Impact of Food Processing Industry Wastewater on Root Growth and DNA Damage in Allium cepa L. as Assessed by the Comet Assay

Wastewater from food processing industries contains synthetic dyes and preservatives that may pose phytotoxic and genotoxic risks. The present work represents an exploratory study based on a wastewater source and sampling period. Wastewater was characterized by physicochemical analysis and high-performance liquid chromatography (HPLC). Onion seeds and bulbs were exposed to 0% (control), 20%, 40%, 60%, 80%, and 100% wastewater dilution. DNA was extracted from root cells using the cetyltrimethylammonium bromide (CTAB) method. The DNA damage was analyzed by the comet assay. HPLC analysis confirmed the presence of sorbic acid, citric acid, benzoic acid, butylated hydroxyanisole (BHA), and butylated Hydroxytoluene (BHT) by showing corresponding peaks. The mean root length in wastewater was significantly reduced by 55%, 50%, and 65% on days 3, 5, and 7, respectively, relative to the control. On day 3, the highest genotoxicity at 100% wastewater was indicated by 96.69% tail DNA, a tail moment of 108.3 a.u., an Olive tail moment of 58.01 a.u., and a comet length of 136 µm. Enhanced DNA damage persisted on days 5 and 7, with comet lengths reaching 127–149 µm and 111–182 µm, respectively. Although the observed effects may reflect general cytotoxicity arising from a complex wastewater mixture and showed that untreated food processing wastewater presents a significant genotoxic risk and requires effective treatment prior to reuse.