Outer dermal exposure

Both inner and outer whole-body dosimeters are common tools to measure successfully dermal exposure to pesticide workers and are employed in a variety of ways in mixer-loader/applicator or re-entry studies. 

In order to determine the dermal exposure of volunteers to chlorpyrifos, the penetration of chlorpyrifos through the outer whole-body dosimeter (coveralls) to the inner body dosimeter (t-shirt and briefs) was measured. The penetration factor was calculated for each volunteer in the study from the experimental data by dividing the amount of chlorpyrifos on the t-shirt and brief sample by the amount of chlorpyrifos on the torso section of the coveralls. This method of calculation assumes that the surface area of the torso section of the coveralls is nearly the same as the surface area of the t-shirt and briefs worn directly under the torso section of the coveralls. A mean penetration factor for each worker type was calculated by averaging all the worker volunteer... 

The skin is a complex multilayered tissue with a large surface area exposed to the environment. Skin anatomy, physiology, and biochemistry vary among species, within species, and even between anatomic sites within an individual animal or human. Logically these biological factors alone can influence dermal absorption. What is consistent is that the outer layer, the stratum corneum (SC), can provide as much as 80% of the resistance to absorption to most ions as well as aqueous solutions. However, the skin is permeable to many toxicants, and dermal exposure to agricultural pesticides and industrial solvent can result in severe systemic toxicity. 

Hepatic Effects. No studies were located regarding hepatic effects in humans after dermal exposure to nitrobenzene. In mice dermally exposed to nitrobenzene, the liver was the most severely affected organ. There was diffuse necrosis in the outer two thirds of the lobules of the liver (Shimkin 1939). 

California regulations require daily provision and use of clean coveralls or other clean outer clothing to mixers, loaders, flaggers, and applicators of any pesticide in toxicity Categories I and II (12). These requirements serve to reduce the potential dermal exposure of workers to pesticides by decreasing the area of bare skin available for contact with the chemicals. 

Caution should be exercised in comparing the dermal exposure values found in these studies with other studies. These dermal exposure levels are as much as one-tenth of the amount found for other similar applications of similar pesticides outside of California. All persons were working in accord with California Worker Safety and Restricted Materials Regulations and all applications were made by trained employees of California Pest Control Operators. All of these formulations studied were California Restricted Pesticides and almost all were toxicity Category I liquids which are required to be mixed and loaded through closed systems. All workers put on clean outer clothes daily and all wore impervious gloves when contact with the concentrate was a possibility. On the other hand, caution was exercised to avoid special training, extra instructions or excessive observation because the employers and employees had been instructed to apply the pesticides in the usual manner. 

The best practice is to always minimize or avoid dermal exposure to chemicals. This can be accomplished in a number of ways. Protective or outer clothing, such as a lab apron or a laboratory coat, can be worn to protect your body. It s best to wear long sleeved shirts, pants or long skirts, and closed-toe shoes so that if you spill the chemical it will not come in direct contact with your skin. Your college probably has rules about what clothes you can and cannot wear in the lab. 

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... 

Liver effects have been reported in both humans and animals exposed to nitrobenzene. Hepatic enlargement and tenderness, jaundice, and altered serum chemistries were reported in a 47-year-old woman who had been occupationally exposed to nitrobenzene for 17 months (Ikeda and Kita 1964). The authors considered these changes to be related to increased destruction of hemoglobin and enlargement of the spleen. Liver effects observed in animals following nitrobenzene exposure are hepatocyte necrosis in rats (Medinsky and Irons 1985) and increased liver weight, hepatocyte hyperplasia, and multinucleated hepatocytes in mice (Hamm 1984). Hepatic effects have not been reported in oral studies. Dermal painting studies in mice resulted in diffuse necrosis in the outer two- thirds of the lobules of the liver (Shimkin 1939). 

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