RESUMEN
DNA damage and DNA repair ability by means of the comet assay and the hydrogen peroxide challenge in lymphocytes from 65 children exposed simultaneously to As and Pb in Region Lagunera, Mexico. The first exposure scenario was concerned with natural As contamination in drinking water affecting all children, particularly those attending the schools farthest from (Gomez Palacio) and closest to the smelter (Pedro Garcia). The second scenario related to additional Pb and As soil and dust contamination in the schools located in the smelter vicinity (Heroe de Nacozari and Pedro Garcia). Most children (93%) had As in urine (AsU) above 50 microg/L and 65% had blood Pb (PbB) above 10 microg/dL. The highest AsU median levels were observed in the school farthest from the smelter, whereas the highest PbB values were observed in the closest school. DNA damage and a decreased repair ability observed in children attending the schools were more severe than those reported for healthy Mexican children. However, the multivariate analysis did not show significant associations between DNA basal damage and PbB or AsU. Lymphocytes from 58% of the children did not respond to the peroxide challenge, and those had a more severe basal DNA damage. DNA repair capacity showed a slowed response and was negatively associated with AsU. Thus, in addition to reduced exposure, further studies are needed to ascertain if the deficiency in DNA repair is transient or if children are already displaying a mutator phenotype and are at risk of developing cancer.