Macroscopic and microscopic effects of various chemicals on the degreasing of bone

Abstract

Bone degreasing is a vital but challenging procedure which ensures that remains can be safely stored and handled. This practice is used in both anatomy and forensic anthropology, and trichloroethylene is the chemical commonly used as a degreasing agent in South Africa. However, this chemical poses a few difficulties. Not only is it highly carcinogenic and various safety precautions need to be taken when working with it, but specialized machinery and skilled operators are needed to operate them. Both trichloroethylene and the machinery are extremely expensive and most institutions in South Africa are not financially able to make use of this technique. A pilot study was previously done to analyse the degreasing effect of other chemicals (acetic acid, ammonia, bleach, ethanol and peroxide) on bone trying to find a suitable alternative which degreases the fastest, most effectively, with the least amount of destruction of bone, while taking into consideration price and safety. However, this study did not include the effect of these chemicals on the microscopic morphological characteristics of bone. Therefore, the aim of this study was to investigate the effect of these alternative degreasing methods on the microscopic bone morphology in order to identify the most suitable alternative to trichloroethylene. Bone slides were made of human metacarpal and phalangeal bones used in the pilot study to analyse microscopic damage caused by the abovementioned chemicals. A scoring system with various criteria i.e., microfractures, flaking of small particles of bone from the bone surface, bone loss in the cortex and medullary borders and overall changes in bone, was used to quantify the amount of damage caused by the chemicals. In contrast to the pilot study where peroxide visually seemed the best degreaser, when viewed microscopically, peroxide scored the worst during this study and caused extensive microscopic damage to the bone. Ammonia and bleach also caused elaborate microscopic damage at all concentrations. Acetic acid did not cause significant damage with the low concentration but caused substantial damage with medium and high concentrations. Ethanol at low concentrations is regarded the most successful in this study, as it caused minimal microscopic damage to the bone while still being a suitable degreasing agent. However, higher concentrations of this chemical still caused extensive damage. Therefore, ethanol should be considered as an alternative degreasing method as it has not only shown to be a successful degreaser but caused low levels of microscopic damage while also being considered less expensive and much safer to handle, store and dispose of than trichloroethylene. However, other factors such as time taken to degrease and other concentrations of these chemicals should still be explored in order to establish an optimum degreasing method. This study only made use of metacarpal and phalangeal bones and thus the effect of these chemicals on other bones of the human body remains unknown and further research should be done accordingly.

Keywords: forensic anthropology, bone, degreasing, trichloroethylene, microscopy, macroscopic damage, microscopic damage, metacarpals, forensic analysis, human remains.