**7. References**


**3** 

*Brazil* 

**Histological Biomarker as Diagnostic** 

**Tool for Evaluating the Environmental** 

It has been reported that in recent decades the level of foreign compounds known as xenobiotics in aquatic ecosystems has increased alarmingly as a result of domestic, industrial and agricultural effluents. In the 20th century, many thousands of organic trace pollutants, such as polychlorinated biphenyls (PCBs),organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and dybenzon – p – dioxins (PCDDs) have been produced and in part, released into the environment (van der Oost et al., 2003). This has led to substantial reduction in environmental quality, adding to the deterioration of human health and living organisms that depend on these ecosystems (Cajaravlle et al., 2000). However, the presence of a foreign compound in a segment of an aquatic ecosystem does not, by it self, indicate injurious effects. Connections must be established between external levels of exposure, internal levels of tissue contamination and early adverse effects and determining the extent and severity of such contamination only by the results of water chemical analysis is insufficient and often overestimates the proportion and duration of exposure to the toxic agent (van der Oost et al., 2003 & Giari et al., 2008). Thus, studies using biomarkers are essential to complement such environmental monitoring, given that in order to control pollution effects of effluents on the animals that inhabit the water bodies must be understood (Martinez & Colus, 2002; Camargo & Martinez, 2006). Biomarkers are defined as responses to any exposure evidenced in histological, physiological, biochemistry, genetic and behavioral modification (Leonzio & Fossi, 1993). More recent, van der Oost et al. 2003 defined biomark as a biological indicator from an expousure to a stressor responding in various ways such a response can be seen and adaptation as a defense. Some authors note that biomarkers are used as a warning sign to emerging environmental problems (Au, 2004). In this type of environmental assessment, the health of an ecosystem can be measured by the health of its individual components (Hugget et al., 1992). It is essential to this study, as there is a variety of responses that can be used as tools to assess the health of animals exposed to certain chemicals, to provide information on spatial and temporal changes in pollutant concentrations and indicate the occurrence of environmental quality or adverse ecological consequences (Kammenga et al., 2000). In Brazil there are few studies about impact of

**1. Introduction** 

**Quality of Guajará Bay – PA - Brazil** 

José Souto Rosa Filho and Rossineide Martins Rocha

Caroline da Silva Montes,

*Universidade Federal do Pará,* 

