DNA damage in Mexican children living in high-risk contaminated scenarios.

The aim of this study was to evaluate the deoxyribonucleic acid (DNA) damage (as a biomarker of biological effects) in children living in areas at high risk of contamination in Mexico using the comet assay. The alkaline comet assay was performed in order to assess DNA damage levels in blood cells of 276 children living in eleven communities in four states of Mexico. Moreover, levels of arsenic and 1-hydroxypyrene (1-OHP) in urine and lead and total DDT [sum of 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE) and 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT)] in blood were quantified. We found urinary 1-OHP levels between

Assessment of exposure to organochlorine pesticides and levels of DNA damage in mother-infant pairs of an agrarian community.

Exposure to organochlorine pesticides was studied in a group of mother-infant pairs living in a rural area where agriculture is the main economic activity. Fumigation in this zone is performed with airplanes, thus affecting the inhabited areas around them, including schools. Heparinized venous blood of mothers and umbilical cords was used to evaluate the olive tail moment in the comet assay, and micronuclei, chromatin buds, and nucleoplasmic bridges in peripheral blood lymphocytes. Cord blood samples were taken at the moment of birth only from natural and normal parturitions. Determinations of hexachlorobenzene, aldrin, heptachlor epoxide, oxichlordane, t and c-chlordane, cis-nonachlor, mirex, alpha and beta-endosulfan, alpha, beta and gamma hexachlorocyclohexane, and p'p'-DDT, p'p'-DDE were conducted to establish the differential distribution of the toxicants between compartments, i.e., mother and umbilical cord. Significantly higher pesticide levels were found in umbilical cord plasma than in mothers' plasma for almost all compounds tested, except DDE and oxychlordane. Significantly higher olive tail moments were found in umbilical cords than in mothers, whereas micronuclei frequencies were higher in mothers than in umbilical cords. However, neither the levels of micronuclei nor the olive tail moment were correlated with pesticide levels. Given that no other exposure to toxic compounds has been identified in this region, the lack of correlation between genotoxicity biomarkers and pesticide levels may be due to the variability of the exposure and to endogenous processes related to lipid mobility during pregnancy, the metabolism of the compounds, and individual susceptibilities.

DNA damage and decreased DNA repair in peripheral blood mononuclear cells in individuals exposed to arsenic and lead in a mining site.

The aim of this study was to evaluate DNA damage and the capacity for DNA repair in children exposed to arsenic and lead. During 2006, we studied a total of 85 healthy children (aged 4-11 years) who were residents of Villa de la Paz (community A), Matehuala (community B), and Soledad de Graciano Sanchez (community C) in San Luis Potosi, Mexico. The quantification of arsenic in urine (AsU) and lead in blood (PbB) was performed by atomic absorption spectrophotometry. The alkaline comet assay was used to evaluate DNA damage and DNA repair. The highest levels of AsU and PbB in children were found in community A (44.5 µg/g creatinine for arsenic and 11.4 µg/dL for lead), followed by community B (16.8 µg/g creatinine for arsenic and 7.3 µg/dL for lead) and finally by children living in community C (12.8 µg/g creatinine for arsenic and 5.3 µg/dL for lead). When DNA damage was assessed, children living in community A had the highest DNA damage. Analysis of these same cells 1 h after a challenge with H(2)O(2) 10 µM showed a dramatic increase in DNA damage in the cells of children living in community B and community C, but not in the cells of children living in community A. Moreover, significantly higher levels of DNA damage were observed 3 h after the challenge ended (repair period) in cells from individuals living in community A. Our results show that children exposed to metals might be more susceptible to DNA alterations.

Indoor air pollution in a Mexican indigenous community: evaluation of risk reduction program using biomarkers of exposure and effect.

