**5. Clinical application of the comet assay in buccal cells**

Significant stepwise increase in the DNA damage (basal/MNNG-treated/post-repair) was observed in buccal epithelial cells from control to pre-cancer patients and from pre-cancer to cancer patients. Considerable inter-individual and intercellular variability in DNA damage was observed, which also increased from control to pre-cancer patients and from pre-cancer to cancer patients [64]. Similar results were found in patients with oral squamous cell carci‐ noma (OSCC) and control group and suggested that comet assay may be used effectively to assess the prognosis of OSCC [73].

Among population studies regarding the health effects of air pollution, special attention should be given to children as a high-risk group, since some studies have shown significant correlation between early childhood exposure and development of chronic diseases in adulthood. Genotoxic biomarkers have been studied largely in adult population, but few studies so far have investigated children exposed to air pollution. Children are a high-risk group as regards the health effects of air pollution, and some studies suggest that early exposure during childhood can play an important role in the development of chronic diseases in adulthood. Genotoxic effects among farm children assessed with comet assay in buccal cells showed a significant increase in chromosome breakage and DNA strand breaks [85]. In other similar study, the exposure to pollutants was associated with markers of genotoxicity in exfoliated buccal cells of children living in a region with chipboard industries. The increase of outdoor formaldehyde was associated with a higher comet tail intensity and a higher tail moment [86].
