Black carbon accumulation in extrapulmonary human tissues

Black carbon is a product of incomplete combustion and is associated with a number of adverse health outcomes in epidemiologic studies. To date, anatomic studies investigating the pathogenic mechanisms of black carbon in humans have confirmed black carbon particles accumulate in the lung and in the placenta of pregnant women, and are excreted in urine. In this feasibility study, the presence of black carbon particles was demonstrated in post-mortem spleen, myocardium, and hilar lymph node samples obtained from three de-identified sources. A protocol validated for extraction of chemically inert particles from fish tissue was utilized to extract black carbon particles from human tissue. Visual examination and micro-Raman scattering spectroscopy were used to identify recovered black carbon particles. Recovered particles ranged from 2 to 45 m in greatest dimension. The highest concentrations of black carbon particles were recovered from hilar lymph nodes, followed by the myocardium, with lowest concentrations recovered from the spleen. Particles extracted from the spleen were, on average, larger than particles extracted from the heart or hilar lymph nodes. These findings confirm black carbon particles accumulate in human extrapulmonary organs. Based on the size and concentrations of recovered particles, it is suggested that black carbon particles are transported to extrapulmonary sites via the lymphatic system. Furthermore, the noted concentration differentials suggest reduced black carbon particle clearance from the myocardium compared with the spleen.