Jesús Mejía-Saavedra

Exposure to persistent organic pollutants (POPs) and DNA damage as an indicator of environmental stress in fish of different feeding habits of Coatzacoalcos, Veracruz, Mexico

The region of Coatzacoalcos, Veracruz hosts one of the largest and most important industrial areas of Mexico and Latin America. Industrial development and rapid population growth, have triggered a severe impact on aquatic ecosystems of the region. The aim of this study was to determine the levels of POPs in sediment and in muscle tissue of five fish species from different trophic levels in downstream residents of the Coatzacoalcos River, and their integration with DNA damage in the fish, evaluated with the comet assay in whole blood as a biological indicator of stress, in order to obtain a baseline of the ecological condition of the region. The compounds detected in sediment and in muscle tissue were hexachlorobenzene (HCB), α-, β-, γ-hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethylene (DDE), mirex and polychlorinated biphenyls (PCBs). Sediment concentrations of these pollutants (except for mirex) exceeded the values of protection provided by international guidelines, suggesting a potential risk to aquatic life in the region. DNA damage recorded in the fish species is evidence of exposure to a mix of genotoxic pollutants, which combined with exposure to POPs, reflects the degree of environmental stress of aquatic organisms in the region. The results of this study show the importance of determining the presence of contaminants in the environment, the bioaccumulation in tissues and their effects on exposed organisms, providing an integrated approach in assessing the health of aquatic ecosystems.

DNA damage in earthworms (Eisenia spp.) as an indicator of environmental stress in the industrial zone of Coatzacoalcos, Veracruz, Mexico.

Coatzacoalcos, Veracruz is one of the major industrial areas of Mexico. Presently, the Coatzacoalcos River and the areas surrounding the industrial complex are considered by various authors to be some of most polluted sites in Mexico. The objective of this study was to determine if earthworms could be used as indicators of environmental stress in the Coatzacoalcos industrial zone. Often, detritivores and decomposers such as earthworms are the first to be affected when the soil is contaminated. We collected soil samples to be used for persistent organic pollutants (POPs) quantification by gas chromatography. Concentrations of hexachlorobenzene, lindane and total polychlorinated biphenyls (PCBs) in the soil were above the maximum permissible limits of the Canadian Environmental Quality Guidelines (CEQG). Comet assay was conducted in coelomocytes of wild earthworms collected in Coatzacoalcos and compared with the control earthworms. We found DNA damage in earthworms from Coatzacoalcos that was significantly higher (P < 0.05) in comparison to laboratory earthworms. Earthworms are an appropriate organism to use as an indicator of environmental impact in contaminated sites. DNA damage recorded in the earthworms provides clear evidence of environmental impacts by the chemical industry on the wildlife of this region.

Effect of coexposure to DDT and manganese on freshwater invertebrates: Pore water from contaminated rivers and laboratory studies

An environmental survey of several rivers of the southern Huasteca area of Mexico revealed high concentrations of manganese (Mn) and the presence of DDT in the sediments and pore water. Therefore, acute (48-h) toxicities of Mn and DDT were assessed both independently and as a combination on 24-h-old neonates of Daphnia magna Strauss and Lecane quadridentata Ehrenberg. Daphnia magna showed high sensitivity to both toxicants, whereas L. quadridentata was highly resistant to DDT and less susceptible to Mn. For D. magna, the Mn and DDT coexposure was significantly more toxic than any of the singly tested compounds. When D. magna was exposed to sediment pore water, no association was found between the Mn content in the samples and the observed toxicity. Preliminary particle analysis of pore water showed different compounds of Mn, which apparently were not in bioavailable form.

Effect of Mining Activities in Biotic Communities of Villa de la Paz, San Luis Potosi, Mexico

Mining is one of the most important industrial activities worldwide. During its different stages numerous impacts are generated to the environment. The activities in the region have generated a great amount of mining residues, which have caused severe pollution and health effects in both human population and biotic components. The aim of this paper was to assess the impact of mining activities on biotic communities within the district of Villa de la Paz. The results showed that the concentrations of As and Pb in soil were higher than the national regulations for urban or agricultural areas. The bioavailability of these metals was certified by the presence of them in the roots of species of plants and in kidneys and livers of wild rodents. In regard to the community analysis, the sites that were located close to the mining district of Villa de la Paz registered a lower biological diversity, in both plants and wild rodents, aside from showing a change in the species composition of plant communities. The results of this study are evidence of the impact of mining on biotic communities, and the need to take into account the wildlife in the assessment of contaminated sites.

