Genotoxicity and phytotoxicity comparison of cigarette butt with cigarette ash.

The damage potential of cigarette butt and cigarette ash was determined and compared using genotoxicity and phytotoxicity assessments. The concentrations of five heavy metals, As, Cr, Cd, Pb, and Ni, were determined in both cigarette butt and ash leachates to find out if the results of heavy metals are in parallel with toxicity findings. Cigarette ashes and cigarette butts were soaked in distilled water for 7 days. Six leachate butt concentrations, including 200, 100, 50, 25, 12.5, and 6.25 piece/L, were examined. HUVEC cells (human umbilical vein endothelial cells) were exposed to these dilution series for genotoxicity, and Vicia faba seeds were exposed to the same dilution series for phytotoxicity assessments. Three parameters of genotoxicity, including tail length, %DNA in tail, and tail moment, were obtained by the comet assay method, and three parameters of phytotoxicity, including germination rate, root length, and water content percentage, were employed. The results showed that cigarette ash at the concentrations of 50, 25, 12.5, and 6.25 pc/L brings about DNA damage. Meanwhile, cigarette butt causes DNA damage at the concentrations of 100, 50, 25, and 12.5 pc/L. The highest concentrations (200 pc/L for cigarette butt and 200 and 100 pc/L for cigarette ash) were considered lethal for HUVEC cells. Besides, the levels of genotoxicity in the cigarette ash were twice as high as those in the cigarette butt. The Vicia faba phytotoxicity test demonstrated a germination rate restriction from 100 to 52 and 100 to 0% for cigarette butt and cigarette ash, respectively. It also caused a reduction in the length of roots from 35 to 7.85 and 3 mm for cigarette butt and cigarette ash, respectively. The moisture amounts of cigarette remnants had a decline from 93.14 to 44.61 and 36.72% for cigarette butt and cigarette ash, respectively. Concentrations of As, Cr, Cd, Pb, and Ni were 17.45, 2.5, 0.15, 6, and 0.62 ppb in the butt leachate and 7.21, 2.64, 0.29, 13.61, and 1.24 ppb in the ash leachate, respectively, indicating that heavy metals could explain the higher toxicity of cigarette ash. Based on the present study, cigarette ash imposes not only higher levels of genotoxicity and phytotoxicity but also more values of toxic heavy metals on our planet. Thus, cigarette ash plays a major role in environmental pollution, and the importance of cigarette ashes should receive attention even more than cigarette butts. This paper casts new light on the toxic impacts of cigarette ash.