Sublethal Dermal Toxicity of Drilling Fluid and Its Effects on Hematological, Biochemical and Histopathological Parameters in Rats.

The aim of this study was to evaluate the toxic effects of drilling fluid (DF) on the skin in a subacute experimental model. Sexually mature outbred rats of both sexes were used (8 males and 8 females per group), weighing 180-220 g. Dermal exposure was performed for 14 days with monitoring of general condition, behavior, and feed and water intake. Body weight, vertical rearing, and grooming behavior were recorded on days 1, 7, and 14. At the end of the experiment, animals were euthanized for biological sample collection. Peripheral blood parameters, including hemoglobin, erythrocytes, leukocytes, platelets, erythrocyte sedimentation rate (ESR), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), gamma-glutamyl transferase (GGT), and C-reactive protein (CRP), were analyzed. Morphohistological examination of the epidermis, dermis, hair follicles, liver, and kidneys was performed. The elemental composition of the drilling fluid and drill cuttings was determined using atomic absorption and emission spectroscopy. Experimental animals exhibited reduced mobility and decreased feed and water intake by day 7. Body weight initially declined and subsequently increased. Dermal exposure to DF resulted in a significant increase in leukocyte, neutrophil, and eosinophil counts and was associated with alterations in detoxification enzyme activity (ALT, AST, and LDH). Histopathological changes were observed in the skin, liver, and kidneys, indicating dermal-resorptive toxicity. The results demonstrate that drilling fluid possesses dermal-resorptive toxicity following cutaneous exposure, causing not only local skin alterations but also systemic disturbances involving the hematopoietic, immune, and detoxification systems. The combination of clinical-behavioral, hematological, biochemical, and morphological changes confirms the potential occupational hazard of dermal contact with drilling fluids and substantiates the need to consider this route of exposure in occupational risk assessment. The findings provide an experimental basis for improving sanitary and hygienic standards, developing preventive measures, and conducting further toxicological studies, including investigations of chronic exposure, dose-response relationships, and the contribution of individual drilling fluid components.