Biological responses of human cell lines to biochar dusts from different biomasses

Biochar is a carbon-based biosolid produced by pyrolysis of waste and biomasses. Given its physical-chemical properties, it is largely employed to ameliorate soil quality and retain contaminants from polluted waters. To date, only a few studies have explored the effects of biochar on living organisms and the potential risks also for human health, as a consequence of biochar environmental diffusion. Here, we investigated the biological effects of three biochar obtained from different raw biomasses (pruning chippings, almond shells, and stabilized organic fraction) on human keratinocyte and lung cell lines. We found that 24 h of treatment with biochar, even at low doses (1-10 μg/mL) caused a reduced cell viability, a cytoskeleton reorganization, and an increased apoptosis. Moreover, biochar seemed to perturb homeostatic physiologic responses, such as autophagy and antioxidant activity. Different properties of the three biochar, mainly particle dimension, composition, and roughness, could be responsible of differences in intensity of biological responses we registered. We also noticed that each cell line displayed an own intrinsic sensibility to each type of biochar. On the whole, our findings highlight that the large employment and the consequent diffusion of biochar in the environment might have detrimental consequences for living organisms, including humans.