Wild rodents (Dipodomys merriami) used as biomonitors in contaminated mining sites.

Mining is one of the most important industrial activities globally; however, mining processes have critical environmental impacts, as mining is a major source of metals and metalloids that contribute significantly to the pollution of soil, sediment, water and air. Heavy metals can impact the health of exposed human populations and nonhuman receptors. This study focused on arsenic because its genotoxicity is well-known. Previously, we proposed a methodology to evaluate and integrate risk from a single source affecting different biologic receptors. Here, we propose an alternative approach estimating arsenic exposure in children and kangaroo rats using probabilistic simulation with Monte Carlo modeling. The estimates are then associated to measured DNA damage and compared to both populations of children and rodents living in contaminated and in reference areas. Finally, based on the integrated analysis of the generated information, we evaluate the potential use of wild rodents (Dipodomys merriami) as a biomonitor at mining sites. Results indicate that the variation of genotoxicity in children of the reference site is ≈ 2 units when compared to the children of the contaminated site. In the rodents we observed a variation of ≈ 4 units between those of the reference site when compared to those living on the contaminated site. We propose that D. merriami can be used as a biomonitor organism in sites with mining activity, and that a non-lethal test can be used to evaluate risk from metal exposure.

Collagenase 1A2 (COL1A2) gene A/C polymorphism in relation to severity of dental fluorosis.

OBJECTIVES The aim of this study was to evaluate the putative association between the presence of the COL1A2 gene A/C polymorphism and the severity of dental fluorosis in a sample exposed to high concentrations of fluoride. METHODS A cross-sectional study was carried out that included 80 children residing in a community with high concentrations of fluoride in the drinking water. To determine whether the presence of this polymorphism and dental fluorosis are associated, the presence of the dental fluorosis was considered to be a response variable, while fluoride concentration in water and urine was designated as independent variables. In addition, the childrens parents completed questionnaires with general information about drinking and cooking with tap water, consumption of milk and soft drinks, and other putative risk factors. RESULTS Individuals with the polymorphism had nonsignificant odds (OR = 2.24; 95% CI = 0.55-9.02) of having dental fluorosis at higher exposures to fluoride. This finding was similar in individuals without the polymorphism (OR = 1.65; 95% CI = 0.44-6.17). CONCLUSIONS The presence of polymorphism in the COL1A2 gene was not associated with the severity of dental fluorosis.

Exposure Assessment to Persistent Organic Pollutants in Wildlife: The Case Study of Coatzacoalcos, Veracruz, Mexico

Until the early 70s, it was thought that pollution was a phenomenon circumscribed to zones where pollutants were generated. Because of that, in each country concern was limited to regions where pollutant concentration was higher or its danger was greater. However, it has gradually become aware that pollution is a problem that affects everybody and, because of that, everybody is responsible to control it, regardless of the sites distance where pollutants are produced. Therefore, the problem of pollution has become a global phenomenon. Mankind has always depended on natural resources located in the region where they dwell. Nevertheless, the fast population growth coupled with a fast agricultural and industrial development as well as life style changes have increased emissions of pollutants in different ecosystems. Persistent organic pollutants (POPs) is a group of compounds chemically very stable, able to travel considerable distances and it is resistant to natural degradation processes, most of them were produced to be used as pesticides and certain chemicals to be used as industrial processes, and others are generated as by-products unintentionally from human activities, such as combustion processes or power generation (PNUMA, 2005). Most of these compounds are highly toxic; they bioaccumulate in human and animal tissue, mainly in the fatty tissues, and can damage different organs and systemic targets such as the liver, kidney, hormonal system, nervous system, etc., of both humans and wildlife. According to the Stockholm Convention held in 2001, there are twelve compounds known as POPs: pesticides (DDT, aldrin, chlordane, dieldrin, endrin, mirex, toxaphene and heptachlor), industrial chemicals (hexachlorobenzene and polychlorinated biphenyls -PCB-) and unintentional compounds (dioxins, furans, PCDD-and PCDF-) [Albert, 2004]. In May of 2009 nine new Chemicals were added to the POPs list: alpha hexachlorocyclohexane, beta hexachlorocyclohexane; hexabromodiphenyl heptabromodiphenyl ether and ether tetrabromodiphenyl pentabromodiphenyl ether and ether chlordecone, hexabromobiphenyl, lindane, pentachlorobenzene, perfluorooctane sulfonic acid, its salts and perfluorooctane sulfonyl fluoride.