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Microplastics (MPs) are contaminants widely distributed in the environment and biota. Previously, most studies focused on identifying and characterizing microplastics in the marine environment, while their impact on freshwater ecosystems remains to be determined. This review summarizes recent findings regarding MPs physiological, immunological, and genetic effects on amphibians based upon the biological relevance of this species as indicators of freshwater pollution. Data demonstrated that MPs contamination may potentially alter various physiological processes in aquatic animals, mainly in the embryonic stages. It is worthwhile noting that adverse effects might be enhanced in synergy with other pollutants. However, amphibians might counteract the effect of MPs and other pollutants through microbiota present both in the intestine and on the skin. In addition, amphibian microbial composition might also be altered by MPs themselves in a manner that leads to unpredicted health consequences in amphibians.

This work aimed to conduct a laboratory study to evaluate the use of Pseudomonas putida CB-100 and nutrient addition for the removal of PAHs from an aged oil-polluted soil of Veracruz, Mexico. Pseudomonas putida is a biosurfactant-producing bacterium capable of metabolizing polycyclic aromatic hydrocarbons (PAHs), which are toxic compounds with low water solubility, high melting, and boiling points, and low vapor pressure; characteristics that increase as their molecular weight increases and make them more recalcitrant. The methodology consisted in sampling the long-term oil-polluted soil and testing the use of Gamma irradiation (25 kGy) for the sterilization of the soil for abiotic control. We evaluated serological bottles containing 20 g of 35% moist soil (irradiated and non-irradiated) with the following treatments: the addition of nutrients (NH

To assess the exposure to lead in children living in various types of contaminated sites.The study was conducted from June 2008 to December 2009 at four sites in Mexico: Avalos metallurgical, Chihuahua; Morales metallurgical, San Luis Potosí (SLP); Trinidad pottery area, Tlaxcala and Cedral mine site, SLP. These sites contain different sources of lead. The metal levels were quantified in outdoor dust and in peripheral blood of children.Lead dust concentrations exceed the National Guidelines for residential soils (400 mg/kg) in a range of values for the four sites from 62 to 5 187 mg/kg. Regarding biological monitoring, the studied children showed maximum lead blood levels of 22 µg/dL in Cedral, 31 µg/dL in Morales, 32 µg/dL in Avalos, and 52 µg/dL in Trinidad. It is important to mention that in all the studied sites, a significative positive correlation was found between blood lead levels and the lead concentrations in dust.These sites are an example of the health risks related to lead exposure in Mexico; therefore, there is an urgent need for a national public health program aimed at reducing lead exposure in vulnerable populations.

Resumen en español: "La cuenca del río Grijalva abarca parte del sureste de México y noroeste de Guatemala, por lo que su carácter transfronterizo le asigna relevancia política, económica y social. El desarrollo minero en el río Cuilco, afluente del Grijalva en Guatemala, y una incipiente actividad minera en Chiapas, podrían generar impactos ambientales en las cuencas alta, media y baja, por lo que se requiere de estudios que evalúen las concentraciones actuales de metales en medios ambientales y estimen el riesgo de exposición humana a dichos elementos, para establecer mecanismos de control de contaminación en el futuro. El objetivo de esta investigación fue estimar de forma preliminar, los niveles de riesgos de exposición y efectos a la salud por arsénico (As), cadmio (Cd), mercurio (Hg) y plomo (Pb) de suelos y sedimentos en niños de comunidades ribereñas del río Grijalva. Para tal fin, se tomaron muestras en las riberas de las cuencas alta, media y baja, determinando las concentraciones de los metales a través de espectrometría de absorción atómica; y se siguió la metodología de evaluación de riesgos para la salud en sitios contaminados de la Organización Panamericana de la Salud. La proporción de niños afectados en las cuencas media y baja por exposición al As es 10% y 20% mayor que la de niños en la cuenca alta. Para el Cd y el Hg, se considera que los riesgos a la salud en la zona son mínimos. En cuanto al Pb, la proporción de niños expuestos es mayor en las riberas de la cuenca alta, con 2.6%. Sin embargo, en sitios específicos dentro de la cuenca alta y baja, el porcentaje de niños posiblemente expuestos puede ser del orden de 34 a 86%, por lo que se requiere una evaluación de riesgos detallada y específica para dichas zonas. "