Interlaboratory evaluation of the genotoxic properties of pencycuron, a commonly used phenylurea fungicide.

Pencycuron, a phenylurea-type antifungal agent, is used in agriculture worldwide for inhibiting the growth of various fungal pathogens of crops. Pencycuron residues were found in vegetables, soil and drinking water. Accordingly, both occupational and consumer exposure can be expected and may be significant. However, human toxicity studies on its genotoxic, mutagenic or carcinogenic potential are lacking. Therefore, a collaborative study was performed in two laboratories to investigate whether pencycuron exposure can induce DNA damage. The genotoxic effect of 0-100 μg/ml pencycuron in in vitro cultures of human mononuclear white blood cells (MWBCs) and human hepatocytes (HepG2) was detected by cytokinesis-block micronucleus assay and comet assay. The combined results of the two labs showed a dose-dependent DNA damage detected by micronucleus frequency, which reached statistical significance at 100 μg/ml concentration after 21-h exposure in HepG2 cells (p = 0.048). Significant genotoxic effect could also be observed in the comet assay from 50 μg/ml concentration in MWBCs, and at 100 μg/ml concentration in HepG2 cells in one lab. Nevertheless, this finding was not confirmed by the other lab in HepG2 cells, where Fpg-dependent oxidative DNA damage could also not be detected. The results indicate that pencycuron may have DNA-damaging potential as well as point out inter-laboratory variability that calls for further studies to confirm the genotoxicity of this fungicide.