Re-entry workers

Dislodgeable soil residue (DSR) studies are used to determine exposure of re-entry workers to soil surface residues. Soil surface residues are defined as test substance residue levels in <150-q.m soil particles (i.e. soil dust which can stick to a worker s skin, or can be inhaled). 

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. 

Current field methods for measuring mixer-loader and re-entry worker exposure to pesticide residues... 

One of the most important aspects of designing a successful worker exposure or re-entry study is the selection of the agricultural site at which to perform the study. One must first define the growing region in which the pesticide is to be used to the widest extent possible. This is important since this region would have the most farms, farmers, commercial applicators, or re-entry workers which would have work habits, equipment, and land, which would best represent the use of the product. 

In addition, there are hand-held psychrometers for measuring air temperature and relative humidity available, and also hand-held wind meters, which measure wind speed. When using such hand-held equipment, readings should be taken each hour during the course of the day when worker exposure volunteers or re-entry worker volunteers are performing the test. 

Hand exposures of mixer-loader/applicator and re-entry workers have been measured using a variety of techniques in the past. The most common methods are using gloves as dosimeters and washing the hands with various solvents post-exposure. 

The calculation of potential total dermal exposure of mixer-loaders and re-entry workers using dosimetry data and calculation of the internal dose using biological monitoring data is complex but will be discussed briefly. 

Arizona cauliflower scouting represented low crop activities. Five orange harvesters and five lemon tree pruners were tested using concurrent dosimetry and urinary monitoring techniques. The re-entry intervals were 43, 2, and 1 days for the orange harvesters, lemon tree pruners, and scouts, respectively. Re-entry workers were monitored for 5- to 6-hr work days in California and for a 4-hr work day in Florida and Arizona. 

Honeycutt, R.C., Day, Jr., E.W., Shurdut, B.A., and Vaccaro, J.R., Use of simultaneous biological monitoring and dermal dosimetry techniques to determine the exposure of chlorpyrifos to applicators and re-entry workers, in Worker Exposure to Agrochemicals Methods for Monitoring and Assessment, Honeycutt, R.C. and Day, E.W., Jr., Eds., Lewis Publishers, Boca Raton, FL, 2000, chap. 2. 

Because the whole idea of a tiered approach of the kind outlined above is in its initial stages, it will have to be validated and discussed further and will in all probability need to be refined afterwards. The aim here is to introduce the idea of a stepwise approach to the assessment of the risk to re-entry workers. The outlined procedure should be used to calculate the dermal re-entry exposure for real examples of rather dermally toxic compounds in order to gain experience with the recommended procedure. 

Workers associated with the application of carbaryl (applicator, mixer-loader, bystander and aerial flagger) and re-entry workers (apple thinners) were monitored by a modification of the procedure of Durham and Wolfe (3). The workers were fitted with a disposable jacket (Safety and Supply Co., Seattle, WA) to which 10 x 10 cm pads were attached with masking tape. One pad was attached as close to the neck as possible on each shoulder and on the chest and the back of each subject. One pad was also placed on each forearm midway between the elbow and wrist. The pads were constructed by backing an 8 ply gauze compress with two pieces of heavy filter paper and attaching these together in the center with a staple. 

The field of pesticide exposure assessment is complex and challenging. Exposures occur through multiple routes and are highly variable. Risks associated with pesticide handling differ substantially for the different activities and from those experienced by agricultural re-entry workers. Different assessment and control strategies are needed for each population. Eamilies of pesticide handlers can be... 

Table 2.1 Example transfer coefficients for various re-entry worker activities ...

Further work needs to be conducted in order to obtain a better understanding of the sources of variability in DFRs, TCs and re-entry worker exposure data. Stochastic methods may provide a way to better quantify the uncertainties associated with these data. 

In addition, when considering the appropriateness of the area dose levels in the dermal absorption study to the subpopulations under consideration in the risk assessment, it is important to recognize that different area dose levels may be experienced depending on the scenario. For instance, with an agricultural worker, the mixer/loader may be exposed to the concentrated product, the applicator to the diluted spray mixture and the re-entry worker to dried residues on vegetation. As such, it is possible that different dermal absorption values have to be used for each work-function scenario. 

Furthermore, the exposure assessor should also recognize that vehicles are typically different for the mixer/loader versus the applicator versus re-entry workers or bystanders. Again, any uncertainties should be noted in the overall risk assessment. 

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