Municipal landfill leachate induces cytogenetic damage in root tips of Hordeum vulgare

With increasing use of municipal solid waste landfills for solid waste disposal, municipal landfill leachate has become a serious concern for aquatic environments. Therefore, it is important to study its toxic effects on plants, animals, and humans. In the present study, the genotoxicity of leachate was investigated with the Hordeum vulgare root-tip cytogenetic bioassay, using Chemical oxygen demand (CODCr) as a measure of leachate concentration. Leachate decreased the mitotic index (MI) in a concentration-dependent and a time-dependent manner. Compared with the negative control, reductions of MI of 37%, 56%, and 70% were detected for the highest leachate concentration (CODCr 800 mg/L) in root tips treated for 24, 48, and 72 h, respectively. Leachate caused significant increases of micronucleus (MCN) frequencies in a concentration-dependent and a time-dependent manner. Among the exposure groups, CODCr 40 mg/L leachate induced MCN formation after 24, 48, and 72 h of exposure, and the frequencies of MCN significantly increased with increasing concentrations of leachate from CODCr 40 to 640 mg/L. In addition, pycnotic cells (PNC) occurred in root tips at all leachate concentrations tested after 24, 48, and 72 h of exposure, and PNC frequencies had a positive relation with the treatment concentration and the exposure time. The results also indicate that the concentration required to produce cytogenetic damage was lower in cells that had a longer exposure time. The results confirm that components of leachate may be genotoxic in plant cells and imply that long exposure to leachate at low concentrations in the aquatic environment may pose a potential genotoxic risk to organisms. The results suggest that the H. vulgare cytogenetic bioassay is efficient, simple, and reproducible in genotoxicity studies of leachate, and that there appears to be a correlation between the genotoxicity in a plant system and the CODCr of leachate.