Cytogenetic biomonitoring of Almadinah Almunawarah municipal wastewater treatment plant using the Allium cepa chromosome aberration assay

This study aims to find out if the cytotoxic and genotoxic responses of Allium cepa are valuable biomarkers of the current conventional wastewater treatment protocols, used in the municipal wastewater plant located in Almadinah Almunawarah city (Kingdom of Saudi Arabia). Wastewater samples were collected at two different times, winter (February 2016) and summer (July 2016) seasons from the municipal wastewater plant. Allium cepa bulbs were exposed to different concentrations (100, 50, 25, and 12.5%) of treated wastewater for 12 h. In addition, Allium cepa bulbs were exposed to tap water, which was used as a negative control. The Feulgen reaction was used to stain three root tips from each onion bulb. Subsequently the frequency of different types of chromosome aberrations (CA), percentage of aberrant cells (%Abc), and mitotic index (%MI) were determined and compared to tap water, treated wastewater induced CA and decreased MI in a dose dependent manner. In addition, the %MI and %Abc in winter and summer were similar. To conclude, the treated wastewater may contain toxic compounds leading to mutagenicity and CA. According to these findings, the biomonitoring studies and the treatment of wastewater in Almadinah Almunawarah are needed. (author)