Gauze patches

Among the first dermal dosimeters used in exposure research were 4 x 4-in cellulose or gauze patches which were pinned to the outer and inner surfaces of clothing or vests which farm workers would wear during the application or re-entry phase of the smdy. These patches were easy to manufacture and when pinned to the shirt or pants of the worker made for an easily used dosimeter pad. The major advantage to the use of the patch to estimate worker exposure was this method s ability to differentiate the relative contributions of pesticide residues to different parts of the worker s body. This sampling technique in turn could lead to recommendations (i.e., the use of... 

If the test substance is a solid or a semisolid, a 0.5-g portion is weighed and placed on the gauze patch. The test substance patch is placed on the appropriate skin site and secured. The patch is subsequently moistened with 0.5 ml of physiological saline. 

The negative control site is covered with an untreated 12-ply surgical gauze patch (1 in. x 1 in.). 

The positive control substance and vehicle control substance are applied to a gauze patch in the same manner as a liquid test substance. 

The DEE levels to which the applicator was exposed during the study were measured from 4 x 4- cm gauze patches inside and outside a coverall worn during the 7 hour duration of the field test (Table III). DEF levels outside the coveralls were as high as 250-260 ug/cm% and ranged from above 1 to almost 7 ug/cm inside of the garment, comparable to levels to which the chickens were exposed. 

Values determined from 4 x 4 cm gauze patches worn for 7 hours hy the applicator. Means of values in parentheses. (Modified from Wilson et al., 8.)... 

Table I. Micrograms 2,4,5-T detected on 100 cm2 gauze patches of individual mist blower crewmembers.

A dose of 0.5 mL of liquid or 0.5 g of solid or semisolid test chemical is applied to the site. Separate animals are not required for an untreated control group, since adjacent areas of untreated skin serve as controls for the test. The test chemical should be applied to a small area (approximately 6 cm2) of skin and covered with a gauze patch, held in place with nonirritating tape. In the case of liquids or some pastes, it may be necessary to apply the test chemical to the guaze patch and apply that to the skin. The patch should be loosely held in contact with the skin by means of a suitable occlusive dressing for the duration of the exposure period. The animals access to the patch and resultant ingestion of the test chemical by licking or by inhalation should be prevented. 

In conducting studies to determine temporal decay rates, sampled areas should be identified so that the same areas are not re-sampled pre-application and post-application. Likewise, if deposition coupons (e.g. a-cellulose filter paper or cotton gauze patches backed with aluminum foil) are placed on the floor during application of the pesticide formulation to estimate initial deposition rates, care should be exercised to avoid sampling in the areas covered by the coupons during subsequent monitoring visits. 

Personal Samples Data from the gauze patches on the outside of the coveralls, and on the T-shirt immediately beneath the coveralls are presented in Table VI with values expressed as micrograms per sq cm of gauze monitor. Consistent with the data from the rig samples. Workers 2, 4, and 5 show relatively high levels of... 

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