Assessment of acute and subchronic skin toxicity of drilling fluids

IntroductionThis study investigates the skin-irritating and skin-resorptive effects of drilling fluid (DF) through acute and subacute experiments conducted on adult rabbits and sexually mature male and female rats.MethodsAcute and subacute experiments were conducted on adult rabbits and sexually mature male and female rats. The acute experiment involved a single exposure to DF, while the subacute study involved repeated dermal exposure. Various physiological, biochemical, and histopathological assessments were performed to evaluate the effects.ResultsThe results of the acute experiment demonstrated that DF exhibits a mild skin-irritating effect but causes significant irritation to the ocular mucous membranes in rabbits. In the subacute study, dermal exposure to DF led to notable alterations in the physiological and biochemical status of rats, including reduced food and water intake, decreased body weight gain, and significant changes in hematological and biochemical parameters. An increase in the relative count of certain leukocyte populations was observed, with a statistically significant elevation in absolute eosinophil counts in both sexes. Similar trends were observed for basophils and lymphocytes. Moderate elevations in serum enzyme levels (ALT, AST, ALP, GGT, and LDH) indicated systemic toxicity. Morphological and morphometric analysis of the skin further supported the dermal toxicity of DF, revealing epidermal keratinization, marked proliferation of germinative layer cells, and cellular heterotopia. In the basal layer of the epidermis, cells exhibited signs of intracellular edema. The papillary layer showed moderate focal inflammatory infiltrates, while the reticular dermis displayed edema of fibrous structures, swelling of collagen fibers, and increased fiber thickness.DiscussionThese findings collectively demonstrate that the tested drilling fluid possesses significant dermal and systemic toxicity, indicating potential health risks for mammals upon repeated exposure.