimate whether a given exposure represents a hazard to any specific entity or ecosystem. 

The purpose of this article is to present a detailed description of the current field methods for collection of samples while measuring exposure of pesticides to farm workers. These current field methods encompass detailed descriptions of the methods for measuring respiratory and also dermal exposure for workers who handle the pesticide products directly (mixer-loaders and applicators) and for re-entry workers who are exposed to pesticide dislodgeable residues when re-entering treated crops. 

Portable weather stations are useful to have available at the field laboratory for acquiring weather data during the course of the worker exposure/re-entry study. There are a variety of portable weather stations available from a variety of suppliers. Weather data to be collected are rainfall, wind direction, wind speed, air temperature, and relative humidity. These electronic weather stations will record the necessary weather parameters on a routine basis. The data are stored and can be transferred to a laptop computer or disk as desired by the Field Scientist. Such portable electronic weather stations are useful during the course of the dislodgeable residue portion of a worker re-entry study when dislodgeable residue samples are taken from remote test sites over the course of a 30-day period. 

Doses of chlorpyrifos in human volunteers were also estimated using physical measurements. Air sampling was conducted in order to estimate the inhalation dose to each volunteer. Dislodgeable residues were also measured throughout the study to estimate the dermal contribution to total dose. Finally, hand rinses were conducted on each volunteer immediately following the 4-hr activity period to assess the potential contribution to total dose from hand exposure and to estimate an oral dose to a crawling child. 

Doses for each volunteer were estimated by two methods. The first approach was to sum the contributions of the inhalation and dermal routes (whole body and hands). These contributions were estimated using calculations based on the air sampling data, the dislodgeable residue data, and the hand-rinse data. 

DR = Mean dislodgeable residue during the activity period (average of T4 and T8 values)... 

Table 2 Liquid Turf Study Adult Dermal Dose of Chlorpyrifos Based on Dislodgeable Residue Data...

Volunteer Weight (kg) Average dislodgeable residue (pg/ft2)a Dose (Pg/kg)... 

Research has shown a clear relation between the amount of dislodgeable residues on the crop and the level of dermal exposure (van Hemmen, 1995). The maximum amount of dislodgeable residues is found immediately after application and depends on ... 

Extracts of gloves, extracts of foliar dislodgeable residue and absolute foliar residues, and filters containing thiophanate-methyl were analyzed by reversed-phase HPLC and ultraviolet detection at 254 nm (Engel, 1988). The LOD was 50 mg/L for extracts of filters and gloves, and 10 mg/L for leaf samples. Recovery was > 90%, and the "between days" CV of the analytical chemical method was < 5%. 

Curalan DF is a fungicide produced by BASF Corp. for the purpose of treating such diseases as brown patch and fusarium patch on turf. Curalan DF was applied to turf in California, Florida, and Pennsylvania at a rate of 5.6 lb of active ingredient in 80 gallons of finished spray solution per acre using a tractor-mounted boom sprayer. Four applications were made 14 days apart. These conditions were selected to reflect the maximum level of dislodgeable residue when the product is typically used in agricultural practice. 

With respect to worker safety and re-entry studies, reference substances are necessary to assay the test substance (and, if applicable, any control substance) and determine its stability and for the analyses of specimens collected in the study. Specimens may include plant material (dislodgeable residues), adsorbent media (inhalation), or clothing/dosimeter materials collected during a worker safety study to assess exposure. If biomonitoring is involved, blood and/or urine specimens may be analyzed against reference substances of known purity. 

Sears, M.K., Bowhey, C., Braun, H., and Stephenson, G.R. Dislodgable residues and persistence of diazinon, chlorp3uifos and isofenphos following their application to turfgrass. Pestle. Scl, 20(3) 223-231, 1987. 

The dislodged residues may not remain in the pump chamber. After cleaning is completed check the pump for operability by slowty turning the impellers by hand. There may be no resistance to rotation. It is generally not necessary to dismantle the roots pump. If this should nevertheless be required due to heavy soiling, then it is highly advisable to have this done by the manufacturer. 

The procedure involves converting oxon to thion toxicity equivalents by multiplying the oxon value by its relative toxicity (ED of thion r ED,.q of oxon) in Table I. The ED. value is the aermal dose in ug/cnr of total body surface which produces 50% inhibition of red cell ChE activity 72 hours after application. The total thion and oxon level is then divided by the thion toxicity equivalents and the factor is multiplied by the safe level established for thion in Table I. This procedure was conducted for the dislodgeable residues of parathion-paraoxon, methidathion-methidathion oxon, and azinphosmethyl-azinphosmethyl oxon. The safe levels for the total disloggeable residues were determined to be 0.06, 0.2 and 1.6 ug/cm, respectively, for... 

Cloth patches were attached to the clothing in four areas to collect dislodgeable residues. Blood and urine samples were collected at the end of each work day. Leaf samples were taken daily to determine dislodgeable residues of phosalone and its... 

Low urinary excretion of metabolites and a low (15% or less) cholinesterase depression were noted over 5 exposure days. In a reentry study of California citrus trimmers and pruners exposed to phosalone, results were unremarkable (15). No cholinesterase depression or urinary metabolites were noted. Reentry was at 14 and 21 days with exposure to 2.6 and 3.6 yg/cm2, respectively, on each reentry day. In a major study of peach thinners (previously referenced, ]2, J 4, J 6), lettuce harvesters, and artichoke harvesters, low or no urinary metabolites were observed and cholinesterase values were within the normal ranges. Phosdrin and methomyl had been applied to lettuce, and parathion and methyl parathion to artichokes. Dislodgeable residues were... 

The HDE s to the hands of the thinners versus the total residue found on the leaves is shown in Figure 2. The regression equation is Y = 690X-45 where Y is the HDE in (Jg/h and X is the leaf residue in pg/cm2, and the correlation coefficient was 0.99. Since the regression line does not go through zero, the value of the X intercept corresponds to non-dislodgeable residues which is only 4% when the initial value was 1.71 pg/cm2 and 9% when the initial value was 0.70 pg/cm2. 

Iwata et al. (5) published a procedure for the extraction of dislodgable residues from foliage. It involved the extraction of residues with a water-detergent solution and then partitioning the residues from this solution into dichloromethane. In our work, the total carbaryl residues were extracted directly from apple leaves with dichloromethane, and are not equivalent to dislodgeable residues. Nevertheless, because the total extractable residues correlate with HDE, they have the same value for predicting human exposure as... 

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