Indoor air pollution can be an important risk factor for human health, considering that people spend more than 60% of their time indoors. Fifty percent of the world population and approximately 90% of the rural population in developing countries are using biomass as energy source. Latin America represents 12% of the global consumption of biomass; in Mexico, 27 million people use wood as an energy source. Therefore, in this study we evaluated a 3-stage risk reduction program. The stages were: 1) removal of indoor soot adhered to roofs and internal walls; 2) paving the dirt floors; and 3) introduction of a new wood stove with a metal chimney that expels smoke outdoors. The complete intervention program was applied. In 20 healthy subject residents from an indigenous community in San Luis Potosí, Mexico, we measured blood carboxyhemoglobin (% COHb), DNA damage (comet assay) in nucleated blood cells, and urinary 1-OHP levels before and after the program. Before intervention individuals had a geometric mean COHb level of 4.93% and 53% of the population presented levels above 2.5% considered a safe level. However, in all the studied individuals the levels of COHb were reduced to below 2.5% (mean level 1.0%) one month after the intervention. Moreover, when compared, DNA damage in people exposed before the intervention was higher (5.8+/-1.3 of Tail Moment) than when the program was introduced (2.8+/-0.9 of Tail Moment) (P>0.05) and a same trend was observed with urinary 1-OHP levels; 6.71+/-3.58 micromol/mol creatinine was the concentration before intervention; whereas, 4.80+/-3.29 micromol/mol creatinine was the one after the program. The results suggest that the intervention program offers an acceptable risk reduction to those families that use biomass for food cooking.

An integrated health risk assessment approach to the study of mining sites contaminated with arsenic and lead.

In order to test the value of an integrated approach for the analysis of health risks at contaminated sites, an integrated health risk assessment in a mining area was performed following 3 steps: 1) Environmental monitoring of surface soil, 2) assessment of exposure to metals in children and native rodents, and 3) DNA damage evaluation (comet assay) in children and rodents. These aspects also were studied in less exposed populations. Our results in humans showed that children living in the most polluted area (Villa de la Paz, Mexico) had higher lead blood concentrations (geometric mean of 13.8 microg/dL) and urinary arsenic levels (geometric mean of 52.1 microg/g creatinine) compared to children living in a control area (Matehuala, Mexico; blood lead of 7.3 microg/dL; urinary arsenic of 16.8 microg/g creatinine). Furthermore, the exposed children also had increased DNA damage (tail moment mean in Villa de la Paz of 4.8 vs 3.9 in Matehuala; p < 0.05). Results in rodents were identical. Animals captured in the polluted area had higher levels of arsenic (geometric mean of 1.3 microg/g in liver and 1.8 microg/g in kidney), lead (0.2 microg/g in liver and 0.9 microg/g in kidney), and cadmium (0.8 microg/g in liver and 2.2 microg/g in kidney), and increased DNA damage (tail moment mean of 18.2) when compared to control animals (arsenic in liver of 0.08 microg/g and kidney of 0.1 microg/g; lead in liver of 0.06 microg/g and kidney of 0.3 microg/g; cadmium in liver of 0.06 microg/g and kidney of 0.6 microg/g; and tail moment of 14.2). With the data in children and rodents, the weight-of-evidence for health risks (in this case DNA damage) associated with metal exposure in Villa de la Paz was strengthened. Therefore, a remediation program was easier to justify, and a feasibility study at this site is under way.

Genotoxicidad en niños que viven en una zona metalúrgica del estado de San Luis Potosí, México / Genotoxicity in children living in a smelter area in San Luis Potosí, Mexico

Al poniente de la Ciudad de San Luis Potosí, México, se encuentra ubicadauna metalúrgica alrededor de la cual se ha encontrado contaminación por arsénico y plomo tanto en aire como en suelo/polvo. Varios estudios han mostrado que los niños que habitan cerca de este lugar están expuestos a dichos metales. Considerando lo anterior y tomando en cuenta reportes de genotoxicidad asociada al arsénico y al plomo, en este trabajo se evaluó el daño al ADN en los niños expuestos empleando el ensayo cometa. Los resultados indican que casi la mitad de los niños que viven en este lugar presentan valores por encima de los límites de acción que marca CDC para arsénico (50 ug/g de creatinina) y paraplomo (10 ug/dL de sangre). En cuanto al daño al ADN el 35% de los niños sobrepasa el máximo valor de daño encontrado en la población control.

A smelter area where arsenic and lead have been found in air and soil/dust is located in San Luis Potosi, México. Some studies have reported that children living in this area are exposed to those metals. Therefore, DNA damage usingthe comet assay was assessed in the exposed children. Our results showed that almost 50% of the studied children had urinary arsenic and blood lead levels higher than the CDC´s guidelines (50 ug/g creatinin for urinary arsenic and 10 ug/dL for lead in blood). With regard to DNA damage 35% of the children had damage values above the control population.