Cytotoxicity of Spent Pot Liner on Allium cepa root tip cells: A comparative analysis in meristematic cell type on toxicity bioassays

• Spent Pot Liner (SPL) is a waste generated during the production of aluminum.
• Toxic effects of SPL on meristematic cells are carried on to cells of differentiation/elongation zone.
• The recovery period in water is not enough to repair DNA damages caused by SPL.
• Cells exposure to SPL continues impair cell division, trigger cell death and cause genomic damage.
• Data obtained indicates the need to manage SPL properly prior to disposal on the environment.

Spent Pot Liner (SPL) is a waste generated during the production of aluminum. It is comprised of a mixture of substances most of which, like cyanide, aluminum and fluoride, are toxic. Previous studies indicate the highly toxic nature of SPL. However studies using cells of the differentiation/elongation zone of the root meristem (referred as M2 cells in this study) after a proper recovery period in water were never considered. Using these cells could be useful to further understanding the toxicity mechanisms of SPL. A comparative approach between the effects on M2 cells and meristematic cells of the proximal meristem zone (referred as M1 cells in this study) could lead to understanding how DNA damage caused by SPL behaves on successive generations of cells. Allium cepa cells were exposed to 4 different concentrations of SPL (2.5, 5, 7.5 and 10 g L−1) mixed with soil and diluted in a CaCl2 0.01 M to simulate the ionic forces naturally encountered on the environment. A solution containing only soil diluted on CaCl2 0.01 M was used as control. M1 and M2 cells were evaluated separately, taking into account four different parameters: (1) mitotic alterations (MA); (2) presence of condensed nuclei (CN); (3) mitotic index (MI); (4) presence of micronucleus (MCN). Significant differences were observed between M1 and M2 roots tip cells for these four parameters accessed. M1 cells was more prompt to reveal citogenotoxicity through the higher frequency of MA observed. Meanwhile, for M2 cells higher frequencies of MCN and CN was noticed, followed by a reduction of MI. Also, it was possible to detect significant differences between the tested treatments and the control on every case. These results indicate SPL toxic effects carries on to future cells generations. This emphasizes the need to properly manage this waste. Joint evaluation of cells from both M1 and M2 regions was proven valuable for the evaluation of a series of parameters on all toxicity tests.