Identification of black carbon in placental tissue using scanning electron microscopy and energy dispersive X-ray fluorescence.

Currently, there are very few standardized and developed analysis methods for detecting the deposition of black carbon (BC) in human tissues, and they have certain limitations. A non-destructive and robust method has been developed for identifying BC deposits in soft biological tissue using placental tissue matrix as a case study. Placental tissues were obtained from 50 pregnant women in their third trimester. The method employs a correlative workflow, utilizing a scanning electron microscope (SEM) for high-resolution morphological screening of suspected BC particulates and energy-dispersive X-ray fluorescence (EDXRF) for specific elemental confirmation. The method's specificity was first tested in a preliminary experiment conducted by externally embedding charcoal in two placental tissues, which confirmed its ability to distinguish the exogenous BC particles from the native biological matrix based on definitive elemental analysis. Subsequently, this method was applied to 48 original placental tissues without external embedding of charcoal. The deposition of BC was identified on the surface of placental tissue, specifically at the foetal side of the placenta. This correlative SEM-EDXRF method provides a robust and effective framework for identifying exogenous BC in biological tissues, as demonstrated by the clear distinction between the elemental signatures of BC particles and the native biological matrix. The method has limitations in terms of quantification.