Chromium CONTAMINANTS emanating from industrial activities pose a significant threat to human’s well-being. Chromium (III) and Chromium (VI) are the forms in which they are commonly encountered, of which the trivalent form is relatively benign. Hence, biological reduction of hexavalent chromium has been widely explored by researchers, yielding fruitful outcomes, opening up exciting avenues and also throwing up new challenges. This article attempts to review this area of research. Microbes, especially bacteria capable of Chromium (VI) reduction, belonging to a heterogeneous group have been isolated from contaminated sites. They exhibit plasmid-mediated chromate resistance and the reduction is enzymatically mediated. Reduction studies have been carried out with free and immobilized enzymes as well as whole cells. Experiments have been carried out in specifically designed bioreactors operated in batch and continuous modes. Although significant progress has been made, much needs to be done for its successful in situ application as the organism may not withstand the Chromium concentration or may be impeded by the presence of other toxicants. With molecular engineering, it may be possible to derive strains with improved performance even under stressful field conditions.

Nowadays, Water contamination is one of the major problems and challenges in the world that can be considered as one of the main factors of diseases and mortalities in the world. Both surface and ground waters are exposed to the different CONTAMINANTS. With regard to the nature and source of their entrance (man-made or naturally occurring), various classifications have been considered for CONTAMINANTS. The main organic CONTAMINANTS of water are agricultural, chemical, oil, and food CONTAMINANTS. Each of these four groups has sub-criteria. In this research, water CONTAMINANTS in oil and petrochemical industries have been identified and ranked through using Principle Component Analysis (PCA) as well as Analytical Network Process (ANP) methods. Results of Principle Component Analysis method reveal the fact that lead, nitrate and sodium contaminations have been ranked at the highest level from the environment experts’ point of views regarding water contamination. Furthermore, results of ANP show that agricultural and oil CONTAMINANTS with the weights of 0. 321 and 0. 152 ranked first and fourth respectively. Finally, I hope that the relevant organizations can take effective steps to prevent environmental degradation which is created by oil and chemical industries CONTAMINANTS.

Male reproductive health has deteriorated considerably in the last few decades. Nutritional, socioeconomic, lifestyle and environmental factors (among others) have been attributed to compromising male reproductive health.In recent years, a large volume of evidence has accumulated that suggests that the trend of decreasing male fertility (in terms of sperm count, quality and other changes in male reproductive health) might be due to exposure to environmental toxicants. These environmental CONTAMINANTS can mimic natural oestrogens and target testicular spermatogenesis, steroidogenesis, and the function of both Sertoli and Leydig cells. Most environmental toxicants have been shown to induce reactive oxygen species, thereby causing a state of oxidative stress in various compartments of the testes. However, the molecular mechanism (s) of action of the environmental toxicants on the testis have yet to be elucidated.This review discusses the effects of some of the more commonly used environmental CONTAMINANTS on testicular function through the induction of oxidative stress and apoptosis.

A mathematical model presented in this paper describes the dispersion and con- centration of CONTAMINANTS (ne and coarse) in porous medium with the effect of chemical reaction. Solute transport in porous media is discussed by means of advection-dispersion equation. The effect of particle mass parameter and reaction rate parameter on the dispersion coefficient and mean concentration of a chemical solute is studied by introducing a slug of finite length. Analytical solutions are obtained by varying the dimensionless time, axial distance and length of the solute. The results are depicted using graphs.