Pesticide dislodgeable

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. 

When humans contact a chemical residue such as a pesticide on a treated surface, some of the deposit can be dislodged or transferred to skin or clothing. Ultimately, a portion of the amount transferred may be absorbed and constitute the absorbed daily dose (ADD). The ADD provides the most precise estimate of exposure that can be practically obtained for humans and has become the most useful expression of exposure for risk assessment and risk management. 

Iwata, Y, Knaak, J.B., Spear, R.C., and Foster, R. J. (1977) Worker re-entry into pesticide-treated crops. I. Procedure for the determination of dislodgeable pesticide residues on foliage, Bull. Environ. Contam. Toxicol., 18 649-655. 

Re-entry exposure can be considered to be the result of a chain of processes ending with the transfer of pesticide residues to the worker. Popendorf (1985) assumed a linear relationship between dermal exposure (DE) and the amount of residue available to transfer from the foliage to the worker. This is called the dislodgeable foliar residue (DFR) ... 

Dislodgeable foliar residue as a function of time and estimating half-lives of the pesticides after high-volume application... 

Data on the DFR of chlorothalonil on carnation crops in previous studies indicated an increase in DFR of 10 to 20% with solvent extraction (unpublished data). However, in all of the current experiments, no differences were observed between dislodgeable foliar residue and solvent-extracted foliar residue for the pesticides methiocarb and thiophanate-methyl. 

Half-life estimates of approximately 28 days for thiophanate-methyl indicate a very slow decay compared to methiocarb with an estimate of half-life of about 11 days. The application of a model based on a first-order decay process resulted in fairly high R2 and significant fit. The results suggest that both pesticides are relatively stable compared to other compounds under similar environmental conditions (Brouwer et al., 1994). With respect to the objectives of the study and the proposed model, it can be stated that the results confirm the assumption of a linear relationship between application rate (for both application techniques) and the increase of dislodgeable foliar residue. This relationship holds for modeling purposes. The contribution of the crop density or total crop surface area to the process of interception cannot be quantified with the results of the present study. Because the interception factor ranges from about 0.35 to 0.9 (Willis and McDowell, 1987), the... 

Brouwer, D.H., de Haan, M., Peelen, S., van de Vijver, L., and van Hemmen, J.J. (1994) Dislodgeable foliar residue as an estimate of source strength for worker exposure to pesticides, in Book of Abstracts from the 8th International Congress of Pesticide Chemistry, American Chemical Society/IUPAC, July 4r-9. 

There are several suggested sources which are useful guidelines for determining residues of pesticides on soil and leaf surfaces (dislodgeable) and conducting field reentry studies involving human volunteers (3), (4), and (5.). Human... 

Gunther, F.A., W.E. Westlake, J.H. Barkley, W. Winterlin and L. Langbehn (1973). Establishing dislodgeable pesticide residues on leaf surfaces. Bull Environ. Contam. 

USEPA (1996a). Occupational and Residential Exposure Test Guidelines, OPPTS 875.2100, Eoliar Dislodgeable Residue Dissipation, EPA Report No. 712-C-96-267, Office of Prevention, Pesticides and Toxic Substances, Washington, DC, USA. 

Zweig, G., J.T. Leffingwell and W.J. Popendorf (1985). The relationship between dermal pesticide exposure by fruit harvesters and dislodgeable foliar residues, J. Environ. Scl Health, B20, 27-59. 

If wet wipes are used, care must be exercised to avoid damaging the surfaces being monitored. Solvents other than water may remove substances (e.g. furniture and floor waxes) from the surface that can cause analytical interferences. In addition, if the solvent is capable of extracting the pesticide residue from beneath the surface being wiped, the residue recovered may overestimate the amount of dislodgeable residue. Special care should be taken when using flanunable solvents indoors. Toxic solvents should never be used in occupied buildings. While 2-propanol and ethanol are relatively safe for use in occupied indoor... 

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